Best Practice Guide for maintenancepiarc.rmto.ir/DocLib/انگلیسی/روسازی راه/راهنمای مناسب... · maintenance methods used world-wide; a case study of full-depth

www.piarc.org2013R06EN

Best Practice Guide for maintenance of concrete roadsJointed Plain concrete Pavement and continuously reinforced concrete PavementTechnical Committee D.2 – Road Pavements

The World Road Association (PIARC) is a nonprofit organisation established in 1909 to improve international co-operation and to foster progress in the field of roads and road transport.

The study that is the subject of this report was defined in the PIARC Strategic Plan 2007 – 2011 approved by the Council of the World Road Association, whose members are representatives of the member national governments. The members of the Technical Committee responsible for this report were nominated by the member national governments for their special competences.

Any opinions, findings, conclusions and recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of their parent organizations or agencies.

This report is available from the internet site of the World Road Association (PIARC)http://www.piarc.org

Copyright by the World Road Association. All rights reserved.

World Road Association (PIARC)La Grande Arche, Paroi nord, Niveau 292055 La Défense cedex, FRANCe

International Standard Book Number 978-2-84060-317-7

statements

Best Practice Guide for maintenance of concrete roads...2

2013R06EN

This report has been prepared by Working Group 1, lead by Technical sub-committee D2c “Concrete Roads” of the Technical Committee D2 “Road Pavements” of the World Road Association (PIARC).

Working Group Members contributing to this report:

Ralf Alte-Teigeler (Germany),Randolf Anger (Germany),Anne Beeldens (Belgium),Raymond Debroux (Belgium),André Jasienski (Belgium),Stefan Höller (Germany), team leaderCarlos Jofré (Spain),Katalin Karsai (Hungary),Franci Kavcic (Slovenia),Solomon Kganyago (South Africa),Hennie Kotze (South Africa),Beata Krieger (Germany),Anne-Séverine Poupeleer (Belgium),Luc Rens (Belgium): Working Group Coordinator,Robert Mesnard (France)Thierry Sedran (France),Juan J. Orozco (Mexico),Bryan Perrie (South Africa),Johannes Steigenberger (Austria),Tim Smith (Canada),Suneel Vanikar (United States of America). Other Contributors:Rudolf Bader (Germany),Betty Bennet (United States of America),Rudi Bull-Wasser (Germany),Tibor Bors (Hungary),Laszlo Gaspar (Hungary),Karin Keglevich (Austria),Lars Keller (Germany),Nick Kong Kam Wa (South Africa),Becca Lane (United States of America),Franz Lecker (Austria),Junichi Noda (Japan),Bernd Nolle (Germany),Reinhard Pichler (Austria),Arno Piko (Austria),


2013R06EN

Peter Schöller (Austria),Kurt Smith (United States of America),Shiraz Tayabji (United States of America).

The english Version of this report has been edited by Luc Rens (Belgium) and translations into French has been made by Raymond Debroux and Thierry Sedran and Spanish translation has been made by Juan J. Orozco (Mexico) respectively.

The Technical sub-committee D2c was chaired by Mr Raymond Debroux (Belgium) and Anne-Séverine Poupeleer (Belgium), Thierry Sedran (France) and Mr Juan J. Orozco (Mexico) were the english, French and Spanish speaking secretaries, respectively.

The French version is available under the reference 2013R06FR, ISBN: 978-2-84060-318-4.


2013R06EN

contents

executive summary ........................................................................................................................6introduction .......................................................................................................................................7

1. status assessment ......................................................................................................................101.1. degradations For all types oF concrete pavements ......................................10

1.1.1. Damaged joint filler ............................................................................................................101.1.2. Surface damage ...................................................................................................................121.1.3. Reduced skid resistance .......................................................................................................14

1.2. degradations speciFic to Jointed plain concrete pavements (Jpcp) .......151.2.1. Vertical slab movement, offset slabs ....................................................................................151.2.2. edge damage and broken-off corners ..................................................................................171.2.3. Displacement of slabs ..........................................................................................................181.2.4. Longitudinal and transverse cracks .....................................................................................19

1.3. degrasations speciFic to continuously reinForced concrete pavements (crcp) ............................................................................................211.3.1. The punchout phenomenon ..................................................................................................21

2. maintenance measures .........................................................................................................242.1. For all types oF construction ....................................................................................24

2.1.1. Repair and renewal of joint fillers .......................................................................................242.1.2. Removal of concrete .............................................................................................................272.1.3. Strip-wise replacement.........................................................................................................302.1.4. Surface treatment with reactive resin...................................................................................342.1.5. Surfacing with reactive resin mortar ...................................................................................362.1.6. Renewal ................................................................................................................................392.1.7. Surface crack filling ............................................................................................................412.1.8. Injection ...............................................................................................................................422.1.9. Improving drainage .............................................................................................................43

2.2. For the construction type Jointed plain concrete pavement (Jpcp) ......442.2.1. Widening and filling cracks .................................................................................................442.2.2. Doweling and anchoring cracks ..........................................................................................452.2.3. Repair of edge damage and broken-off corners .................................................................492.2.4. Lifting and securing slabs ....................................................................................................512.2.5. Replacement of slabs and slab sections ...............................................................................54

2.3. For the construction type continuously reinForced concrete pavement (crcp) ...............................................................................................562.3.1. Replacement of areas with punchout ...................................................................................56

aPPendices ............................................................................................................................................611. results of the survey on maintenance of concrete roads ........................612. california – full dePth rePlacement of concrete Panels

with raPid strenGth concrete .........................................................................................683. south africa – rehaBilitation of crcP with hiGh early

strenGth concrete on the schoemann freeway .................................................73


2013R06EN

executive summary

the report firstly examines the different types of degradations of concrete pavements distinguishing those which are specific to jointed plain concrete pavements and those which relate to continuously reinforced concrete pavements. For each type of degradation, status indicator, status assessment, causes and remedial measures are presented.

the report then describes the maintenance techniques providing precise indications on the products to use and the repair method.

three appendices complete the report: a survey on concrete pavements and the maintenance methods used world-wide; a case study of full-depth replacement of concrete panels with rapid strength concrete in california; a case study of rehabilitation of continuously reinforced concrete with high early strength concrete in south africa.


2013R06EN

introduction

concrete pavement surfaces reach a high durability and good long-term performance. to ensure this, long-life constructions, sufficient design, qualitatively high-grade execution and the necessary maintenance are needed.

the construction method is regionally employed to very different extends. hence, the experiences concerning the maintenance measures differ greatly.

in order to foster knowledge sharing, the World road association (piarc) has taken an interest in this topic. the subcommittee d2c “Concrete Roads” was given the task to identify the best maintenance measures for concrete pavement surfaces under the issue 2: “Improved Maintenance Methods”.

initially, a survey was conducted in which 35 countries, or 56% of the land surface of the earth, participated. the complete network of paved roads contains 26 million kilometres, of which 2 million, or 7.7%, are concrete roads. in 20 countries, concrete pavement surfaces are entailed to a larger scale, which means more than 200 kilometres. hence, in the respective countries, the experiences with preservation measures of concrete pavements are correspondingly large.

maintenance measures are being conducted in order to maintain, restore or adapt the road to increase traffic volume. they start by determining the condition within regular intervals. in doing so, the characteristic features of the pavements structures are depicted and illustrated. damages and deficiencies are qualitatively and quantitatively being captured. this can be done visually, metrological and by means of additional tests, for example core tests, bearing capacity measurement or the detection of cavities. Besides the determined condition or the damage, the aspired remaining usage of the road construction has to be considered.


2013R06EN

all maintenance measures gathered in the framework of the survey have been analyzed and the best and tested are determined here.

some measures are applicable for all concrete structures ( figure 1). these include the renewing of damaged and/or leaking (longitudinal) joints, the restoration of the grip by removing concrete or the application of coating, the filling of near-surface cracks, strip-wise renewal as well as the improvement of the drainage.

concrete Pavement

continuously reinForced

concrete pavement (crcp)

- 0,7 - 2,5 m - 0,7 - 2,5 m 5,0 m

Jointed plain concrete

pavement (Jpcp)

crackwidth up to 4 mm

crackwidth up to 4 mm

crackwidth up to 0.5 mm



Figure 1 – concrete pavement, types oF construction

other measures refer specifically to jointed plain concrete pavements (Jpcp). these comprise the expanding and backfilling of cracks, the subsequent anchoring and mounting of cracks and joints, the repair of edge damages and broken-off corners, the lifting and securing of concrete slabs and the renewing of slabs and slab sections.

For continuously reinforced concrete pavements (crcp), the removal of punch-out damages is being described.

With this manual, the best measures are accessible to everybody and can be adapted to regional conditions. When implemented consequently, the working life of concrete road pavements can be prolonged, the security and the driving comfort increased and the construction method made economically more efficient.


2013R06EN

representatives from austria, Belgium, canada, czech republic, France, germany, hungary, india, iran, italy, republic of Korea, madagascar, mexico, morocco, portugal, romania, slovakia, slovenia, south africa, spain, cuba and the united states of america participated in the drafting of this report.

the results of the survey are depicted and explained in detail in appendix 1. as an illustration, two case-studies from south-africa and the u.s. are presented in appendices 2 and 3, in which single sections of a concrete pavement in Jpcp and crcp are being renewed.

nevertheless, the maintenance of concrete pavements is not over. the survey has shown that new building materials or process engineering allow for continued development. reactive resin, as an example, can be employed as a coating to improve or renew the grip of a concrete surface. this relatively young procedure is already included in this manual.

another procedure is the application of prefabricated elements for the renewal of single slabs. this is made possible by using innovative concretes and lifting gear. however, the procedure is still very young and only applied in north america. yet, it will be included after further positive experiences.


2013R06EN

Best Practice Guide for maintenance of concrete roads...

1. status assessment

the characteristic status indicators for the road pavement structure are described and illustrated below, followed by notes concerning the qualitative and quantitative assessment of faults and damage.

common causes of damage are listed for some particular examples (table 1 - Allocation of status indicators to possible causes), and may occur individually and in combination. it should be noted that the order of the causes of damage in the list does not provide an indication of their frequency of occurrence.

possible construction measures and construction methods for removing the damage are mentioned, however the order of the construction measures and methods presented does not provide an indication of their value.

the status of the road and, where required, the cause of the damage were determined by visual inspections, measurements and additional tests. drill cores were extracted to test the properties of the concrete, and other extracted parts were only used in exceptional cases. however, the performance of the road pavement structure or of individual layers cannot be determined via these test methods. therefore, determining the causes of damage may require additional investigations such as determining the sagging or load-carrying properties, investigation of water drainage or cavities under the slabs, measurements of horizontal or vertical movement, and checking the position and state of the dowels and anchors.

1.1. deGradations for all tyPes of concrete Pavement

1.1.1. damaged joint filler

damaged joint filler (including profiles and hot or cold processed joint filler) is typically detached from the sides of the joint, is pressed upwards or has sagged, is internally cracked or porous, or is no longer present ( figure 2, following page).

10

2013R06EN


Figure 2 – damaged Joint Filler

status indicators

• Percentage of damaged joint filler; • appearance:

– missing or removed joint filler (for profiles, particularly at intersection points), – lacking lateral adhesion, – sagged joint filler, – porosity, – other forms of damage (chemical, thermal, mechanical).

status assessment

visual (documented using photographic methods).

causes

• Ageing of the joint filler,• unsuitable joint filler or overheated joint sealing compound,• insufficient joint maintenance (tightness),• erosion or destruction of the bedding layer ,• slab length too large or joints not broken (indicated by large cracks between

unbroken sections),• unsuitable joint formation or arrangement,• faulty joint creation,• missing or no longer effective doweling or anchoring (resulting in excessive

horizontal or vertical movement of the slabs),• edge damage.

11

2013R06EN


measures

successful repair or maintenance measures require the slabs to be firmly supported and the joint gap width to be adjusted to the expected range of longitudinal movement.

preparatory securing or lifting of the slabs by injecting material and possibly, retrospective doweling and anchoring as well as re-cutting the joint can remedy the conditions mentioned.

the following measures can be applied:

• repair of the joint filler,• moving excess sealing compound downwards,• replacement of the joint filler,• enlargement of the joint gap,• placement of additional joints.

1.1.2. surface damage

typical examples of surface damage are chipping ( figure 3), repaired chipping ( figure 4, following page), weathering ( figure 5, following page) or a missing road surface layer ( figure 6, following page).

Figure 3 – chipping

12

2013R06EN


Figure 4 – pc mortar repaired chipping

Figure 5 – Weathering

Figure 6 – missing road surFace layer

13

2013R06EN


status indicator

• percentage of affected slabs, • percentage area per affected slab.

status assessment

visual inspection, photographic methods.

causes

• unsuitable concrete composition (e.g. cement, aggregate, additives, added agents, added materials, air void contents),

• insufficient properties of hardened concrete (e.g. pressure, bending pressure, surface tension resistance, frost-dewing and frost-de-icing-salt resistance),

• faulty surface construction (e.g. separation during concrete installation),• unfavourable weather conditions during pavement construction (e.g. heat,

precipitation, frost, wind),• insufficient curing time,• the effects of other chemical, thermal, or mechanical factors (e.g. de-icing agents,

oils, fire, vehicle crashes).

measures

the surface tension resistance of the existing concrete pavement must be tested to ensure the effectiveness of the maintenance or repair measure. the surface tension resistance must be at least 1.5 n/mm².

• treatment with reaction resin and coating with reaction resin mortar, • removal of the concrete,• localised repair.

1.1.3. reduced skid resistance

visual evaluation methods are not sufficient to provide an assessment of skid resistance. skid resistance can only be accurately measured via recognised test methods and test equipment.

status indicator

length of track in the lane section considered.

14

2013R06EN


status assessment

By measurements (scrim , skid resistance tester (srt)).

causes

a reduction in skid resistance is caused by normal wear as a result of the passage of traffic over time, however in some cases the following causes may be applicable where abnormally high reductions in skid resistance have occurred:

• unsuitable concrete composition (unsuitable aggregate, low polishing resistance, e.g.• faulty surface production (quality and thickness of the fine mortar layer, mortar

accumulation in the top concrete layer, surface texture),• insufficient drainage of the surface.

measures

the surface tension resistance of the existing concrete pavement must be tested to ensure the effectiveness of the maintenance or repair measure. the surface tension resistance must be at least 1.5 n/mm².


• removing the concrete (grinding),• treatment with reaction resin,• coating with reaction resin mortar,• application of asphalt layers (e.g. stone mastics asphalt (sma)).

1.2. deGradations sPecific to Jointed Plain concrete Pavements (JPcP)

1.2.1. vertical slab movement, offset slabs

slabs or parts of slabs may move under traffic load which may eventually result in offset slabs ( figure 7, following page).

15

2013R06EN


Figure 7 – oFFset slaBs

status indicators

• percentage of affected slabs,• appearance,• maximum height displacement (mm).

status assessment

measurements, visual.

causes

• lack of carrying capacity of the bedding layer,• cavities in the joint or crack area as a result of erosion,• missing or damaged doweling or anchoring.

measures

the selection of an appropriate maintenance or repair measure depends on whether the slabs are doweled and/or anchored, whether the slabs are damaged by crack formation, and whether they are supported from underneath or lie on a hollow.


• stabilising or lifting by injection,• retrospective doweling and/or anchoring,• removal of concrete,• replacement of slabs or parts of slabs.

16

2013R06EN


1.2.2. edge damage and broken-off corners

edge damage is characterised by chipping or damage to the concrete at the joint location ( figure 8).

Figure 8 – edge damage

Broken-off corners are another typical form of damage of the concrete slab ( figure 9).

Figure 9 – BroKen-oFF corner

status indicators

• percentage of slab area damaged, • number of broken-off corners.

status assessment

visual inspection.

17

2013R06EN


causes

• Insufficient concrete strength,• deformation of the bedding layer,• faulty joint condition,• obstructed horizontal or vertical slab movement,• mechanical stress (e.g. from heavy vehicles such as tracked vehicles).

measures

the success of the maintenance or repair measure selected depends on careful removal of the damaged and loose parts of the slab.


• repair with reactive resin mortar,• replacement of slabs or slab sections (with quick-setting concrete, where required).

1.2.3. displacement of slabs

slab displacement is apparent where there is a gap of up to several centimetres in width at the location of longitudinal joints between adjacent lanes ( figure 10).

Figure 10 – displacement oF slaBs

status indicator

specification of the length in metres (m) with gap widths (mm) and the distribution in the road section taken into account.

status assessment

visual inspection, photographic methods.

18

2013R06EN


causes

• missing anchoring,• anchoring no longer effective.

measures

the success of the maintenance and repair measures is dependent upon the early application of retrospective anchoring to prevent a further increase in the joint gap width.


• retrospective anchoring,• replacement of joint filler,• replacement of slabs or parts of slabs.

1.2.4. longitudinal and transverse cracks

this form of damage is characterised by cracks near the surface, or deep cracks in a longitudinal and transverse direction, with the exception of ‘hairline’ cracks ( figure 11 and figure 12, following page).

Figure 11 – Widened and sealed longitudinal cracK

19

2013R06EN


Figure 12 – transverse cracK

status indicator

percentage of cracked slabs.

status assessment

measurement, visual inspection, photographic methods.

causes

• cracking of the bedding layer, • insufficient thickness of the concrete pavement (under-dimensioned),• insufficient carrying capacity of the road structure,• inappropriate slab size or slab form,• unbroken dummy joint, • insufficient concrete strength,• inappropriate concrete composition,• fault during joint construction (cutting depth insufficient, improper cutting time

(too late)),• faulty pavement construction (e.g. installation, installation devices, curing),• unusually high stresses (e.g. from heavy traffic).

measures

the effectiveness of the maintenance or repair measure are improved when further damage (e.g. slab offset, broken-off corners, etc.) is delayed by early anchoring (e.g. diagonal tie-bar).

20

2013R06EN



• retrospective doweling and/or anchoring, • widening and sealing of the cracks,• stabilising the slabs (e.g. by addressing deformation of bedding layer, or erosion

damage in the base course),• replacing slabs and parts of slabs.

1.3. deGradations sPecific to continuously reinforced concrete Pavements (crcP)

1.3.1. the punchout phenomenon

the “punchout” problem first appeared in Belgium at the end of the eighties on certain sections of motorway that had been built after 1981. observations soon showed that the phenomenon was similar to what had already been observed in the united states. punchouts are pavement failures that usually occur close to the outside edge of the pavement and which lead to the fragmentation of the concrete and the loss of blocks or wedges of paving material as a result of the dynamic impact of the traffic. the occurrence of punchout is the consequence of multiple causes whose simultaneous action causes the problem to lead to a dangerous final stage that makes immediate action necessary, even if this is only provisional. the four essential factors needed for the occurrence of this kind of damage are the presence of water in the interface between the concrete slab and the road base, a base that is sensitive to erosion, heavy intense traffic at the edge of the slab, and closely spaced transverse cracks. the observed sequence of events is as follows.

Water that penetrates under the edge of the concrete slab is subjected to pressure when heavy vehides pass over the pavement. this causes the erosion of the base by repeated pumping at the outer edge of the pavement, giving rise to small voids under the slab. the presence of such voids reduces the transfer of loads over the cracks. this in turn leads to a sharp rise in the transverse bending stresses, which after a while results in the development of a longitudinal crack at a distance of 0.5 to 1 m from the edge of the pavement. the concrete block that is isolated in this way rapidly become unstable under the action of the traffic and will disintegrate entirely, and will eventually lead to the loss of the fragments. Figure 13, following page, illustrates the various steps in the formation of a “punchout”. it must nonetheless be pointed out that the existence of successive cracks alone will not lead to a “punchout”. the numerous motorways that display this kind of cracking, without any impact on the performance of the pavement, are evidence of this. in addition to the factors mentioned above, all kinds of other causes contribute to a greater or lesser extent to the premature appearance of “punchouts”.

21

2013R06EN


Figure 13 – punchout

1.3.1.1 the suppression of a bituminous interlayer between the pavement and the road base

the role of this layer originally was to provide a homogenous and smooth surface underneath the concrete. the structural contribution of the interlayer was not taken into consideration when designing the road. in view of the progress that had been made in the finishing of lean concrete and the high price of bitumen in the early 80s, the asphalt interlayer was eliminated. however, the benefits of the interlayer are numerous. it ensures extremely good attachment of the crc to the underlying surface. good attachment leads to homogenous cracking of the pavement, which reduces the presence of water under the concrete slab. resistance to erosion also means that it can withstand the combined impact of water, traffic and road salts. it protects the lean concrete road base and makes it impermeable, even before the concrete pavement is applied. Furthermore its rheological properties means that it can accommodate deformations of the pavement due to the temperature gradient more easily as well as providing a flexible insulating layer between two rigid layers. Finally it also contributes to the overall strength of the structure.

1.3.1.2 the quality of the lean concrete

the risk of erosion is considerably increased if the lean concrete, and its surface in particular, is of poor quality. this also reduces the ability to withstand frost and road salts. the surface of the base must therefore be protected by a compact layer that is insensitive to the effects of road salts. nonetheless the following defects have been observed on certain sections of affected motorways:

• lean concrete with a very low compressive strength, a heterogeneous nature and mediocre quality;

• little or no protection of the lean concrete against drying out during construction, whereas the emulsion layer provided for in the specifications contributes to making

22

2013R06EN


the surface impermeable; construction in the winter months with insufficient protection against frost;

• construction in two layers, one 15 cm thick and the other 5 cm thick, which results in the delamination of the concrete at the interface between the two layers and the erosion of the upper.

1.3.1.3 weather conditions

the number of “punchouts” rises mainly in the winter months as a result of frost and road salts. moreover the roads that are most affected usually lie in areas with severe climates and higher frequencies of freeze-thaw cycles.

1.3.1.4 the drainage at the edge of the slab and the degree to which the longitudinal joints are watertight

good drainage of the hard shoulder at the junction between the pavement and the base is essential to prevent water, which infiltrates primarily via the longitudinal joint between the pavement and the hard shoulder, from being trapped under the edge of the slab. For this reason the seal of the longitudinal joints must be as good as possible and be properly maintained. Where applicable a permeable base must be provided under the hard shoulder.

1.3.1.5 the thickness of the pavement in crc

the fatigue strength of a concrete slab increases as a function of slab thickness. in view of the increase in heavy traffic the risk of damage increases because the bituminous layer was suppressed and the thickness of the pavement was not adjusted.

1.3.1.6 the importance of edge effects

the stresses in a concrete slab increase progressively as the load moves towards the edge of the slab. the increased aggressiveness of heavy traffic, namely as a result of the use of tridem axies, and any overloading, makes this situation even worse. this problem can be resolved in various ways:

• on existing roads: lane markings should be applied to the concrete pavement and not to the hard shoulder; this approach allows heavy traffic to be shifted 30 cms towards the inner edge of the slab;

• on new roads: the widening of the pavement at least 50 or even 75 cm should be considered. alternatively the hard shoulder should be laid in concrete at the same time as the pavement, in other words without a longitudinal construction joint.

23

2013R06EN


1.3.1.7 the depth of the reinforcing steel and the percentage of longitudinal reinforcement

increasing the depth of the reinforcing steel, and reducing the percentage of reinforcement, leads to an increase in the degree of openness of the cracks on the pavement surface as a result of thermal and hygrometric effects. more open cracks lead to reduced watertightness and poorer load transfers and will therefore be more subject to spalling. it is thus more favourable to place the reinforcement in the upper third of the pavement and to use higher percentage of reinforcement.

1.3.1.8 distance between the reinforcement and the edge of the pavement

if the distance between the first longitudinal reinforcing rod and the edge of the slab is too great, load transfers at that location will be reduced and the transverse bending stresses will increase. the first reinforcing rod should be located at less than 13 cm from the edge, whereas a distance of more than 25 cm was observed in some motorway sections. the blow-up phenomenon in a crcp is confined to those locations where the concrete has a certain fragility, often as a result of the poor compaction of the concrete. Blow-ups usually occurs at the location of end-of-day joints or casting joints as a result of poor compaction or a lack of care during construction. concrete expands in very hot weather, and the horizontal forces are transferred in their entirety to the upper layer of the better compacted concrete (eccentric force), leading to its fracture and fragmentation and finally to a upward fold in the pavement. moreover the very porous or high-void concrete below the reinforcing steel is often saturated with brine originating from road salts. over time this causes accelerated deterioration of the concrete as a result of freeze-thaw cycles and ultimately the corrosion and even the breakage of the reinforcement. in general blow-ups occur at the end of spring, towards the end of may or in early June. this is when the concrete is still full of moisture and is still “swollen up”. any expansion that occurs during the first warm weather is thus much more severe. moreover, in June the hours of sunshine are approaching the maximum and the difference between night and day temperatures can still be very large.

2. maintenance measures

2.1. for all tyPes of construction

2.1.1. repair and renewal of joint fillers

repairs to joint fillers are small scale repair measures that can be performed with little effort, usually by hand, and should be conducted immediately after localised damage has occurred, in order to restore the sealing effect of the system.

24

2013R06EN


repairs to joint fillers should be performed with the same materials that were initially used to seal the joints. they may be hot or cold-processed joint fillers or joint profiles.

the filler in either dummy, pressure or running joints should be replaced when it no longer seals (e.g. due to ageing of the joint filler and/or joint profiles). it is desirable to treat all joints in consecutive sections across the entire width of the carriageway when the concrete pavement is fairly evenly used.

economic considerations indicate that joint filler should be replaced with joint filler and joint profiles should be replaced with joint profiles. cost-effective repair of minor edge damage in the joint area can be achieved by filling the damaged areas with hot-processed joint filler. the traffic area must be kept free of traffic during joint-filling work.

remains of the old joint filler that may still adhere to the gap walls must be considered when new joint filler is to be used. it must be checked before the installation of the new joint filler whether the edges have to be re-cut in order to provide clean joint edges as a new attachment surface. re-cutting the joint gap provides the best possible conditions for good adherence of the new material. re-cutting the joint edges may also be necessary when the joint filler to be replaced was not able to accommodate the experienced variation in joint gap width without damage because the joint gap was initially under-dimensioned.

When joint sealing materials are replaced by joint profiles, the joint edges must always be re-cut so that the joint profiles can be installed in an appropriate manner.

When old joint profiles are replaced by new ones, it must be checked whether the joint gaps have the correct width to ensure the required parallel alignment of the joint edges. they have to be re-cut when this is not the case to fulfil this requirement. re-cutting and additional chamfering can be used to remove minor edge chippings. major edge chippings must be repaired with concrete replacement systems before the installation of the joint profiles. the existing joint filler must be removed down to the new installation depth while simultaneously protecting the joint edges. the residue of firmly adhering joint filler and usable under-filling materials may remain in the joint gap.

the edge adhesion of the residue as well as the compatibility of the residual material with the new joint filler must be ensured and is required to be tested in an appropriate manner. the joints must be re-cut if these requirements are not fulfilled.

re-cutting can be omitted when joint profiles are replaced by hot-processed joint filler. the joints are in this case cleaned, provided with under-filling material (heat-resistant, foamed material or sponge rubber) to prevent sagging of the joint filler and then coated with a primer and sealed.

25

2013R06EN


the brushing machine must be cleaned after removing old joint filler. dirt at the joint edges must be removed.

a primer is recommended to improve the adhesion of the hot-processed joint filler to the joint edges.

Joint filler work may only be performed when the weather is dry and the surface temperature of the joint edges is at least 0° c. the joint edges must be dry and dust-free.

hot-processed joint filler materials must be applied in a way that ensures that a tray-shaped recess of at least 1 mm and at most 6 mm is formed below the road surface. this is necessary to prevent the joint filler from protruding at higher temperatures. overfilling must be avoided.

transverse dummy joints that are not chamfered must be chamfered before they are filled. chamfering can be omitted when the joint filler is installed in joints with widths > 15 mm or when joint profiles are installed in joints with widths > 20 mm. Joint profiles ( figure 14) have an advantage over hot-processed joint material as far as installation is concerned, because they can also be installed in wet weather. however, the joint gap must be free of ice at the time of installation. Butt joints and intersection points must be dry when adhesives are applied.

Figure 14 – installed Joint proFile

care must be taken that all joints have an even joint cross-section when joint profiles are used. the joints must be re-cut, where required.

the current joint depths must be inspected. existing profiles that are more than 15 mm deep cannot be used as under-filling material for hot-processed joint filler, as this would cause detachment of the joint filler.

26

2013R06EN


2.1.2. removal of concrete

concrete is removed in the event of:

• unevenness,• surface damage to individual areas,• drainage obstructions for surface water,• formation of steps at joints and cracks,• lack of skid resistance.

suitable methods are:

• milling,• high-pressure water blasting,• water blasting with or without water additive, steel blasting,• chiselling,• machine chiselling,• grinding,• groove cutting.

the measures listed in table 1 are used to prepare the concrete for the application of coatings, surface area protection layers, road markings or as a final measure to provide better surface properties:

taBle 1 – removal of concretemethod application

removal of concrete as preliminary treatment as final treatment

milling for removal xmilling for roughening xhigh-pressure water blasting xhigh-pressure water blasting for cleaning xBlasting with water additive, steel ball blasting xchiselling* xmachine chiselling xgrinding xgrooving x*only for small areas

27

2013R06EN


2.1.2.1 milling

in the past, machine milling of concrete surfaces was used to improve skid resistance. however, the rough surface texture created by milling leads to increased tire-road noise and milling is therefore now uncommon, except for the removal of bulges and steps (danger points) that occur unexpectedly.

2.1.2.2 high-pressure water-blasting method

high-pressure water-blasting methods are suitable for surface cleaning and removal of layers with low strength, e.g. paint, coatings and worn-off tyre rubber).

high-pressure water blasting is commonly used on newly created concrete pavements as a preparatory measure before the application of the first road markings.

the waste water produced may not be drained over surfaces that are used by traffic.

2.1.2.3 Blasting with or without water additive, steel blasting

Blasting methods are gentle methods for removing surface pollution and thin layers and to roughen a surface (improve the micro-roughness). also whole, uneven areas can be treated without affecting the surface strength.

steel blasting (steel ball blasting) was found to be a high-performance method (daily capacity approx. 5,000 m²), which is used instead of sand blasting when the surface has to be processed without dust formation and residue, in particular for improving skid resistance.

2.1.2.4 chiselling

chiselling is suitable for removing thick concrete layers in small areas, e.g. broken-off edges and corners. the concrete structure in the broken-off area is loosened and weakened by chiselling. additional treatment of the broken-off areas might be required to repair the surface, depending on the thickness and size of the layers. it is recommended to surround the damaged area to be chiselled off with a vertical separating cut (down to 5 cm depth) to prevent damage to the concrete structure.

2.1.2.5 machine chiselling

machine chiselling makes use of chiselling machines with vertically acting chisels. machine chiselling is particularly useful for removing concrete layers with low strength and for improving the evenness of small areas. the concrete structure in the

28

2013R06EN


broken-off area is loosened and weakened. subsequent coatings require additional treatment (e.g. by steel blasting).

2.1.2.6 Grinding

devices with diamond cutting discs on horizontal shafts are used for grinding. grinding facilitates very accurate removal of concrete and can be used to create groove patterns with varying fineness ( figure 15, following page) without altering the strength of the surface. grinding is suitable for improving the evenness and skid resistance of the surface and for reducing noise emission. the processing depth is usually up to 10 mm. the removal of a 2-3 mm thick layer is usually sufficient to improve skid resistance. hardened, repaired areas as well as joint edges are not damaged by grinding. the grinding sludge must be cleared by vacuum.

2.1.2.7 Grooving

grooving is used for surfaces with inadequate surface drainage, where there is a risk of aquaplaning or to improve grip. grooving may result in increased tire-road noise.

the reference values for execution are as follows:

• for transverse grooves:

– Width and depth 6 mm each; – the distance between the transverse grooves should be between 100 and 150 mm; – for longitudinal grooves: Width 4 mm, depth 6 mm, centre-to-centre distance 25 mm.

the grooves must have sharp edges and no chippings. once a grooving distance has been selected, it must be retained.

to drain the surface of sections with a change in the transverse incline, one diagonal cut (see sketch) with a width of 10 mm must be made in each slab. the cutting debris must be cleared by vacuum.

29

2013R06EN


Figure 15 – grooving

2.1.3. strip-wise replacement

an unforeseen increase in the amount of heavy traffic, and especially an increase in axle loads, has resulted in concrete layers with a depth of 22 or 24 cm being under-dimensioned. damage is mainly found in the main driving lane. replacing only this lane constitutes an economical alternative to a complete replacement. under-dimensioned shoulders are to be replaced with a view to future shoulder use.

strip-wise replacement is to be used as an alternative when the replacement of individual slabs or slab components does not result in any improvement in driving quality or in any long-term improvement of the layer substance, and where future damage to the concrete layer can be expected.

the use of machines to fit the slabs will usually result in better quality and a more even finish. strip-wise replacement must take the form of an underground construction, retaining the original height and transverse incline ( figure 16 and figure 17, following page).

Figure 16 – strip-Wise replacement: preparation and concreting

30

2013R06EN


Figure 17 – strip-Wise replacement: smoothening the concrete and cutting grooves

When replacing strips of concrete and increasing the existing layer depth (e.g. a 30 cm concrete layer on a gravel base course), the edges of the un-bonded layers under the remaining concrete layer of the adjoining lane or shoulder must be secured to avoid material chipping as a result of vibrations or wash-outs ( figure 18).

existing

concrete pavement

cement-Bonded Base

gravel Base

existing frost protection

concrete pavement

tie Bar

new

Figure 18 – concrete surFace course on gravel Base course

Where there is a bonded base course underneath the remaining concrete layer, care must be taken that any surface water that has penetrated can be drained along the expansion joint.

a suitable way to achieve this is to fit drainage concrete and non-woven fabric according to figure 19, following page, or a drainage profile.

31

2013R06EN


existing

concrete pavement

cement-Bonded Base cement-Bonded Base

porous concrete existing frost protection

non-Woven geotextile

concrete pavement

tie Bar

new

Figure 19 – concrete surFace course With Bonded Base course, cross-section

Where a concrete lane is to be replaced in strips, the existing traffic surfaces must be joined to the new concrete surfaces using dowels for the transverse grooves and anchors for the longitudinal grooves. a precondition for well-functioning anchors and dowels is that the roadway slabs should be firmly fitted into the existing concrete lane (overtaking lane or shoulder).

to insert the dowels, holes must be drilled sideways into the existing concrete slabs; care must be taken that guides or templates are used to ensure that the hole pattern is even in the direction of the gradient or parallel to the surface.

Where the depth of the existing concrete layer and the lane to be renewed differ, the anchors ( figure 20) and dowels must be fixed half-way down the existing concrete slab to prevent any chipping. the risk of damage to the dowels and anchors caused by cutting is negated, as the expansion joints will not require deep notching, but only a vault cut.

Figure 20 – gluing in the anchors

32

2013R06EN


the hole diameter for dowels is 27 mm, with a hole depth of 25 cm. adherence to the hole diameter within a tolerance range of +/- 1 mm is important. an under-dimensioned hole diameter may result in damage to the plastic sheath of the dowels during installation. an over-dimensioned hole diameter will prevent the horizontal positioning of the dowels, resulting in an incline of the dowels inside the hole.

the dowels are inserted into the holes and are used for transverse force transmission. this should make it possible for the slabs to move horizontally and the dowels are therefore not glued. in the case of running joints, the free ends of the dowels must be covered with caps.

adhesive anchors must be horizontally fitted into the longitudinal expansion joints to prevent any joint movements or lateral displacement of the concrete slabs. adhesive anchors usually have a diameter of 20 mm and a length of 650 mm. in the vicinity of the subsequent joint, they must be coated in plastic to a minimum length of 200 mm and symmetrically sharpened at one end.

When using two-component adhesive cartridges, the anchor must be screwed in to ensure mixing of the two components. the hole diameter depends on the adhesive cartridge used and the existing material volume of the cartridge. execution shall be in line with the certification of the accredited systems. the hole depth in the case of injected two-component adhesive systems shall be 25 cm, while the diameter of the hole should be at least 27 mm. a larger hole diameter will not cause a problem, but will result in higher material costs. For both systems, the part of the anchor steel projecting into the hole must be fully sheathed. adhesive anchors must withstand extraction forces of at least 80 kn.

Where the existing bonded base course is to be used as a bedding layer and the existing (possibly under-dimensioned) layer depth is to be retained, with only strips being replaced, the distances between the transverse and longitudinal joints may be halved to extend the service life of the slabs.

the use of road-building concrete with a high flexural tensile strength of up to 8 n/mm² should be considered if the existing (possibly under-dimensioned) surface thickness is to be retained. the strip to be replaced must be removed in such a way that neither the adjoining strip nor the base course is damaged. the concrete layer must be cut to its full depth. any anchors and dowels must be cut.

additional length and crosswise cuts can be made into the slabs to ensure that they can be carefully removed.

33

2013R06EN


Where the bedding layer is damaged (cracks, chipping), reflection cracks in the new concrete layer can be avoided by repairing the bedding layer and covering it with non-woven fabric.

any loose pieces on the base course must be removed before laying the concrete.

the joint pattern of the existing slabs must be taken into account when determining the location of transverse joints.

the slab length shall be in accordance with the adjoining slab grid. the crosswise joints in the concrete slabs must have a uniform dowel distance of 25 cm.

2.1.4. surface treatment with reactive resin

during surface treatment using reactive resin, the reactive resin/hardener mixture is automatically determined, mixed and applied to the prepared concrete layer, which is hereafter referred to as the bedding layer. depending on the surface structure (macro-textural depth) of the bedding layer and the desired texture of the surface treatment, the binder volume will range from 700 to 1,600 g/m². depending on the amount of binder used, a broken stone mixture with a grain size of 1/2, 2/3 or 3/4 is to be used for gritting (table 2).

taBle 2 - Binder volume, Grit Grain size and Grit volume for surface treatment, dePendinG on the averaGe macro-textural dePth of the

Base course

no.

average macro-textural

depth [mm]Binder volume

[g/m²]Grit grain size

[mm]Grit volume

[kg/m²]

1 2 3 41 ≤ 0.5 700 à 1,000 1 / 2 102 > 0.5 à 1.0 > 1,000 à 1,300 2 / 3 123 > 1.0 à 1.5 > 1,000 à 1,600 3 / 4 14

separate to using suitable resin components and gritting materials, this type of repair will only be durable in the long term if the concrete base is of a high quality, to ensure good adhesion between the reaction resin and the concrete. the durability will be increased by working carefully and choosing favorable weather conditions to promote setting.

Joints in the concrete roadway to be treated should normally not be masked, as the function of the joint will not be adversely affected due to the small amount of material applied.

34

2013R06EN


a particularly careful investigation and possible pre-treatment of the surface is required before applying the surface treatment.

the smoothness cannot be improved by means of a surface treatment. the reaction resins and stones used for gritting must be dry and dust-free. the most important precondition for long-term adhesion (adhesion and durability) of surface treatments with reaction resins is to provide a dry and carefully prepared concrete surface.

the surface tensile strength on the concrete base must be at least 1.5 n/mm², otherwise long-term surfacing cannot be guaranteed. the surface tensile strength may be improved by means of shot-blasting.

the surfaces must be free from substances such as oils, greases, rubber debris, post-treatment media and marking materials.

any unstable fine mortar layers must be removed from the concrete surface. the type of preparatory work (cleaning and/or stripping) depends on the state of the concrete surface. as well as a visual inspection, the strength of the concrete near the surface is to be determined.

the reaction resin applied must have hardened to such an extent that vehicle and pedestrian traffic will not cause any damage by the time the road is opened for traffic - at the latest after 24 hours, depending on the prevailing temperature. reaction resins may only be processed at concrete surface temperatures of at least + 8° c to a maximum of + 40° c, while the temperature of the concrete base and the materials used must be at least 3 K higher than dew point temperature.

Where the surface temperature is rising rapidly, the application of reaction resins must be discontinued, as air escaping from the concrete layer will cause bubbles to form at the surface of the reaction resin. application shall take place while the component temperatures are dropping. no surfacing may take place in humid weather (e.g. rain, fog, dew).

the reaction resin is usually applied by machine ( figure 21, following page). the broken, dust-free aggregate is to be evenly applied immediately after the reaction resin and either pressed down or rolled on ( figure 22, following page).

the aggregate must be applied in such a way that the required traction and long-lasting embedding can be ensured; the largest aggregate should be embedded in the reaction resin to a depth of approximately half its diameter.

35

2013R06EN


Figure 21 - application oF epoxy resin By machine

Figure 22 - application oF aggregate

after setting, the excess aggregate must be swept away ( figure 23). it may be reused. to check the adhesive tensile strength, three adhesive tensile tests must be carried out before opening the coated concrete surface to traffic.

Figure 23 - sWeeping aWay the excess aggregate

2.1.5. surfacing with reactive resin mortar

during application, the composition of the reactive resin/hardener mixture with added minerals is automatically determined, mixed, applied to the prepared and pretreated

36

2013R06EN


concrete layer - hereafter referred to as the bedding layer - and gritted. the reaction resin mortar volume and grit size used during surface coating depends on the surface structure (macro-textural depth) of the bedding layer and the average layer thickness For average textural depths of 0.5 to 1.5 mm and for average course thicknesses ranging from 2 to 5 mm, the information in table 3 must be taken into account.

apart from using suitable resin components and gritting materials, this type of repair will only be durable in the long term if the concrete base is of a good quality, to ensure good adhesion between the reaction resin and the concrete. the durability will be increased by working carefully and choosing favorable weather conditions to promote setting.

a particularly careful investigation and possible pre-treatment of the surface is required before applying the surface treatment.

taBle 3 – reaction resin mortar volume and Grit size used durinG surface coatinG, dePendinG on the averaGe macro-textural dePth

of the Base course and the averaGe course thickness

no.

average macro-textural

depth [mm]

average course thickness [mm]

reaction resinmortar volume*)

[kg/m²]

Grit grain size(quartz sand)

[mm]1 2 3 4

1 ≤ 0.5

2 to 3

> 3 to 4 > 4 to 5

4 to 6

> 6 to 8 > 8 to 10

0.3 to 0.8 ou 0.7 to 1.2

0.7 to 1.2 0.7 to 1.2

2 > 0.5 to 1.02 to 3

> 3 to 4 > 4 to 5

5 to 7 > 7 to 9 > 9 to 11

0.7 to 1.2

3 > 1.0 to 1.52 to 3

> 3 to 4 > 4 to 5

6 to 8 > 8 to 10 > 10 to 12

0.7 to 1.2

*the listed volume includes the bonded grit

the surface coating consists of a prime course using unfilled reaction resin and grit, as well as a surface course using reaction resin mortar and grit. aggregates must be dry and free of foreign bodies.

the most important precondition for the long-term adhesion and durability of a surface coating using reaction resin mortar is to have a dry, carefully prepared and pretreated concrete surface. the surface tensile strength on the concrete base must be at least 1.5 n/mm². the surfaces must be free from substances such as oils, greases, rubber debris, post-treatment media and marking materials.

any unstable fine mortar layers must be removed from the concrete surface. the prepared surface is usually pretreated (primed).

37

2013R06EN


concrete surfaces generally have to be prepared. the preparatory process is determined by the results of the concrete surface evaluation. after preparation, the surface tensile strength should be 1.5 n/mm².

depending on the prevailing conditions, various processes may be used to prepare the concrete surfaces. after preparation, the surfaces to be coated must be swept and cleaned with oil-free, dry compressed air (wind direction must be taken into account).

While the concrete surface is being cleaned, heat damage or contamination, for example by condensation or particles suspended in the hot air, should be avoided.

the joint fillings must be removed from the joints and any remaining casting compound removed from the edges. damaged joint edges must be cut back down to stable concrete. the joint edges must be repaired according to section 3.4. Before coating, the prepared joints must be provided with a provisional insert that can be easily removed after coating.

deep cracks in the roadway slabs must be cleaned to remove dirt or any sealing compound and provided with a provisional insert, so that they can be filled with filler after coating. Where required, these cracks must be expanded before coating.

roadway markings must be removed from the coating.

the layer of mortar applied must have set to such an extent that vehicle and pedestrian traffic cannot result in any damage, before the road is opened for traffic. the setting time should not be longer than 24 hours. the surface of the mortar after installation must be even and provide adequate grip in the long term. the choice of aggregate should be in accordance with the concrete surface and its color should contrast sufficiently with the road markings.

2.1.5.1 structure and production of reaction resin mortar

the reaction resin components and the aggregate must be subjected to forced mixing, for example via the use of a mechanical mixer.

Where reaction resin components already containing aggregate and/or pigments are delivered to the construction site, the content of these containers must be thoroughly stirred before application.

the installation depth of the reaction resin mortar depends on the requirements. reaction resins may only be processed at concrete surface temperatures of at least + 8° c to a maximum of 40° c, while the temperature of the concrete base and the materials used must be at least 3 K higher than dew point temperature.

38

2013R06EN


Where the surface temperature is rising steeply, the application of reaction resins must be discontinued, as air escaping from the concrete layer will cause bubbles to form at the surface of the reaction resin. application shall take place while the component temperatures are dropping. no surfacing may take place in humid weather (e.g. rain, fog, dew).

the concrete surfaces must be primed. the primer must be thin and free of solvents and must be applied in such a way that the concrete surface is evenly wet and covered. Where bubbles form, they must be opened up immediately and evened out.

the primer is usually applied to the prepared surface by machine, directly followed by the application of an aggregate with a grain size of 0.3 to 0.9 mm to ensure good adhesion of the mortar. any non-adhering grit must be thoroughly swept off the surface, and may be reused.

2.1.5.2 coating

Before coating, the prepared joints and deep cracks must be provided with a provisional insert that can be easily removed once the coating has set. coatings must be separate for the entire joint or crack width in places where there are joints or cracks.

the reaction resin mortar is usually applied to the prepared and primed surface using a machine.

immediately after application, sharp-edged, dust-free aggregate must be liberally and evenly applied to the mortar and pressed down or rolled on to improve grip.

the aggregate must be applied in such a way that the required grip and long-lasting adherence to the surface can be ensured; the largest aggregate should be embedded in the reaction resin to a depth of approximately half its diameter.

after setting, the excess aggregate must be swept away, and may be reused.

2.1.6. renewal

renewal is the restoration of the utility value of a traffic surface by applying a new coat of concrete to the existing surface or by replacing one or several layers of roadway. it is important to differentiate between:

• renewal of surface constructions, • renewal of both surface and underground constructions.

39

2013R06EN


renewal is necessary when the factors causing the identified state cannot be removed by maintenance or repair measures. renewals particularly become necessary when faults have been caused by inadequate carrying capacity (e.g. under-dimensioning).

Before carrying out the renewal, it should be checked whether it is necessary to improve the substrate, base or surface and to what extent the functionality of the drainage system can be guaranteed. changes required to the gradient and transverse incline may be implemented during renewal.

during renewal, the depth of the new concrete layer must be adjusted. in each case the composition of the bedding layer, the available construction heights, the state of the remaining superstructure and changes in load levels are to be taken into account.

2.1.6.1 renewal of surface constructions

When only the superstructure is being renewed, the existing substructure can remain in place. this may also take the form of a new asphalt surface.

Where the existing concrete surface is to be recoated with concrete, it must be broken up into pieces measuring no more than 0.5 x 0.5, while recoating with asphalt requires a maximum piece size not exceeding 1.0 x 1.5 m. the unstressed surface should then be re-compacted, using a suitable compacting device (static, vibration) and used as a base course for the new superstructure.

the unstressed concrete surface can then either be covered with a concrete compensation layer with a minimum compression resistance of 25 n/mm² ( figure 24) or an asphalt compensation layer.

Figure 24 – concrete compensation layer

the concrete compensation layer must be notched according to the joint grid of the future concrete layer, and taking into account the grid of the old concrete layer. notching will not be required where non-woven fabric has been used.

40

2013R06EN


improvements in the transverse incline and the gradient can be made by correctly dimensioning the concrete compensation layer.

in the vicinity of overhead structures, a minimum clearance height of 4.50 m must be maintained. Where this cannot be guaranteed, the overhead structure must either be raised or, where this is not possible (e.g. framework construction), the road surface must be lowered in the area by lowering the gradient for a corresponding distance in front of and behind the construction.

the design for a possible superstructure must be checked in the vicinity of underpasses. Where such a superstructure is not possible for structural reasons, a reduction in the gradient to the correct length must be planned and the corresponding section in front of and behind the structure must take the form of an underground construction.

2.1.6.2 renewal of both surface and underground constructions

When a renewal takes place as a combination of underground and surface work, only the surface coating of the existing roadway is removed and replaced with a newly dimensioned surface coating (possibly on top of a concrete compensation layer), retaining the existing bedding layer.

Where the bedding layer consists of a notched base course with hydraulic binder, the surface course can be applied to this base course, provided that the existing concrete surface is divided up, using separation cuts or other techniques, to ensure that the surface course can be removed without damaging the base course.

By installing a non-woven fabric across the entire width of the roadway, any cracks in the hydraulically bonded base course can be prevented from resulting in reflection cracks in the new concrete surface.

mechanically compacted non-woven fabric made of polypropylene fiber, with a mass per unit area of 500 g/m², is to be used.

gradient and transverse incline changes can be achieved by applying a concrete compensation base course with a compression resistance of at least 25 n/mm².

2.1.7. surface crack filling

concrete road constructions may have surface cracks caused by water or de-icing salt solutions penetrating into the concrete and resulting in structural damage. it is difficult to fill these fine cracks with a joint filler and then subsequently with an appropriate filler material to effectively treat them. during filling, the cracks are filled up without pressure from above. low-viscosity resins are used as filler material.

41

2013R06EN


Filling may not be carried out in wet weather. the cracks to be treated are to be dried and cleaned before filling, using an appropriate method (e.g. industrial vacuum cleaner). to achieve the required filling depth, an adequate flow of material into the crack must be ensured within the processing period for the filler material and is dependent on the construction temperature. the possibility of aerating the crack must be considered.

Wider cracks may necessitate preparatory work, e.g. expansion of the cracks.

the cracks must be filled up to a minimum depth of 5 mm or up to 15 times the width of the crack (whichever is smaller).

the lowest application temperature for filling with epoxy resin is 8°c.

the treated surface is to be gritted with quartz sand before the working life of the treatment has expired. additional subsequent filling is not permitted.

2.1.8. injection

cracks and small hollow spaces may form in single-layer concrete surfaces above the dowels and anchors that have been embedded in the fresh concrete by vibration. resulting long-term damage may occur (microstructural damage to the concrete as a result of the effects of frost / de-icing salt, anchor corrosion).

this type of damage may be prevented by filling up such cracks or hollow spaces by injecting them with low-viscosity resin, using a low-pressure process (e.g. a pressure of 1.5 bar). Before injection, the concrete surface around the cracks must be cleaned, using an appropriate procedure (e.g. industrial vacuum cleaner). cement sludge must be removed using suitable equipment. the concrete surface must be dry and clean.

the cracks and hollow spaces must be continuously grouted with a self-injecting piston injection device at low pressure. cracks and hollow spaces up to a depth of 25 cm can be filled up in this way.

When injecting the cracks and hollow spaces with epoxy resin, the temperature of the concrete surface may not fall below 8°c, while the component temperature must be 3 K above dew point.

the treated surface is to be gritted with quartz sand before the working life of the treatment has expired.

42

2013R06EN


2.1.9. improving drainage

When planning and carrying out maintenance measures, it should be checked whether any measures to improve drainage are required.

it is essential to keep water out of the superstructure of the road in order to maintain the road. constant drainage is required to maintain the carrying capacity of the road. penetrating water must therefore be drained, using an effective drainage system, to avoid saturating the bedding layer.

some examples of retrospective drainage systems are described below. in each case, a decision must be taken about the measures that can be taken to drain the water under the given circumstances.

Where drainage pipes are to be provided, these should have adequate cross-sections.

2.1.9.1 additional seepage pipes along the edge of the roadway

a seepage pipe must be installed along the edge of the roadway. to ensure that the seepage pipe cannot freeze, it must be installed at a depth and a lateral distance from the surface of the embankment that is greater than the frost-proof thickness of the superstructure. connection to a drain pipe is essential.

2.1.9.2 drainage when replacing strips or slabs

Where thicker concrete layers and base courses than the existing structures are required for strip or slab-wise replacement, the local conditions must be taken into account when taking the necessary steps to drain the lower-lying soil (also see section 2.1.3 and figure 18 and 19.

2.1.9.3 subsequent drainage of the bedding layer

Where water has penetrated underneath the concrete layer because of a lack of lateral drainage, e.g. in older layers with thicker road markings or when the base courses are of different heights, drainage can be ensured by incorporating a seepage line into the base course. the seepage line (drain pipe, drainage channel, etc.) must be drained by a transverse collector pipe.

2.1.9.4 improving the surface water drainage

Where water remains on the roadway, e.g. due to a lack of transverse or longitudinal incline or a drainage obstacle, water drainage can be ensured by cutting transverse or longitudinal grooves into the roadway, by grinding or by using box channels

43

2013R06EN


( figure 25) and slot channels ( figure 26) positioned horizontally to the direction of travel.

Figure 25 – suBsequent installation oF a Box channel

Figure 26 – suBsequent installation oF a slot channel

2.2. for the construction tyPe Jointed Plain concrete Pavement (JPcP)

2.2.1. widening and filling cracks

it is necessary to differentiate between surface cracks and deep cracks. deep cracks often lead to a height offset of the crack edges. drill cores from the crack area provide more detailed information. surface cracks may remain untreated under continued observation. deep cracks must generally be expanded and filled.

the treatment of the cracks depends on their width and the variation in the crack width.

the crack must be closed in a manner that allows expansion when the crack edges move. in such cases, permanent renewal requires the installation of dowels.

44

2013R06EN


deep cracks that penetrate through the entire depth of the slab must be expanded with suitable devices, so that joint filler can be applied. they must be filled with hot-processed joint filler. chippings at the crack edge must be repaired with reaction resin mortar or cement mortar with a plastic additive.

sufficient material must be applied to the crack during the processing time. the amount required to ensure complete filling of the crack depends on the temperature of the building structure. care must be taken to ensure that air can escape from the crack.

the cracks must at least be filled to a depth of 5 mm or 15 times the crack width (the smaller of these values applies). the cracks must be treated in the same way as joints before they are closed.

surface cracks (hairline cracks, shrinkage cracks and cracks with a width of up to 1 mm) must first be investigated to determine whether any treatment is required or useful (e.g. for expansion reaction damage caused by an alkali-silica reaction) or whether observation of the damage should be continued.

cracks of up to approximately 1 mm width can be filled with low-viscosity reaction resins.

during the filling procedure, the cracks are filled from the top without pressure. Filling with appropriate filler material (low-viscosity resins) can be used to fill cracks close to the surface.

the cracks must be cleaned using appropriate methods before filling and must be dry during the filling procedure.

2.2.2. doweling and anchoring cracks

the following measures are to be considered for anchoring or doweling longitudinal and transverse cracks in pavement slabs, depending on the crack width, the location of the crack and the crack pattern:

the interlocking effect, which is present even with small crack widths, e.g. ≤ 2 mm, contributes to the transmission of transverse forces. no measures are required as long as no height offset is found. however, the crack development should be monitored. it should be decided in each individual case whether maintenance measures are required, e.g. widening the crack and filling it with hot sealing material. maintenance or repair measures become necessary when the crack width exceeds 2 mm. it might be necessary to remove the height offset of neighbouring slabs as a preliminary step.

45

2013R06EN


longitudinal or transverse cracks at a distance of more than 75 cm from the longitudinal or transverse joint must be widened and sealed with hot sealing material. the crack should be widened to a width of 8 mm and a depth of 25 mm.

larger crack widths require doweling or anchoring of the slab parts as shown in figure 27 to figure 32. two methods are of particular interest for retrospective anchoring; anchoring with additional bracing and anchoring with diagonal tie-bars.

anchoring with round-profile steel bars provides additional bracing due to the angled ends of the round steel profiles, which are to be inserted into two holes that are required to be drilled for this specific purpose.

diagonal anchoring uses diagonal tie-bar pairs as follows:

transversal cracks: 5 diagonal tie-bar pairs per slablongitudinal cracks: 5 diagonal tie-bar pairs per slab within the wheel track 3 diagonal tie-bar pairs per slab outside the wheel track

the appropriate measure for longitudinal or transversal cracks at a distance of less than 75 cm distance from a longitudinal or transverse joint is cutting out and replacing a part of the slab (slab strip). the slab strips should have a minimum width of 1.50 m. damage to the base course (if evident) is to be repaired during this step. the connections of the slab strips to the remainder of the slab are to be implemented as expansion joints and, for example, provided with four adhesive anchors with Ø 20 mm per metre.

dowels according to figure 27 are to be provided for transversal joints.

Figure 27 – 1 retrospective doWeling

46

2013R06EN


in the event of branched cracks, cracks across the lane or several parallel cracks in a slab, it has to be decided in each case whether doweling or anchoring with diagonal tie-rod pairs is a suitable maintenance measure, whether a slab strip should be replaced, or whether it would be more appropriate to replace the entire slab.

dowels are rods made of coated, smooth, round steel, e.g. d = 25 mm and l = 500 mm, that are inserted into transverse joints. they are used to transfer load and ensure that the neighbouring slabs remain the same height. they allow free movement of the slabs and should be installed according to figure 28.

cut a-a

hull

resin Based mortar

resin Based mortarconcrete pavement

plastic covered dowel Joint sealant

Figure 28 – cross section oF retrospectively installed doWel

deep transverse cracks that are required to perform the function of transverse expansion joints must be dowelged in the longitudinal direction.

anchors are rods made of profiled, round steel bars, e.g. d = 20 mm and l = 800 mm, that are inserted into longitudinal joints. they are intended to prevent adjoining slabs from moving apart.

deep longitudinal cracks as well as other cracks that do not have to perform the function of transverse expansion joints must be anchored.

three installation methods can be used for retrospective anchoring, and are described in the following series of figures.

• anchoring as shown in figure 29, following page, with profiled, round steel bars, d = 20 mm and l = 800 mm.

47

2013R06EN


multi-ric reinforcing tie-bar (in center plastique covered)

Joint sealant

concrete pavement resin Based mortar

Figure 29 – cross-section oF retrospectively installed anchor

• anchoring as shown in figure 30 with profiled, round steel bars with angled ends, d = 20 mm and l = 650 mm,

multi-ric reinforcing bent tie-bar

drill Ø 40 mm

Joint sealant

Bent radius 36 mm

resin Based mortarconcrete pavement

Figure 30 – cross-section oF retrospectively installed anchor With angled ends

• anchoring as shown in figure 31, following page, with diagonal tie-bar-pairs with profiled, round steel bars, d = 20 mm and l = 450 mm at a pavement thickness of 26 cm.

48

2013R06EN


polyurethane foam

Joint sealant

concrete pavement

resin Based mortar

Figure 31 – cross-section oF retrospectively installed diagonal anchoring

retrospective diagonal anchoring as shown in figure 32 is performed as follows: two diagonal holes (d = 32 mm) are prepared at a distance of 50 cm and filled with liquid reaction mortar, and the anchor pair is inserted.

Figure 32 – retrospective diagonal anchoring

the holes are drilled at an angle of 27° to 30°. the anchor length and hole depth depends on the depth of the pavement.

2.2.3. repair of edge damage and broken-off corners

edge damage and broken-off corners that may lead to water penetration in the joint area and/or affect traffic safety are required to be repaired. repair of edge damage and broken-off corners should be combined with other maintenance measures, e.g. repair of the joint filler, where possible.

49

2013R06EN


such repair measures may only be performed on slabs that are firmly supported. the joints must remain functional under all circumstances.

repairs of this kind can only be effective when the mortar composition is optimised and the concrete base is properly prepared to ensure good bonding between the reaction resin mortar and the concrete base (bottom layer).

edge damage concerns chippings that do not penetrate through the entire concrete pavement. they may be the result of mechanical damage, or may have already existed as a product of cutting the slab too early during construction. however, timely cutting is necessary to prevent uncontrolled crack formation. the risk of cracking is particularly high when the pavement is exposed to rapid temperature fluctuations, e.g. cooling down due to a thunderstorm. in such cases it may be sensible to risk small edge chippings due to cutting too early in order to prevent uncontrolled cracks, as chippings up to 5 mm are removed during the creation of the joint gap and the chamfering of the joint edges.

pc mortar is to be used for the repair of edge damage (earliest possible use is 7 days after the concrete was laid). appropriate tested mortars with graded aggregates are to be used for different layer thicknesses.

the utilisation value of the concrete pavement is not affected by appropriate repairs.

chipped corners ( figure 33) are edge faults in the corner area of a concrete slab and have to be treated in the same manner.

Figure 33 – chipped corner

Broken-off corners ( figure 34, following page) are a form of damage to the corners of concrete slabs. usually, a crack with some minor additional chipping is visible on the surface. Broken-off corners show cracks that are either straight or diagonal and penetrate through the entire concrete slab. the area between the crack and the existing joints has often sagged.

50

2013R06EN


Figure 34 – BroKen-oFF corner

small, broken-off corners can be repaired with a concrete replacement system. early high-strength concrete and quick-setting concrete can be used to repair broken-off corners larger than 50 mm. the material used depends on the period for which the road can be closed. however, replacement of the affected part of the slab, which is also required when larger parts of the corners are broken off, is the preferred method, because experience has shown that repair with concrete replacement materials is not a successful long term solution. care should be taken to ensure that the minimum dimensions for the replacement of slab parts are adhered to.

2.2.4. lifting and securing slabs

lifting and securing slabs can prevent the premature destruction of roadway surfaces and long sections. as the various lanes are subject to different loads, it is rare to have slabs lifted up over the entire width of a roadway; however, when the main lane is subject to high loads, the overtaking lane may also be affected, with under-filling possibly being required in such cases as well.

injection mortar with hydraulic binder is used to lift and secure slabs. this mortar must be free-flowing and quick-setting. Where necessary, an accelerating mixture may be used. the consistency must be constantly checked during installation. care must be taken that the water/solid ratio according to the test certificates is accurately adhered to, as changes to these values are used to adjust the compression strength. the uncontrolled addition of water is not permitted.

the mortar is to be injected into the boreholes under controlled pressure conditions. When securing slabs, the injection pressure must be selected in such a way that unintentional lifting of the slabs is avoided. the injection pressure must be automatically controlled. Work may only be carried out at air and mortar temperatures of between 5°c and 30°c. if the temperatures are exceptionally low during injection, the setting time of the injection mortar will be too long. Where the

51

2013R06EN


temperatures are too high, the compression stress as a result of the longitudinal expansion of the slabs is so high that it becomes very difficult to lift the slabs. during the months with high day-time temperatures, injection work should take place during the night (night-time construction).

there is as yet no adequate experience with lifting and securing un-bonded base courses. as un-bonded base courses will rarely be subject to “pumping” in the vicinity of the transverse joints, it is rare to find settling in the joint area, which means that securing and lifting the slabs will only become necessary in exceptional cases.

When lifting and securing slabs on base courses using hydraulic binders and an intermediate layer of non-woven fabric, individual measures have shown that this process may be used without problems. as the non-woven fabric prevents any “pumping”, with material being squeezed out through the transverse joints, it is rarely necessary to secure newly laid slabs. only when sagging occurs on a significant scale, usually caused by factors related to the base course, can the evenness of the concrete layer be restored by lifting the sagging slabs.

Before under-filling, the slabs must first be separated from the bedding layer in a separate work step, using compressed air. only then can the slabs be fully under-filled.improper execution of the slab lifting process may accelerate the destruction of the slabs. this would, for example, be the case when an attempt is made to lift the slabs using only the material injection pressure. this may result in incomplete under-filling of the slab. cones of material will form underneath the drill-holes. hollow spaces between these cones will result in cracks forming between the holes and ultimately in the destruction of the slabs.

to check the quality of execution, it should be ensured that the material injected is squeezed out through the adjoining drill-holes.

to ensure that the injection mortar is evenly distributed and that the lifted slab is supported over its entire area, a vibration roller with a service weight of 3 to 4 t is to be used directly after under-filling the slabs. For lifting purposes, the slabs must be loosened from their base before under-filling (e.g. using compressed air).

Where lifting is prevented by dowels and anchors, these must be cut and subsequently replaced.

the slab movement must be constantly checked during the lifting process. When mortar is being squeezed out of adjoining drill-holes before the lifting process has been completed, these holes must be doweled with pegs.

52

2013R06EN


once the mortar has set, the drill-holes previously filled with injection mortar must be filled with cement or resin-based mortar up to a depth of at least 3 cm. any injection mortar that may be present in the drill-holes must be removed to an appropriate depth first.

once the slabs have been lifted, the joint fillings around the under-filled slabs must be replaced.

securing of slabs is carried out at a maximum pressure of 0.5 mpa (5 bar).

to achieve the desired long-term results with slab lifting, the correct time to open the road to traffic must be observed. this is determined by the setting process of the mortar, as specified by the manufacturer and as proven by the results of initial tests. the road may be opened to traffic no less than one hour after the process of setting the injection mortar with hydraulic binders has begun, with the minimum compression resistance of the injection mortar being 2.0 n/mm². tests, e.g. indentation tests, must be carried out at regular intervals to check whether setting has begun. to determine the degree of setting of the injection mortar, a rod with a diameter of about 3 mm at its tip (e.g. a pencil cap) is to be pressed into an injection mortar cake (with a diameter of 100 mm and a thickness of 10 mm) placed onto a glass plate. the commencement of setting is characterized by the fact that a crack forms during the indentation test, running in a radial direction from the edge to the point of indentation.

When using expansion resins or compact silicate resins, the time for opening the road to traffic is determined by the manufacturer’s specifications. this can be easily referenced via the product data sheet. compact silicate resins are normally formulated in such a way that the roads can be opened to traffic immediately after execution of the work.

in addition to the commonly used injection mortars (such as hydraulic binders), silicate resins and expansion resins (foams) may also be used.

silicate resin has easily controllable flow properties. it does not foam, thus the slabs will not lift up at a later stage. the silicate resin hardens to become solid matter and has good elastic properties. it hardens immediately after injection, which means that load can be placed on it only a short time after injection. Work may be carried out when the ground is saturated, as the resin will adhere to both humid slabs and slabs contaminated with dirt on the surface. any stagnant water will be pressed out. the material has good long-term stability, is water-resistant and will not become saturated.

For economic reasons, this material has only previously been used on a small scale.

53

2013R06EN


after injection, expansion resins will form an open-celled foam, usually with plastic qualities. controlled foaming when combined with water should be investigated further before use. use of such resins is more economical than the use of compact silicate resins, but not as economical as the use of hydraulic injection mortar. the long-term characteristics under traffic load and in combination with saturation have not yet been proven. application should therefore currently only take place as part of projects with a limited service life.

2.2.5. replacement of slabs and slab sections

slabs that have been damaged by cracking, have broken corners or sufficiently large vertical slab movements that have resulted in step formation must be partially or completely replaced to their full depth. the long-term replacement of individual slabs and slab sections (minimum dimensions length- and cross-wise 1.50 m) must be done with concrete of the same thickness as the existing concrete slabs ( figure 35).

Figure 35 – replacement oF slaB section, using doWels and anchors

the replacement of entire slabs must be considered in the event of crack patterns 1 and 2 ( figure 36, following page) and when there are multiple cracks, larger offsets or sagging of slabs or slab components. however, where crack patterns 3 to 6 are observed, only sections of the slabs are required to be replaced. these slabs or slab sections must be attached to the adjoining slabs using dowels and/or anchors ( figure 35). in the case of crack patterns 7 to 10, it will not be necessary to replace slabs or slab sections, unless offsets or sagging are evident. subsequent doweling/anchoring of the cracks according to section 2.2.2 should be undertaken.

54

2013R06EN


Figure 36 – cracKing patterns

the slabs and slab sections to be replaced must have the same thickness as the adjoining concrete slabs. the edges of the slab sections to be replaced should run parallel to the longitudinal or transverse grooves along the entire length or width of a slab. the strip width should be at least 1.50 ( figure 37). the transverse contraction joints of the replaced slabs must form part of the joint grid of the adjoining slabs.

Figure 37 – replacement oF a slaB section With a Width oF 1.5 m

By reducing or halving the distances between joints, the traffic load can be increased without increasing the slab depth.

the surface texture of the slabs and slab sections to be replaced should be similar to adjoining slabs. excessive roughening, for example to increase grip, will result in changes in the noise level and thus have an adverse effect on driving comfort. texturing is usually completed with the aid of a brush designed specifically for that purpose. the choice of an appropriate texturing brush and the technique to be used are to be carefully coordinated.

55

2013R06EN


differences in the surface texture between existing and new slabs shall not be regarded as constituting a fault.

it is recommended to fit the slabs at a time at which the minimum joint gap is to be expected.

quick-setting concrete can be used for rapid repairs of slab components; and can be opened to traffic after only a few hours. the slabs to be replaced must be removed in such a way that adjoining slabs are not damaged. the slabs or slab parts must be cut to their full depth along the edges and then lifted out. dowels and anchors must be cut. the slab components can be lifted more easily by making additional separation cuts at a slight incline to the initial cuts.

repairs to the base course which may be required should be carried out using the same construction method as for the existing base course.

When the hydraulically bonded base course is cracked, a non-woven fabric or membrane should be inserted between the concrete layer and the hydraulically bonded base course.

When used as a substrate, unbound base courses must be compacted.

Before laying the concrete, dowels and anchors should be fitted into the existing concrete slabs and slab sections.

appropriate measures are to be taken to ensure that no fresh concrete can penetrate the transverse grooves and cracks of the adjoining concrete surface.

Where the aim is to ensure stable bonding with the existing layer, the surface of the cross-cut is to be roughened to a depth of up to 75% of the layer depth.

Where joint profiles are used, they may be installed immediately after the vault cut. to avoid damage to the edges, the compression strength of the concrete when fitting the profiles should amount to at least 70% of the values required for the road to be opened to traffic. in this way, the road can be opened for traffic at an early stage.

2.3. for the construction tyPe continuously reinforced concrete Pavement (crcP)

2.3.1. replacement of areas with punchout

damage to pavements in continuous reinforced concrete is manifested by the failure of the concrete above the reinforcing steel (punchout) or pavement blow-up. the

56

2013R06EN


causes are in construction errors (poorly constructed end-of-day construction joints, defective operation of the concrete paver) with the result that the lowest layer of concrete - in the main - is insufficiently compacted, or in design errors (lack of a bituminous interlayer, inadequate drainage, etc.) the area requiring repair is usually limited to a few metres, although in certain cases it may be tens of meters long. in such cases it is a matter of a succession of local defects. in technical terms repair comprises the following phases.

First there has to be a determination and marking of the areas that have to be repaired. visual inspection makes it possible to pinpoint zones suffering scaling, spalling and high concentrations of irregular cracks. in some cases more intensive sounding of the bordering areas may be required. such examination may possibly be supplemented by taking cores. the length of the area to be repaired, measured parallel to the axis of the road, is never less than 1.50 m, whereas its minimum width is 1.50 m. should more than one lane show defects, the work must be carried out in successive phases. the repairs are carried out on one lane at a time, so that a gradual transfer of the internal stresses in the reinforced concrete structure is assured. it is for example advisable to repair the fast lane first and then to repair the slow lane. Where the road has three traffic lanes, it may sometimes be possible to deal with the two faster lanes at once. 2.3.1.1 making the sawcuts

once the area to be repaired has been marked out (always as a rectangle), the concrete is cut through its entire thickness (including the reinforcement). the sawcuts are made perpendicularly to the road surface. two additional sawcuts with a depth of between 4 and 7 cm, depending on the position of the reinforcement, are made at least 1 m beyond the first 2 sawcuts. these latter sawcuts may in no case cause damage to the longitudinal reinforcement. this procedure makes it possible to expose the existing reinforcement during demolition and the new reinforcement may be attached to the existing reinforcement using steel wire. however, this method cannot be applied if the bituminous interlayer or the road base must be repaired. in such cases the reinforcement must be replaced by drilling holes with a diamond drill and using chemical anchoring.

2.3.1.2 demolition

the marked zone is demolished using a suitable method. the adjoining areas of the pavement may not be harmed. in those places where the existing longitudinal reinforcement is recovered the concrete is removed using pneumatic hammers taking care not to damage the reinforcement (the reinforcement may not be bent, etc.). the concrete around the edges ofthe area to be repaired is cut away vertically beneath the sawcut. should it appear during the removal of the concrete that the poorly sealed area is more extensive than anticipated, a new sawcut will be made and the concrete

57

2013R06EN


removed as far as the new sawcut. damage caused to the bituminous interlayer or the base during the removal of the concrete must of course be repaired. repairs to the base are made with rolled concrete with a depth of at least 15 cm. minor damage to the base (e.g. mildly eroded lean concrete) may after cleaning be repaired by treating with a poured bituminous mortar.

2.3.1.3 repairing the reinforcement

the original reinforcement is repaired with reinforcing steel with a diameter at least the same as that of the existing reinforcement. if the existing reinforcement has been cut off so that a length of least one metre is exposed, the new reinforcement is attached to it with steel wire in at least 2 places over the distance of one metre. if the existing reinforcement has been cut off (as in the case where the interlayer and/or the road base has to be repaired), the new reinforcement must anchored chemically in holes drilled with a diamond drill. the holes, which shall have a diameter at least 6 mm greater than the reinforcing steel, are drilled so that they lie parallel to the surface and the axis of the pavement with a depth of 40 cm, close to the existing longitudinal reinforcement. any overlapping of new reinforcing rods should be at least 75 cm. these must be secured with steel wire in at least 2 places. to strengthen the attachment of the new concrete to the old concrete, it is advisable to double up the longitudinal reinforcement by placing new reinforcement in the lower third of the pavement. the depth of the reinforcement is maintained by one or more supports made by a transverse bar with a diameter of 12 mm placed at right angles to the axis of the road on chairs with suitable dimensions. the maximum distance between the transverse steel bars or between a transverse steel bar and the sawcut side of the concrete is 75 cm. the anchor rods in the longitudinal joint have a diameter of 16 mm and a length of 800 mm. they are provided every 80 cm in such a way that the existing transverse and longitudinal reinforcement is not touched during drilling. the anchors are installed so that they lie parallel to the surface of the concrete pavement. after drilling they are fixed over half their length in the concrete by casting. small repairs (with a length of less than 2 m), however, may be completed without providing anchoring.

2.3.1.4 composition of the concrete

a quick setting concrete (fast-track or even ultra fast-track) is used. Where long repairs must be made (>6 m) the repair will be made in two separate phases using 2 different concrete compositions, as shown schematically in figure 38, following page. only the end pieces with a length of ± 2.0 m are made from quick setting concrete. First of all concrete is laid in the central section. this section is built in the same way as a newly built crcp. the longitudinal reinforcement is replaced over the entire length of the repair in advance. the concrete of the end pieces is laid at least 3 days after the placement of the concrete of the central section.

58

2013R06EN


saw cut over full depthsaw cut 5 cmremoval of the concrete – sound vertical faceKeeping in place of the reinforcement steel over 1 mBroken up concretenew reinforcement steel – tied splice over 1 mextra reinforcement steel in lower third part of the pavementtransverse reinforcement

Figure 38 – punchout repair

2.3.1.5 application of the repair concrete

the road base is moistened prior to laying the concrete. if the area of the repair is only a few m2, the concrete may be compacted using a poker vibrator or beam vibrator. a double beam vibrator is, however, essential if the area is larger. nonetheless the concrete at the edges must be carefully compacted using a poker vibrator. a slip form paver will be used when repairing long sections. the profile of the repaired area must be carefully integrated into the path of the existing lane. the quick setting concrete must of necessity be laid in the morning (the ideal time is usually between 10 and 11 a.m). the tensile strength of the concrete must be high enough to absorb the tensile stresses by the time of the first contraction of the crc after the completion of the repair (i.e. when the ambient temperature first starts to fall). if the concrete is laid in the morning, the quick setting concrete will have several hours during which it can build up tensile strength. it has been estimated that the compressive strength of concrete that is 10 hours old should approach at least 20 n/mm².

2.3.1.6 finishing the concrete

the repaired area should have a surface texture similar to that of the surrounding pavement. the concrete is immediately protected from drying out by application of a treatment product and by covering with a protective layer with a view to improving the development of mechanical strength by retaining the released hydratation heat in the concrete.

59

2013R06EN


2.3.1.7 weather conditions at the time of the repair

if the repair has to be carried out in extremely warm weather, it is advisable to cool the adjoining concrete for 50 m on both sides by spraying water on to it in order to reduce longitudinal pressures. other possibilities include spreading a layer of wet sand over the same 50 m or covering it with a reflecting foil (polyethylene with a silvered layer).

2.3.1.8 opening for use

the repaired pavement is opened for use after it has been restored to its original condition (sealing of longitudinal joints, cleaning, etc.) and as soon as the concrete has reached a minimum strength of 40 n/mm² as measured on 100 cm2 cores, or of 35 n/mm² on expanded polystyrene test cubes with a side of 15 cm.

60

2013R06EN


aPPendices

1. results of the survey on maintenance of concrete roads

authors: stefan höller, hennie Kotze

a survey on the maintenance of concrete roads was conducted by the committee d.2 “Road Pavement” / subcommittee d2c “Concrete Roads” in 2009 - 2011. the aim of the survey was to determine in which countries and to what extent concrete roads exist, and which maintenance measures are being applied.

in order to obtain an overview, the total length of the network of paved roads worldwide needed to be established. three road categories were specified: major roads (highways, interstate highways, etc.), national roads (federal roads, rural roads, etc.) and other roads (district roads, village roads). Furthermore, the total length or which proportion concrete roads represented, and which type of construction had been used, were to be determined. thereafter, the type of status assessment, maintenance measures and the intervals at which these measures were carried out were determined. Finally, financial and time aspects of new construction and maintenance were discussed.

With these points, a questionnaire was prepared and sent out worldwide. 35 countries participated, including in europe, Belgium, germany, Bulgaria, estonia, greece, great Britain, ireland, italy, lithuania, luxembourg, norway, austria, poland, portugal, romania, russian Federation, sweden, spain, the czech republic, hungary, serbia and slovenia.

in north america, canada, mexico and the usa participated, which is the whole north american continent. From south america, argentina, Brazil, chile and el salvador participated. From africa, there was feedback from morocco, namibia and south africa. in asia, china and south Korea participated in the survey. Finally, there was a response from australia. With these 35 of the 207 countries in the world, 56% of the world s land area was involved in the survey. to account for the remaining countries, the reference book elsner [1] - [4] and two internet sites were referred to [5], [6] and relevant data was perused. it was established that in total, there are 26.6 million kilometres of paved roads, including 2.1 million kilometres of concrete roads.

Paved roads worldwide

of the 26.6 million kilometres of paved roads, 10.3 million kilometres are in asia, 7.6 million kilometres in europe and 7.2 million kilometres in north america. this

61

2013R06EN


is followed by south america with 0.6 million kilometres, africa with 0.5 million kilometres and australia with 0.4 million kilometres. When considering only the major road network (highways or interstate highways), most are located in asia, north america and europe, 422.6 thousand kilometres, 419.1 thousand kilometres and 119.5 thousand kilometres respectively. in australia, south america and africa, there are considerably less: respectively 18.9 thousand kilometres, 10.8 thousand kilometres and 1.9 thousand kilometres. Table 1 shows all road lengths in the individual continents, divided into three categories of roads, in detail, and figure 1, following page, in graphical form. For certain countries only the total length of roads, but not the length of the major, national and other roads, was available. accordingly, there are discrepancies between the three road categories and the totals.

taBle 1 – Paved roads worldwide

continent countries major roads

national roads

others road

roads in total

[1,000 km]

[1,000 km]

[1,000 km]

[1,000 km]

africa 53 roads in total: all countries 1,9 20,2 93,5 551,7

asia 45 roads in total: all countries 422,6 223,6 4.842,0 10.282,1

australia 18 roads in total: all countries 18,9 38,7 284,1 416,5

north america 3 complete 419,1 756,5 6.039,3 7.214,9

south america 38 roads in total: all

countries 10,9 144,6 107,7 566,5

europe 49 roads in total: all countries 119,5 800,6 6.131,9 7.617,6

∑ 206 992,9 1.984,3 17.498,5 26.649,4

62

2013R06EN


Figure 1 – paved roads WorldWide

concrete roads worldwide

in the 35 countries that participated in the survey, concrete roads amount to a total length of 2.1 million kilometres. this represents 8.0% of all paved roads. of these, 1.4 million kilometres are in asia, 0.6 million kilometres in north america and 127.4 thousand kilometres in europe. in the continents of south america, australia and africa, there are less concrete roads at 8.6 thousand kilometres, 2.1 thousand kilometres and 800 kilometres respectively. if one only considers the major road network, one finds most concrete roads in asia, at 125.3 thousand kilometres, followed by north america with 76.8 thousand kilometres and europe with 9.9 thousand kilometres. in the continents of australia, south america and africa, there are not many concrete roads in the major road network with 2.1 thousand kilometres, 0.9 thousand kilometres and 0.3 thousand kilometres respectively. the percentage of concrete roads in the network of paved roads was highest in asia with 13.2%. this is followed by north america at 9.0%. all remaining continents have low proportions of 0.2 to 1.7%. Table 2, following page shows the total lengths of the concrete roads in the individual continents, divided into the three road categories in detail and graphically in figure 2, following page.

63

2013R06EN


taBle 2 – concrete roads worldwide

continent countries major roads

national roads

others road

roads in total %

[1,000 km]

[1,000 km]

[1,000 km]

[1,000 km]

africa 3 morocco, namibia, sa) 0,3 0,4 0,2 0,8 0,2

asia 3 vr china, s. Korea, Kirgi. 125,3 30,3 1.200,4 1.355,9 13,2

australia 1 australia 2,1 0,0 0,0 2,1 0,5north america 3 complete 76,3 58,0 512,9 647,2 9,0

south america 4 argentina, Brazil,

chile, el salvador 0,9 7,7 0,0 8,6 1,5

europe 21 ... 9,9 16,4 101,1 127,4 1,7∑ 35 214,7 112,8 1.814,4 2.142,0 8,0

Figure 2 – concrete roads WorldWide

the total length of concrete roads varies in the individual countries from 0.0 km to 1.4 million kilometres. For further studies the participating countries were divided into three categories. countries with no or few concrete roads (up to 200 kilometres) and countries with concrete roads on a larger scale (> 200 kilometres). Bulgaria, estonia, ireland, italy, luxembourg and namibia do not have concrete roads. greece, lithuania, morocco, norway, portugal, sweden, serbia, slovenia and hungary each have less than 200 kilometres of concrete roads. the remaining countries, argentina, australia, Belgium, Brazil, chile, china, germany, el salvador, great Britain, canada, mexico, austria, poland, romania, russian Federation, spain, south africa, south Korea, the czech republic and the usa possess concrete pavements on a larger scale and are included in the further consideration. these are shown graphically with the total

64

2013R06EN


lengths of concrete roads in figure 3 most concrete roads are found in china, the usa, the czech republic and Belgium.

Figure 3 – countries With more than 200Km concrete roads

in the questionnaire, the concrete pavements were divided into the construction types “ jointed unreinforced concrete pavement”, “ jointed reinforced concrete pavement”, “continuously reinforced concrete pavement” and “continuously reinforced concrete base”. in all 20 countries jointed unreinforced concrete pavements are used. in 6 countries jointed reinforced concrete pavements have been built. in 10 countries, continuously reinforced concrete pavements are used and in 4 countries, continuously reinforced concrete bases.

maintenance of concrete roads

17 countries have a pavement management system (pms). all stated that maintenance measures are carried out at irregular intervals, or that there was no data on the maintenance intervals. in 16 countries, guidelines for the maintenance of concrete pavements exist. these are between 2 to 25 years old, on average 8 years old. in most cases they were issued by state authorities and some by the cement and concrete industry.

repair and renewal of joint fillers are being carried out in all countries. Widening and filling of cracks is performed by almost all 19 countries. repair of edge damage and broken-off corners are rectified in 14 countries.

the repair of surface damages is applied in varying degrees. in most cases, in 14 countries, the texture restoration by diamond grinding is applied, followed by diamond grooving in 9 countries, and jet blasting which is applied in 5 countries. reactive resin coatings and reactive resin mortar is only used in 6 and 3 countries respectively.

65

2013R06EN


subsequent doweling and stitching/tie-ing of joints and cracks, the stabilising of slabs and partial and complete replacement of slabs are applied in little more than half, 13 to 17 countries.

the vertical re-alignment of slabs and the renewal of single lanes is only performed in 10 and 11 countries respectively. the repair of punch out damages in continuously reinforced concrete pavement is performed in 6 of the 10 user countries. White topping can be carried out bonded or unbonded to the base. 12 countries perform this with a bond and 6 unbonded.

When surveying the financial and time aspects of new construction and maintenance, the following results were gained: 4 countries pay attention to use cost delays due to construction work. if the intended service life of the structure is not observed, in 14 countries, this has consequences for the contractors. conversely, in 6 countries bonuses are paid when the planned service life is maintained. Bibliography

[1] der elsner – handbuch für straßen- und verkehrswesen, edition 1989[2] der elsner – handbuch für straßen- und verkehrswesen, edition 1990[3] der elsner – handbuch für straßen- und verkehrswesen, edition 1995[4] der elsner – handbuch für straßen- und verkehrswesen, ausgabe 2004[5] Web site: cia the World Fact Book[6] Web site: Welt auf einen Blick, straßen: absolute Zahlen

66

2013R06EN


summary

a survey on maintenance on concrete roads was conducted by the piarc in the years 2009 through 2011. the survey indicated that the entire network of paved roads worldwide amounts to a length of 26.6 million kilometres, of which 2.1 million kilometres are concrete roads. most of these are located in the continents of asia, north america and europe. in 20 countries, concrete roads are present on a larger scale (more than 200 kilometres). most commonly, jointed unreinforced concrete pavements are being built and jointed reinforced concrete pavement and continuously reinforced concrete bases are less common.

in terms of maintenance, smaller measures such as the repair of joint fillers and to a smaller extend, edge and corner break-offs are performed everywhere. larger measures such as subsequent doweling and stitching of joints and cracks and partial and complete replacement of slabs are performed by little more than half of the user countries. measures to repair surface damages are not commonly used, with the exception of the texture restoration by diamond grinding which is used more often in 14 countries.

“Contractors rarely participate in ensuring high quality maintenance through providing long term guarantees for their workmanship.”

67

2013R06EN


2. california – full dePth rePlacement of concrete Panels with raPid strenGth concrete

authors: B. stein, B. Kramer, r. ryan, t. Kumar twining, inc., long Beach, ca, usa t. pyle california department of transportation, sacramento, ca, usa s. shatnawi shatec engineering, el dorado hills, ca, usa

during the past decade rapid strength concrete (rsc) has been extensively used in california for rehabilitation and improvement of highways, city streets, and airfields, where acceleration of construction was a concern. the required rate of strength gain, the prime constructability consideration for proportioning of rsc, is defined by the minimum strength required for opening lanes to traffic within the planned curing time. most frequently technical specifications require that prior to opening lanes to traffic rsc achieves minimum flexural strength of 2.8 mpa (400 psi). When work is performed during short-time lane closures allowing for curing of the last load paced into pavement within 1 to 4 hours, contractors have been frequently using the following two types of rsc: rsc with calcium sulfoaluminate rapid hardening cement (astm c1600) - for maximum duration of curing of 1 to 2.5 hours, or rsc with type iii high-early strength portland cement (astm c150) and non-chloride accelerator of hardening (addition rate of accelerator of hardening based on its dry weight is approximately 2 to 3.5% by weight of portland cement) – for maximum duration of curing of 2.5 to 4 hours plus.

the project description below explains typical scope and sequence of work performed during full depth replacement of individual slabs.

68

2013R06EN


construction of replacement concrete Pavement at state route 710 (freeway) in los angeles county, california, usa

this project (caltrans contract 07-244704), executed from september 2005 through october 2006, involved the replacement of concrete pavement slabs. most sections to be rehabilitated were less than a mile in length but extended into more than one lane. the contractor, All American Asphalt, was permitted by caltrans to replace panels in one lane at a time for approximately six hours. construction was permitted only during night time in order to minimize traffic impact and commuter inconvenience.

during closures (with minimum duration of 6 hours) work performed by the contractor’s team included:

• Traffic control and closure of lanes, • removal of old pavement by full depth saw cutting and lifting, method not

impacting base and adjacent pavement left in place, • Installation of bond-breaker (flexible plastic material) over the existing base left in

place, • installation of foam-material insulation at transverse and longitudinal contact joints

with old concrete left in place, • installation of load transferring devices, where required, • Placement, consolidation, screeding-off (using roller screed), hand finishing, and

texturing of rsc, • application of curing compound, • Curing for achieving flexural strength required for opening lanes to traffic (Note:

limiting time is the time since last rsc load had been placed), • saw cutting contraction joints, where needed, • On-site testing for flexural strength prior to opening lanes to traffic, and • Opening lanes to traffic.

69

2013R06EN


• RSC was designed to achieve flexural strength of 400 psi in approximately 1.5 hours and 600 psi in 7 days. the production mixture was designed as follows:

– rapid set® cement (cts cement manufacturing company) - 658 lb/yd3 or 390 kg/m3,

– set-controlling admixture citric acid - to extend time within which rsc retains workable consistency,

– high-range water reducer glenium 3400 (BasF) – to reduce water requirement, limit W/C to 0.43, and provide near-flowable consistency of RSC, and

– siliceous aggregate consisting of washed concrete sand and 1-inch (25 mm) maximum size aggregate.

rsc was produced on-site by short load concrete using volumetrically measuring and continuously mixing equipment (also referred to as mobile mixers). preconstruction mix design studies of rsc, according to the requirements by caltrans, encompassed development of strength gain curve. Figure 1 presents data of strength gain up 24 hours (such studies also include 7-day and 28-day testing).

300

350

400

450

500

550

600

650

700

0 5 10 15 20 25 30

Flex

ural Stren

gth (psi)

Time since finishing (hrs.)

Figure 1 – Flexural strength development data oBtained during construction oF the trial slaB

rsc with rapid hardening cement is most often produced in california using volumetric measuring and continuous mixing equipment. this reduces time between mixing and placing. the demand for set controlling admixtures is significantly reduced and uniformity of workability and strength in early age is improved. hourly rate of rsc production and placement depends on the capacity of volumetric mixers, as well as on the site access conditions, location of panels to be replaced, their size, etc. on the average, hourly production rate of panel replacement reaches ~ 35 to

70

2013R06EN


55 yd3 (~ 27 to 38 m3) per hour. on the opposite, rsc with type iii portland cement has typically been produced using transit mixers. high-range water reducer and hydration controlling admixture are added at the batch plant. accelerator of hardening is added on-site.

prior to opening lanes to traffic beams fabricated during pavement replacement were tested for flexural strength using mobile laboratories designed and built by twining, inc. the mobile laboratory is a self-sufficient facility set in a box truck or trailer and equipped with portable testing machines (capable of testing specimens for compressive and flexural strength), and carrying on board curing equipment, temperature monitoring devices, weather stations, equipment for testing fresh concrete for air content, plastic unit weight, consistency, setting time, generators, etc. immediately upon completion of fabrication, beams are transferred to thermal insulated portable enclosures, where they are cured at a temperature matching temperature of the replacement pavement within ~ 3°c.

taBle 1 – analysis of flexural strenGth data, ct 07-244704duration of analyzed period september 2005 through october 2006number of analyzed sets of data 74

Flexural strength @ ~ 1.5 hoursaverage (mpa) 3.31standard deviation (mpa) 0.358

Flexural strength @ 7 daysaverage (mpa) 5.04standard deviation (mpa) 0.33coefficient of variation (%) 7

initial concrete temperatureminimum (oc) 17 (in december)maximum (oc) 32 (in July)

ambient temperatureminimum (oc) 9 (in January)maximum (oc) 22 (in July)

We analyzed strength data for a total of 74 sets of specimens fabricated and tested over the course of construction of the subject project. each set consisted of three beams tested prior to opening lanes to traffic in the field and three beams tested at 7 days in off-site laboratory. ambient and concrete temperatures were recorded at the time of sampling of concrete. our analysis is summarized in table 1. Flexural strength of rsc in 7 days appears to be more predictable and field data more uniform than often it is deemed to be, and is comparable with regular portland cement concrete for pavements. standard deviation of early age strength largely depends on the actual time of testing.

71

2013R06EN


lessons learned

experience acquired during the subject and other projects built during the past decade in california demonstrate that acceleration of strength gain of concrete can be achieved in practice by:

• using fast hardening cements,• using chemical accelerators,• lowering W/c, • enhancing early-age bonding of cement paste to coarse aggregates (for

example, by using crushed rock), • increasing initial temperature of concrete, and • increasing temperature during curing.

design of rsc should account for properties of fresh concrete influencing constructability and contributing to acceleration of construction, among them:

• consistency, • minimum time within which fresh rsc is required to retain design consistency,• resistance to segregation in the selected range of consistency (figure 2),• ability to be placed, formed, and consolidated quickly and conveniently, and• Ability to be finished promptly upon completion of consolidation (figure 3).

rsc is the central, but not the only component of pavement rehabilitation strategy. For the best quality of replacement pavement:

• rehabilitation strategy should include pre-evaluation of base, and of adjacent pavement slabs left in place,

• Base, where needed, should be repaired or replaced (most typically using rapid hardening lean concrete),

• replacement rsc pavement should be separated from existing (old) concrete pavement left in place with isolation contact joints to prevent restraint,

• replacement rsc panels should be de-bonded from the existing or new rigid base,• time of saw cutting of contraction joints depends on setting and strength

gain of rsc; the depicted rsc type with rapid hardening cement should be saw cut in approximately 50 – 60 minutes after placement,

• load transferring devices should be designed and installed to minimize stress development in the new rsc at their interface with the adjacent old concrete,

• rsc production and paving operations should be planned with consideration for properties of rsc, site and ambient conditions, total closure time, optimum duration of curing prior to opening lanes to traffic, and prevention of early age cracks, and

• rsc shall be proportioned (designed) with consideration for constructability, ambient, and site conditions.

72

2013R06EN


3. south africa – rehaBilitation of crcP with hiGh early strenGth concrete on the schoemann freeway

authors: hennie Kotze Br

in the year 1986/88 the Ben schoeman freeway was built as a continuously reinforced concrete pavement (crcp). it is the main corridor connecting Johannesburg and pretoria and for the national economy of great importance. the crcp performed very well during the past 15 years. however, during the last few years the number of punchout failures occurring on the pavement has been on the increase mainly due to water ingress through the joints. With the average annual daily traffic bordering on 150,000 on one section of the freeway, any repair activities on the freeway, even during weekends, impacts severely on the traffic. concrete repairs on a crcp make it even worse due to the generally longer road closures required. this necessitates the use of innovative technologies for the concrete repairs so as to minimize the road user cost and at the same time reduce the risk of accidents which is fairly high during construction.

literature review

the existing punchouts on the schoeman freeway had to be quickly and durable repaired. to avoid major traffic back-up, the rehabilitation had to be done in a night shift from 21:00 p.m. to 05:00 a.m. the only solution could be high early strength concrete. While this has never been attempted in south africa a literature review revealed that it is being done in north america albeit recently. it was found, that the mix design has to meet the following requirements before opening to traffic: flexural strength and compressive strength 2.1 mpa and 20 mpa and a lowl shrinkage value. Furthermore all materials had to be available in south africa and the workability had to be guaranteed. 7 mix designs were found to be suitable.

73

2013R06EN


laboratory testing

to find out which of these 7 mix designs fullfilled the requirements best, laboratory testing was carried out. critical criteria of the approved mix satisfied specified requirements of strength, shrinkage, durability and workability. the mix comprised the following components 507 kg/m³ cement (cem i 42,5 r), 1263 kg/m³ 19mm coarse aggregate (dolomite) and 630 kg/m³ fine sand (silica sand). Figure 1 shows the development of the flexural and the compressive strength. due to the many risks and unknowns in this contract, an experimental panel was constructed in the contractor s yard prior to the repair of a trial section on the road.

Figure 1 – average concrete strength oBtained

Preparation work

once repair areas were identified, they were scanned with ferro scanners to identify the position of steel reinforcement. this was in order to cut marked areas within reinforcement boundaries so as to minimize cutting of further bars in existing concrete with the inevitable over cuts. it was decided from the outset, due to time restraints, that the concrete would be cut full depth and lifted out in full panels. the following is a summary of the construction sequence and observations made during the process:

• saw cut into panels of 1.5 x 1.2 m. reinforced concrete needs specially designed diamond blades.

• lift out panels. a 12 ton truck mounted crane was used to lift out the panels (± 1 ton). however, lifting equipment must be rated at 10 tons as concrete tends to adhere to the underlying layer.

• drill tie bars (longitudinal and transverse). a 2,000 watt rotary hammer drill mounted horizontally on rails with adjustable depth settings was used. tie bars were placed using a 1,250 watt rotary drill to ‘spin’ the bar mixing a two part epoxy on embedment. it was found that the position of distribution bars in the crcp pavement

74

2013R06EN


repairs determined the transverse crack spacing of the repaired area. For instance, transverse steel placed at 1.2 m centre to centre induced cracks 1.2 m apart.

• scabble all vertical faces.• reinstate all longitudinal main and transverse distribution steel.• prime all vertical faces with concentrate of contec qsF binder.

Pouring and Placing the concrete

• load and mix preweighed and bagged aggregate, sand and cement in a pan mixer. quality control was achieved by preweighing and bagging of aggregates and binders in a controlled area.

• place concrete using high frequency poker vibrators and high frequency heavy duty screed beam. the high frequency is essential to achieve good compaction of the mix.

• Finish concrete with hand floats and leveling beam. Hand floats give acceptable finish on small widths. Bull floats should be used on widths greater than 2.5 m. it was found that workability of the mix is very good at temperatures less than 18ºc. aggregates were stored in a cold room at temperature below 18ºc in order to slow down the setting process and allow enough time to finish off the concrete. At this temperature, working time was a maximum of about 15 minutes. this means the mix behaviour is very critical and requires constant supervision.

• Finish off surface texture with soft broom (micro texture) and spring steel tine (macro texture).

• curing was done with a resin based curing compound.• in very cold weather (night time) a thermal blanket is placed over the new concrete

to retain heat.• some of the construction activities are illustrated in figure 2. the time window

to complete the construction process was from 21:00 hrs to 05:00 hrs. like any fast-track construction, well-planned construction sequencing was imperative. apart from the slab saw cutting which was done on the night before, the average duration of the activities was as shown in figure 3.

• due to good quality control in the mixing and placing of the concrete, test results were generally good, consistent and within acceptable limits. to date all the patches are performing very well. none one of the patches were damaged from lack of strength at time of opening to traffic (no tyre imprint/shoving or induced cracks). the oldest patch is approximately a year old.

Figure 2 - pouring and placing the concrete and Finishing the surFace texture

75

2013R06EN


Figure 3 – time schedule oF the punch-out repair

conclusions and way forward

south africa is starting to face similar problems facing many road authorities worldwide: the maintenance and renewal of urban freeway pavements. this paper summarises the experience gained on concrete repairs on a crcp pavement on one of the busiest freeways in southern africa. it showed that very early concrete strength can be achieved with the right technology. on average, flexural strength of at least 3.7 mpa was obtained within four hours of placement.

the case study also showed the importance of good integration between the design and construction stages. meticulous planning of all activities and good relationship between the client, the engineer, the contractor and his suppliers are the other critical elements that contributed to the success of this contract.

although this concrete repair contract was not a research study, the client was supportive in many ways in making it a case study. however, with the ageing pavement network in south africa there is a definite need for more research. one of the areas that will require urgent attention is long life pavement rehabilitation strategies (perpetual pavement concepts). research work is also required on using incentives and penalty-driven contracts coupled with lane rentals on very busy freeways. it is foreseen that with the increasing challenges facing the engineer, the contractor will be given more and more financial incentive to participate in reducing the road user cost by working more effectively and efficiently. active participations from all the role players are a must when dealing with such challenges.

76

2013R06EN

Documents

Best Practice Guide for maintenancepiarc.rmto.ir/DocLib/انگلیسی/روسازی راه/راهنمای مناسب... · maintenance methods used world-wide; a case study of full-depth