I N T E R N AT I O N A L C O N F E R E N C E

PROTECTION AND RESTORATIONOF THE ENVIRONMENT XI

P R O C E E D I N G S

E D I T O R S:K. L. KatsifarakisN. Theodossiou

C. ChristodoulatosA. Koutsospyros

Z. Mallios

THESSALONIKI, JULY 2012

PROTECTIONAND RESTORATIONOF THE ENVIRONMENTXI

DEVELOPMENT OF ENVIRONMENTALLY-FRIENDLY CONCRETE

WITH THE UTILIZATION OF FLY ASH, C&D WASTE AND STEEL

SLAG

E. Anastasiou

1, K. Georgiadis Filikas and S. Mavridou

Division of Structural Engineering,

Dept. of Civil Engineering, A.U.Th,

GR- 54124 Thessaloniki, Macedonia, Greece

E-mail:elan@civil.auth.gr 1

ABSTRACT

The production and disposal of large volumes of materials from industrial practices has always been

an environmental burden and the most common solution for such materials is their disposal in

landfills, unless some added-value use is available. Moreover, extraction of natural resources has

negative environmental impacts due to consumption of energy, while during cement production

large amounts of CO2 are released into the atmosphere. The cement and concrete industry have

provided a solution for the utilization of large volumes of recycled and secondary materials such as

fly ash, slag and other industrial by-products, in an attempt to reduce the negative environmental

impacts mentioned above. Nowadays, due to stronger environmental legislation, there is also a

stronger financial incentive for by-product utilization in order to diminish the amount of disposed

materials. Along these lines, an experimental program was carried out in order to investigate the

possibility of producing concrete incorporating large volumes of industrial by-products and

secondary materials. The alternative materials tested were fly ash as binder for cement replacement,

construction and demolition waste (CDW) as fine aggregate and steel slag as coarse aggregate.

Different concrete mixtures were prepared and tested for mechanical strength. Moreover,

environmental evaluation of the inclusion of the different alternative materials is examined through

life cycle analysis. The results show that it is possible to produce an environmentally friendly, good

quality concrete by using large volumes of alternative construction materials.

Keywords

Concrete; fly ash; steel slag; construction/demolition waste; environmental evaluation

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2627

1 INTRODUCTION

As concrete technology evolves and environment deteriorates, it is now clear that the unlimited use

of construction materials, with initial cost being the prevalent selection criterion is a practice of the

past. Environmental concerns expressed by new legislation and commercial trends have pushed the

concrete industry towards minimizing its environmental impact, mainly by reducing CO2 emissions

as well as natural resource consumption (Limbachiya et al, 2011). Concrete-making materials

benchmarking nowadays refers not merely to mechanical performance and durability requirements

but also to life-cycle analysis and environmental performance. Since the environmental cost of

utilizing energy-intensive construction materials tends to be included in the life-cycle cost of

concrete, the concrete industry is inclined to using low carbon footprint alternative materials as well

as incorporating marginal or secondary aggregates. Maximizing concrete durability, using

supplementary cementing materials (SCM) and alternative aggregates, all contribute to sustainable

concrete engineering and their environmental performance can be measured when life-cycle

analysis is used in the mix design process (Anastasiou and Papayianni, 2011). Depending on

available resources, SCMs can be used as partial replacement for Portland cement (Berndt, 2009),

while alternative aggregates can be used to substitute raw materials as aggregates (Poon et al,

2002), producing a greener concrete in terms of resource and energy consumption.

The fact that the use of SCMs can, in many cases, increase the durability of concrete without

compromising strength (Papadakis and Tsimas, 2005), while at the same time it can reduce overall

cost (Limbachiya et al, 2011) has attracted a lot of attention regarding their incorporation in

concrete. Plenty of research has been undertaken over the past decades on the use of fly ash, blast-

furnace slag, silica fume, metakaolin and rice husk ash as binders in concrete mixtures (Berndt,

2009), to the extent that their potentially beneficial use in concrete can be considered common

knowledge. The extensive use of alternative materials as aggregates in concrete was delayed,

mainly because cheap, good quality natural aggregates were readily available in most parts of the

world. However, legislation against quarrying and restriction in landfilling and deposition of waste

(EC Directive 1999/31) has pushed research forward in this area. Construction and demolition

waste (CDW) as well as industrial by-products are materials in abundance which provide possible

alternative aggregates for concrete and will continue to be produced in large volumes in the future.

Research has shown that steelmaking slag (Papayianni and Anastasiou, 2010), recycled concrete

aggregates and CDW (Limbachiya, 2010; Limbachiya et al, 2011) can be used to substitute natural

aggregates in concrete successfully.

The objective of the research described in this paper was to test the feasibility of producing concrete

of sufficient strength and durability and at the same time of minimum environmental impact by

using the maximum possible amount of locally available alternative materials. High calcium fly ash

(HCFA) as Portland cement replacement, electric arc furnace steel slag (EAF slag) as coarse

aggregate and recycled aggregates from construction and demolition waste (CDW) as fine

aggregate were used in various laboratory concrete mixtures, which were tested for their mechanical

properties. A conventional concrete mix was produced and used as reference. Combinations of all

the available materials were used in different concrete mixtures in order to determine the effect of

each parameter on strength and durability. The use of Greek HCFA as cement replacement in

concrete, as well as the use of EAF slag as aggregate has been documented in earlier research and

results show that HCFA results in lower early strength and increased water demand while final

strength and durability is enhanced (Swamy, 1983). The annual production of fly ash in Greece is

estimated at about 9,500,000 t, only 10% of which is used in blended cement production while the

rest is landfilled in quarries (Papadakis and Tsimas, 2005).

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2628

The use of EAF slag aggregates in concrete mixtures can contribute to increased concrete strength

and durability (Manso et al, 2006), while CDW is most commonly used as coarse aggregates and is

expected to reduce concrete strength and increase porosity (Agrela et al, 2011). EAF slag is a by-

product that is produced during the melting of scrap metals in an electric furnace for the production

of steel and the annual production in Greece is estimated at 250,000 tons (Anastasiou and

Papayianni, 2011). The by-product is water cooled, creating irregularly shaped porous grains of

various sizes, which shows good physical and mechanical properties as concrete aggregate

(Maslehuddin et al, 2003), while its expansion risk is minimal when free CaO and MgO content is

limited (less than 5%) and when EAF slag is exposed in outdoor conditions for a period longer than

9 months (Papayianni and Anastasiou, 2010). CDW aggregate, on the other hand, is produced by

crushing waste originating from various construction sites, building materials and with variable

initial strength. As expected, CDW aggregates may contain some ceramic material, gypsum, glass

and bituminous particles. The presence and amount of these impurities depend on the origin of the

CDW and the various processes of the recycled plant.

The proper combination of the above materials could produce a concrete with properties similar to

those of the reference mix with minimum usage of raw materials. Moreover, examination of the

environmental performance of concrete mixtures made with alternative binder and secondary

aggregates and comparison to conventional mixtures made with natural aggregates and cement has

been conducted by the use of Life Cycle Analysis (LCA). The examined stages are the extraction of

raw materials and production of the concrete mixtures, since the increase in negative impacts

(energy consumption etc) occurs mainly in these stages and little or no change occurs in the

operation and maintenance stages.

2 ENVIRONMENTAL EVALUATION

2.1 LCA

Life Cycle Assessment (LCA), widely used all over the world, is a method which according to ISO

14040, is defined as the “compilation and evaluation of the inputs- raw materials, energy

consumption-, outputs- waste materials, noise and emissions- and potential environmental impacts

of a product system throughout its life cycle”. It also provides a method of comparing different

scenarios, in order to take a more environmentally friendly decision. The main scope of this

analysis is to optimize the system examined in order to improve the outputs, which are in most

cases harmful to the environment. For example, a life cycle solution might be using an alternative

raw material, which results in fewer harmful emissions or less wastes (solids or liquids) than the

virgin material.

In order to apply LCA, a system must be precise regarding its input and outputs. The standards used

for the conduction of an LCA are ISO 14040, and especially the guides: ISO 14040-Life Cycle

Assessment-Principles and Framework and ISO 14044-Life Cycle Assessment-requirements and

Guidelines (ISO 14040). LCA application in civil engineering applications, as a tool for assessing

solid waste management options, has started only in the last decade. So far, relevant practice in civil

engineering applications and especially in green concrete mixtures, where various solid wastes (by-

products) are combined and used as alternatives either to natural aggregates or to cement, is limited,

while the majority of the studies examining mixtures from an environmental point of view are

limited to the use of those wastes alone.

Comparison of concrete mixtures made with virgin aggregates and alternative by-products either as

aggregates or as binder

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2629

Alternative aggregates, such as recycled concrete and steel slag, provide a good example of the

application of secondary materials in concrete production. These materials can be easily collected

from plants, where they are produced as by-products of an industrial process or from plants where

materials are treated and classified after the end of their life cycle, and under certain circumstances,

may be of a relative consistent quality. Secondary aggregates with satisfactory properties are, in

many cases, appropriate for civil engineering applications (Berndt, 2009; Chowdhury, 2010).

However, the main benefit of substituting natural with alternative aggregates in concrete production

is the resource saving as well as the decrease in environmental impact from waste landfilling, which

is also usually costly due to transportation fees and landfill space rental or even due to fines

imposed for illegal deposition.

The system boundaries determine which stages of the life cycle and contributing product life cycles

are included in the foreground of the study. Since this is a comparative study, it was decided to

exclude areas of the system which were not affected by material substitution, since no changes in

the impacts of the system will result. The inputs of the system are raw materials and energy while

the outputs, are air emissions, noise and waste materials created during production. The stages

examined are raw material extraction and production of concrete mixtures. Virgin aggregate

extraction requires the use of explosives during the mining process, while crushing of recycled

aggregates requires no additional materials input (eg explosives), so the cost of such materials as

well as their environmental impact (dust, heat and emissions) is avoided. As a result, at this first

stage virgin aggregates produce more air emissions than recycled aggregates, while they also

require increased fuel consumption. Moreover, during virgin raw material extraction about 24% of

the total cost is spent on the opening of wholes which will be filled in with explosives for blasting

(Metso Minerals, 2007). This cost is saved in the case of recycled and steel slag aggregates.

As far as energy consumption is concerned, the energy used to crush virgin or CDW aggregate

depends on the quantities of the input material as well as on its purity, in case of CDW. The energy

needed for the production of 1 ton of recycled concrete aggregates resulting from input material of

high purity, comes up to 0.90 kWh/tn for fine aggregate and 0.90 kWh/tn for coarse aggregate,

assuming that the final recycled product consists of 50% fine and 50% coarse material. For virgin

aggregates, the energy consumption comes up to 1.74 kWh/tn and 1.60 kWh/tn for fine and coarse

aggregate, respectively. As far as slag and fly ash are concerned, energy consumption for

granulation and dewatering of 1 kg of ground granulated blast furnace slag comes up to 0.00215

kWh, for drying and stocking of 1 kg of ground granulated blast furnace slag is about 0.07 kWh

whereas the energy consumption for drying and stock of 1 kg of fly ash is estimated to be 0.00682

kWh (Chen et al, 2010). According to Mroueh et al (2001), in road construction where fly ash,

crushed concrete and blast furnace slag have been used as alternative materials, it was found that

consumption of energy during the construction phase, which is the most energy consuming phase,

was higher for the mixtures with the fly ash, then followed by the mixtures with slag and finally less

energy consuming were found to be the mixtures with crushed concrete –which stands for

aggregates deriving from CDW. Mixtures with crushed concrete and slag were found to be more

environmentally friendly, while fly ash as aggregate consumed almost the same energy as natural

aggregates did. During pre-handling of the by-products, negligible amount of energy is being

consumed. As far as the production stage is concerned, there are no significant differences in

energy consumption, which means that the addition of alternative aggregates does not result in

increased energy. Marinkovic et al (2010) calculated that for the production of 1 m3 of concrete

with either natural or recycled aggregates, electricity‟s required amount came up to 20.07 MJ for

both concrete types. Moreover when cement is replaced by fly ash and given that cement production

is far more energy consuming than fly ash, the energy savings are more pronounced.

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2630

As far as air emissions are concerned, according to Mroueh et al (2001), in road construction where

fly ash, crushed concrete and blast furnace slag have been used as alternatives to primary raw

materials, it was found that the pavement generated mainly the following emissions: CO, NOx, SO2,

CO2, VOC. When these alternatives were used, all emissions were found to be lower than the

reference mixtures produced with natural aggregates. More specifically, when alternatives were

compared as far as NOx, SO2, CO2, VOC emissions, the aggregates deriving from crushed concrete

(CDW) were more environmentally friendly. Furthermore, recycled aggregates generally show

much lower toxicity compared to natural aggregates, while in some cases fly ash shows higher. In

particular, in toxicity potential category (eg HTP) all the materials have very low toxicity, while in

TETP categories, fly ash has higher impact compared to natural aggregates. In addition to the above

and mainly for the use of fly ash, energy consumption, Global Warming Potential and acidification

potential generated are almost one-third of the values for natural aggregates (Chowdhury et al,

2010).

According to Marinkovic et al (2010) production of concrete with natural and recycled aggregates

have the following emissions: CO, NOx, SOx, CH4, CO2, N2O, HCl, HC, NMVOC and Particles in

the same amounts. However, it must be noted that total environmental impacts in terms of energy

use, global warming, eutrophication, acidification and photochemical oxidant creation depend on

transport distances and it is positive for concrete with recycled aggregates in case that the transport

distance is smaller for recycled rather than natural aggregates. Finally, regarding energy use, CO2,

PM10, SO and NOx emissions, the impact of fly ash compared to Portland cement is about an order

of a magnitude lower (Van den Heede and De Belie, 2012).

3 EXPERIMENTAL PROCEDURE

3.1 Material properties

The binders used in the laboratory mixtures were Portland cement type I42.5 N and unprocessed

high calcium fly ash originating from a local lignite power plant. The aggregates used were crushed

limestone as reference and EAF slag and CDW replaced partially or fully the natural aggregates.

The bulk material produced by the recycling plant (CDW) was tested as fine aggregate despite its

impurities and its potentially lower quality compared to natural aggregates. EAF slag was used both

as coarse and fine aggregate (filler) in order to achieve the desired gradation and all mixtures had a

maximum aggregate size of 16 mm. The chemical composition of HCFA, EAF slag and CDW used

is shown in Table 1.

TABLE 1. Chemical composition of HCFA, EAF slag and CDW

Sample Na2O K2O CaO MgO Fe2O3 Al2O3 SiO2 L.I.% Cl- NO3

- SO4

2-

HCFA 1.08 0.75 36.2 3.08 5.43 10.8 33.1 4.75 0.02 0.01 -

EAF slag 0.70 0.09 20.6 3.63 32.6 8.46 22.8 5.41 0.02 0.01 -

CDW 0.92 0.8 29.7 2.19 3.66 6.27 38.1 18.42 0.02 0.01 0.26

The acid soluble sulfate and chloride content is low both for EAF slag and CDW aggregates as well

as magnesium oxide content. From the visual inspection, as well as from the results in Table 1, it

can be seen that CDW sand has considerable amount of impurities (ceramic particles, organic

material). However, since current standards do not tend to reject aggregates unless they prove to be

harmful for concrete strength development and durability, it was decided to produce laboratory

concrete mixtures with CDW as fine aggregate and measure its performance. CDW aggregate was

also tested for density, fineness modulus, sand equivalent and water absorption mixture production

and the results were compared to those of crushed limestone which is most commonly used as fine

aggregate in Greece (Table 2).

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2631

TABLE 2. Physical properties of CDW and crushed limestone sands

Sample App. specific density Water absorption Sand equivalent Fineness module

(kg/m3) (%) (%) (%)

Crushed limestone 2.65 1.1 70.1 3.63

CDW 2.45 4.0 66.6 4.97

The results show that CDW has lower density and considerably increased water absorption

compared to crushed limestone, due to increased porosity which is common for recycled

aggregates. The sand equivalent test, which is a rapid field test to show the relative proportions of

fine dust or clay-like materials in fine aggregate and was performed according to EN 933-8, shows

that CDW is comparable to crushed limestone. The fineness module, on the other hand, which was

calculated according to EN 12620, shows that CDW is a considerably coarser fine aggregate than

crushed limestone, which already classifies as coarse fine aggregate (CF category). This, along with

increased porosity and water absorption of CDW need to be taken into account in the concrete mix

design process.

3.2 Concrete mix design

Four different aggregate gradation curves were used combining either CDW or limestone sand and

EAF slag or limestone coarse aggregates as shown in Table 3. Since CDW sand was extremely

coarse, as measured in the previous paragraph, it proved very difficult to produce acceptable

aggregate gradation mix curves and, hence, workable concrete mixtures only with CDW sand. It

was decided to improve to aggregate mix gradation curves when using CDW sand by including fine

material (filler <125 μm) as part of aggregate mix (about 8% wt. of the total of aggregates).

Crushed limestone filler and EAF slag filler were used in mixtures with natural and slag coarse

aggregate, respectively. The resulting aggregate mix gradation curves are shown in Figure 1.

TABLE 3. Aggregate combinations used in test concrete mixtures

Name 1-L 2-CDW+L 3-L+S 4-CDW+S

Fine aggregate Crushed limestone CDW +

limestone filler Crushed limestone

CDW +

EAF slag filler

Coarse aggregate Crushed limestone Crushed limestone EAF slag EAF slag

Figure 1. Aggregate gradation curves

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2632

The binder content selected for the test concrete mixtures was 350 kg/m3 and the water to binder

ratio (w/b) 0.50, aiming at a 28-day compressive strength of at least 30 MPa. 16 mm maximum

aggregate size was selected and the desired workability was S2 (50-90 mm slump). Four concrete

mixtures were prepared with Portland cement type I42.5 N as binder, one for each aggregate

gradation described above, and four more were prepared with HCFA substituting 50% of the

cement, resulting in a total of eight test mixtures. Aggregate water absorption and HCFA water

demand increase were taken into account in the design process when calculating the effective w/b

ratio and a superplasticizer was used at the dosage required to achieve the desired workability.

When HCFA was used to replace cement, workability loss was accounted for by increasing the

superplasticizer dosage. This was not possible, however, when using CDW sand and workability

loss there was so great that it had to be adjusted by increasing water content. Naturally, this would

have adverse effects on concrete strength development, but it was deemed necessary in order to

have a workable homogeneous mixture that could be compacted adequately. Also, mixtures with

slag aggregates show considerably increased density, which is expected due to the increased density

of EAF slag itself, which is estimated at 3300 kg/m3 according to previous studies (Papayianni and

Anastasiou, 2010). Table 4 shows the test mixture proportions for the eight mixtures, as well as the

fresh concrete properties measured.

TABLE 4. Laboratory test mixture proportions and fresh concrete properties

Concrete mixture

C-L C+FA-L C-CDW+L C+FA-

CDW+L C-L+S

C+FA-

L+S C-CDW+S

C+FA-

CDW+S Mixture proportions

(kg/m3)

CEM I24.5N 350 175 350 175 350 175 350 175

HCFA - 175 - 175 - 175 - 175

Limestone filler - - 156 153 - - - -

EAF slag filler - - - - - - 186

Crushed limestone

sand 962 939 - - 1010 986 -

CDW sand - - 726 709 - - 744 907

Coarse crushed

limestone 943 921 947 609 - - -

Coarse EAF slag - - - - 1114 1088 1161 1133

Water 138 139 198 198 137 137 196 196

Superplasticiser 0 1.8 5.3 7.0 0.7 3.5 5.25 7.00

Mixture properties

HCFA cement

replacement 0% 50% 0% 50% 0% 50% 0% 50%

Effective w/b ratio 0.50 0.50 0.56 0.56 0.50 0.50 0.56 0.56

Fresh concrete

density (kg/m3)

2359 2326 2350 2329 2633 2542 2533 2501

Slump (mm) 60 90 50 50 70 90 50 50

The concrete was mixed in a laboratory mixer where the aggregates along with cement and fly ash

were dry mixed for about a minute and then water and superplasticizer were added. After a total

mixing time of 5 minutes, concrete was cast in cubes (150 x 150 x 150 mm), cylinders (150 x 300

mm) and prisms (100 x 100 x 400 mm) and was compacted properly using a vibrating table. All

concrete specimens where demoulded after 24 hours and cured in a controlled environment

chamber at 20 °C and 95% RH until testing.

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2633

4 RESULTS AND DISCUSSION

The cubic specimens produced from the different laboratory mixtures were tested to determine the

unit weight of hardened concrete at 28 days as well as compressive strength at different ages. More

specifically, three specimens from each mixture were tested at 7 days, three at 14 days and six at 28

days. Also, cylindrical specimens from each mixture were used to calculate the elastic modulus and

the split tensile strength and prismatic specimens were used to determine the modulus of rupture.

The mechanical strength test results are shown in Table 5.

TABLE 5. Mechanical properties of the various mixtures

Property C-L C+FA-L C-

CDW+L

C+FA-

CDW+L C-L+S

C+FA-

L+S

C-

CDW+S

C+FA-

CDW+S

28-d unit weight

(kg/m3) 2386 2328 2268 2303 2650 2548 2536 2486

7-d compressive

strength (MPa) 35.6 26.5 25.0 13.0 43.3 26.4 26.8 14.2

14-d compressive

strength (MPa) 36.4 33.2 26.0 15.2 41.4 32.6 28.8 19.0

28-d compressive

strength (MPa) 41.7 38.6 29.3 18.7 48.2 40.2 30.8 23.4

28-d split tensile

strength (MPa) 3.28 3.42 2.72 2.32 4.02 3.32 3.18 2.67

28-d modulus of

rupture (MPa) 8.25 7.50 6.01 5.54 9.03 8.38 5.97 5.01

28-d elastic

modulus (GPa) 38.1 34.3 23.8 22.7 40.8 33.6 24.3 22.7

Ordinary concrete unit weight (usually between 2300 and 2400 kg/m3 – 2386 kg/m

3 for the

reference concrete mixture) was slightly decreased when HCFA and/or CDW sand were used due to

their lower apparent specific density compared to cement and limestone, respectively, but was

considerably increased when EAF slag aggregate was used (due to its apparent specific density of

3300 kg/m3), reaching unit weight up to 2650 kg/m

3 which could be categorized as heavyweight

concrete. The use of EAF slag aggregate in concrete mixture increased compressive strength and

either increased or did not affect significantly all the other mechanical properties. The rate of

strength increase ranged from 4% (when comparing mixtures C+FA-L to C+FA-S) to 25% (when

comparing mixtures C+FA-CDW+L to C+FA-CDW+S at 28 days) (Figure 2).

Figure 2. Relative change in compressive strength development of various mixtures compared to the

reference mixture at different ages

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2634

The substitution of 50% of cement in the binder system with unprocessed HCFA resulted in lower

early compressive strength (25% decrease when comparing C-L to C+FA-L at 7 days), while this

trend decreased at later ages (7.5% decrease when comparing C-L to C+FA-L at 28 days). The

lower early and 28-day mechanical properties of mixtures with HCFA are expected due to the

slower rate of the pozzolanic reaction compared to cement hydration (Malhotra and Mehta, 2002).

The ultimate strength of mixtures with HCFA are probable to increase further, even reaching higher

values than those of the respective mixtures with 100% cement as binder.

The use of CDW as fine aggregate in the mixtures resulted in all cases in considerably lower

mechanical properties at all ages, ranging from 30% (when comparing mixtures C-L to C-CDW+L)

to 52% (when comparing mixtures C+FA-L to C+FA-CDW+L). This is mostly due to the increased

w/b ratio of the mixtures with CDW, as stated earlier. The strength development rate, however, is

unaffected which means that the use of CDW does not seem to hinder the cement hydration process.

Furthermore, the combination of CDW with EAF slag as aggregate (mixture C-CDW+S) recovers

part of the strength reduction and produces a concrete of considerable mechanical properties (28-

day compressive strength of 30.8 MPa) reaching 74% of the strength of the reference concrete

without using any new material as aggregate. When the maximum amount of alternative materials

was used (HCFA, EAF slag and CDW, in mixture C+FA-CDW+S) the produced concrete shows a

28-day compressive strength of more than 20 MPa, which means that it could find utilization in

construction applications of lower strength requirements. In order for such mixtures to provide

alternative options for concrete production, their durability needs to be assessed in long-term

experimental programs, especially since the increased water absorption rate of CDW sand could

cause durability issues.

Although these two test concrete mixtures (C-CDW+S and C+FA-CDW+S) do not show the best

results regarding their mechanical properties, they are of greater interest and show considerable

potential from a technical and an environmental point of view, since they incorporate the maximum

amount of alternative materials. In such cases, the environmental benefit of utilizing large amounts

of industrial by-products and recycled construction materials needs to be quantified in order to be

taken into account in the decision process. At this point it should be noted that all results and

conclusions related to environmental impacts are dependent on the availability and quality of

relevant data in the literature and of data provided by specific recycling plants-quarries in the area

of Thessaloniki.

By making specific assumptions –quantity and quality of input materials for CDW, quantity of

produced natural aggregate– it can be concluded that substitution of virgin with alternative

materials can lead to mixtures with less negative environmental impact, especially in the stage of

extraction of raw materials and during their crushing to smaller fractions. The same environmental

gain is achieved when cement is replaced by fly ash and, in general, the use of slag and CDW

decreases the environmental loads compared to reference concrete. Yet, quantitative and

comparative life cycle assessment results of alternative concrete mixtures, as well as extensive

concrete durability measurements are essential first steps in order to make informed decisions

towards more sustainable practices in concrete production.

REFERENCES

1. Agrela F., M. Sánchez de Juan, J. Ayuso, V.L. Geraldes, and J.R. Jiménez, (2011) „Limiting

properties in the characterisation of mixed recycled aggregates for use in the manufacture of concrete.‟

Construction and Building Materials, Vol. 25, pp. 3950-3955.

2. Anastasiou E. and I. Papayianni (2011) „Concrete incorporating high-calcium fly ash and EAF slag

aggregates.‟ Magazine of Concrete Research, Vol. 63, pp. 597-604.

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2635

3. Berndt M.L. (2009) „Properties of sustainable concrete containing fly ash, slag and recycled concrete

aggregate.‟ Construction and Building Materials, Vol. 23, pp. 2606-2613.

4. Chen C., G. Habert, Y. Bouzidi, A. Jullien, A. Ventura, (2010) “LCA allocation procedure used as

an incitative method for waste recycling : An application to mineral additions in concrete”, Resources,

Conservation and Recycling, 54, pp.1231-1240.

5. Chowdhury R., D. Apul and T. Fry (2010) „A life cycle based environmental impacts assessment of

construction materials used in road construction‟ Resources, Conservation and Recycling, Vol. 54, pp.250-

255.

6. European Council (2002) ‘EC Directive 1999/31 on the landfill of waste’. Environmental Policy

Division, Department of the Environment.

7. ISO 14040 (1997) ‘A standard on principles and framework of LCA’, 1st Edition.

8. Limbachiya M.C., M.S. Meddah and Y. Ouchagour (2011) „Use of recycled concrete aggregate in

fly-ash concrete‟ Construction and Building Materials, Vol. 27, pp. 439-449.

9. Limbachiya M. C. (2010) „Recycled aggregates: Production, properties and value-added sustainable

applications.‟ Journal of Wuhan University of Technology-Mater. Sci. Ed., Vol 25, pp. 1011-1016.

10. Malhotra V. M. And P.K. Mehta (2002) ‘High Performance, High Volume Fly Ash Concrete;

Materials, Mixture Proportioning, Properties, Construction Practice, and Case Histories‟, Ottawa:

Marquardt Printing.

11. Manso J.M., J.A. Polanco, M. Losañez and J.J. Gonzalez (2006) „Durability of concrete made with

EAF slag as aggregate‟ Cement & Concrete Composites, Vol. 28, pp. 528-534.

12. Marinković S., V. Radonjanin, M. Malešev and I. Ignjatović (2010) „Comparative environmental

assessment of natural and recycled aggregate concrete‟ Waste Management, Vol. 30, pp. 2255-2264.

13. Maslehuddin M., A.M. Sharif, M. Shameem, M. Ibrahim and M.S. Barry (2003) „Comparison of

properties of steel slag and crushed limestone aggregate concretes.‟ Construction and Building Materials,

Vol. 17, pp.105-112.

14. Metso Minerals (2007) ‘Crushing and Screening Handbook, Brochure No. 2051-04-07-CBL’,

Tampere.

15. Mrouech U.M., P. Eskola and J. Laine-Ylijoki (2001) „Life-cycle impacts of the use of industrial by-

products in road and earth construction‟, Waste Management, Vol.21, pp. 271-277.

16. Papadakis V.G. and S. Tsimas (2005) „Greek supplementary cementing materials and their

incorporation in concrete.‟ Cement and Concrete Composites, Vol. 27, pp. 223-230. 17. Papayianni I. and E. Anastasiou, (2010) „Production of high-strength concrete using high volume of

industrial by-products.‟ Construction and Building Materials, Vol. 24, pp. 1412-1417.

18. Papayianni I. and E. Anastasiou „Utilization of electric arc furnace slags in concrete products‟ in:

First International Conference on Advances in Chemically-Activated Materials CAM'2010, 9-12 May

2010, Jinan, China, (conference proceedings in CD).

19. Poon C.S. and D. Chan (2006) „Paving blocks made with recycled concrete aggregate and crushed

clay brick.‟ Construction and Building Materials, Vol. 20, pp. 569-577.

20. Swamy R. N. (1993). „Fly ash and slag: standards and specifications – help or hindrance?‟ Materials

and Structures, Vol. 26, pp. 600-613.

21. Van den Heede P. and N. De Belie (2012) „Environmental impact and life cycle assessment (LCA)

of traditional and “green” concretes: Literature review and theoretical calculations‟ Cement & Concrete

Composites, article in press.

Special session - Improving resource efficiency and sustainable use of various wastes - The Life+ Roadtire projectProtection and restoration of the environment XI

2636