COURSE NAME: PAVEMENT Management System

Master of Highway and Transportation Engineering

Faculty of Engineering

Department of Civil Engineering

Universiti Putra Malaysia

November 2012

SAEED BADELI

GS 32514

Assignment 1

1.0 Bitumen hardening is one of the possible causes for several pavement distresses. State the

pavement distresses that can be linked to hardening of bitumen. Explain how you would

curtail bitumen hardening at the production, construction and in-service stages.

Pavement Distresses :

A. Cracking

B. Patching and Potholes

C. Surface Deformation

D. Surface Defects

E. Miscellaneous Distresses

A) CRACKING

1. Fatigue Cracking

2. Block Cracking

3. Edge Cracking

4. Longitudinal Cracking

5. Reflection Cracking at Joints

6. Transverse Cracking

Pavement Distress In This Category That Can Relate To Hardening :

1)Fatigue Cracking :

Fatigue cracking is a interconnected cracks and can be created by reapeated

traffic.This crack can begin at the top of the surface.

Aligator cracking is a load-associated distress.

Hardening issue can affect to this type of distress with the traffic issue.

2)Block Cracking :

Block cracking is an interconnected crack that can divide the pavement in the

rectangular blocks.Block cracking is not a load-associated cracks and that can be

caused primarily by shrinkage of asphalt and daily temprature cycling.

Block Cracking can show that asphalt has hardening highly.

3)Longitudinal Cracking

These type of cracks are parralell to the center line .

They may be caused by:

1. A poorly constructed paving lane joint.

2. Shrinkage of the AC surface due to low temperatures or hardening of the asphalt and/or

daily temperature cycling.

3. A reflective crack caused by cracking beneath the surface course

4)Transverse Cracking

This crack extend across the center line and They can be caused by a shrinkage of asphalt

surface due to low temperatures or to asphalt hardening or can result from reflective cracks

caused by cracks beneath the asphalt surface.

5) Ravelling

Raveling is deterioration due to water entering the asphalt mat through interconnected air

voids.

Wearing away of the pavement surface caused by the dislodging of aggregate particles and

loss of asphalt binder. Raveling ranges from loss of fines to loss of some coarse aggregate

and ultimately to a very rough and pitted surface with obvious loss of aggregate.

Raveling can indicate that asphalt is hardening .

Effective Factors That Can Cause Hardening

Introduction

Bitumen is common binder and has gradually replaced road tar for construction purposes

mainly because of the cancer risk. It is a mixture of organic liquids that are highly viscous,

black, sticky and entirely soluble in carbon disulfide. Hot mix asphalt normally known as

asphalt, is a composite material commonly used for construction of pavement, highways and

parking lots. It is a proportionately mixture of mineral aggregates (filler, sand, gravel or

crushed stone) that are glued together by a bituminous binder. It is produced in asphalt plant,

then lay down in layers and compacted.

Although the binder is the component having the lowest percentage in asphalt mixture, its

characteristics are those which predominantly influence the properties and the performance

of the mix as a whole. Varieties of asphalt mixture exist. Asphalt concrete, stone mastic

asphalt, hot rolled asphalt; porous asphalt and gussaspalt are produced according to the layer

type and local conditions. All these mixtures display different rheological properties

depending on binder and aggregate characteristics.

Bitumen, like any organic matter, is affected by factors like presence of oxygen, changes in

temperature. These factors are responsible for hardening of bitumen. Hardening results in

decline in penetration increase in softening point and grow in penetration index (PI). For

increased life of bituminous pavement it is essential that excessive hardness does not take

place. Hardening of bitumen takes under the influence of external factors in the following

ways:

1)Oxidative Hardening :

When bitumen is exposed to atmosphere for a prolonged period the oxygen starts reacting

with the bitumen components and higher molecular weight molecules are formed. Larger

molecules results in lesser flexibility and hence increased hardness. The degree of hardness is

dependent on factors like ambient temperature, exposure time & thickness of bitumen film. It

is observed that for 10 0C increase in temperature above 100 0C the oxidation rate doubles.

2) Hardening Dou To Loss Of Volatile:

Over a period of time the volatile components in bitumen evaporate. The rate of evaporation

is dependent on temperature only. The volatiles in bitumen are relatively very low and hence

hardening due to loss of volatiles is relatively small.

3) Physical Hardening:

At ambient temperatures bitumen molecules slowly reorient themselves .This result in

physical hardening. This process is an extremely slow process and hence actual hardening

due to the above factor is very low.

4) Exudative Hardening:

Educative hardening takes place due to the movement of oily components out of bitumen

over a period of time. The rate of hardening due to this process is dependent on the type of

bitumen and also on the porosity of the aggregate.

5) HardeningOf Bitumen During Storage:

Hardening of bitumen during storage can be easily minimized by taking a few simple

precautions. Bitumen is stored in above ground tanks at high temperatures and high

temperature and presence of oxygen are the two primary factors responsible for hardening of

bitumen. Hence it is very important that bitumen be handled at the lowest possible

temperature, consistent with efficient use.

Also the storage tanks should have low surface to volume ratio so as to minimize the exposed

surface area. Lower exposed surface area would mean lower oxidation rate.

While designing the tanks it should be ensured that the recirculation pipelines always enter

the tank below the bitumen surface. This will reduce splashing during recirculation. When the

recirculation line enters the tank above the product surface all the three factors which

promote oxidation viz. high temperature, access to oxygen and high exposed surface to

volume ratio, are present. Therefore bitumen quality deteriorates very fast. If handled

properly the hardening in tanks can be insignificant as the product is stored for shorter

durations. If bitumen is to be stored for long durations(4 to 5 days) then the temperature

should be reduced to 20 0C to 25 0C above softening point.

In case where bitumen is to be reheated to increase the temperature adequate precautions

have to be exercised. Bitumen should not be heated continuously in the beginning.

Continuous heating can result in very high localized temperatures in area close to the heating

source.

6) Hardening Of Bitumen During Mixing:

During with a thin film of bitumen the size of which may vary from 5 microns to bituminous

macadam is approximately 10, 000 sqm. Therefore again the conditions are very favorable

for oxidation and hardening. It is generally observed that bitumen hardens by one grade

during mixing and laying. The above factor is taken into consideration while selecting the

right grade of bitumen.

7) Hardening Of Bitumen On Road:

Some hardening of bitumen can take place on the road also due to oxidation. The level of

oxidation is purely dependent on the access to oxygen. If the pavement is well graded and

well compacted the hardening is nominal as the void content will be low.

2.0 Production of a consistent and good quality bituminous mixtures by the quarry/asphalt

plant is one of the quality requirement in a road project. Explain how do you approve the

bituminous mixture to be used in your road project.

Introduction:

Good QC/QA practices are important to gain a satisfactory product.QC refers to those tests

necessary in order to control the product and to establish the quality of the product being

produced. Those tests are usually done by the contractor.QA mentions to those tests to make

a decision on acceptance of a project and hence to ensure that the product being assessed is

intended what the owner specified. These QA tests are normally performed by the owner.

Testing of the asphalt mixture during the production is essential to ensure that a satisfactory

product is obtained. The tests that should be performed during manufacture and placement of

the asphalt mixture ,including : aggregate gradation , asphalt content , temperature , mixture

properties of laboratory samples, theoretical maximum density , in-place density , smoothness

elevations , and visual inspections.

The contractor is responsible for quality throughout hot mix asphalt production and laying

down. Therefore, the contractor must ensure that the materials and work provided by

subcontractors, suppliers, and producers are adequate and meet the specifications of the

project.

Process monitoring has action limits and specified steps to be taken if the action limits are

broken. The specified steps are taken for the following reasons:

• To keep the process in control.

• To quickly determine when the process has gone out of control.

• To respond adequately to correct the situation and bring the process back into control.

QC/QA program consist of following major components:

A.Quality control

B.Quality assurance

C.Independent assurance

D.Dispute resolution

E.Acceptance and payment

A. Laboratory

The contractor is responsible for providing adequate laboratory facilities to fulfill the

specified testing requirements and quality control needs for production and placement of hot

mix asphalt. The Engineer will be notified by the contractor prior to the first day of

production of mix that the lab is ready for inspection by the Resident Engineer for this

project, which must also be done prior to any mix production. In the event of laboratory

equipment breakdown, the equipment will be repaired or replaced immediately or the

mix production will be shut down until the equipment is in working order.

B. Materials and Inspection

materials must coming from appropriate sources.Materials which use for the HMA should be

e code material be examined by the manufacturer for compliance with the requirements of th

acceptable materials are used in the -Inspectors must verify that only codespecifications.

rials have The properties of materials are various, and mate els.fabrication of pressure vess

differs.

Mix DesignsC.

The contractor should provide appropriate mix design with complete understand about type

of road and minimum requirements and standards for that. Design also demands close

attention to the details of testing procedures to ensure an economical blend and gradation of

aggregates. Durable asphalt mixes must provide for stability, sufficient voids and workability

to permit efficient construction.

1. Marshall Mixture Designs

The basic concepts of the Marshall mix design method were originally developed by Bruce

Marshall of the Mississippi Highway Department around 1939 and then refined by the U.S.

Army. Currently, the Marshall method is used in some capacity by about 38 states. The

Marshall method seeks to select the asphalt binder content at a desired density that satisfies

minimum stability and range of flow values (White, 1985).

Today the Marshall method, despite its shortcomings, is probably the most widely used mix

design method in the world. It has probably become so widely used because (1) it was

adopted and used by the U.S. military all over the world during and after WWII and (2) it is

simple, compact and inexpensive.

Marshall Mix Design Procedure

The Marshall mix design method consists of 6 basic steps:

1.Aggregate selection.

2.Asphalt binder selection.

3.Sample preparation (including compaction).

4.Stability determination using the HveemStabilometer.

5.Density and voids calculations.

6.Optimum asphalt binder content selection.

2. Superpave Mixture Design

The Superpave mix design method was designed to replace

the Hveem and Marshall methods. The volumetric analysis common to the Hveem and

Marshall methods provides the basis for the Superpave mix design method. The Superpave

system ties asphalt binder and aggregate selection into the mix design process, and considers

traffic and climate as well. The compaction devices from the Hveem and Marshall procedures

have been replaced by a gyratory compactor and the compaction effort in mix design is tied

to expected traffic.

Superpave Criteria for the Mixture Design

a. Superpave Mix Design General Guidelines

For all projects containing the Special Provision for Superpave Bituminous Mixtures, the

Contractor will supply the Superpave Mix Design to the PWD .The Superpave Mix Design

must be prepared by a private testing laboratory, either the Contractoror consultant.

Superpave Mix Designs must be prepared in accordance with the SUPERPAVE.

3. Superpave Procedure

The Superpave mix design method consists of 7 basic steps:

1. Aggregate selection.

2. Asphalt binder selection.

3. Sample preparation (including compaction).

4. Performance Tests.

5. Density and voids calculations.

6. Optimum asphalt binder content selection.

7. Moisture susceptibility evaluation.

The PWD will only accept one passing design per course, per project. The maximum number

ofdesigns per course, per project, that any one Contractor or Consultant laboratory may

submit istwo.

D. HMA Plant

Hot mix asphalt is used primarily as paving material and consists of a mixture of aggregate

and liquid asphalt cement, which are heated and mixed in measured quantities. Hot mix

asphalt facilities can be broadly classified as either drum mix plants or batch mix plants,

according to the process by which the raw materials are mixed. In a batch mix plant, the

aggregate is dried first, then transferred to a mixer where it is mixed with the liquid asphalt.

In a drum mix plant, a rotary dryer serves to dry the aggregate and mix it with the liquid

asphalt cement. After mixing, the HMA generally is transferred to a storage bin or silo,

where it is stored temporarily. From the silo, the HMA is emptied into haul trucks, which

transport the material to the job site. Figure 1 presents a diagram of a typical batch mix

HMA plant; a typical drum mix HMA plant is depicted in Figure 2.

Material Sampling Frequency and Testing

Refer to appendix for frequency and testing of material samples

E. Testing

Aggregate Tests:

1. Gradation Test

2. Sieve

3. Coarse Aggregate Specific Gravity

4. Coarse Aggregate Angularity

5. Sand Equivalent

6. Flat and Elongated Particles

7. Los Angeles Abrasion

8. Fine Aggregate Angularity

9. Fine Aggregate Specific Gravity

10. Triaxial Test

Aggregate Gradation:. 1

There are several aggregate properties that are important but routine testing during

construction is usually limited to gradation only. Visual inspections must be made to ensure

the aggregate being produced is similar to the aggregate tested during development of the mix

design. For QC/QA testing, aggregate samples are typically taken from the stockpile , cold

feeder belt , hot bins , and extracted asphalt mixture. The gradation of the aggregate from the

asphalt mixture is most important since this is the end product ; however, the aggregate

gradation must be controlled at the other points to ensure that the gradation of the final

product is satisfactory.

The stockpile should be sampled and tested during the mix design process and approve for

use. Once production begins, it is only necessary to sample new material that is added to

stockpile since the overall stockpile gradation has already been determined. The new material

added to the stockpile must have the same gradation as the original stockpile, within

reasonable tolerance , otherwise the gradation of the final mixture is affected. Causes in

gradation variations at the stockpile include changes at sources , segregation during or

stockpiling , and sampling and testing errors.

2. Asphalt Content:

Another mixture property that must be evaluated is asphalt content. The asphalt content of a

mixture is a very important to ensure satisfactory performance. A mixture with low asphalt

content is not durable, and one with high asphalt content is not stable and can lead to rutting.

The actual asphalt content directly affects mixture properties such as asphalt film thickness,

voids, stability, and marshal flow. Therefore, it is important to monitor asphalt cement, but it

is really these mixture properties that need to be controlled.

ASTM D 70 Test Method for Specific Gravity and

Density of Semi-Solid Materials

ASTM C 117 Test Method for Materials Finer than 75 μm

(No. 200) Sieve in Mineral Aggregates by

Washing

ASTM C 136 Sieve or Screen Analysis of Fine and Coarse

Aggregate

ASTM C 566 Total Moisture Content of Aggregate by

Drying

ASTM D 75 Sampling Aggregates

ASTM D 1559 Resistance to Plastic Flow of Bituminous

Mixtures Using Marshall Apparatus

ASTM D 2041 Theoretical Maximum Specific Gravity and

Density of Bituminous Paving Mixtures

ASTM D 2172 Quantitative Extraction of Bitumen from

Bituminous Paving Mixtures

ASTM D 2726 Bulk Specific Gravity of Compacted

Bituminous Mixtures using Saturated Surface

Dry Specimens

ASTM D 3203 Percent Air Voids in Compacted Dense and

Open Bituminous Paving Mixtures

ASTM D 2950 Density of Bituminous Concrete in Place by

Nuclear Method

ASTM D 4125 Asphalt Content of Bituminous Mixtures by

Nuclear Method

ASTM C 127 Standard Test Method for Specific Gravity

and Absorption of Coarse Aggregate

ASTM C 128 Standard Test Method for Specific Gravity

and Absorption of Fine Aggregate

IDOT Ignition Method for Determining Asphalt

Content

F. Mix Production

The quality of hot mix asphalt (HMA) is directly related to the quality of the input aggregates

and thecontrol of the production process. . Many factors such as aggregate gradation and

moisture level affect thequality of hot mix asphalt. As state agencies dictate certain standards

on quality of the product, somequality assurance techniques have been used in HMA plants.

One of the important and basic luxuries to know the quality of HMA production is that an

adequate supply of suitable materials be available in previously and during mixing operation.

These control policies work according to the moving average of the sieve gradations. As

variability inthe inputs can cause natural spikes in the gradation, detection of a sudden and

temporary shift may not bethe best option. By using moving average the persistent shifts in

the process can be detected easily.

G. Laydown

The mix will be laid on the prepared base in accordance with the specifications using the

following equipment:

Should any adverse mix characteristics be observed, the laydown superintendent will notify

the QC Officer to review the manufacture of the mix and make adjustments if necessary to

correct the situation. No changes to the mix shall be made without concurrence by the

Division of Aeronautics.

Placement of hot mix asphalt is a two-part process. The first portion of placement is laydown,

accomplished using an asphalt paver. An asphalt paver has two major components - the

tractor and the screed. The tractor is the prime mover that is used for self-propulsion of the

asphalt equipment. The screed is the working tool, the equipment that spreads the HMA into

asphalt pavement.

The operator must judge three factors when determining paving speed:

First, the operator must see how much hot mix asphalt is being delivered to the asphalt paver.

Second, the operator must look down at the width and thickness of the asphalt pavement

panel being laid.

Third, the operator must check behind the asphalt paver to see if the compactor train is able

to keep up with the paver.

This balance between production and placement needs to be maintained throughout asphalt

paving. If the delivery of asphalt mix to the paver is interrupted, the asphalt paver needs to

stop. Current practice is to rapidly stop and start the paver so the screed level does not

fluctuate because of asphalt paving speed or head-of-material in front of the screed. If the

paver outruns the compactor train, the entire asphalt paving operation is at risk of failing to

achieve target density and/or asphalt pavement smoothness.

References:

Roberts, F. L., P. S. Kandhal, et al. (1996). "Hot mix asphalt materials, mixture design and

construction".

Whitoeak, D. (1991). "The Shell Asphalt Hand Book." Shell Asphalt--Surrey, UK: 332.

Miller, J. S. and W. Y. Bellinger (2003). Distress identification manual for the long-term

pavement performance program.

Mubaraki, M. (2010).Predicting deterioration for the Saudi Arabia Urban Road Network,

University of Nottingham.

Roberts, F. L., P. S. Kandhal, et al. (1996). "Hot mix asphalt materials, mixture design and

construction."

Brown, E. R., Kandhal, P. S., & Zhang, J. (2001).Performance testing for hot mix

asphalt. National Center for Asphalt Technology Report, (01-05).

Little, D. N., Epps, J. A., &Sebaaly, P. E. (2001). The benefits of hydrated lime in hot mix

asphalt. National Lime Association.

Mubaraki, M. (2010).Predicting deterioration for the Saudi Arabia Urban Road Network,

University of Nottingham.

Roberts, F. L., P. S. Kandhal, et al. (1996). "Hot mix asphalt materials, mixture design and

construction."