[Laboratory Test For Rutting And Stripping Of Hot-Mix Asphalt Concrete]

by

ACKNOWLEDGEMENT

I would take this opportunity to thank my research supervisor, family and friends for their support and guidance without which this research would not have been possible.

DECLARATION

I, [type your full first names and surname here], declare that the contents of this dissertation/thesis represent my own unaided work, and that the dissertation/thesis has not previously been submitted for academic examination towards any qualification. Furthermore, it represents my own opinions and not necessarily those of the University.

Signed __________________ Date _________________

TABLE OF CONTENT

ACKNOWLEDGEMENTii

DECLARATIONiii

CHAPTER 1: INTRODUCTION5

Background of the study5

Objectives of the Research Project/ Tasks8

Task 1: Validate a new ERSA unit.8

Optimum binder %9

Binder Grade9

Task 2: Finalize Stripping Criteria for ACHM mixture design.10

Optimum binder %10

Binder Grade10

CHAPTER 2: LITERATURE REVIEW11

Rutting12

Causes of Rutting15

Accelerated Pavement Testers18

Creep Tests21

Triaxial Testing22

Stripping25

Types of Stripping28

Factors responsible for Stripping35

Corrective Treatment for Stripping40

Laboratory Wheel Tracking Devices41

Concrete45

CHAPTER 3: EXPERIMENTAL DESIGN52

REFERENCES55

CHAPTER 1: INTRODUCTION

Most surfaced roads are made of flexible pavement which requires a huge investment in terms of installation and maintenance. One of the most serious problems is stripping, which is the loss of adhesion between asphalt coating and aggregate in the bituminous mixture, caused by the existence of moisture. Stripping might result in different types of distress such as creep, raveling, rutting, shoving, cracking and low stability. Hot mix asphalt (HMA) environmental damage (stripping) is a material compatibility problem (Shahin, 1994).

If the materials are compatible, they will form strong and long-term bonds, so the HMA will resist stripping. However, if the mix has poor bonding, its resistance to stripping will be lower. In this case, the bonds should be enhanced or the material combinations should be adjusted to achieve satisfactory performance. Stripping is one of the most difficult conditions to identify because it can take numerous forms and it is influenced by different variables, some of which are related to the materials forming the HMA (i.e. aggregate, asphalt cement and anti-stripping agents). Other variables are connected to the weather conditioning, compaction, air voids, testing method, handling and storage of additives. Moreover, stripping is a rate process based on the viscosity/temperature dependency of bituminous binders. Also, stripping occurs as a function of the surface tension between aggregate and bitumen.

Background of the study

Damage to highways mostly takes place in the top layer of the road pavement at the binder and erosion layers as opposed to the foundation and lower layers. Damage to the binder and abrasion layers generally comprises surface cracks, deformations, wheel ruts and potholes. Changes in temperature are the main cause of the damage to highway pavements and gaining greater knowledge of the impact of increasing or decreasing temperature is very important to the achievement of asphalt concrete stability. This stability determines the performance of the highway pavement. Low stability in asphalt concrete may lead to various types of distress in asphalt pavements. The stability of asphalt concrete pavements depends on the stiffness of the mix, bitumen content, the softening point of the bitumen, viscosity of bitumen, grading of aggregate, construction practice, traffic and climate ...