Modifiers have been used to improve the performance of asphalt/aggregate mixtures for building roads for over the past hundred years and during that time the industry has evolved into a sophisticated sector that is heavily regulated by national and European standards.

The modifiers used take many different forms: polymers, latex, and many chemical additives. Determining how modifiers actually affect the performance of a mixture and establishing construction quality control procedures for these modifiers can be extremely difficult. In the past these difficulties have caused many specifying agencies to avoid the use of mixture modifiers when they could be of benefit to the performance of the road.

This review explores the type of polymers used in asphalt, why they are used, where they are used in terms of applications and the benefits they offer to industry and the road user. In particular, the reader will understand how polymers can be used to enhance the functionality of asphalt, that is to overcome deterioration mechanisms by enhancing asphalt stiffness or flexibility, or by making it more resistant to deformation (rutting) caused by traffic.

This review of polymers in asphalt is supported by an indexed section containing several hundred key references and abstracts selected from the Polymer Library. It is aimed at anyone who has an interest in polymers and their highway applications.

About the author...
Howard Robinson has been actively involved with company and industry level research and development for about 20 years. He has been employed for most of that time by Tarmac and is currently Head of Product Development for the Tarmac Group based in Wolverhampton. He has published more than 25 papers and presented at many national and international conferences. Howard was appointed Visiting Professor at Liverpool John Moores University, School of The Built Environment in 2001 and is chairman of the annual LJMU conference that addresses recycling and sustainability issues affecting the aggregates and asphalt industries.

CONTENTS

1 Introduction

2 The Asphalt Industry
2.1 Industry Overview
2.2 Recent Market Trends
2.2.1 Growth in Traffic
2.2.2 Trends in Market Demand for Asphalt and Bitumen
2.2.3 Surface Maintenance Treatments
2.3 Regulations
2.3.1 Background
2.3.2 New Product Approvals Scheme
2.4 Distinct Technologies
2.4.1 Background
2.4.2 Asphalt Material Description
2.4.3 Typical Asphalt Road Structure
2.4.4 Asphalt Production and Laying
2.4.5 Analytical Pavement Design
2.5 Environment/Sustainability Issues
2.5.1 Legislative Drivers
2.5.2 Availability of Secondary Aggregates
2.5.3 Sustainability Issues Affecting Asphalt

3 Key Bitumen Properties
3.1 Background
3.2 Bitumen Characteristics
3.2.1 Background
3.2.2 Bitumen Chemistry
3.2.3 Bitumen Ageing
3.3 Standard Bitumen Specification Tests
3.4 Polymer-Modified Binders
3.4.1 Background
3.4.2 Reducing Permanent Deformation (Rutting)
3.4.3 Improving Asphalt Cohesive Strength
3.4.4 Reduced Temperature Susceptibility (Thermal Cracking)
3.4.5 Modifying Bitumen Rheology

4 Key Asphalt Properties
4.1 Temperature Susceptibility
4.2 Factors Influencing Asphalt Stiffness
4.3 Standards for Asphalt Mixtures and Flexible Pavement Design
4.4 Measuring Mechanical Properties
4.4.1 Elastic Stiffness
4.4.2 Deformation Resistance
4.4.3 Fatigue Cracking
4.4.4 Adhesion between Aggregates and Binders

5 Polymers Used in Asphalt
5.1 Overview
5.2 Different Polymer Types
5.2.1 Elastomers
5.2.2 Plastomers
5.2.3 Natural Rubber

6 Polymer-Modified Asphalt Applications
8.1 The Construction Products Directive (CPD)
8.2 European Product Standards
8.3 European Technical Approvals

7 Polymer Used as Aggregate

8 Legislation

Acknowledgements
Abbreviations and Acronyms
References
Further Reading from the Rapra Abstracts Database
Subject Index
Company Index