Advances in Asphalt Materials

Road and Pavement Construction

Shin-Che Huang, Hervé Di Benedetto

• Publisher: Woodhead Publishing
• Year: 2015
• Print ISBN: 9780081002698
• eBook ISBN: 9780081002711
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

The urgent need for infrastructure rehabilitation and maintenance has led to a rise in the levels of research into bituminous materials. Breakthroughs in sustainable and environmentally friendly bituminous materials are certain to have a significant impact on national economies and energy sustainability. This book will provide a comprehensive review on recent advances in research and technological developments in bituminous materials.Opening with an introductory chapter on asphalt materials and a section on the perspective of bituminous binder specifications, Part One covers the physiochemical characterisation and analysis of asphalt materials. Part Two reviews the range of distress (damage) mechanisms in asphalt materials, with chapters covering cracking, deformation, fatigue cracking and healing of asphalt mixtures, as well as moisture damage and the multiscale oxidative aging modelling approach for asphalt concrete. The final section of this book investigates alternative asphalt materials. Chapters within this section review such aspects as alternative binders for asphalt pavements such as bio binders and RAP, paving with asphalt emulsions and aggregate grading optimization.- Provides an insight into advances and techniques for bituminous materials- Comprehensively reviews the physicochemical characteristics of bituminous materials- Investigate asphalt materials on the nano-scale, including how RAP/RAS materials can be recycled and how asphalt materials can self-heal and rejuvenator selection

1

A perspective of bituminous binder specifications

M. Southern [email protected] Eurobitume, Brussels, Belgium

Abstract

This chapter covers the concept and content of specifications for petroleum bitumen for use in paving applications. Specifications are required so that producers and users of bituminous binders can agree on the functional properties of the binder at the point of sale. The chapter covers characteristics, properties, test methods, and values in the context of specifications. It also provides a background to the regulatory frameworks used to develop specifications in Europe and the United States. An overview of the main elements of binder specifications in current use is provided.

Keywords

Specifications

Performance

Characteristic

Property

Test method

CEN

ASTM

AASHTO

Acknowledgments

I would like to thank Eurobitume for providing me with support in my work on this chapter. I would specifically like to thank the Technical Committee of Eurobitume for their help and assistance in providing information and for taking the time to review and comment on the chapter in its draft form.

1.1 Scope and terminology

This chapter will cover the concept and content of specifications for petroleum bitumen produced by the refining of crude oil. Although bitumen-like deposits occur naturally in natural asphalt, rock asphalt, lake asphalt, and oil sands, and such materials may be used in similar applications as refined bitumen, they are not considered within the scope of this chapter.

Bitumen is known by different names throughout the world. In most European countries, the term “bitumen,” or “refined bitumen,” is used predominantly and is synonymous with the term “asphalt,” or “asphalt cement,” used in the United States. Outside the United States, the term “asphalt” is often used to describe a mixture of bitumen with aggregate, sand, and filler. In this chapter, the term “bitumen,” or “bituminous binder,” will be used to refer to the liquid product.

Different types of binders exist, including paving-grade bitumens, polymer-modified binders, hard paving-grade binders, and multigrade binders, and these are used for numerous different applications. The predominant focus of the chapter will be specifications for binders for asphalt pavements, but it is recognized that in many regions there are large numbers of pavements that are either unbound, or paved using thin surfacings, or some form of surface treatment. The same principles of specifications apply to these products and processes, but the specific end use is not considered in detail in this chapter.

The chapter will cover the important aspects of specifications and test methods, what makes a good specification, and considerations for development of new specifications. It is not the intention to provide detailed listings of individual product specifications, although the concepts of different specifications will be discussed.

1.2 Introduction

Bitumen is an engineering material, and is produced to meet a variety of specifications in which the properties are defined based on physical properties. It is the residual product from the distillation of crude oil in petroleum refining. It is a viscoelastic waterproofing and construction material. It behaves like a Newtonian liquid at high temperatures (> 100 °C), exhibits relatively complex rheological behavior at intermediate temperatures, and is an elastic solid at low temperatures (< 0 °C). The main characteristics of bitumen that make it suitable as a binder for asphalt are that it is adhesive, waterproof, thermoplastic, durable, inexpensive, modifiable, and recyclable.

1.3 What is a specification?

A specification can be considered to be a detailed description of a given material, enabling parties on either side of a commercial transaction to understand what can be expected in performance terms at the point of transfer of ownership. In the context of bituminous binder specifications, the specification should address properties that are relevant to the end use for construction products in which they are used.

1.3.1 Characteristics, properties, test methods, and values

The starting point for development of a bituminous binder specification is the identification of the characteristics required for performance. The binder imbues certain characteristics important to the performance of the asphalt. For this reason, it is important that the role played by the binder in the asphalt mixture is understood so that a binder specification focuses on the relevant characteristics of the binder.

For asphalt mixtures, pertinent characteristics might include

• Mechanical properties and stability

• Durability

• Safety in use

Additional properties are often included in a specification relating to specific characteristics that might not be directly relevant to performance, but that provide important practical information relating to handling and application.

After the important characteristics of the end product have been defined, the properties of the binder that relate to these characteristics can be considered for inclusion in the specification. Once the properties have been defined, the properties can be measured using a defined test method under identified test conditions, which will then provide specific values that can be introduced to a product specification.

The importance of the above process is to define a range of values, tested under specified conditions so that important properties of the binder can be compared by different laboratories. For this reason, standardized test methods are required for use within specifications.

The above concepts can be illustrated as follows.

Stiffness of an asphalt mixture is an important property that relates to the load-bearing capability of the road pavement. The binder plays a role in providing stiffness to the mixture, and this is evident from the fact that a stiffer binder provides a stiffer asphalt mixture. Therefore, binder stiffness is a characteristic that is important to define within a specification. A binder property that relates to the stiffness might be the needle penetration value or the complex shear modulus G*. Therefore, a specification that considers binder stiffness important should include a measurement relating to this property. Having identified the property, the next step is to identify a test method that measures the property; this might be carried out using a needle penetrometer, or a dynamic shear rheometer (DSR). Bitumen stiffness is highly temperature and loading-time dependent; therefore, the test method must include the conditions under which the property should be measured. These would include details of the test equipment geometry, test conditions, and temperature.

Having identified the property and test method to be used to measure a characteristic, it is necessary to include in the specification a value or range of values that are required in order for the binder to be considered fit for purpose.

A good specification will measure important properties of the binder that are relevant to the performance of the product in which it is being used. Furthermore, the properties will be measured using test methods that are relevant to the property, provide a reasonable precision of measurement, and establish appropriate limits for the measured property.

1.3.2 Attributes of a good specification

A well-written specification should be able to differentiate between a binder that will be suitable for purpose and one that will not, although it must be recognized that the binder is not the sole determinant of end-product performance.

Most binder specification systems evaluate the properties of binders to consider the predominant failure modes of the pavement, such as elevated service-temperature properties (to address permanent deformation), low service-temperature properties (to address low-temperature cracking), and intermediate service-temperature properties (to address pavement stiffness under “normal” service conditions, or to evaluate fatigue behavior on an aged binder).

Road pavements have a long life cycle; therefore, durability is important. Depending on the failure property under evaluation, the binder might be subjected to some form of aging/conditioning step prior to establishing the property of interest. In addition, a specification might include nonperformance-related requirements, such as information that is important for safety, handling, storage, or application of the material, such as viscosity, solubility, or storage stability.

1.3.3 Geographical considerations

Road pavements must be able to withstand geographic, seasonal, and diurnal (day–night) variations in temperature, which may be quite extreme. In some countries, such variations might exceed 70 °C, and range from extreme periods of heat or cold to frequent heavy precipitation. Many specifications are designed to cover the range of climatic conditions that can be reasonably anticipated during the service life of the pavement. In some regions, specifications are “imported” from other areas, or countries. In such cases, it is essential to consider whether the criteria used in the development of the original specifications remain valid for the new region in which the specification is to be used.

Bituminous binders are used to build road pavements, which are engineering structures; therefore, the engineering properties used within specifications must be appropriate for the climatic and traffic conditions that the pavement will experience during its lifetime. For any sizable geographic region, it is unlikely that a single grade of bitumen will be suitable for the range of conditions likely to be encountered over the lifetime of a pavement. To that end, many specifications list not only a range of properties to be measured, but also a series of grades of bitumen that may be selected for the appropriate performance required.

Specifications can be national, regional, or local, depending on the contract in which they are being used. Generally, t...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of contributors
• Woodhead Publishing Series in Civil and Structural Engineering
• Preface
• Introduction
• 1: A perspective of bituminous binder specifications
• Part One: Characterization and analysis of asphalt materials
• Part Two: Damage mechanisms
• Part Three: Alternative asphalt materials
• Index