English Language Unit
Pre-sessional 2011
The development and application of the modified asphalt
Written Project
by
Zuxun Zhang
31st August 2011
Contexts
Declaration. 3
The development and application of the modified asphalt 4
Introduction. 4
Theoretical background. 4
Development 6
Conclusion. 7
Reference. 8
Declaration
The work contained in this project is my own and has not been submitted for any other qualification.
All sentences and passages quoted from published sources have been specifically acknowledged by referencing to author, work and page(s).
Name: Zuxun Zhang
Signature:
Date: 31st August 2011
The development and application of the modified asphalt
Asphalt is one of the most important road engineering materials all over the world. Asphalt always appears in different kinds of road construction sites. As well as this, as a new kind of asphalt, modified asphalt play a more and more significant role in field of engineering. Asphalt modification using additives dates back to the last century_(King et al.1999). [1] Patents for using polymers to modify asphalts date back to 1823_ (Isacsson and Lu 1998). By 1982 more than 1000 technical articles had been published on polymer modified asphalts or mixtures(Zeneke,1985) and there is a great emphasis continuing on this subject (Isacson and Lu 1998). There are two main reasons why people modify asphalt. At first, asphalt is a kind of sensitive material. Its performance and status will change a lot as soon as the environment changes. This is a serious disadvantage for the use of asphalt. At second, because of the needs of traffic, especially for some high-level roads, they have a common feature which is a busy traffic situation. Because asphalt already cannot fit for the modern road’s conditions, so modified asphalt with high-quality will play a more and more important role in the future. This project expounds the definition, advantages and different kinds of modified asphalt. It also gives an analysis of the modification mechanism, basic process and key technology of modified asphalt. The existing problems of modified asphalt are some contexts are discussed and an application of modified asphalt is proposed.
At first, asphalt is a most useful kind of polymer hydrocarbons and at the same time is a kind of organic cementing materials. Also asphalt is been called Bitumen, that is a sticky, black and highly viscous liquid. People can refine it from most crude petroleum and some natural deposits. It is also been called asphaltum as a term until the 20th century. The primary use of asphalt is in some road constructions, for example the main raw material of asphalt concrete is asphalt which is used as the glue or binder mixed with aggregate particles. Modification of asphalts is prompted mainly by the limitation of the conventional refining practices used today in production of asphalts from crude petroleum. Therefore, in planning refining strategies, production of better performing asphalts is not one of the common one. As soon as the produced asphalt cannot fit for the climate, traffic and pavement structure requirements, modification has been used as one of the attractive alternatives to improve asphalt properties. [2] According to the relative information, asphalt, however, it is a real short time after its debut in the UK around the early 1900s. Edgar Purnell Hooley obtained the first British patent for Tar Macadam in 1902(a.1) and the following year developed to the Tar Macadam Syndicate Ltd., in Denby, Denbyshire. It was, however, several years later before it became widely used, aligned with the growth in traffic volumes. Before the 1960s, asphalt was just been used in the construction of civil road and special road. The asphalt material mainly consisted in coal tar pitch and petroleum asphalt which was took from raw oil. A critical need for improving asphalt performance has been the growth in traffic using Great Britain roads over the past decade. During the decade from 1992-2002, the figure of road traffic grew on about 18%. The more serious situation of traffic is, the serious situation of a road is. As a result more and more roads must require high-level maintenance or rebuilt. Using polymer-modified binders in asphalt is the best strategy to resolve this serious problem. These materials deliver high levels of traffic noise reduction whilst retaining high surface texture under heavy traffic loading for maintained skidding resistance. They also offer less disruption to the road user during installation, and when specified as an asphalt overlay there is less need to adjust kerb levels. [3] Due to this, modified asphalt became a more and more popular issue in the field of engineering.
As early as 1973, Samue White had already applied for a patent for mixing 1% natural rubber into asphalt for improved performance. So, the concept of asphalt modification is not a new one. However, this patent was not put in practice from beginning to end by him. In 1902, the French built a road using modified asphalt. From then on, every engineer all over the world tried to improve the quality by mixing the additive. Asphalt modification is also a relatively new technology, and was first invented by Richard Phil Singer Group from Austria. As well as this, during the recent 15 years, it achieved evident improvement and developed gradually. This technology was already widely applied and received good evaluations in many developed countries such as in some European countries and the United States. In addition, in recent years, it was used by some countries in Asia like Saudi, Singapore and Malaysia. Especially, in recent years, research and manufacture and applications to asphalt modifications reached a peak-level. At present, there are mainly four kinds of modifier in the world:
(1) Modification of rubber: natural rubber, synthetic rubber. Such as NR, SBR, CR, BR, EPDM etc;
(2) Thermoplastic elastomer: different kinds of segmented copolymer. Such as SBS, SIS;
(3) Resene: PE, PVC, EVA, thermoset resin;
(4) Minerals class (such as sulfur carbon black asbestos fibres, etc.)
There are also two types of asphalt modification in road engineering at present. The first kind is putting modifier, mineral aggregate and asphalt mixture directly into asphalt mixing equipment._(the modifier is SBR latex, solid powder, SBS powder). The other kind of that is mixing modifier and asphalt in advance. Also there exist many shortcomings about asphalt modification now. For example there is little large-scale systematic engineering like the SHRP (in the USA) around the world. This means there is much more randomness of researches. As a result, this causes waste to a certain extent. Generally it is considered that the modified asphalt pavement has a longer lifespan about 1/4-1/3 of the whole life more than general roads’ in some developed countries. And also some countries think the figure is 50 %_( in Australia). Due to this, there exists a large economic advantage. At the same time, research shows that SBS modification has two-way modification effects. This means there is a evident improvement of the mixture performance as doing success in SBS modification. As newest researches, there are two kinds of modifier: Duroflex_(in German) and P R PLAST.S_(in France) which can improve modulus of elasticity of modified asphalt dramatically. [4] In the near future, there is a strong need to put these two kinds of researches into practice.
Issues about modified asphalt are widespread in research of modified asphalt, and on some engineering constructions problems, and on the innovations about modified asphalt. This article has only touched on some special issues about the history and application and development about modified asphalt. To sum up, after the development in such a long time, modified asphalt has became one of the most important and popular engineering materials. The research and applications are becoming more and more efficient and practical. Now modified asphalt can be used in many fields of engineering instead of just in the field of road engineering construction in the past. Continuing reducing the cost of research and applications and achieving the better performance are basis of the research of asphalt modification. Knowing about the newest information, studying experience from other countries, sharing the vital information and doing some systematic research cooperation is the most effective way to speed up the modified asphalt research and application.
1. Lee, K. &Wayne, M (2006): Asphalt Mix Design and Construction: Past, Present, and Future State of the Practice: a Special Publication Os the 150th Anniversary of ASCE.ASCE pp.84-85
2. Abraham, H (1938): Asphalts and Allied Substances: Their Occurrence, Modes of Production, Use in the Arts, and Methods of Testing (4th ed.).New York: D. Van Nostrand Co. Retrieved 2009-11-16. Full text at Internet Archive (archive.org)
http://www.archive.org/details/asphaltsandallie031010mbp (Access date 31/08/2011)
3. Robinson, H. L. (2004): Polymers in asphalt. Smithers Rapra pp. 3-29
4. Qingmei Y (2010): Applications of Modified asphalt in road constructions.
http://www.cnki.com.cn/Article/CJFDTotal-QHKJ2010S1078.htm (Access date 31/08/2011)
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