Bitumen rubber asphalt in South Africa and experience in China

Abstract

Paper presented at the 26th Annual Southern African Transport Conference 9 - 12 July 2007 "The challenges of implementing policy?", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT:This paper describes an update and overview of the use of Bitumen-Rubber (BR) in South Africa. The South African experience with the transfer of the Bitumen-Rubber Technology to mainland China is also discussed briefly. The design procedures and construction practices used for the construction of Bitumen-Rubber Asphalt in rehabilitation projects in South Africa are also discussed. Bitumen- Rubber Asphalt / Hot Mix Asphalt (BRHMA) is normally used where the other asphalts have already failed or where the existing base courses are in severe distress. In addition they must also provide additional structural capacity for 10 to 15 years under severe traffic conditions. This paper describes and discusses the following aspects -The constituent materials used in the manufacture of BR binder and the BRHMA. The South African materials specification is furnished and discussed. -The SA asphalt mix design process including the type selection; the volumetric design process and the BRHMA end point specification. -Further developments (rutting, fatigue, energy methods, moisture sensitivity, Dynamic Creep). -BRHMA structural equivalency which is based on the work done by the CSIR on behalf of the California Department of Transport (CALTRANS). -Construction of BRHMA. -Environmental aspects and costs related to this technology. -A South African experience in the introduction of this technology to mainland China. Summary and Conclusions The perception that the cost of BRA is higher than conventional or polymer asphalt fails to take into account the costs related to -The use of reduced thicknesses of BRHMA versus other asphalts as per the CALTRANS / CSIR Projects -Savings in traffic accommodation and bypasses when alternative crusher run designs are used. -The cost implications related to the environmental issue of disposing of scrap tyres.