Bitumen rubber chip and spray seals in South Africa

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:Bitumen rubber chip and spray seals have been used successfully in South Africa since 1982 and mostly on road rehabilitation projects. The main advantage of bitumen rubber seals extra over a standard binder is its superior waterproofing as well as its ability to prevent reflective cracks breaking through the newly placed chip seals or asphalt overlays and its longevity. The higher spray rates together with the better rheological properties of bitumen rubber modified binders provide the following additional benefits. •Widening of working temperature range (Fraass freezing point up to softening point). •Reducing temperature sensitivity. •Longevity due to anti-oxidants in tyre buffings. •Better adhesion. •Stress absorbing qualities. •Better Average Least Dimension (ALD) aggregate stands because of high B-R stiffness. •Lesser stone embedment because of higher softening point. •Resistance to binder absorption. •Lesser pre-treatments. •Superior elasticity and fatigue. The aim of this paper is to present the South African design and construction procedures which have had widespread success. This paper describes the latest design methods as well as construction procedures of bitumen rubber chip and spray seals. Case studies are presented to describe the performance history. It is concluded that bitumen rubber chip seals are a viable and successful option on especially badly deteriorated roads where normal binders are ineffective.