In-situ recycling of a cement treated base course using foamed bitumen

Abstract

Paper presented at the South African Transport Conference 17 - 20 July 2000 "Action in transport for the new millennium", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT: In-situ recycling of road pavement base materials using one-pass recycling machines is becoming an important pavement rehabilitation procedure for heavily trafficked urban roads. The reasons for this are : • Reduced construction time with a consequent reduction in the amount of disruption to traffic. • Space constraints. • Urban road surfaces generally have level constraints which reduce the number of rehabilitation options which can be employed. • Cost effectiveness. • Improved quality of construction compared with conventional reconstruction techniques. 5th Avenue in Grassy Park, Cape Town is an urban road which carries between 3000 and 4000 vehicles per day in each direction. It was rehabilitated at the beginning of 1999 using the in-situ recycling process. During the recycling process the existing cement treated base was milled up and treated with foamed bitumen and ordinary Portland cement. The recycled material was then compacted and surfaced with a new continuously graded asphalt wearing course. This paper discusses the following aspects pertaining to this project : • The in-situ recycling process. • Achieved production rates. • Properties of the recycled material. • Construction costs. • Performance of the recycled pavement to date. This project showed that in-situ recycling can be done cost effectively and that the process provides a high quality finished product. It is foreseen that this procedure will become more popular in future as the demand for urban road rehabilitation increases and as road maintenance budgets remain under pressure.