The use of Silcrete and Other Marginal Materials for Road Surfacing

Abstract

The scarcity of good quality stone, which could be used as road surfacing aggregate in some parts of Botswana, dictated the use of stones, which marginally meet the conventional specifi cations. This Guideline on the use of Silcrete and other marginal materials for road surfacing is a very useful document in that it captures the experiences gained, over a period of twenty years, towards utilizing marginal/inferior materials available in Botswana when constructing road surface treatments. Experience has shown that under appropriate circumstances the use of marginal stones in surface treatments has produced durable and cost effective seals, which performed adequately under traffi c and the harsh, semi arid climate that prevails in Botswana. The Guideline makes the experiences gained over the years readily available for consideration and will act as a practical reference for engineers and technicians involved in the road building industry in Botswana. The guideline deals specifi cally with the properties, applications and performance of marginal aggregates in surface treatments. It is my sincere hope that this guideline will be useful to the road building industry in Botswana and will assist in ensuring that, under appropriate circumstances, marginal materials will fi nd their optimal use in road surfacing without necessarily compromising on quality and performance of the surface treatment as well as assist practicing engineers in judicious selection of marginal aggregates towards their appropriate use in the construction and maintenance of surface treatments in the most cost – effective manner.