The Use of Sasol Ash in Bitumen Emulsion Treated Road Base Layers

摘要

The CSIR's Division of Roads and Transport Technology was commissioned by Sasol Chemical Industries to undertake a study on the use of ash from their coal gasification plant in Sasolburg, South Africa. If an effective method of using the ash in roads could be developed, the demand on natural aggregate reserves for road construction could be reduced, as could the environmental impacts of stockpiling the ash. One technology currently being actively pursued in South Africa is the use of emulsion treated bases (ETBs), since the addition of small quantities of a bitumen emulsion and cement improves the strength, durability and water susceptibility of materials, while preventing the shrinkage cracks that are typical of cement stabilized layers.rnDetailed laboratory testing was undertaken to determine the possibility of treating Sasol ash with a bitumen emulsion. Testing was undertaken to determine the optimum emulsion and cement contents, based on the results of California Bearing Ratio (CBR) and unconfined compressive strength (UCS) tests. It was found that the addition of emulsion lowered the CBR of the material, while the addition of emulsion and cement, at volumetric ratios comparable to those used in natural gravel, resulted in significant strength gains and improved resistance to permanent deformation.rnA trial section, with a 100 mm ash base treated with 2.5 per cent emulsion and 1 per cent cement, was constructed using labour-based methods and is currently being subjected to accelerated pavement testing under the Heavy Vehicle Simulator (HVS), developed by the CSIR, as part of a study undertaken by the Gauteng Department of Transport and Public Works (Gautrans).