The Use of Sasol Ash in Labour-based Road Construction

摘要

The CSIR's Division of Roads and Transport Technology was commissioned to undertake a study on the use of ash from Sasol Chemical Industries' coal gasification process at their Sasolburg plant in South Africa. If the ash could be used as an aggregate in roads, the demand for natural for road construction materials could be reduced and an effective method of using the ash could be developed. If labour-based construction techniques could be used, the use of the ash pavement layers could create employment for the many unemployed in South Africa. This would be in line with the Government's Reconstruction and Development Programme (RDP).rnSasol ash has a significantly lower density than that of conventional road construction materials (approximately 40 per cent less) and this makes it easier to transport and use with labour-based methods. The ash from Sasol's ash blending plant is delivered at the construction site at the optimum moisture content for compaction and all that is required is placement and compaction of the layers.rnIn trial road base sections constructed by labour-based methods, the ash was placed between two shuttering boards and levelled with a screed. This is a technique commonly used for emulsion treated bases (ETBs) constructed with labour-based methods. As the maximum particle size of the ash is 16.0 mm, the screeding operation is simplified as no large exposed aggregates are pulled out during the screeding.rnBoth unstabilized and bitumen emulsion stabilized ash were used in construction of the trial sections. The bitumen emulsion stabilized ash required the emulsion to be mixed in, which complicated the construction process. Mixing of the emulsion stabilized ash was performed in a portable drum mixer.rnQuality control was undertaken using a dynamic cone penetrometer (DCP). Falling weight deflectometer (FWD) testing was performed after construction was completed. Level testing was performed by means of the electronic gravel loss meter developed by the CSIR.rnAlthough no trial sections were constructed with conventional construction techniques, Sasol ash can also be used for conventional construction.