ABSTRACT
The characteristic of silica fume that is most important in making goodquality DSP materials is the absence of particle aggregates. To avoid or minimize the presence of such aggregates, only silica fume products that have not been mechanically compacted may be used (Aldridge et al, 1992). Microsilica slurries must also be excluded, as the quantity of water contained in them would exceed the total quantity required for making the DSP mix. Best results have been reported with silica fume coming from the zirconia industry, as it has the lowest tendency to aggregation, and is free from impurities (Richard and Cheyrezy, 1995). The particle size and specific surface area of the silica fume are secondary factors, and products with specific surface areas ranging between 10 m /g and 20 m /g may be considered acceptable. The most injurious impurities that may be present in silica fume products are residual carbon and alkalis (de Larrard, 1989).
