MICA IN CONCRETE

The fine and coarse aggregates produced from the rocks available within these scarps contains an abundant amount of mica. The pit-run sand which is formed from mechanical and chemical disintegration of the parent rocks available within these scarps are equally contaminated with mica.

Depending upon some geological formation, the mica content [biotite, muscovite] of Udzungwa scarp aggregates is invariably high. In this paper, the effect of mica on compressive strength and on the water demand of the concrete made using fine aggregates from these scarps is presented. From the laboratory test results, it was established that the presence of mica in fine aggregates causes a reduction of the compressive strength in the range of 8-23% while the water demand of the concrete was found to increase in the range of 8-16% [17-33 l/m3].