This report describes the effects of the presence of mica in china clay sand on its physical properties as a roadmaking material. It shows that the addition of coarse mica to a sand reduces the density achieved for a given state of compaction, but that this effect is as much due to the resultant change in grading as to the resilience of the mica. Other effects are considered, including that of fine mica on frost susceptibility. The results are also compared with others from earlier work using a silty-clay thus bringing the known effects of mica together in a single report. Work on measuring the mica content showed that the inclined vibrating table used previously failed to separate the mica in the china clay sands but that a modified density-column separator could be used as an alternative to the dielectric separator. Conclusions from the study confirm that the quantity of mica normally present in the china clay sands is not deleterious and suggests that many problems attributed in the past to mica are quite likely to have resulted from other causes, such as the overall particle-size distribution. (Author/publisher)
Abstract