Effect of the kaolin particle size on the pozzolanic behaviour of the metakaolinite produced

This paper reports an investigation of the effect of the particle size of kaolin on its transformation to metakaolinite. Kaolin from the island of Milos was either crushed or ground in order to produce four samples with different degrees of fineness (residue at 500 mu m: 0-71.8%). The samples were treated thermally under different conditions in order to determine the optimum treatment conditions. The conversion of kaolinite to metakaolinite and the structural changes in the material during treatment were investigated by means of TG and XRD, respectively. Each sample was incorporated into a type I cement, at 20% by mass of cement, and the compressive strengths of the resulting blended cements were measured. It is concluded that the particle size of the raw kaolin does not affect the thermal conversion or the pozzolanic activity of the material. The use of crushed kaolin has many benefits since the furnace load can be increased, while the grinding process is needed only to reduce the size of the metakaolinite particles.