Hydrothermal solidification of kaolinite-quartz-lime mixtures

The strength development of hydrothermally solidified kaolinite-quartz-lime systems with kaolinite as the aluminum source was studied. The starting ma terials were mixed so that the Ca/(Si + Al) atomic ratio was in the range 0 .23 to 0.25, and the Al/(Si + Al) ratio was between 0 to 0.50. Specimens we re formed by uniaxial pressing and hydrothermal treatment under saturated s team pressure at 200 degrees C for 2 to 20 h. For quartz-rich systems with Al/(Si + Al) = 0 and 0.05, strength development by the formation of calcium silicate hydrates, such as CS-H and tobermorite (Ca-5(Si6O18H2).(4H(2)O), was observed. On the other hand, in the case of kaolinite-rich systems with Al/(Si + Al) = 0.24 to 0.50, strength development by the formation of hydr ogarnet (Ca3Al2(SiO4)(OH)(8)) was recognized, resulting in flexural strengt hs between 15 to 20 MPa. It is proposed that strength development is relate d to the formation of mesopores (similar to 0.04 mu m) that accompanied for mation of the hydrogarnet.