文摘
A coarse mineral with 70 % kaolinite and 30 % quartz was calcined and chemically activated by alkaline solutions of Na2SiO3 and NaOH. The compressive strength evolution was investigated as a function of the curing temperature at 20 and 80 ¡ãC, and the molar ratios of SiO2/Al2O3 (2.64?.04) and Na2O/Al2O3 (0.62?.54). For curing at 20 ¡ãC, the best composition was SiO2/Al2O3 = 2.96 and NaO/Al2O3 = 0.62, reaching 85 MPa at 28 days. Curing at 80 ¡ãC had a positive effect on the strength development only in the first 3 days. X-ray diffraction of the geopolymeric formulations showed the formation of amorphous silicoaluminates of similar nature. The microstructure consisted of unreacted quartz and metakaolinite particles in a matrix of silicoaluminate polymer and condensed silica gel from the unreacted sodium silicate.