PHASE EVOLUTION DURING AUTOCLAVING PROCESS OF AERATED CONCRETE

The reactions were investigated that occur when lime, cement, and quartz sand are mixed together and molded, then treated at 180-degrees-C under saturated steam pressures to produce autoclaved aerated concrete. The hydrothermal treatment of mixtures gives Ca-rich C-S-H with varying Ca/Si ratios as an initial product, which reacts further with silica dissolved from quartz to form 1.1-nm tobermorite with increase of curing time. During autoclaving, the composition of C-S-H and tobermorite as a binder continues to change until after 8 h, when the Ca/(Al + Si) ratio becomes constant at 0.8. As the reaction proceeds, the number of micropores increases, and the strength also increases due to the binder effect of the tobermorite. However, the total pore volume does not change, remaining constant values.