Mechanical property evolution during autoclaving process of aerated concrete using slag: II, Fracture toughness and microstructure

The mechanical properties were investigated for autoclaved aerated concrete (AAC) block samples, prepared using blast furnace slag at 180 °C under saturated steam pressures for various times from 1 to 128 h. The mechanical properties of AAC made using slag are comparable to those made without slag. With increased autoclaving time, the compressive strength increases due to the binder effect of the 1.1-nm tobermorite. In contrast, the fracture energy G_F and resistance to crack growth decrease with increase of autoclaving time. This dependency is caused by the formation of voids around unreacted slag particles.