Experimental investigation and molecular simulation of the damage process of alkali-activated slag at high temperatures

The damage decay process of alkali-activated slag (AAS) at high temperatures is studied through molecular dynamics simulation and performance testing of AAS at different calcination temperatures. The experimental results show that when the calcination temperature is less than or equal to 400 degrees C, no cracks appear on the surface of the specimen and the compressive strength reaches its maximum. However, when the temperature exceeds 400 degrees C, cracks appear on the surface of the AAS specimen after calcination for 3 h, and the compressive strength of the AAS specimen decreases. The molecular dynamics simulation results show that the potential energy of the sodium aluminosilicate hydrate (NASH) gel structure in AAS decreases initially and then increases as the temperature rises. The intramolecular pressure peaks at 400 degrees C when the intermolecular attraction within the NASH gel structure reaches its maximum and the nano-groups, such as Si and Al, produce high aggregation energy. As the temperature continues to increase, the intermolecular attraction within the NASH gel structure decreases and the cohesion between the nano-groups also weakens.