At 1000 oC, the residual strengths were very low for all the tested mixtures. The GPH, GPN and OPC concrete samples retained average residual compressive strengths of 18%, 16% and 11% respectively. The severe strength loss of the specimens at this tem- perature occurred mainly because of the extensive cracking of the specimens. Furthermore, there was spalling of substrates in the OPC concrete specimens. The OPC concrete specimens suffered disintegration because of the greater loss of bonding between the binder and 3.5. Mass loss and microstructure of geopolymer concrete after exposure to fire