Standard 100 mm x 200 mm cylinders were cast using the OPC and GPC mixtures given in Table 2. Some of the freshly cast cylin- der specimens are shown in Fig. 1. As shown in Fig. 2, a thermocou- ple was inserted at the centre of some cylinders to measure the temperature at that point during heating of the cylinders inside the furnace. The OPC concrete specimens were cured in water and the geopolymer concrete specimens were heat-cured by using steam. The geopolymer concrete cylinders were divided into two groups and subjected to two different curing regimes. The speci- mens of the first group were subjected to steam curing at 60 oC for 24 h immediately after casting. Steam curing of the second group of specimens started three days after casting and the curing was done at 80 oC for 24 h. It was shown by Hardjito and Rangan [29] that strength of geopolymer concrete increased by increasing the curing temperature and applying a rest period of up to three days before the start of the steam curing. Therefore, different curing regimes were used to the geopolymer concrete cylinders to achieve a normal strength and a higher strength after the differ- ent types of steam curing regimes. The cylinders of the first curing regime are designated by GPN and those of the second curing regime are designated as GPH.