The mean compressive strengths obtained from the cylinder samples of GPN, GPH and OPC concrete before and after exposure to fires at different temperatures are given in Table 3. The percent- age residual strengths for each temperature exposure are also given in the table. It can be seen from the table that the normal strength geopolymer concrete It can be seen from Table 3 that all three types of concrete lost strength rapidly after 400 oC exposure. The normal strength geo- polymer concrete displayed higher residual strength than the other two types of concrete up to 650 oC exposure. At this temperature range, the normal strength geopolymer concrete samples yielded a mean residual compressive strength of 83%. The high strength geopolymer concrete and OPC concrete showed average residual strengths of 59% and 51% respectively. Thus, the normal strengthgeopolymer concrete retained higher percentage of strength than the high strength geopolymer concrete and OPC concrete after
650 oC exposure. This is because of additional reaction of the binder in the normal strength geopolymer concrete specimens by the heat of fire since they were initially cured at a lower tempera- ture than the high strength geopolymer concrete specimens.