Geopolymer was prepared by using potassium silicate as activator solution

metakaolin and fly ash blend as main silicoaluminate materials.The bending and compressive strength before and after exposure to high temperature was tested on geopolymer paste

mortar and concrete specimens

and the results were compared with that of cement paste

mortar and concrete specimens.The trends of test results and phenomena were explained by thermogravity analysis and thermal contraction measurement of geopolymer.The test results show that the bending and compressive strength of geopolymer paste

mortar and concrete decrease with increase of temperatures

but either at ambient temperature or after exposure to high temperature the strength of geopolymer paste

mortar and concrete prepared in this study can almost reach or exceed that of cement paste

mortar and concrete.The incompatibility between thermal contraction of geopolymer and thermal expansion of aggregates induces cracking of geopolymer concrete at elevated temperatures.