Characterization of the geopolymers produced from Hiswa clay, Jordan

New low cost green building materials were developed by the geopolymerization process. The new geopolymer products were synthesized by thermal activation of Jordanian Hiswa kaolinite with sodium hydroxide solution. The effect of the main synthesis and processing parameters on the development of compressive strength was studied. Physical, thermal, mineralogical and microstructural properties were investigated. The compressive strength of 41.20MPa was obtained for a geopolymer mixture cured at 80 °C for 24 hours. The petrography results indicated that the geopolymeriztion process has increased the compaction and decreased the porosity. The mineralogical and microstructure results on the hardened geopolymer indicated the formation of amorphous sodium aluminosilicate gel and crystalline phases of sodium zeolite and feldspathoids. The new phases are mostly present as a filling material in the pore spaces and cement binding the matrix. The increase in the compressive strength is directly related to the formation of the new phases.