Strength and microstructure of class C fly ash based geopolymer activated with sodium silicate powder

The compressive strength and microstructural characteristics of class C fly ash based geopolymer activated with sodium silicate powder were investigated. The geopolymer samples with the highest strength 44.6MPa were obtained when the mass ratio of water to milled fly ash (W/F) was 0.28 and then followed by curing at 70°C for 30h. In the XRD patterns, many crystalline zeolithic phases were found. The results of SEM-EXDA indicated that for geopolymer with lower W/F, the structure was more compact and excess calcium played an important role in the form of geopolymeric gel.