Study on Influence Factors of Cement-Free Binding Material Based on Fly Ash and Slag

The cement-free binding material, namely geopolymer, is a novel binding material made from solid waste such as fly ash and slag activated by the alkali. In this research, orthogonal tests were carried out on 20 x 20 x 20mm cube paste specimens cured at room temperature to explore the rules of influence factors according to the compressive strength for 3d, 7d and 28d. The results revealed that the ratio of fly ash/slag is the most significant factor, the ratio of water/ (fly ash+ slag), the modulus of alkali activator and the dosage of desulfurized gypsum also play great role in strength development of the binder. The compressive strength of the specimens can be obtained to 65.0 MPa and 51.21MPa at maximum for 28d when the ratios of fly ash/slag are 30/70 and 40/60 respectively.