Response surface design of solid waste based geopolymer

Abstract

Solid waste (slag and fly ash) based geopolymer (SWG-SF) was developed on the basis of response surface methodology (RSM), using the fly ash to slag ratio (FSR), alkali content (AC), makeup of alkali activator (n) and binder to water ratio (BWR) as design parameters. Flexural strength (f_f-3d) and compressive strength (f_c-3d) after 3 days of standard curing were tested, the early strength systems were established, the prediction of strength system was validated by comparison, and the effects of design parameters on f_f-3d were studied. The test result shows that the reliability and accuracy of the early strength system of SWG-SF by adopting RSM can be verified in terms of mathematics and application, and the early strength system can be used for theoretical study and practice guidelines; according to analysis on the strength system, f_f-3d increases linearly with BWR, and the increasing rate is closely related to FSR; f_f-3d increases linearly with n, and the increasing rate is closely related to AC; f_f-3d decreases continuously with FSR, but the decreasing rate gets slower and slower, and BWR has certain influence on the change rate of strength; and f_f-3d increases at the beginning and then decreases with AC, which suggests that AC has an optimum value (0.146–0.055n). Thus it can be seen that RSM can be widely used in the preparation of new solid waste based geopolymer and has promising applications in the utilization of solid waste.