APPLICATION OF RESPONSE SURFACE METHODOLOGY IN THE OPTIMIZATION OF FLY ASH GEOPOLYMER CONCRETE

A series of research experiments was designed and conducted in this study using the Box-Behnken design method of response surface methodology (RSM) to solve the optimization problem of parameters effectively in fly ash geopolymer concrete preparation. First, single-factor gradient analysis was adopted to determine the reasonable level of various factors in the response surface analysis. The 28-day compressive strength development was investigated in terms of the water-binder ratio, dosage of alkali, unit water dosage, and sodium silicate modulus. Results showed that the order of the factors in terms of their influence on concrete strength was dosage of alkali, sodium silicate modulus, and water-binder ratio, and the unit water dosage exerted a minimal influence. Second, the preparation parameters were optimized to improve the 28-day compressive strength of the concrete based on the single-factor analysis using the RSM. The optimum parameters were a water-binder ratio of 0.35, an alkali dosage of 7.9%, and a sodium silicate modulus of 1.66. This study also analyzed the response surface optimization results through a validation test to prove the effectiveness of the RSM in optimizing the preparation of geopolymer concrete.