Optimization of fly ash geopolymer dosage for California bearing ratio using response surface method

In this paper, the optimization of stabilizer dosage was calculated using the response surface method (RSM). The soil was stabilized using fly ash-based geopolymer and the mechanical strength of the soil was evaluated in terms of the California bearing ratio (CBR) as the response parameter. The input parameters were the ratio of fly ash to activator (R) and curing duration (CD), which ranges from 0.6 to 2.0 and 0 to 28 days, respectively. The mathematical equation between the input variables was developed using the response surface method (RSM) based on a face-centered central composite design to predict the CBR values. An analysis of variance (ANOVA) was used to determine the statistical significance of the developed model and it reveals that the developed model predicts excellent agreement with the experimental data for all values of R and CD. The ratio of fly ash to activator imparts more contribution towards the development of equations. The optimization study was carried out to find the optimum dosage of these stabilizers using the desirability function method. The optimal dose for R was 2, i.e., fly ash content of 30% and curing days of 27.98 days, resulting in the highest CBR (40.03%). As the RSM is a local analysis; the developed response surface was invalid for regions other than the studied ranges of factors. It can be believed that the suggested optimization technique was useful to designers or engineers who need a preliminary strength estimate before testing. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.