Optimizing compressive strength of sand treated with MICP using response surface methodology

Abstract

In the present study, the optimization of the microbiologically induced calcium carbonate precipitation (MICP) to produce biosandstone regarding the compressive strength is shown. For the biosandstone production, quartz sand was treated sequentially with the ureolytic microorganism Sporosarcina pasteurii (ATCC 11859) and a reagent containing urea and calcium chloride. Response surface methodology (RSM) was applied to investigate the influence of urea concentration, calcium chloride concentration and the volume of cell suspension on the compressive strength of produced biosandstone. A central composite design (CCD) was employed, and the resulting experimental data applied to a quadratic model. The statistical significance of the model was verified by experimental data (R2 = 0.9305). Optimized values for the concentration of urea and calcium chloride were 1492 mM and 1391 mM. For the volume of cell suspension during treatment 7.47 mL was determined as the optimum. Specimen treated under these conditions achieved a compressive strength of 1877 ± 240 kPa. This is an improvement of 144% over specimen treated with a reagent that is commonly used in literature (1000 mM urea/1000 mM CaCl2). This protocol allows for a more efficient production of biosandstone in future research regarding MICP.