Utilization of Soybean as Catalyst Material in Enzyme-Mediated Calcite Precipitation (EMCP) for Crack Healing Concrete

Abstract

This paper discussed the effect of soybean as the catalyst in the Enzyme-Mediated Calcite Precipitation (EMCP) method for crack healing concrete. The existence of cracks in the concrete will reduce the quality of the concrete, so it needs concrete repair efforts, one of which was by injection using the EMCP method. The EMCP technique employs the plant-derived urease enzyme catalyze the reaction between calcium chloride (CaCl2) and urea (CH4N2O) to precipitate as calcium carbonate (CaCO3). The EMCP method was evaluated using a test tube experiment, and the optimum combination of urease, urea, and calcium chloride was selected. It was used as preliminary data for the addition of the soybean as the catalyst. Concrete samples were prepared in the form of 5 cm x 10 cm cylindrical concrete, then crack on samples was made by Universal Testing Machine (UTM) with a controlled area that is in the range ± 0.2-0.3 mm. The injection solution was added to the concrete using the percolation method until the height of the solution was 5 mm above the concrete surface. The injection was carried out several times, and its effect on concrete cracks was evaluated through permeability tests, which can be used as one of the concrete quality parameters. The permeability coefficient value was inversely proportional to the quality, meaning that the smaller the permeability coefficient value, the better the concrete quality, and vice versa. The results showed that after the 4th injection, the total of calcite formed in the sample was 18.3% of the total surface area of the concrete crack, which was able to reduce the concrete permeability value by 95.43%. So that the use of soybean in the EMCP method is considered feasible for repairing concrete cracks.