Garlic extract addition for soil improvement at various temperatures using enzyme-induced carbonate precipitation (EICP) method

Enzyme-induced carbonate precipitation (EICP) is an emerging technique to improve the soil and most studies are carried out at room temperature. However, considering some foundations are in high-temperature environments (>40 °C), the higher urease activity at high temperature results in the solidification inhomogeneity, limiting the application of EICP. The higher urease activity at high temperature hampers the application of EICP because of solidification inhomogeneity. The garlic extract has been used as a type of urease inhibitor in medical science and food engineering. Here, we propose to use it to control urease activity for sand solidification at high temperature. The effects of garlic extract addition on urease activity and precipitation rates for calcium carbonate (CaCO₃) were studied. Extra tests were conducted to study the effect of garlic extract addition on the solidification homogeneity. The results showed that the garlic extract addition significantly decreased urease activity. To reduce the rate of CaCO₃ precipitation at different temperatures, a suitable concentration of garlic extract was necessary to obtain a suitable urease activity. In the sand solidification test, garlic extract addition resulted in a smaller difference in sonic time values or CaCO₃ contents at different parts of samples. The improved solidification homogeneity can achieve higher strength. The correlation between sonic time values and CaCO₃ content was higher than that between CaCO₃ content and strength. Appropriate concentrations of garlic extract were obtained at 35 °C, 40 °C, 45 °C, 50 °C, and 55 °C. The proposed garlic extract addition method was significant to improve the homogeneity of solidified soil in practical engineering applications.