Effect of adding urease enzyme on uniaxial strength of soil stabilized by cement and zeolite

Nowadays, modern and environmentally friendly methods have been used to stabilize soils and to improve soil engineering properties. One of these methods is formation of calcium carbonate precipitation in soil pores for increasing strength, cohesion, hardness of soil and decreasing soil permeability. Since most studies have been performed on the formation of calcium carbonate precipitation by using urea hydrolysis by bacteria. In this study, calcite precipitation was made by direct use of urease enzyme. In this method there is no limitation like using of bacteria and also there is no harmful effects on planting. This study investigated the effect of adding urease enzyme to cement and zeolite-stabilized sandy soils as well as the effect of fine aggregates. The results of the uniaxial strength tests showed that with 10% replacement of zeolite instead of cement while 10% fine grains were used, more resistance was observed to the samples without zeolite and with less fine grains. On the other hand, by adding urease enzyme with 4% cement, 10% fine grains and urease enzyme in the comparison of samples without enzyme increased the compressive strength at 14 and 28 days, 5.12 and 4.107, respectively.