@article{R.A.N. Dilrukshi_Jun Watanabe_Satoru Kawasaki_2021, title={STRENGTHENING OF SAND CEMENTED WITH CALCIUM PHOSPHATE COMPOUNDS USING PLANT-DERIVED UREASE}, volume={11}, url={https://geomatejournal.com/geomate/article/view/2740}, abstractNote={<p>The effect of plant-derived urease enzyme to induce the precipitation of calcium phosphate <br>compounds (CPCs) and hence, to improve the unconfined compressive strength (UCS) of sand was examined <br>as a novel, eco-friendly ground improvement method. Initially, Toyoura sand test pieces were cemented only <br>from CPC solution. Furthermore, another sand test pieces were cemented by different concentrations of urea, <br>concentration fixed plant seeds extract (Watermelon) to obtain optimal cementation, and different <br>concentrations of CPC solutions made from calcium and phosphate stock solutions. All test pieces were cured <br>up to 28 days in an airtight container at high humidity at 25oC. The UCS tests and scanning electron <br>microscope (SEM) observations of sand test pieces were carried out. The UCS of test pieces cemented with <br>CPC and plant extract were significantly higher than that of test pieces cemented without plant extract and <br>increases with time. The best ratio of Ca: P in CPC solution was 0.75 M: 1.5 M, reaching a maximum UCS of <br>125.6 kPa after 28 days of curing. In addition, pH concentration was measured after UCS test and it has <br>increased with time. Results indicate that the best pH for optimal cementation is 8.0. A specific crystal <br>structure could not be identified from SEM observations in the segments of the test pieces cemented with <br>CPC in all cases in this study. These results suggest that the addition of plant extract to CPC significantly <br>enhances the mechanical properties of sand.</p>}, number={25}, journal={GEOMATE Journal}, author={R.A.N. Dilrukshi and Jun Watanabe and Satoru Kawasaki}, year={2021}, month={Nov.}, pages={2461–2467} }