Sand cementation test using plant-derived urease and calcium phosphate compound

Abstract

The investigation of urease containing plant species and the calcium phosphate compounds (CPCs) precipitation along with plant derived urease were performed at laboratory scale. At first, small scale laboratory samples (height, h = 10 cm "inner diameter, δ = 5 cm) were made using Toyoura sand and only from CPC solution having different Ca/P ratios to use as control samples. Afterward, another Toyoura sand test pieces were made by mixing watermelon seed extract, urea with different concentrations and CPC solution having different Ca/P ratios to study the optimal cementation. Test pieces were cured up to 28 days in an airtight container at high humidity at 25°C and carried out unconfined compressive strength (UCS) test. The UCS of the sand test pieces cemented by CPC with urease containing plant extract and urea were larger than that of the test pieces without plant extract. Furthermore, the best CPC solution mixture for highest cementation was with the concentration of Ca/P ratio of 0.5. In addition, pH content was measured after UCS test. Maintaining pH around 8 in the specimen at 28 days was significant to get optimal cementation.