Effect of Plant-Derived Urease-Induced Carbonate Formation on the Strength Enhancement of Sandy Soil

Abstract

The formation of the carbonate biomineral using the byproducts of enzymatic urea hydrolysis is widely explored within different areas of the field of engineering. Various types of urease sources such as ureolytic bacteriaUreolytic bacteriaand microalgae, soil ureaseUrease, and plant ureasePlant ureasehave been applied for the formation of carbonate. At present, the potential of using plant-derived ureaseUreaseenzyme-induced carbonate (mainly calcium carbonate (CC))Calcium carbonateprecipitation has been demonstrated at laboratory scale. BiomineralsBiomineralsare formed by byproducts resulting from a series of chemical reactions. Those reactions are managed by biological activities. SandSandcementationCementationusing biomineral precipitation helps to improve mechanical properties and hence to improve bearing capacity and to resist liquefaction, control of soil erosion by surficial stabilization, and to reduce the hydraulic conductivity of sand. In this study, plant-derived urease (crude extract of watermelon (Citrullus lanatus)Citrullus lanatusseeds)-induced CC precipitation was considered. A significant strength improvement ranging from estimated UCS of 500 kPa to 4.0 MPa was observed in urea–ureaseUrease-treated sand specimens under different concentrations of CaCl2–urea, urease, and different curing periods (days) rather than the non-treated sandSandspecimens. The carbonate ions (hereafter, $${\text{CO}}_{3}^{2 - }$$CO32-) resulting from urea hydrolysis play a major role to precipitate CC. The use of the biomineralsBiomineralsthat cause minimal negative impact on the ecology and the environmentEnvironmentcontributes to the sustainable developmentSustainable development.