Advances in the enzymatic stabilisation of soils

The demands of innovative, cost effective and sustainable construction practices requires the development of energy-efficient and environmental friendly building techniques. The achievement of this objective is helped by the exploitation of knowledge from different disciplines, including physics, biology and chemistry. In geotechnical engineering, Enzymatic Induced Calcite Precipitation (EICP) is a new stabilisation treatment that can improve the mechanical properties of soils without the use of hazardous or costly chemical binders. EICP employs the urease enzyme, a widely occurring hexameric protein of plants, to catalyse the hydrolysis of urea. This reaction creates a strongly alkaline environment, which in turn favours precipitation of calcium carbonate, thus binding soil grains together. This study investigates the key factors controlling the kinetics of urea hydrolysis with the objective of proposing an optimised EICP methodology. The proposed methodology is then applied to the stabilisation of a silty clay to assess the improvement of material durability in the presence of excess water.