Factors affecting the bio-cementing process of coarse sand

Microbial-induced calcite precipitation (MICP) has received increased attention in recent years as a potential technique for green soil improvements. MICP mimics natural biochemical processes, but utilises cultured urease-producing bacteria that more efficiently catalyse the hydrolysis of urea in the presence of calcium ions to induce precipitation of calcium carbonate. However, optimisation of the MICP method for practical use has hindered its widespread uptake and application. This paper explores the impact of factors such as equimolar and non-equimolar cementation solution (CS), various reaction times and reaction temperatures, which may impact on engineering design of MICP projects. The results reveal that MICP is strongly influenced by the choice of CS concentration, reaction times and temperatures adopted. Higher strength and time-efficient bio-cementation of coarse sand columns were achieved over 24 h incubation time with equimolar CS (1 M) at a temperature of 20°C. The effect of molarity of CS and temperature were also analysed and confirmed by scanning electron microscopy and energy-dispersive spectroscopy.