Enzyme-Induced Carbonate Precipitation (EICP)-Based methods for ecofriendly stabilization of different types of natural sands

Enzyme-induced carbonate precipitation (EICP) has attracted increasing attention as a bio-inspired technique that can be employed in-situ for ground improvement. One of the obstacles to the widespread use of this technique is the lack of data on natural soils treated using EICP compared to soils treated using conventional methods such as ordinary Portland cement (OPC) and lime. This study focuses on the influence of the soil type on the strength of the treated soil using different stabilization techniques. Further, the feasibility of combining EICP treatment with soil improvement using OPC was also explored in order to reduce the consumption of cement (and hence the carbon footprint). The study involved three types of local natural sands of Saudi Arabia and a standard sand (Ottawa 20/30 sand). Three different recipes of EICP cementing solutions were investigated. Moreover, hybrid methods were used to treat the soil using a combination of 10% OPC with an EICP cementing solution paired with different curing schemes. The unconfined compressive strength of sands treated using EICP after one cycle of treatment was higher than the sands stabilized using 10% OPC. The addition of cement to the EICP treatment in the hybrid methods had a negative effect on the strength of the stabilized sand; this was confirmed by a microstructure analysis. This study proves that EICP biocementation technique can be used alone efficiently without mixing cement, hence saving the environment from the harmful effects associated with cement production. (c) 2020 Elsevier Ltd. All rights reserved.