Abstract
The global construction industry consumes huge amounts of mined materials that are considered unsustainable for earth resources. In addition, Portland cement which is a key element in concrete and most construction materials is considered one of the main contributors to worldwide CO2 emissions. On the other hand, natural cemented soil deposits are examples of sustainable structures that have survived decades of severe environmental conditions. Mimicking these natural biological systems provide an alternative to the current practices of construction materials production. Enzyme-induced carbonate precipitation (EICP) is a bio-inspired technique based on the precipitation of calcium carbonate for enhancing the geo-mechanical properties of soils. In this technique, calcium carbonate acts as a cementitious agent that binds the soil particles together at the points of contact, hence, increasing the strength and stiffness of treated soils, while relatively reducing the soil permeability and porosity. The achieved enhancements make EICP useful for applications such as ground improvement, construction materials, and erosion control over traditional binders. This paper presents a state-of-the-art review of EICP for ground improvement including the fundamental basics of EICP treatment. The paper also discusses the chemical and physical factors affecting the performance of EICP such as enzyme source, enzyme activity and solution constitutes. Moreover, the paper reviews the different methods and testing techniques used in the application of EICP for soil treatment. Furthermore, the paper compares EICP with other biomineralization techniques in terms of performance and applicability on ground improvement. Finally, the paper discusses the research gaps and existing challenges concerning the commercialization and large-scale implementation of the technology.
Highlights
More sustainable and environmentally friendly solutions have been demanded to mitigate the adverse effects of pollution on the environment
Urea hydrolysis utilizing bacteria as a source of urease enzyme for soil cementation was first discussed by Whiffin [10] and later called “microbial-induced carbonate precipitation (MICP)”
They reported that specimens cured at 10 ◦C exhibited the lowest unconfined compressive strength (UCS) results with an average UCS of 669 kPa while specimens cured at 25 ◦C was and 40 ◦C had a UCS of 1411 and 1537 kPa, respectively
Summary
More sustainable and environmentally friendly solutions have been demanded to mitigate the adverse effects of pollution on the environment. Urea hydrolysis utilizing bacteria (sporosarcina pasteurii) as a source of urease enzyme for soil cementation was first discussed by Whiffin [10] and later called “microbial-induced carbonate precipitation (MICP)”. To overcome the abovementioned problems associated with MICP, free urease enzymes derived from a plant source was first suggested by Nemati and Voordouw [9] and used as a catalyst in hydrolysis This hydrolysis technique is usually referred to as “enzyme-induced carbonate precipitation (EICP)”. Nemati and Voordouw [9] were the first to propose the use of free urease enzyme derived from a plant source as a catalyst in carbonate biomineralization for geotechnical applications. Few recent studies explored the life cycle assessment (LCA) of EICP as a suppressant for wind erosion control [31] and as a grout for ground improvement [37]
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