State-of-the-Art Review of Enzyme-Induced Calcite Precipitation (EICP) for Ground Improvement: Applications and Prospects

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.

State-of-the-Art Review on Engineering Uses of Calcium Phosphate Compounds: An Eco-Friendly Approach for Soil Improvement

“…As a result of the widespread use of traditional Portland cement, conventional methods for soil enhancement are primary carbon dioxide emitters globally [ 16 ].…”

“…The efficiency of EICP depends on the origin of the enzyme, the activity of the enzyme, the enzyme and calcium concentration in solution, the pH and temperature of the environment and the method of EICP treatment [ 16 , 25 ]. According to the literature, the optimal conditions could be as follows: temperature 25–30 °C, pH of 7–9, concentration of urea 0.5 M, concentration of urease enzyme 1–3 g/L, and a curing time of 7–14 days [ 42 , 45 , 46 ].…”

“…This method has been applied to the following issues: improvement in soil strength, wind erosion prevention, reduction in permeability, sand softening control, reduction in flying dust exposure, bio-brick manufacture, surface water erosion control, restoration of contamination by heavy metals, desert sand stabilization, and the repair of fractures in concrete [ 16 , 42 , 45 ].…”

“…Similar to MICP, EICP produces ammonium as a by-product, which is toxic for humans and hazardous to the aquatic and atmospheric environment, in addition, due to the high pH level as a consequence of this method, the risk of corrosion is increased [ 16 , 27 ].…”

A Review of Enzyme-Induced Calcium Carbonate Precipitation Applicability in the Oil and Gas Industry

“…Prior to the introduction of more eco-friendly techniques, ordinary Portland cement (OPC) was the main source for cementation and ground-improvement technique which aims to improve soil geomechanical properties. OPC, which is a key element in concrete and most construction materials, is considered one of the main contributors to worldwide CO 2 emissions, and it introduced synthetics and sometimes toxic materials into the environment ( Chen et al, 2010 ; Arab et al, 2021b ). Since the production of OPC is a high energy-intensive process, bio-inspired and bio-mediated methods such as MICP and EICP have become major topics of research.…”