One-Phase EICP Biotreatment of Sand Exposed to Various Environmental Conditions

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

“…This method was able to produce carbonate precipitation in soil but was not cost-effective for large-scale applications due to the need for high energy and labour for de-husking the watermelon seeds [47]. Few studies have investigated the possibility of using jack bean meal or industrial grade urease for soil improvement [51][52][53]. Furthermore, Hoang et al [24,49] employed a unique sonication approach that lyses Sporosarcina pasteurii bacteria cells in order to release their intracellular urease enzyme.…”

“…Nemati & Voordouw [9] reported that an increase from 20 to 50 • C enhanced the production rate of calcium carbonate from 0.038 to 0.34 g/L/h. In another study by Zhao et al [74], a 26% decrease in permeability was measured for EICP-treated soil at 30 • C compared to that at 22 • C. Arab et al [53] have studied the effect of temperature during the curing of EICP treated bio-specimens. They reported that specimens cured at 10 • C exhibited the lowest 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.…”

“…Several factors can affect the UCS magnitude, including cementing solution, soil type, and the number of treatment cycles. Several researchers have found a strong correlation between the carbonate content and UCS of EICP-treated soils [44,53,58,61,91]. Therefore, in order to improve treated soil compressive strength, several researchers have used multiple cycles of treatment with EICP solution to increase the amount of carbonate precipitation and hence increase soil compressive strength.…”

“…Nevertheless, the results from the Almajed et al [56] study have shown much higher compressive strength at such lower carbonate content compared to other studies that have also used non-fat milk powder in the EICP cementing solution. In Arab et al [53] study, non-fat milk powder was used with relatively high molarity of urea (3 M) in the EICP cementing solution with urea to calcium chloride ratio of (1:0.67). As shown in Figure 13b the use of high molarity substrate has resulted in relatively higher carbonate precipitation and compressive strength.…”

“…Cui et al [121,122] proposed the use of (one-phase-low-pH method) in which EICP solution consisting of urea and calcium chloride with urease solution of pH = 6.5, is injected into the soil for one phase treatment of sand. Arab et al [53] and Lee and Kim [95] proposed the use of high concentration EICP solution (up to 3 M urea concentration) to induce enough carbonate precipitation after one cycle of treatment.…”