Effects of biocementation on strength parameters of silty and clayey sands

Abstract

Microbially induced calcite precipitation (MICP) is a bioinspired improvement method of granular soils, as it can significantly affect their engineering characteristics. In fact, calcite nanoparticles produced through MICP increase the angle of internal friction and cohesion intercept of granular soils. As a consequence, the shear strength values of granular soils are improved following the increase in these two parameters. However, MICP is not very efficient in strengthening fine-grained soils. In this study, using Sporosarcina pasteurii for MICP treatment, the effects of biocementation and plastic and non-plastic fines (clay and silt) on the shear strength parameters of sandy soils were investigated after 7, 10 and 15 d of treatment to analyse the viability of MICP in different sand mixtures in the field. Direct-shear tests, X-ray diffraction and scanning electron microscopy were used as investigative tools. The results obtained in this study showed that there was a significant improvement in the shear strength of the samples, while noticeable modification occurred within the first 7 d of treatment and fines reduced the MICP potential for strengthening of sandy soils. Although MICP boosted the cohesion intercept and the angle of internal friction of the samples, a great amount of the gained strength was due to cohesion growth.

Assessment of Microbial Induced Calcite Precipitation (MICP) in Fine Sand Using Native Microbes under Both Aerobic and Anaerobic Conditions

“…9(c), calcite production in the samples with different treatments also increased with time after the treatments, but the significant calcite content for all treatments produced in 7 days after applying the treatments. This is consistent with the findings by Pakbaz et al (2018), Amini Kiasari et al (2018, and Behzadipour et al (2019).…”

“…Considerable increase in the value of this parameter with time for samples in group B (135 − 246%), minor increase for samples in group A (29 − 59%), and no increase for samples in group C (40 − 43%) as compared with the control sample were observed. This finding is consistent with those made by Pakbaz et al (2018), Amini Kiasari et al (2018), and Behzadipour et al (2019. It should be added that a significant part of the increase in the cohesion intercept reported here and before have occurred seven days after the treatment.…”

Strength and Durability of Cement-Treated Lateritic Soil

“…Since emerging in 1995, the MICP method has been compatible with green construction requirements [40] such that it has had minimal impacts on the environment compared with conventional methods. However, considering the granular material, the MICP method does not significantly stabilize fine-grained soil [41]. Nevertheless, some studies have been conducted on the effectiveness of MICP in stabilizing fine-grained soil.…”

Numerical Simulation of Pervious Concrete Pile in Loose and Silty Sand After Treating With Microbially Induced Calcite Precipitation

“…MICP technique suffers from some drawbacks when using with fine grains because of bacteria incapable of growth in very low permeability to oxygen and moving freely in tiny pore space [9]. Behzadipour [9] addressed the impacts of plastic and non-plastic fines on the bio-mediated soil improvement of shear strength parameters of sandy soils. The results presented that the presence of fine particles can decrease the efficiency of MICP treatment.…”