Effect of Glutinous Rice Slurry on the Reinforcement of Silt in the Yellow River Basin by Microbially Induced Carbonate Precipitation (MICP): Mechanical Property and Microcosmic Structure

Abstract

The silty clay in the lower reaches of the Yellow River is characterized by loose structure, low strength, and strong capillary effect. Based on the technology of ancient glutinous rice mortar and microbial-induced calcium carbonate precipitation (MICP), experiments on optimal mass ratio of cementitious liquid to bacterial liquid and optimal concentration of cementitious liquid for MICP and improved MICP technology were carried out by measuring the production of CaCO3, and direct shear test and unconfined compressive strength test of plain silt, glutinous mixing silt, and improved silt with MICP and modified MICP were conducted. The microstructure of the reaction products of MICP and improved MICP technology were also evaluated based on scanning electron microscopy (SEM). Research results showed that the mechanical properties of silt with glutinous rice slurry were effectively improved. With the increase in the concentration of glutinous rice slurry, the strength and internal friction angle of soil samples first increased and then decreased, and the cohesion presented a linear increasing trend. When the concentration of cementitious liquid was 0.5 M and the mass ratio of cementitious liquid to bacterial liquid was 2 : 1, the amount of CaCO3 formed was the most, and the conversion rate of Ca2+ was more than 80%. The improved MICP could increase the conversion rate of Ca2+ (93.44%). An improved MICP showed that glutinous rice slurry could improve bacterial activity, increase the urease content in the bacterial solution, and promote the production of CaCO3. Silt cohesion and internal friction angle of the silt were improved by the improved MICP technology, and the strengthening effect of mechanical properties of modified MICP-reinforced soil is better than that of the MICP-reinforced soil; conventional MICP technology could also improve the soil cohesion, but the improvement in the internal friction angle was not obvious. The SEM results indicated that compared with the reaction product of MICP technology, the structure of the product of improved MICP technology is more compact, resulting in a marked reinforcement of MICP performance with glutinous rice slurry. This study provides new insights into enhancing the mechanical behaviour of MICP-treated silt in the Yellow River Basin with glutinous rice slurry.

Investigating the Potential of Biobinder for Bottom Ash Solidification/Stabilization: Leaching Behaviour and pH Dependence

“…This indicates that increasing the bacterial concentration can improve biomineralization, namely by increasing the bioprecipitation of CaCO 3 . The solidification ability of biobinder is closely related to the formulation of CaCO 3 , and the biobinder produced by the MICP reaction has a compact structure [31], which can make some contribution to reducing the leaching concentration of heavy metals in the samples to a certain extent. Compared to the sample control, some new compounds are formed in the sample BIs, such as CuCO 3 , ZnCO 3 , CaPbSiO 6 , and so on.…”

The Effect of Bacteria-to-Calcium Ratio on Microbial-Induced Carbonate Precipitation (MICP) under Different Sequences of Calcium-Source Introduction

“…A variety of mineralisation models exist in microorganisms, including nitrate reduction models, sulphate models [2], and denitrification models [3]. The model of carbonate precipitation through urea hydrolysis by urease microorganisms [4] is the most direct and controllable of the MICP processes, capable of generating large quantities of carbonate in a short period of time. Thus, urease microbial hydrolysis of urea is a widely used model of microbial mineralisation in which urease-producing microorganisms, represented by Sporosarcina pasteurii, metabolically secrete urease and hydrolyse urea in the environment [5][6][7].…”

Experimental Study on Silt Soil Improved by Microbial Solidification with the Use of Lignin

“…Among these, the hydrolysis of urea can quickly produce carbonate ions so the generated calcite can be cemented between soil particles to produce a bonding effect and improve the overall strength. The factors affecting the formation of calcium carbonate can be divided into five parts: the properties of the cemented soil particles [ 22 , 23 , 24 ]; the type, quantity, and activity of microorganisms involved in the reaction [ 25 , 26 , 27 ]; the concentration, type, and pH of the cementitious solution [ 28 , 29 , 30 , 31 ]; the content and uniformity of the calcium carbonate [ 32 , 33 , 34 ]; and other environmental factors, including the mixing method of bacteria, the cementation reagents and soil, the nutrients required for microbial growth and metabolism, and Ca 2+ [ 35 , 36 , 37 , 38 , 39 ].…”