Improvement of characteristics and freeze-thaw durability of solidified loess based on microbially induced carbonate precipitation

2021 ◽  
Author(s):  
Xiaohao Sun ◽  
Linchang Miao ◽  
Hengxing Wang ◽  
Runfa Chen ◽  
Xin Guo
Keyword(s):  
Carbonate Precipitation ◽  
Freeze Thaw ◽  
Microbially Induced Carbonate Precipitation

scholarly journals Experimental Study on Sand Stabilization Using Bio-Cementation with Wastepaper Fiber Integration

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5164
Author(s):  
Meiqi Chen ◽  
Sivakumar Gowthaman ◽  
Kazunori Nakashima ◽  
Shin Komatsu ◽  
Satoru Kawasaki
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Velocity Analysis ◽  
Carbonate Precipitation ◽  
Freeze Thaw ◽  
Green Materials ◽  
Caco3 Content ◽  
Microbially Induced Carbonate Precipitation ◽  
Sand Stabilization ◽  
Strength And Stiffness

Recently, green materials and technologies have received considerable attention in geotechnical engineering. One of such techniques is microbially-induced carbonate precipitation (MICP). In the MICP process, CaCO3 is achieved bio-chemically within the soil, thus enhancing the strength and stiffness. The purpose of this study is to introduce the wastepaper fiber (WPF) onto the MICP (i) to study the mechanical properties of MICP-treated sand with varying WPF content (0–8%) and (ii) to assess the freeze–thaw (FT) durability of the treated samples. Findings revealed that the ductility of the treated samples increases with the increase in WPF addition, while the highest UCS is found with a small fiber addition. The results of CaCO3 content suggest that the WPF addition enhances the immobilization of the bacteria cells, thus yielding the precipitation content. However, shear wave velocity analysis indicates that a higher addition of WPF results in rapid deterioration of the samples when subjected to freeze–thaw cycles. Microscale analysis illuminates that fiber clusters replace the solid bonding at particle contacts, leading to reduced resistance to freeze–thaw damage. Overall, the study demonstrates that as a waste material, WPF could be sustainably reused in the bio-cementation.

scholarly journals The role of bacterial urease activity on the uniformity of carbonate precipitation profiles of bio-treated coarse sand specimens

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Charalampos Konstantinou ◽  
Yuze Wang ◽  
Giovanna Biscontin ◽  
Kenichi Soga
Keyword(s):  
Calcium Carbonate ◽  
Calcium Chloride ◽  
Urease Activity ◽  
Coarse Sand ◽  
Carbonate Precipitation ◽  
Population Densities ◽  
Carbonate Cements ◽  
Microbially Induced Carbonate Precipitation

AbstractProtocols for microbially induced carbonate precipitation (MICP) have been extensively studied in the literature to optimise the process with regard to the amount of injected chemicals, the ratio of urea to calcium chloride, the method of injection and injection intervals, and the population of the bacteria, usually using fine- to medium-grained poorly graded sands. This study assesses the effect of varying urease activities, which have not been studied systematically, and population densities of the bacteria on the uniformity of cementation in very coarse sands (considered poor candidates for treatment). A procedure for producing bacteria with the desired urease activities was developed and qPCR tests were conducted to measure the counts of the RNA of the Ure-C genes. Sand biocementaton experiments followed, showing that slower rates of MICP reactions promote more effective and uniform cementation. Lowering urease activity, in particular, results in progressively more uniformly cemented samples and it is proven to be effective enough when its value is less than 10 mmol/L/h. The work presented highlights the importance of urease activity in controlling the quality and quantity of calcium carbonate cements.

Desert Aeolian Sand Cementation via Microbially Induced Carbonate Precipitation

IFCEE 2021 ◽  
2021 ◽  
Author(s):  
Xichen Xu ◽  
Hongtao Wang ◽  
Wenbin Lin ◽  
Xiaohui Cheng ◽  
Hongxian Guo
Keyword(s):  
Carbonate Precipitation ◽  
Aeolian Sand ◽  
Microbially Induced Carbonate Precipitation

scholarly journals Microbially-induced Carbonate Precipitation for Immobilization of Toxic Metals

2016 ◽  
pp. 79-108 ◽  
Author(s):  
Deepika Kumari ◽  
Xin-Yi Qian ◽  
Xiangliang Pan ◽  
Varenyam Achal ◽  
Qianwei Li ◽  
...  
Keyword(s):  
Toxic Metals ◽  
Carbonate Precipitation ◽  
Microbially Induced Carbonate Precipitation

Tensile strength of sands treated with microbially induced carbonate precipitation

2020 ◽  
Vol 57 (10) ◽  
pp. 1611-1616 ◽  
Author(s):  
Ashkan Nafisi ◽  
Douglas Mocelin ◽  
Brina M. Montoya ◽  
Shane Underwood
Keyword(s):  
Tensile Strength ◽  
Large Earthquake ◽  
Carbonate Precipitation ◽  
Direct Tension ◽  
Sem Images ◽  
Cemented Soil ◽  
Tension Tests ◽  
Deformational Behavior ◽  
Microbially Induced Carbonate Precipitation ◽  
Sand Type

During large earthquake events where bending moments within soil cements are induced, the tensile strength of cemented soil may govern the deformational behavior of improved ground. Several studies have been conducted to assess the tensile strength of artificially cemented sands that use Portland cement or gypsum; however, the tensile strength of microbially induced carbonate precipitation (MICP)-treated sands with various particle sizes measured through direct tension tests has not been evaluated. MICP is a biomediated improvement technique that binds soil particles through carbonate precipitation. In this study, the tensile strength of nine specimens were measured by conducting direct tension tests. Three types of sand (coarse, medium, and fine) were cemented to reach a heavy level of cementation (e.g., shear wave velocity of ∼900 m/s or higher). The results show that the tensile strength varies between 210 and 710 kPa depending on sand type and mass of carbonate. Unconfined compressive strength (UCS) tests were performed for each sand type to assess the ratio between tensile strength and UCS in MICP-treated sands. Scanning electron microscopy (SEM) images and surface energy measurements were used to determine the predominant failure mode at particle contacts under tensile loading condition.

scholarly journals Freeze-thaw durability and shear responses of cemented slope soil treated by microbial induced carbonate precipitation

2020 ◽  
Vol 60 (4) ◽  
pp. 840-855
Author(s):  
Sivakumar Gowthaman ◽  
Kazunori Nakashima ◽  
Satoru Kawasaki
Keyword(s):  
Carbonate Precipitation ◽  
Freeze Thaw

Strength and Permeability of Bentonite-Assisted Biocemented Coarse Sand

2020 ◽  
Author(s):  
Guoliang Ma ◽  
Xiang He ◽  
Xiang Jiang ◽  
Hanlong Liu ◽  
Jian Chu ◽  
...  
Keyword(s):  
Unconfined Compressive Strength ◽  
Volume Fraction ◽  
Coarse Sand ◽  
Effective Concentration ◽  
Carbonate Precipitation ◽  
Natural Clay ◽  
High Concentration ◽  
Strength Enhancement ◽  
Microbially Induced Carbonate Precipitation ◽  
Clay Aggregates

To effectively stabilize coarse sand, bentonite was introduced in microbially induced carbonate precipitation (MICP) grouting. Varying concentrations (0 g/L, 20 g/L, 40 g/L and 80 g/L) of bentonite were added to bacterial suspensions (BSs), which were magnetically stirred to form bacterial-bentonite suspensions (BBSs). Then, coarse sand specimens were treated with BBSs and cementation solutions (CSs) to different cementation levels. The results showed that the addition of bentonite could increase the volume fractions of the precipitates consisting of calcium carbonate (CaCO3) and bentonite. The permeability decreased exponentially as the volume fraction of precipitates increased. As the active precipitates increased when a lower concentration (e.g., 20 g/L) of bentonite was added to the MICP grouting, the unconfined compressive strength (UCS) was substantially improved. However, detrimental effects were observed for specimens treated with a high concentration of bentonite. These results indicate that the effective concentration of natural clay aggregates used in MICP grouting was different for different engineering applications, e.g., seepage control and strength enhancement. The current work provides an encouraging method of improving the MICP technique.

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