Biocemented Sand Research Articles

Insight into the Properties of Surface Percolated Biocemented Sand

Most traditional soil improvement methods are time-consuming, expensive, require heavy machinery and environmentally detrimental. As a more ecofriendly ground improvement method, the biocementation of soil offers an alternative to traditional soil improvement techniques. This method is based on microbial precipitation of calcium carbonate serving as cementing or bonding agents between soil grains. To achieve this bonding, the method of in situ soil stabilization by surface percolation under free drainage of solutions containing either bacteria or calcium ions was chosen. This paper investigates the effects of this method on the strength improvement and microstructure of a dry loose poorly-graded sand after bioimprovement. To evaluate the success of treatment, a series of laboratory experiments was conducted, including, shear wave velocity, unconfined compressive strength, calcium carbonate content, triaxial shear test, scanning electron microscopy, etc. The study revealed that this newly emerging biomediated technique causes the improvement of soil strength as a result of the cementation of sand particles via crystal precipitation and the surface percolation method has the potential of stabilizing the loose sand with desirable depth. Results also showed that strength increase depends not only on calcium carbonate content but also on its precipitation location and particle-to-particle binding strength and numbers. In addition, scanning electron microscopy images and X-ray diffraction showed precipitation of biological calcium carbonate is different in polymorph type throughout the sand column.

The Influence of the Addition of Plant-Based Natural Fibers (Jute) on Biocemented Sand Using MICP Method.

The microbial-induced carbonate precipitation (MICP) method has gained intense attention in recent years as a safe and sustainable alternative for soil improvement and for use in construction materials. In this study, the effects of the addition of plant-based natural jute fibers to MICP-treated sand and the corresponding microstructures were measured to investigate their subsequent impacts on the MICP-treated biocemented sand. The fibers used were at 0%, 0.5%, 1.5%, 3%, 5%, 10%, and 20% by weight of the sand, while the fiber lengths were 5, 15, and 25 mm. The microbial interactions with the fibers, the CaCO3 precipitation trend, and the biocemented specimen (microstructure) were also evaluated based on the unconfined compressive strength (UCS) values, scanning electron microscopy (SEM), and fluorescence microscopy. The results of this study showed that the added jute fibers improved the engineering properties (ductility, toughness, and brittleness behavior) of the biocemented sand using MICP method. Furthermore, the fiber content more significantly affected the engineering properties of the MICP-treated sand than the fiber length. In this study, the optimal fiber content was 3%, whereas the optimal fiber length was s 15 mm. The SEM results indicated that the fiber facilitated the MICP process by bridging the pores in the calcareous sand, reduced the brittleness of the treated samples, and increased the mechanical properties of the biocemented sand. The results of this study could significantly contribute to further improvement of fiber-reinforced biocemented sand in geotechnical engineering field applications.

Quantitative method of calcium carbonate in bio-grouting test under multiple treatment factors

Bio-grouting is emerging as a sustainable technology for improving the mechanical properties of sand in which CaCO3 is the main product. Previous studies proved that the amount of CaCO3 affects the mechanical properties of bio-cemented sand, but few studies address CaCO3 quantification. In this paper, we describe a novel method to predict the amount of CaCO3 in the process of bio-grouting. A total of 25 bio-grouting tests were carried out with 6 treatment factors considered: bacterial suspension’s concentration, flow rate and retention time, cementing solution’s concentration, flow rate, and reaction time. Based on the mechanism of microbial-induced calcite precipitate (MICP), a theoretical solution to quantify the amount of CaCO3 was established by researching the effects of environmental substances on urea hydrolyzed rate in a liquid environment. This solution was developed by analyzing the difference between sandy and liquid environments. A series of time-dependent equations that evaluate the relationship between the amount of CaCO3 produced with bacterial concentration, the cementing solution’s concentration, and the reaction time, were derived. Moreover, it was found that the bacterial retention time and the flow rates of grouting solutions affect the distributions of reactants in sand. This can be captured by a residual coefficient in the CaCO3 quantification model. Finally, once the linkage between the improved strength of bio-cemented sand and the CaCO3 content is established, the proposed model can be applied to estimate the strength of bio-cemented sand in real time.

Closure to “Unconfined Compressive and Splitting Tensile Strength of Basalt Fiber–Reinforced Biocemented Sand” by Yang Xiao, Xiang He, T. Matthew Evans, Armin W. Stuedlein, and Hanlong Liu

Closure to “Unconfined Compressive and Splitting Tensile Strength of Basalt Fiber–Reinforced Biocemented Sand” by Yang Xiao, Xiang He, T. Matthew Evans, Armin W. Stuedlein, and Hanlong Liu

Discussion of “Unconfined Compressive and Splitting Tensile Strength of Basalt Fiber–Reinforced Biocemented Sand” by Yang Xiao, Xiang He, T. Matthew Evans, Armin W. Stuedlein, and Hanlong Liu

Discussion of “Unconfined Compressive and Splitting Tensile Strength of Basalt Fiber–Reinforced Biocemented Sand” by Yang Xiao, Xiang He, T. Matthew Evans, Armin W. Stuedlein, and Hanlong Liu

Engineering Properties of Bacterially Induced Calcite Formations

This article presents the engineering properties of bacterially induced calcite formations, which are often referred to as microbially induced calcite precipitation (MICP) via ureolysis ongranular formations consisting of loose and collapsible river sand. Two sets of experiments consisting of five sand columns each were treated using urease-producing bacteria, urea and calcium chloride solutions.The reaction produced biomineralized calcium carbonate crystals (referred to as calcite) that bind and stiffen the sand grains. The reaction was checked by measuring the pH level. The pH values of the effluent solution taken from the initial stage to day 14 of the treatment ranged from 7 to 8. When the pH reading was in alkaline range (<7), there was significant calcite formation. The strength gained in the treated specimens was estimated from the unconfined compression tests and obtained in the range 1.1–2.18 MPa based on 4.0–8.0% calcite content at different reaction times. Calcite formation within the biocemented sand was ascertained from scanning electron microscopic images. The grain-size distribution of the untreated and treated formations was compared. It was observed that the increase in grain size of treated formation was a function of MICP. The collapse potential of the formation reduced as a result of bacterially induced calcite precipitation. The strength of the bacterially induced calcite formations was comparable to soft rocks.

Influence of different fiber types on properties of biocemented calcareous sand

Within recent years, microbial induced calcium carbonate precipitation (MICP) technology has been widely applied to ground improvement. The addition of fiber has a great improvement on properties of biocemented sand. This paper studied the influence of three fiber types on properties of biocemented calcareous sand by using MICP technology and discovered the influence mechanism of three fiber types on biocemented calcareous sand. Unconfined compressive strength (UCS) test, tensile strength test, and calcium carbonate content were carried to estimate properties of biocemented calcareous sand. The microstructures of biocemented calcareous sand with fibers and surface of three fiber types were observed under the scanning electron microscope. The test results showed that the ductility, the bridging role, and calcium carbonate content of biocemented calcareous sand with carbon fiber were better, followed by basalt fiber and glass fiber. The UCS, tensile strength, and calcium carbonate content of biocemented calcareous sand increased with the increasing fiber content. The optimum fiber content of biocemented calcareous sand was found to be 1%. Compared with biocemented calcareous sand without fiber, the unconfined compressive strength of biocemented calcareous sand at optimum glass fiber, basalt fiber, and carbon fiber content increased by 458%, 784%, and 1133%, respectively. Meanwhile, the tensile strength of biocemented calcareous sand at optimum basalt fiber, glass fiber, and carbon fiber content increased by 115%, 129%, and 317%, respectively. Therefore, the properties of biocemented calcareous sand with carbon fiber are better than basalt fiber and glass fiber.

Comparative mechanical behaviors of four fiber-reinforced sand cemented by microbially induced carbonate precipitation

Microbially induced carbonate precipitation (MICP) has been found promisingly to improve soil mass properties with the environmentally friendly biogeochemical process, while MICP-treated soils show brittleness. Discrete fiber inclusion is an effective way to enhance soil ductility. In this study, we collaboratively utilized these two techniques for soil reinforcement. Mechanical behaviors including permeability, unconfined compressive strength (UCS), splitting tensile strength (TS) of biocemented sand reinforced by different contents (i.e., 0–1.8% by sand weight) of carbon fiber (CF), basalt fiber (BF), polypropylene (PP) fiber, and polyester (PET) fiber were accessed and compared. The microstructures of samples were also investigated by X-ray diffraction and scanning electron microscopy. It was found that fiber inclusions had a positive effect on the amount of precipitated calcium carbonate, and furthermore calcium carbonate type would not be changed by the introduction of four fibers. Besides, the beneficial effect of fibers on UCS was most pronounced at approximately 1% fiber volume fraction for four fibers, while permeability and TS were improved with the increase in fiber content. On the whole, the order of performance for the four fibers was as follows: CF > BF > PP > PET, evaluated by the improved behaviors of permeability, strength, and ductility for fiber-reinforced, biocemented sand. While taking cost into account, BF was the most cost-effective material among the four fibers.

Shear Strength Envelopes of Biocemented Sands with Varying Particle Size and Cementation Level

AbstractMicrobial-induced calcium carbonate precipitation (MICP) is a bio-mediated technique that may be used to improve the strength and stiffness of soils. Various parameters affect the behavior ...

Discrete Element Modelling for biocemented sand: effect of calcite distribution at the microscopic scale

The mechanical efficiency of the biocementation process is directly related to the microstructural properties of the biocemented soil, such as, the volume fraction of calcite, its distribution within the pore space (whether localized at the contact between grains or over the grain surfaces) and the contact properties: coordination number, contact surface area, contact orientation, type of contacts (frictional even after treatment, purely cohesive via a calcite bridge or combining friction between particles and cohesion of the localized calcite). Dadda et al, (2018) have used microscopic properties computed from 3D images obtained by X-ray tomography of biocemented sand samples with different levels of biocementation as an input in current analytical models to estimate the elastic properties (Young’s and shear modulus) and the strength properties (Coulomb cohesion). They pointed out the important role of some microstructural parameters, notably those related to the contact, on such effective parameters. However, the precise evaluation of the effect of microstructural parameters such as the contact surface distribution on the global mechanical behaviour of the soil requires the use of more advanced modelling methods. The paper presents the results of Discrete Element Modelling of triaxial tests with the open source code Yade in which the real microstructural properties of biocemented soil computed on 3D X-ray microtomography images are used as input parameters. A particular attention has been paid to take into account the actual distribution of contact surface in the model and not only the average value. It appears that the model is then able to reproduce the evolution of the macroscopic properties (in particular that of the cohesion) with the calcite content.

Temperature Drop Model Based on Discrete Element Method for Simulating Damage of Bio-Cemented Sand by Cold Wave

The microbially cemented sand (MCS) material is a new building material with a broad research prospect, although the nationwide cold wave affects the mechanical properties of the material in the practical application. The microstructure of MCS is obtained by computed tomography (CT) and scanning electron microscope (SEM); the thermodynamic mathematical model is established by considering the particle shapes and bonding state based on direct element method (DEM). By studying the damage of temperature drop amplitude and cooling duration to MCS material under the effect of cold wave, the following conclusions are drawn. For a given temperature drop range, an increased cooling time can aggravate the material damage. In addition, a rapid drop in temperature can cause serious damage to the material. The cracks generated by the temperature stress propagate in the direction of the weaker component of the material. The DEM model can be better used to analyze the damage of the MCS structure induced by cold wave.

Strength and Deformation Responses of Biocemented Sands Using a Temperature-Controlled Method

AbstractThe strength and deformation responses of sands improved by a temperature-controlled biotreatment method were investigated through a series of drained triaxial compression tests under vario...

Biocementation technology for construction of artificial oasis in sandy desert

Artificial oasis could be supported by the trapping and retaining rainfall water by impermeable layer of artificial material. In case of average annual rainfall in Arabian or Pakistani Deserts of 100 mm the watershed area must be at least 1000 ha to ensure rainfall water supply for consumption and irrigation in the artificial oasis of 100 ha area. Minimum cost for the sealing of 1000 ha of the sand slopes with 1 mm geosynthetic liner is about 112 mln Saudi Arabian Riyal, which could be not acceptable price for 100 ha of artificial oasis land. However, this cost could be diminished to 17 mln Saudi Arabian Riyal if to coat watershed slopes with 1 mm of biocemented sand crust using a low viscosity solution of biocement. Conventional cementation is cheaper but it cannot be used to make 1 mm sand crust because of a high viscosity of the cement suspension. The novel biotechnological method is based on the formation of the sand surface crust for water collection and transportation on the surrounding slopes. Most environmentally friendly biotechnology for this biocementation is aerobic biooxidation of cheap calcium formate or calcium acetate. Biocementation of the sand crust could be used to make a low-cost artificial desert oasis fed by rainfall.

Unconfined Compressive and Splitting Tensile Strength of Basalt Fiber–Reinforced Biocemented Sand

AbstractThe strength properties of basalt fiber–reinforced biocemented (BFRB) sand specimens with various calcite contents and fiber contents are investigated through a series of unconfined compres...

A Novel Approach to Enhance the Urease Activity of Sporosarcina pasteurii and its Application on Microbial-Induced Calcium Carbonate Precipitation for Sand

Urease is involved in the formation of carbonate sediments by microbial-induced calcium carbonate precipitation (MICP), and Sporosarcina pasteurii used extensively in this technique owing to its high urease production. In this study, a simple two-step culture method with the appropriate medium was developed to enhance the urease activity of S. pasteurii. Urea played an important role in the culture process, particularly during the pre-cultivation step and the newly developed method improved both urease activity and specific urease activity. Furthermore, the increase in urease activity by MICP resulted in increased production of calcium carbonate and better strength of bio-cemented sand.

Splitting Tensile Strength of Fiber-Reinforced and Biocemented Sand

AbstractThis technical note examines the splitting tensile strength properties of natural sand treated with polyvinyl acetate (PVA) fiber in combination with biocementation using the microbially in...

Solidification of sand by Pb(II)-tolerant bacteria for capping mine waste to control metallic dust: Case of the abandoned Kabwe Mine, Zambia

Environmental impacts resulting from historic lead and zinc mining in Kabwe, Zambia affect human health due to the dust generated from the mine waste that contains lead, a known hazardous pollutant. We employed microbially induced calcium carbonate precipitation (MICP), an alternative capping method, to prevent dust generation and reduce the mobility of contaminants. Pb-resistant Oceanobacillus profundus KBZ 1–3 and O. profundus KBZ 2–5 isolated from Kabwe were used to biocement the sand that would act as a cover to prevent dust and water infiltration. Sand biocemented by KBZ 1–3 and KBZ 2–5 had maximum unconfined compressive strength values of 3.2 MPa and 5.5 MPa, respectively. Additionally, biocemented sand exhibited reduced water permeability values of 9.6 × 10−8 m/s and 8.9 × 10−8 m/s for O. profundus KBZ 1–3 and KBZ 2–5, respectively, which could potentially limit the entrance of water and oxygen into the dump, hence reducing the leaching of heavy metals. We propose that these isolates represent an option for bioremediating contaminated waste by preventing both metallic dust from becoming airborne and rainwater from infiltrating into the waste. O. profundus KBZ 1–3 and O. profundus KBZ 2–5 isolated form Kabwe represent a novel species that has, for the first time, been applied in a bioremediation study.

Using recycled calcium sources to solidify sandy soil through microbial induced carbonate precipitation

The use of calcium solutions is a cost-limiting factor for bio-cement production from microbially induced carbonate precipitation (MICP). The aim of this article is to analyse the feasibility of using recycled calcium sources to solidify sand, including oyster shells, scallop shells and eggshells, by comparing the physical and mechanical properties and microstructural characteristics of solidified sand with different recycled calcium sources and chemical calcium nitrate. The results show that oyster shells have the optimal effect on MICP, with values of permeability, dry density, unconfined compressive strength and calcium carbonate precipitation of 1.12 × 10−4 m s−1, 2.09 g cm−3, 1454.6 kPa and 15.28%, respectively. Strength values of bio-cemented sands made from different recycled calcium sources in this article range from 845.1 to 1454.6 kPa. According to the SEM and XRD analysis, calcium carbonates originating from the above recycled calcium sources precipitate as globular vaterite, whereas the precipitation from calcium nitrate is a cluster mixture of vaterite and calcite. Oyster shells, scallop shells and eggshells derived from kitchen waste, which is more economical and environmentally friendly than calcium nitrate, can be applied as recycled calcium solutions in MICP.

Lattice element method for simulations of failure in bio-cemented sands

Microbiologically induced calcite precipitation following the ureases is a bio-geo-chemical soil improvement technique in which the microorganism facilitates to create an environment for the precipitation of carbonates among the grains. It results in binding the loose granular media and prevention against mechanical failure. Although, the bio-cemented processes and media have been studied in the past in qualitative sense with experimental programs, the mathematical and numerical modelling techniques to quantify the strength parameters are rare. In this article, we propose the lattice element methodology which we applied to perform numerical computations of unconfined compression tests on bio-cemented sands. We also provide the experimental results of the unconfined compression tests on bio-cemented sands treated with a different number of cycles that we conducted in our laboratory. The experimental procedure is explained in details. The ultimate goal is to study the macroscopic response and also to quantify the process for engineering applications. The developed model with an embedded discontinuity can capture the macroscopic behaviour from meso-scale element failure, where the diagonal shear cracks which are seldom inherent to compression failure of highly cemented granular media lead the specimens to final failure. The model can capture the complex interaction of the cracks such as initiation and propagation, branching, coalescence and fingering at a nominal computation cost. The numerical and experimental results show good agreement to a large extent. The developed model is suitable to study brittle, and quasi-brittle behaviour of highly cemented granular media.

Particle-Scale Mechanisms in Undrained Triaxial Compression of Biocemented Sands: Insights from 3D DEM Simulations with Flexible Boundary

Particle-Scale Mechanisms in Undrained Triaxial Compression of Biocemented Sands: Insights from 3D DEM Simulations with Flexible Boundary