Engineering Properties of CIPS Cemented Calcareous Sand

Microbial-induced calcite precipitation (MICP) has been a promising method to improve geotechnical engineering properties through the precipitation of calcium carbonate (CaCO3) on the contact and surface of soil particles in recent years. In the present experiment, water absorption and unconfined compressive strength (UCS) tests were carried out to investigate the effects of three different fiber types (glass fiber, polyester fiber, and hemp fiber) on the physical and mechanical properties of MICP-treated calcareous sand. The fibers used were at 0%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, and 0.40% relative to the weight of the sand. The results showed that the failure strain and ductility of the samples could be improved by adding fibers. Compared to biocemented sand (BS), the water absorption of these three fiber-reinforced biocemented sands were, respectively, decreased by 11.60%, 21.18%, and 7.29%. UCS was, respectively, increased by 24.20%, 60.76%, and 6.40%. Polyester fiber produced the best effect, followed by glass fiber and hemp fiber. The optimum contents of glass fiber and polyester fiber were 0.20% and 0.25%, respectively. The optimum content of hemp fiber was within the range of 0.20–0.25%. Light-emitting diode (LED) microscope and scanning electron microscope (SEM) images lead to the conclusion that only a little calcite precipitation had occurred around the hemp fiber, leading to a poor bonding effect compared to the glass and polyester fibers. It was therefore suggested that polyester fiber should be used to improve the properties of biocemented sand.

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

Materials ◽

10.3390/ma13184198 ◽

2020 ◽

Vol 13 (18) ◽

pp. 4198 ◽

Cited By ~ 2

Author(s):

Md Al Imran ◽

Sivakumar Gowthaman ◽

Kazunori Nakashima ◽

Satoru Kawasaki

Keyword(s):

Fiber Length ◽

Natural Fibers ◽

Construction Materials ◽

Soil Improvement ◽

Fiber Content ◽

Microbial Interactions ◽

Engineering Properties ◽

Precipitation Trend ◽

Calcareous Sand ◽

Jute Fibers

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.

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Effect of relative density and biocementation on cyclic response of calcareous sand

Canadian Geotechnical Journal ◽

10.1139/cgj-2018-0573 ◽

2019 ◽

Vol 56 (12) ◽

pp. 1849-1862 ◽

Cited By ~ 24

Author(s):

Peng Xiao ◽

Hanlong Liu ◽

Armin W. Stuedlein ◽

T. Matthew Evans ◽

Yang Xiao

Keyword(s):

Calcium Carbonate ◽

Relative Density ◽

Pore Pressure ◽

Soil Particle ◽

Engineering Properties ◽

Excess Pore Pressure ◽

Calcareous Sand ◽

Sem Images ◽

Cyclic Response ◽

Excess Pore

Microbial-induced calcium carbonate precipitation (MICP) represents a promising approach to improve the geotechnical engineering properties of soils through the precipitation of calcium carbonate (CaCO3) at soil particle contacts and soil particle surfaces. An extensive experimental study was undertaken to investigate the influence of initial relative density on the efficiency of the biocementation process, the reduction of liquefaction susceptibility, and the cyclic response in biocemented calcareous soils. For this purpose, stress-controlled undrained cyclic triaxial shear (CTS) tests were carried out on untreated and MICP-treated calcareous sand specimens for different initial relative densities and magnitudes of biocementation. Improvement in the cyclic response was quantified and compared in terms of excess pore pressure generation, evolution of axial strains, and the number of cycles to liquefaction. The cyclic experiments show that MICP treatment can change the liquefaction failure mechanism from flow failure to cyclic mobility and can significantly change the excess pore pressure generation response of initially loose specimens. Scanning electron microscope (SEM) images indicate the CaCO3 crystals alter the characteristics of the sand particles and confirm the physical change in soil fabric that impacts the dynamic behavior and liquefaction resistance of MICP-treated specimens. Furthermore, the effect of biocementation was contrasted against the effect of relative density alone, and MICP treatment was shown to exhibit greater efficiency in improving the cyclic resistance than densification.

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Investigation of Engineering Properties of Cement-Stabilized Calcareous Sand Foundation

Advances in Materials Science and Engineering ◽

10.1155/2021/9188560 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Yuan Chai ◽

Dai-Ping Jiang ◽

Fu-Jiang Wang ◽

Hai-Bo Lyu

Keyword(s):

Bearing Capacity ◽

Cement Content ◽

Soft Soil ◽

Friction Angle ◽

Engineering Properties ◽

Calcareous Sand ◽

Uniaxial Compression Strength ◽

Engineering Characteristics ◽

Apparent Cohesion ◽

Engineering Problems

Calcareous sand is widespread around Nansha Islands, South China Sea. In oceanic and coastal engineering, calcareous sand is usually used as a building foundation and backfill material for airport runway embankments. The engineering characteristics of calcareous sand is different from terrigenous sand because of its irregular grain shape, lower particle strength, and internal voids, which have caused many engineering problems in the last decades. Cement-stabilized soil, as a common foundation reinforcement method, can solve these engineering problems and improve the foundation strength effectively. Therefore, it is very important to estimate the engineering characteristics of cement-stabilized calcareous sand foundations. In this paper, the basic engineering characteristics, bearing capacity, and deformational behavior of calcareous sand were studied by carrying out a series of tests on cement-stabilized calcareous sand. It is found that: (1) the uniaxial compression strength of calcareous sand is higher than that of Guangzhou soft soil but lower than that of filter medium quartz sand; (2) the deformation of the calcareous sand under compression is mainly plastic, and the elastic deformation gradually increases with increasing cement content; (3) the apparent cohesion of calcareous sand increases, while internal friction angle decreases with increasing cement content; (4) cement-stabilized method can significantly improve the bearing capacity of calcareous sand foundation, especially for the saturated state. A cement content equal to or more than 15% and a thickness of 1/8 of the foundation can effectively improve the bearing capacity of the foundation; and (5) the ultimate bearing capacity of the foundation by numerical calculation is higher than that by experiments, while the settlement by calculating is lower.

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Unconfined Mechanical Properties of Nanoclay Cement Compound Modified Calcareous Sand of the South China Sea

Advances in Civil Engineering ◽

10.1155/2020/6623710 ◽

2020 ◽

Vol 2020 ◽

pp. 1-16

Author(s):

Wei Wang ◽

Jian Li ◽

Jun Hu

Keyword(s):

Mechanical Properties ◽

Deformation Modulus ◽

Discrete Distribution ◽

Cement Composite ◽

Mechanical Tests ◽

Engineering Properties ◽

Compressive Property ◽

Fusion Algorithm ◽

Calcareous Sand ◽

Cement Compound

Calcareous sand is characterized by low strength, multiporosity, and high-pressure shrinkage. This often leads to poor engineering properties. Therefore, it is often necessary to reinforce the calcareous sand in order to meet the actual engineering demand for bearing capacity. To study the modification effect of calcareous sand of nanoclay by cement, mechanical tests and microscopic tests of the cement calcareous sand (CCS) modified by different nanoclay content and cement content were conducted. Through the unconfined compressive test, the mechanical properties of nanoclay and cement compound modified calcareous sand (NCCS) were studied. The micromechanism of nanoclay and cement composite modified calcareous sand was analyzed by SEM. Representative curves of data groups of stress and strain data were obtained by the fusion algorithm, which effectively circumvented the discrete distribution of determined data. Test results showed that the following: (1) The compressive property of CCS could be improved by the admixture of nanoclay, and the optimum admixture ratio was 8%. (2) The admixture of nanoclay could enhance the deformation modulus of CCS and improve the resistance of CCS against external load deformation capacity. (3) Nanoclay could increase the density of the internal structure of CCS and improve its mechanical properties.

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