Impacts of Water Content and Temperature on the Unconfined Compressive Strength and Pore Characteristics of Frozen Saline Soils

Soil electrical resistivity has been used quite extensively for assessing mechanical properties of chemically treated soils in the recent past. One of the most innovative applications of this technique could be in the field of ground improvement wherein carbonated reactive magnesia (MgO) is employed for treating soils. With this in view, a systematic study that targets the application of electrical resistivity to correlate physical and strength characteristics of the carbonated reactive MgO-admixed silty soil is initiated, and its details are presented in this manuscript. To achieve this, reactive MgO-admixed soils were carbonized by exposing them to CO2 for different durations, and subsequently their electrical resistivity and unconfined compressive strength were measured. In this context, the role of a parameter, the ratio of the initial water content of the virgin soil to reactive MgO content (designated as w0/c), has been highlighted. It has also been demonstrated that w0/c is able to correlate, uniquely and precisely, with the physicochemical parameters of the soils (viz., unit weight, water content at failure, porosity, degree of saturation, and soil pH), electrical resistivity, and unconfined compressive strength at various carbonation times. In addition, microstructural properties have been obtained from the X-ray diffraction, scanning electron microscopy, and mercury intrusion porosimetry analyses. These properties have been used to substantiate the findings related to the carbonation of the reactive MgO-admixed soils.

Download Full-text

Microbial-Induced Carbonate Precipitation for Strengthening Soft Clay

Advances in Materials Science and Engineering ◽

10.1155/2020/8140724 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

J. Z. Xiao ◽

Y. Q. Wei ◽

H. Cai ◽

Z. W. Wang ◽

T. Yang ◽

...

Keyword(s):

Compressive Strength ◽

Water Content ◽

Unconfined Compressive Strength ◽

Soft Clay ◽

High Water ◽

High Water Content ◽

Carbonate Precipitation ◽

Experimental Conditions ◽

Strength Enhancement ◽

Complex Chemical Composition

Currently, calcite produced in sediments by microbial-induced carbonate precipitation (MICP) is mainly used as a strengthening binder in sand because sands are porous and have good permeability. Conventional wisdom does not consider MICP to be suitable for use in soft clay because of the clay particles’ small size and its minimal porosity. Because of the clay’s high water content and complex chemical composition, very little research has been done and not much is known about the use of MICP in soft clay for strength enhancement. For this paper, soft clay specimens were prepared by mixing a solution containing Sporosarcina pasteurii bacteria, solutions with different concentrations of nutrient salts, and soft clay. Unconfined compressive strength tests were carried out on these specimens after they had cured for 28 days in a moisture-controlled environment. These laboratory tests were used to study the chemical reactions, the clay’s strength, and other influencing factors. The results are as follows: (1) directly mixing a S. pasteurii solution, nutrient salts, and soft clay considerably improves the uniformity of the spatial distribution of the bacteria and the nutrients in the soft clay. Directly mixing these constituents promotes the formation of calcium carbonate and greatly simplifies soft clay sample preparation. (2) It is feasible to use MICP to increase the strength of soft clay. Compared to control specimens cured under the same conditions but without introduced nutrients and bacteria solution, the unconfined compressive strength of MICP-treated specimens can be increased by as much as 2.42 times to an unconfined compressive strength of 43.31 kPa. The water content in MICP-treated specimens was significantly reduced by the MICP reactions and in one case decreased from 40% to 30.73%. (3) The strength enhancement of microbially solidified soft clay is the result of two processes: urea hydration catalyzed by enzymes consumes water in the clay and the bacterially precipitated calcite forms in the sediment’s pores. (4) The micro-organism-produced calcite in the soft clay increases the calcite abundance from 0% to as much as 3.5%. (5) The MICP-treated strength of soft clay varies with the concentration of the nutrients provided. For the experimental conditions used for this paper, the optimum concentration of the CaCl2·2H2O and CH4N2O nutrients is 0.5 mol/L.

Download Full-text

Research about the Effect of Polypropylene Fiber on Mechanical Properties of Curing Sludge

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.250-253.788 ◽

2011 ◽

Vol 250-253 ◽

pp. 788-794

Author(s):

Shu Lin Zhan ◽

Shu Sen Gao ◽

Jun Ying Lai

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Shear Strength ◽

Water Content ◽

Unconfined Compressive Strength ◽

Polypropylene Fiber ◽

Physical And Mechanical Properties ◽

Curing Time ◽

Strength Tests ◽

Different Content

In order to study the influence of modified polypropylene (PP) fiber on the physical and mechanical properties of curing sludge, the same amount of cement and different content of polypropylene fiber were mixed into the sludge. Unconfined compressive strength tests, water content tests and shear strength tests were carried out on different specimens with different curing time. The results show that the sludge curing effect is markedly improved by the addition of the polypropylene fiber. As to the curing sludge with the same curing time, when the content of the polypropylene fiber increases, the unconfined compressive strength and the cohesive strength greatly increase, and the internal frictional angle decreases.

Download Full-text

Characterization of a cemented sand with the pulse-velocity method

Canadian Geotechnical Journal ◽

10.1139/t06-008 ◽

2006 ◽

Vol 43 (3) ◽

pp. 294-309 ◽

Cited By ~ 25

Author(s):

Zahid Khan ◽

Anwar Majid ◽

Giovanni Cascante ◽

D Jean Hutchinson ◽

Parsa Pezeshkpour

Keyword(s):

Compressive Strength ◽

Water Content ◽

Wave Velocity ◽

Unconfined Compressive Strength ◽

Void Ratio ◽

Cement Content ◽

Pulse Velocity ◽

Initial Water Content ◽

Strain Property ◽

Cemented Sand

The effect of variation in cement content, initial water content, void ratio, and curing time on wave velocity (low-strain property) and unconfined compressive strength (large-strain property) of a cemented sand is examined in this paper. The measured pulse velocity is compared with predictions made using empirical and analytical models, which are mostly based on the published results of resonant column tests. All specimens are made by mixing silica sand and gypsum cement (2.520% by weight) and tested under atmospheric pressure. The wave velocity reaches a maximum at optimum water content, and it is mostly affected by the number of cemented contacts; whereas compressive strength is governed not only by the number of contacts but also by the strength of contacts. Experimental relationships are developed for wave velocity and unconfined compressive strength as functions of cement content and void ratio. Available empirical models underpredict the wave velocity (60% on average), likely because of the effect of microfractures induced by confinement during the testing. Wave velocity is found to be a good indicator of cement content and unconfined compressive strength for the conditions of this study.Key words: wave velocity, low-strain stiffness, cemented sands, elastic moduli, unconfined compressive strength.

Download Full-text

Application of Stabilizer to Improvement the Saline Soil in Lor Nur Lacustrine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.912-914.53 ◽

2014 ◽

Vol 912-914 ◽

pp. 53-56

Author(s):

Jun Ci ◽

Yuan Fang Zhang

Keyword(s):

Compressive Strength ◽

Experimental Research ◽

Unconfined Compressive Strength ◽

Saline Soil ◽

Engineering Properties ◽

Saline Soils ◽

Lop Nur ◽

Engineering Standards ◽

Special Soil

Considering the Lop Nur Lacustrine plain saline soil is a special soil which with poor engineering properties such as collapsible and expansion. Through an experimental research on the saline soils stabilized by lime, cement and a polymeric solidified material was conducted. The unconfined compressive strengths and water-related stability of stabilized saline soils were discussed. It was shown that unconfined compressive strength and water-related stability of stabilized Lacustrine plain saline soils attained corresponding engineering standards and that it could be used as roadbed fillings., which could provide a reference to prevent and treatment about the dangers of Lop Nur Lacustrine plain saline soil.

Download Full-text

Analysis of Engineering Characteristics of Cement Soil with Low Mix Additions

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.256 ◽

2014 ◽

Vol 580-583 ◽

pp. 256-259

Author(s):

Ai Min Liu

Keyword(s):

Compressive Strength ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Unconfined Compressive Strength ◽

Engineering Characteristics ◽

Curing Condition ◽

Cement Soil ◽

Mixing Water

The mold bag cement soil was used to be as the material of dike core while building cofferdam. So the engineering characteristics of cement soil with low mix additions were analyzed in this paper. It was pointed out the unconfined compressive strength of cement soil is mainly related to the property of soil, water content, cement mixing content and degree of mixing uniformity, but has little to do with curing condition, cement adding way and the property of mixing water.

Download Full-text

Effect of humic acid on the behaviour of solidified dredged material

Canadian Geotechnical Journal ◽

10.1139/t09-045 ◽

2009 ◽

Vol 46 (9) ◽

pp. 1093-1099 ◽

Cited By ~ 14

Author(s):

Wei Zhu ◽

C. F. Chiu ◽

Chun-Lei Zhang ◽

Ke-Lin Zeng

Keyword(s):

Compressive Strength ◽

Humic Acid ◽

Water Content ◽

Acid Content ◽

Unconfined Compressive Strength ◽

Bound Water ◽

Dredged Material ◽

Curing Time ◽

Unconfined Compression ◽

Bound Water Content

Unconfined compression and bound-water content tests were conducted to study the effect of humic acid on the mechanical behaviour of solidified dredged material. It is found that the unconfined compressive strength (qu) and the change in bound-water content (Δmbw) exhibit similar relationships with the humic-acid content and curing time. Both parameters decrease with an increase in humic-acid content until reaching a threshold humic-acid content, above which the magnitudes of both parameters reduce to relatively low and steady values. In addition, both qu and Δmbw increase nonlinearly with the curing time. A relationship between qu and Δmbw is presented; Δmbw may reflect the extent of the hydrates developed in the solidified soil which increases nonlinearly with qu.

Download Full-text

Freezing–Thawing Behavior of Lime Treated Fine–grained Soil

Academic Journal of Nawroz University ◽

10.25007/ajnu.v7n4a273 ◽

2018 ◽

Vol 7 (4) ◽

pp. 75

Author(s):

Abdulrahman Aldaood ◽

Amina Khalil ◽

Marwen Bouasker ◽

Muzahim Al-Mukhtar

Keyword(s):

Compressive Strength ◽

Water Content ◽

Unconfined Compressive Strength ◽

Soil Samples ◽

Treated Soil ◽

Freeze Thaw ◽

Fine Grained ◽

Mineralogical Properties ◽

Fine Grained Soil ◽

The Impact

This research study was carried out to investigate the impact of freeze-thaw cycles on the mechanical and the mineralogical properties of lime treated fine-grained soil. The unconfined compressive strength, wave velocity, volume change, water content, pH and electrical conductivity values were determined during freeze-thaw cycles. Furthermore, Mercury porosimetry and X-ray diffraction tests were carry out to determine changes at microscopic level. The soil used in this study was taken at a site near Jossigny region in eastern part of Paris–France. The soil samples were treated with optimum lime percent 3% depending on the pH method, then cured for 28 days at 20 °C. The soil samples were subjected to 12 cycles of freeze-thaw following ASTM procedure. The result referred that, natural soil exhibit no strength resistance against freeze-thaw cycles and failed during the first hours of freeze-thaw cycles. Analyses indicated that freeze-thaw cycles reduce the unconfined compressive strength of all the tested samples. Moreover, water content during the applied cycles increases and induces significant volume changes. During freeze-thaw cycles, the cracks propagation which caused by the formation of ice lenses in the pores of lime treated soil samples were consider to have significant. The changes in the micro-structural and mineralogical properties reduce the durability of the lime treated soil samples when subjected to freeze-thaw cycles.

Download Full-text

The Role of Superabsorbent Polymer on Strength and Microstructure Development in Cemented Dredged Clay with High Water Content

Polymers ◽

10.3390/polym10101069 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1069 ◽

Cited By ~ 5

Author(s):

Xia Bian ◽

Lingling Zeng ◽

Yongfeng Deng ◽

Xiaozhao Li

Keyword(s):

Compressive Strength ◽

Water Content ◽

Unconfined Compressive Strength ◽

High Water ◽

High Water Content ◽

Strength Increase ◽

Primary Role ◽

Superabsorbent Polymer ◽

Microstructure Development

This paper presents the role of superabsorbent polymer (SAP) on strength and microstructure development in cemented clays with notably high water content. A series of unconfined compressive strength (UCS), scanning electron microscope (SEM) and X-ray diffraction (XRD) tests were performed to identify strength behavior and microstructure. Results showed that SAP significantly influenced the mechanical behavior of cemented clays with notably high water content, characterized by an increase in the unconfined compressive strength and a decrease in the after-curing water content with SAP content. This revealed that the strength increase due to SAP was directly related to the water absorption by SAP. Meanwhile, XRD results showed that the hydration products were controlled by cement and lime content, regardless of SAP content. That meant there was no chemical reaction between SAP particles used in this study and cement or lime. The microstructure analysis by SEM revealed that SAP played an important role in the microstructure of cemented clays. With an increase in SAP content, the water absorbed by SAP increased significantly, leading to a decrease in the pore volume and a denser soil fabric. This behavior indicated that the primary role of SAP on strength increase was to absorb and fix water in cemented clays. Consequently, the clay–cement cluster distance decreased with an increase in solid mass (soil particles and swollen SAP particles) and a decrease in pore water. The corresponding tighter flocculated fabric due to SAP eventually led to the strength increase.

Download Full-text

Analysis of Curing Agent on the Strength of Lightweight Soil Using Recycled Sludge

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.936.1382 ◽

2014 ◽

Vol 936 ◽

pp. 1382-1386

Author(s):

Guo Cai Wang ◽

Lin Chun Yu ◽

Ling Sha

Keyword(s):

Compressive Strength ◽

Unconfined Compressive Strength ◽

Soft Soil ◽

Strength Properties ◽

Strength Test ◽

Curing Agent ◽

Test Results ◽

Pore Characteristics ◽

Optimum Proportion ◽

Compressive Strength Test

In order to study the inorganic composite curing agents of lime, gypsum, fly ash on the strength properties of EPS lightweight soil using recycled sludge, the unconfined compressive strength test and scanning electron microscope test are done to investigate the strength properties of EPS lightweight soil. The effect and scope of each curing agent is investigated and determined by means of single-doped unconfined compressive strength test, and the optimum proportion of the curing agent is further determined by the method of orthogonal unconfined compressive strength test, of which the stabilized effectiveness of the lightweight soil is compared with those only using cement as curing agent. Finally, the SEM test is done to study the microstructure and pore characteristics of the lightweight soil mixed with EPS adding with or without curing agent. The test results and curing agent can be used as conference when stabilizing soft soil and treatment of discarded clay.

Download Full-text