Mechanical Properties Of Cemented Soil Research Articles

Experimental study on dynamic and static mechanical properties of polyvinyl alcohol fiber cement soil under salt freezing cycle

A universal testing machine and a 50 mm split Hopkinson pressure bar (SHPB) were used to conduct salt erosion and freeze-thaw (F-T) cycle coupling tests on cement soil specimens with 0.5% polyvinyl alcohol (PVA) fiber and without fiber in order to study the effects of salt solution and F-T cycles on the dynamic and static mechanical properties of cement soil. In four distinct solution settings (clear water, 9 g/L sodium sulphate solution, 9 g/L sodium chloride solution, and 9 g/L sodium sulphate and sodium chloride mixed solution). After F-T cycles, the cement soil specimens underwent the unconfined compressive strength (UCS) test, SHPB test, and SEM test. The findings indicate that as the number of F-T cycles increases, the dynamic and static mechanical properties of cement soil specimens decrease, and the rate of decline is rapid followed by slow. After five F-T cycles, the combined solution's unconfined compressive strength dropped to 15.91% (without fiber) and 29.41% (with fiber), respectively. After five F-T cycles, the dynamic compressive strength in sodium sulphate solution fell by 95.17% (without fiber) and 93.86% (with fiber). Fibers help to some degree by preventing salt erosion and F-T cycles. With more F-T cycles, the absorbed energy declines exponentially, and the order of the solutions' effects on the absorbed energy is: mixed sodium chloride and sodium sulphate solution > sodium chloride solution > sodium sulphate solution > clear water.

Enhancing Water Resistance and Mechanical Properties of Cemented Soil with Graphene Oxide.

Although cemented soil as a subgrade fill material can meet certain performance requirements, it is susceptible to capillary erosion caused by groundwater. In order to eliminate the hazards caused by capillary water rise and to summarize the relevant laws of water transport properties, graphene oxide (GO) was used to improve cemented soil. This paper conducted capillary water absorption tests, unconfined compressive strength (UCS) tests, softening coefficient tests, and scanning electron microscope (SEM) tests on cemented soil using various contents of GO. The results showed that the capillary water absorption capacity and capillary water absorption rate exhibited a decreasing and then increasing trend with increasing GO content, while the UCS demonstrated an increasing and then decreasing trend. The improvement effect is most obvious when the content is 0.09%. At this content, the capillary absorption and capillary water absorption rate were reduced by 25.8% and 33.9%, respectively, and the UCS at 7d, 14d, and 28d was increased by 70.32%, 57.94%, and 61.97%, respectively. SEM testing results demonstrated that GO reduces the apparent void ratio of cemented soil by stimulating cement hydration and promoting ion exchange, thereby optimizing the microstructure and improving water resistance and mechanical properties. This research serves as a foundation for further investigating water migration and the appropriate treatment of GO-modified cemented soil subgrade.

Experimental investigation on static and dynamic properties of nanosilica modified cement soil

It has been proved that nanosilica can improve the mechanical properties of cement soil, however, the static and dynamic properties of nanosilica modified cement soil and dispersion method study of nanosilica in cement soil were few, thereby investigated by unconfined compression test and dynamic triaxial test in this study. A series of unconfined compression test results indicated that the dispersion method of nanosilica is of importance in the strength of nanosilica modified cement soil (NCS), and soaking in water for 24 h is the optimal dispersion method among designed methods. Unconfined compressive strength (UCS) increases with increasing nanosilica content in the range of 0 to 0.4%, and then reduces gradually while nanosilica content is beyond 0.4%. The optimal nanosilica content can be seen as 0.4%, and the corresponding UCS at the curing age of 7 d is 960 kPa, which increases by 47.2% comparing to the specimen without nanosilica. Dynamic triaxial test reveals that the variation of the cumulative plastic axial strain and dynamic elastic modulus versus nanosilica content are same and opposite to UCS respectively, and the minimum of the cumulative plastic axial strain and maximum of dynamic elastic modulus are obtained while nanosilica content is 0.4%, which reduces by 48.1% and increases by 69.8% respectively comparing to the specimen without nanosilica. Finally, a simple and practical prediction model is developed to capture the evolution of the cumulative plastic axial strain with cycle number, and its simulation effect is validated by dynamic triaxial test results. It is believed that this paper finds an efficient dispersion method of nanosilica in cement soil, and provides the dynamic properties of nanosilica modified cement soil, which can promote practical application of nanosilica in road engineering.

Assessment of strength development of soil stabilized with cement and nano SiO2

In consideration of the significant negative impact of ordinary Portland cement (OPC) on the environment, the use of nanomaterials as an additive to mitigate the amount of cement and enhance the physical and mechanical properties of cemented soil has been introduced. However, the existing empirical formulae to evaluate the strength of cemented soil with nano SiO2 additive are limited. This study aims to investigate the strength behavior of cemented soil with OPC and nano SiO2 additive through a series of unconfined compressive tests. The cemented soils with varying cement content (3 %, 5 %, 10 %, and 15 %) and water content (1LL, 1.2LL, and 1.5LL) were mixed with 0 %, 2 %, 4 %, 6 %, and 8 % nano SiO2. The unconfined compressive strength (UCS) of the cemented soils with nano SiO2 was measured at 7, 14, 28, and 56 days. Empirical models were developed to estimate the UCS of cemented soil with nano SiO2 additive. The results indicate that the incorporation of nano SiO2 can effectively improve the strength of cemented soil. The UCS decreases rapidly with an increase in the ratio of water to content (wc/c) values when the wc/c value is less than 7, while the trend of decreasing UCS stabilizes when it exceeds 7. The developed empirical models based on Gallavresi’s formula can predict the UCS of cemented soil with nano SiO2 at different curing ages from the early strength on Day 7. The average MAPE value at different curing ages is 7.37 % by comparing the experimental value with the calculated value from the empirical model, demonstrating that the developed model has good predictive ability.

Effect of Organic Matter Components on the Mechanical Properties of Cemented Soil.

The organic matter in soft clay tends to affect the properties of cement-stabilized soil. The influence degree of different organic matter varies. In this paper, the influence weights and mechanism of the main organic matter components fulvic acid and humic acid on the mechanical properties of cemented soil were investigated. Impacts of FA/HA (fulvic acid/humic acid) values and curing time on the unconfined compressive strength, deformation characteristics, and microstructure of cemented soil were explored through the unconfined compressive strength test and electrical resistivity test. The results show that with the increase of FA/HA, the unconfined compressive strength of cemented soil gradually decreased and the plastic properties enhanced. The increase in curing time changed the stress-strain relationship of cemented soil, and some specimens showed brittle damage. The initial resistivity and structural property parameters of cemented soil gradually decreased with the increasing FA/HA value and increased with the increase of curing time. It revealed the influence law of FA/HA and curing time change on the microstructure of cemented soil. Based on the experimental results, the quantitative relationship equations between FA/HA and curing time and unconfined compressive strength, failure strain, deformation modulus, and resistivity were established.

Influence of Peat Soil Environment on Mechanical Properties of Cement-Soil and Its Mechanism

The influence of peat soil environment (PSE) on the mechanical properties of cement-soil in the area around Dianchi Lake and Erhai Lake in Yunnan Province has attracted much attention. This study explores the change law of cement-soil UCS in the PSE, and provides guidance for the development and sustained usage of peat soil foundation. The paper discusses the preparation of cement-soil samples by adding humic acid (HA) and cement to cohesive soil with low organic matter content (blending method) and soaking it in fulvic acid (FA) solution and deionized water (steeping method) to simulate the actual working environment of cement-soil. Unconfined compressive strength (UCS), acid consumption, ion leaching, scanning electron microscope (SEM), and X-ray diffraction (XRD) tests are carried out on cement-soil samples soaked for 90 days. The results show that HA can significantly reduce the UCS of cement-soil. FA can reduce the UCS of cement-soil when the content of HA is less than 18%. However, when the amount of HA is more than 18%, the UCS of cement-soil increases slightly. FA makes the deformation and failure type of cement-soil gradually change from brittle shear failure to plastic shear failure. FA reacts with the cement hydration products in the sample so that the cumulative acid consumption of the cement-soil sample continues to increase, and the dissolution of Ca2+, Mg2+, Al3+, and Fe3+ in the sample increases the ion concentration of the soaking solution. In addition, SEM and XRD show that HA can increase the macropores and connectivity of cement-soil, while FA fills part of the pores of the wetting layer. In the PSE, FA can strengthen the inner structure of HA particles and fill and cement the layers of cohesive particles, enhancing the construction of cement-soil with HA content greater than 18%, so that its UCS is relatively improved. However, when the amount of HA is less than 18%, there are more small pores in the cement-soil. The interaction between FA and HA in the cement-soil is weak. The influence of FA on cement-soil is mainly a weakening effect, and its UCS is relatively reduced.

Investigating Mechanical Properties of Cemented Soil under Static and Dynamic Loading after a Freeze-Thaw Cycle

Investigating Mechanical Properties of Cemented Soil under Static and Dynamic Loading after a Freeze-Thaw Cycle

Modification Effect of Nano-Clay on Mechanical Behavior of Composite Geomaterials: Cement, Nano-Silica and Coastal Soft Soil.

To study the modification effect of nano-clay and nano-SiO2 on cement-reinforced coastal soft soil, the effects of the nano-SiO2 and nano-clay on the mechanical properties of cement soil were studied through unconfined compressive and unconsolidated undrained shear tests, and the Duncan-Chang model was used to fit the test results. Results show that adding nano-clay and nano-SiO2 to cement soil improved its compressive and shear strength. The compressive strength and shear strength increased by 18-57% and 3-32%, respectively, with the increase in nano-clay content in a content range of 0-10%. Additionally, nano-clay can enhance the ductility of cement soil. Moreover, nano-clay and nano-SiO2 improve the shear strength by increasing the internal friction angle by 1°-2° and cohesion of 9-25%, and the cement-stabilized coastal soft soil enhanced by nano-SiO2 and nano-clay conforms to the Duncan-Chang model well.

Compressive strength characteristics of hybrid fiber-reinforced cemented soil

ABSTRACT Cemented soil commonly faces issues regarding strength, cracking resistance, and water stability when used in airstrip pavements. Three kinds of soil samples (low-liquid limit clay, high-liquid limit clay, and clayey sand), four kinds of fibers (basalt fiber, glass fiber, fine polypropylene fiber, and coarse polypropylene fiber), and one curing agent (cement) were analyzed in a systematic investigation of the compressive strength of fiber-reinforced cemented soil based on unconfined compressive strength (UCS), water stability, and failure mode. When 38 mm coarse polypropylene fiber at 0.3% content was mixed with 12 mm fine polypropylene fiber at 0.3% content, the hybrid fiber-reinforced cemented soil prepared after 7 d of saturated curing achieved UCS values of 4.18 (low-liquid limit clay), 4.36 (high-liquid limit clay), and 4.16 MPa (clayey sand), which satisfied airstrip requirements for the strength of base course. In this study, coarse polypropylene fiber was adopted and mixed with fine fiber to give full play to their respective advantages and effectively enhance the mechanical properties of cemented soil. The research results improved the understanding of the mechanical properties and reinforcement mechanism of coarse and fine fiber reinforced cemented soil in theory, and enriched the materials and methods of airstrip construction in engineering.

Mechanical properties of cement soil improved using microbial-induced calcite precipitation

Mechanical properties of cement soil improved using microbial-induced calcite precipitation

Study on Mechanical Properties of Cemented Soil Reinforced by Empty Fruit Bunch (EFB)

Study on Mechanical Properties of Cemented Soil Reinforced by Empty Fruit Bunch (EFB)

Experimental Research on the Mechanical Properties of Recycled Aggregate Particle Gradation and Addition on Modified Cement Soil

In order to study the effects of recycled aggregate with different particle gradations and different contents on the mechanical properties of cement soil modified by nano-MgO, unconfined compressive strength and scanning electron microscope (SEM) tests were carried out. The cement content was fixed at 15% and the nano-MgO content was 1.5%. The effects of two ages, three recycled aggregate contents, and three recycled aggregate particle gradations were considered. The test results show that the unconfined compressive strength of natural graded (RA), recycled coarse aggregate (SRA), and recycled fine aggregate (TRA) reached the maximum when the content of recycled aggregate was 20%, and the unconfined compressive strength of SRA was higher than that of TRA and RA. The residual strength of RA and SRA samples first increased and then decreased with the increase in recycled aggregate content, and the residual strength of TRA samples increased gradually with the increase in recycled aggregate content. The variation law of peak strain and peak strength of the three particle graded samples was consistent, and the variation law of brittle failure degree was highly consistent with that of residual strength. When the recycled aggregate content of RA, SRA, and TRA samples was 20%, the deformation resistance and stiffness of the samples were the best. In addition, SRA samples showed the best deformation resistance, followed by TRA samples and, finally, RA samples. The smaller the porosity of the sample, the tighter the sample structure and the stronger the bearing capacity of SRA. The unconfined compressive strength of the WPRA sample was represented by an exponentially negative power function of the porosity.

Effect of different fibers on small-strain dynamic properties of microbially induced calcite precipitation–fiber combined reinforced calcareous sand

Microbially induced calcite precipitation (MICP)–fiber combined reinforcement through the addition of fibers during the MICP process is a novel, natural, and green technique for foundation improvement, which can effectively enhance the mechanical properties of cemented soil. However, the small-strain dynamic properties of this method remain unexplored. The effects of different polyester fiber and hemp fiber contents (0%, 0.1%, 0.2%, and 0.4%) on the dynamic properties of the MICP–fiber combined reinforced calcareous sand under small-strain conditions were studied using resonant column tests, scanning electron microscopy (SEM), and atomic force microscopy (AFM). The maximum dynamic shear modulus of the MICP–fiber combined reinforced calcareous sand under small-strain increases with the fiber content; the stiffness degradation rate of the dynamic shear modulus ratio of the test sample increases with the addition of two types of fibers, and the addition of hemp fibers greatly boosts the increase rate of the damping ratio. The SEM results indicate that excessive fibers distributed between the sand particles occupy the nucleation sites of bacteria, hinder the bonding between sand particles, and ultimately affect the dynamic shear modulus parameters of the sample. The AFM results show that the hemp fiber has much greater surface roughness than the polyester fiber. Therefore, the change rate of the damping ratio of the hemp fiber-doped MICP–fiber combined reinforced calcareous sand is much greater than that of the polyester fiber-doped sample. This is the first report on the basic mechanism of the small-strain dynamic properties of the MICP–fiber combined reinforced calcareous sand with different fiber contents and types. Furthermore, it provides a new theoretical basis for related research on improving the dynamic properties of sand thus reinforced.

Influences of Curing Period and Sulfate Concentration on the Dynamic Properties and Energy Absorption Characteristics of Cement Soil

To study the influences of curing period and sulfate concentration on the dynamic mechanical properties of cement soil, this study used a split Hopkinson pressure bar device. Impact tests were conducted on cement soil specimens with different curing periods and different sulfate concentrations. The relationships between the dynamic stress–strain, dynamic compressive strength, and absorption energy of these cement soil specimens were analyzed. The test results show that with continuous loading, cement soil specimens mainly experience an elastic stage, plastic stage, and failure stage; with increasing curing period and sulfate concentration, the dynamic compressive strength and absorption energy of cement soil specimens follow a trend of first increasing and then decreasing. The dynamic compressive strength and absorption energy of cement soil specimens reached maximum values at a curing period of 14 d and a Na2SO4 solution concentration of 9.0 g/L. Increasing the dynamic compressive strength and absorption energy can effectively improve the ability of cement soil specimens to resist damage. This paper provides a practical reference for the application of cement soil in dynamic environments.

A study on the mechanical properties of cement soil added with ferronickel slag

Unconfined compressive strength test was employed hereby to study the effect of ferronickel slag content and mineral powder content on strength performance of cement soil. In the experiment, 0%, 10%, 20%, 30% and 40% ferronickel slag were added into the cement soil, respectively, to figure out the comparatively better content of ferronickel slag was 20%. The experiment results also indicate the addition of ferronickel slag also significantly affected the early strength of cement soil, but as the time proceeded, the strength of cement soil added with ferronickel slag fell less quickly as before.

Improvement of mechanical behavior of cemented soil reinforced with waste cornsilk fibers

This study focused on exploring the effects of cornsilk fibers on mechanical properties of cemented soil by conducting compaction, compression, and splitting tension tests. The influences of fiber content (0%, 0.25%, 0.5%, and 1% by weight of dry soil), cement content (4%, 8%, and 12% by weight of dry soil), and curing time (7, 14, and 28 days) were investigated in the present work. The multiple nonlinear regression models following the parameters including curing time, fiber content, and cement content for predicting compressive strength as well as tensile strength were established. The effective degree of each parameter on compressive and tensile strength was also evaluated. The experimental results revealed that the addition of cornsilk fibers in cemented soil improved the compressive and splitting tensile strength. The fiber contents of 0.25%–0.5% are recommended to use in cemented soil reinforced by cornsilk fibers. Splitting tensile strength equals to 0.148 times of compressive strength for both cemented soil and fiber-cement stabilized soil. The compressive and tensile strength could be predicted following the regression models with high accuracy. Based on the proposed model and sensitivity analysis, the cement content is the most effective parameter affecting on compressive strength and splitting tensile strength followed by curing time and fiber content.

Research on Static Triaxial Mechanical Properties of New CementSoil Reinforced with Polypropylene Fiber

Through the laboratory test, the mechanical properties of cementsoil with adding desulfurization gypsum, fly ash, and polypropylene fiber were studied. Three different percentages (0%, 0.5%, and 1.0%) of polypropylene fiber were mixed into new cementsoil for which the cement content is 15% of the dry soil weight, the desulfurization gypsum content is 2% of the dry soil weight, and the fly ash content is 1.0% of the dry soil weight. The new cementsoil strength reinforced with polypropylene fiber was studied by triaxial test under different polypropylene fiber mixing ratio, different age, and different confining pressure. The experimental results show that, compared with ordinary soil, the deviatoric stress and the peak shear strength reinforced with polypropylene fiber have different amplitude increase. At the same time, the internal friction angle of new cementsoil with polypropylene fiber increases slightly with the growth of the age. The stress-strain curve of the polypropylene fiber cementsoil has the typical work hardening characteristic and has the characteristics of bulge fracture.

The Effect of Cementation on the Mechanical Properties of Muddy Soil of East-South Coastal Area of China

Based on characteristic of the muddy soil residing in east-south coastal area of China, the effect of cement grade, cement-mixing ration and cement type on mechanical properties of cement-soil was carried out in this paper. The results show that cement-soil increases obviously with increasing of hydration age for different cement types. At early hydration age, strength of cement-soil increases quickly. And at the age of 28d~90d, strength of cement-soil still show quite obvious increasing, but increase rate is slow. Increasing cement-mixing ratio improve strength of cement-soil obviously and 0.15~0.20 cement-mixing ratio is suitable to use. Higher cement grade can bring higher strength of cement-soil. Early strength of cement-soil solidified with P.S32.5 increases slowly, but the middle and late stage strength of cement-soil solidified with P.S32.5 increase quickly. The solidification effect of P.S 32.5 is better than that of AEC32.5 and P.MSR32.5.

Experimental Study on Rubberized Cement-Soil Resistance to Chlorine-Ion Permeation

Mixing abandoned tyre rubberized powder as filler into cement-soil to form rubberized cement-soil can improve physical mechanical properties of cement-soil. By the methods of natural immersion and chemical titration, the rubberized cement-soil resistance to chlorine-ion permeation was tested and measured. With rubber content increasing, the chlorine-ion content and the apparent diffusion coefficient gradually reduces. The effects of large rubber particle size are better than that of the small. The soluble chlorine-ion content decreases with the erosion depth increasing. In the same depth, as erosion solution concentration increases, the apparent diffusion coefficient increases manyfold. It deduces that rubberized cement-soil resistance to chlorine-ion permeation is superior to common cement-soil.