Mechanical Performance and Microscopic Mechanism of Coastal Cemented Soil Modified by Iron Tailings and Nano Silica

In order to explore the effect of composite materials on the mechanical properties of coastal cement soil, cement soil samples with different iron tailings and nano silica contents were prepared, and unconfined compression and scanning electron microscope tests were carried out. The results show that: (1) The compressive strength of cement soil containing a small amount of iron tailings is improved, and the optimum content of iron tailings is 20%. (2) Nano silica can significantly improve the mechanical properties of iron tailings and cement soil (TCS). When the content of nano silica is 0.5%, 1.5%, and 2.5%, the unconfined compressive strength of nano silica- and iron tailings-modified cement soil (STCS) is 24%, 137%, and 323% higher than TCS, respectively. (3) Nano silica can promote the hydration reaction of cement and promote the cement hydration products to adhere to clay particles to form a relatively stable structure. At the same time, nano silica can fill the pores in TCS and improve the compactness of STCS.

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Effects of Soil Properties on the Performance of TRD Cut-Off Wall

Advances in Civil Engineering ◽

10.1155/2019/7098498 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Peng Zhang ◽

Haomin Song ◽

Kaijun Rui ◽

Juncai Li ◽

Shengnian Wang

Keyword(s):

Compressive Strength ◽

Soil Properties ◽

Permeability Coefficient ◽

Unconfined Compressive Strength ◽

Soil Layer ◽

Fine Sand ◽

Unconfined Compression ◽

Microscopic Mechanism ◽

Average Pore ◽

Cement Soil

The trench cutting remixing deep wall (TRD) method is a new cement soil cut-off wall construction technique, which has been widely used in cofferdam, embankment dam, and underground waterproof curtain structures. The chain cutter of TRD moves horizontally to cut and stir different soil layers by up and down to form a cement-mixed soil diaphragm wall with continuous and uniform thickness, the mechanics and permeability of which are obviously different from those of cement soil with a horizontally mixed single soil layer in traditional deep mixing pile (DMP). In this paper, five sets of onsite walling tests with different cement ratios were carried out to analyse the unconfined compression and permeability of undisturbed cement-mixed soil in TRD. The difference of both unconfined compressive and permeability coefficients in between TRD and DMP was analysed to discuss the stirring performance of TRD. Then, the microscopic mechanism of soil properties affecting the performance of cement-mixed soil has been studied by scanning electron microscopy (SEM) in the unconfined compression strength test and permeability coefficient test of cement soil with different mixed soil properties. The test results show that the unconfined compressive strength of cement-mixed soil is closely correlated to its gradation. As the mixed soil gradation curve approaches to the Fuller curve, the unconfined compressive strength would gradually increase. In mesoscopic, cement fine sand has a large pore structure, and the average pore area is 2.46 times as cement clay. The permeability coefficient of cement-mixed soil is controlled by the proportion of fine sand content with high permeability.

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Experimental Study on the Mechanical Performance of Pumice Powder Cement Soil

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.507.383 ◽

2014 ◽

Vol 507 ◽

pp. 383-387

Author(s):

Yong Qin Wen ◽

Xiang Dong Shen ◽

Chao Cui

Keyword(s):

Mechanical Properties ◽

Mechanical Performance ◽

Cement Content ◽

Soft Soil ◽

Cement Composite ◽

Unconfined Compression ◽

Optimum Amount ◽

Composite Cement ◽

Cement Soil ◽

Compression Resistance

With pumice as the additive agent used in cement composite soil . In order to test the mechanical performance of the composite cement soil, the unconfined compression resistance and triaxial test were done in the lab with different additive quantity (25%,50%), different cement content (8%,12%,16%,20%), The results show that the strength of the composite cement soil are significantly increase with increasing cement content , there is an optimum amount 16%.The pumice powder may evidently improve the mechanical properties of soft soil.

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Influence of Glass Fibers on Mechanical Properties of Concrete with Recycled Coarse Aggregates

Civil Engineering Journal ◽

10.28991/cej-2019-03091307 ◽

2019 ◽

Vol 5 (5) ◽

pp. 1007-1019 ◽

Cited By ~ 14

Author(s):

Babar Ali ◽

Liaqat Ali Qureshi ◽

Ali Raza ◽

Muhammad Asad Nawaz ◽

Safi Ur Rehman ◽

...

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Flexural Strength ◽

Mechanical Performance ◽

Volume Fraction ◽

Glass Fibers ◽

Construction Material ◽

Concrete Compressive Strength ◽

Coarse Aggregates ◽

Highly Sensitive

Despite plain cement concrete presenting inferior performance in tension and adverse environmental impacts, it is the most widely used construction material in the world. Consumption of fibers and recycled coarse aggregates (RCA) can add ductility and sustainability to concrete. In this research, two mix series (100%NCA, and 100%RCA) were prepared using four different dosages of GF (0%GF, 0.25%GF, 0.5%GF, and 0.75%GF by volume fraction). Mechanical properties namely compressive strength, splitting tensile strength, and flexural strength of each concrete mixture was evaluated at the age of 28 days. The results of testing indicated that the addition of GF was very useful in enhancing the split tensile and flexural strength of both RCA and NCA concrete. Compressive strength was not highly sensitive to the addition of GF. The loss in strength that occurred due to the incorporation of RCA was reduced to a large extent upon the inclusion of GF. GF caused significant improvements in the split tensile and flexural strength of RCA concrete. Optimum dosage of GF was determined to be 0.25% for NCA, and 0.5% for RCA concrete respectively, based on the results of combined mechanical performance (MP).

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Mechanical Properties and Microscopic Mechanism of Coral Sand-Cement Mortar

Advances in Materials Science and Engineering ◽

10.1155/2020/4854892 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Luoxin Wang ◽

Junshuai Mei ◽

Jing Wu ◽

Xingyang He ◽

Hainan Li ◽

...

Keyword(s):

Mechanical Properties ◽

Cement Mortar ◽

Mineral Admixture ◽

Mineral Admixtures ◽

Hardened Cement ◽

Hydration Reaction ◽

Microscopic Mechanism ◽

X Ray ◽

Volume Stability ◽

Coral Sand

The workability and mechanical performance of coral sand-cement mortar (coral mortar, for short) and the modification effects of mineral admixtures on the coral mortar were studied in this paper. The results showed that the strength of coral mortar was lower than that of standard mortar, but the strength of coral mortar was improved by compositing with the mineral admixture, which can be attributed to the improvement of the microstructure and interface transition area. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to explore the microscopic mechanism involved in the mechanical properties, volume stability, and hydration of mortar. The analyses revealed that the internal curing effect of coral sand improved the mechanical properties of mortar and its ability to resist shrinkage. The uneven surface of coral sand formed a meshing state of close combination with the hardened cement mortar, which helped to improve the volume stability of mortar. The Ca2+ and Mg2+ ions from coral sand participated in the hydration reaction of cement, which contributed to generating more hydration products. Moreover, the microaggregate filling and pozzolanic effects of fly ash and slag improved the mechanical properties of coral mortar and resistance to chloride ion diffusion.

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Influence of Curing Pressure on Unconfined Compressive Strength of Cemented Clay

Materials Science Forum ◽

10.4028/www.scientific.net/msf.928.263 ◽

2018 ◽

Vol 928 ◽

pp. 263-268 ◽

Cited By ~ 1

Author(s):

Anuchit Uchaipichat

Keyword(s):

Compressive Strength ◽

Unconfined Compressive Strength ◽

Cement Content ◽

Soft Clay ◽

Peak Stress ◽

Confining Pressure ◽

Compression Tests ◽

Unconfined Compression ◽

Soil Cement ◽

Curing Pressure

The soil-cement columns are generally installed and cured in the soft clay layers under confining pressure. The strength of the soil-cement columns may be influenced by confining pressure during curing period. In this study, the main objective was to study the influence of curing pressure on unconfined compressive strength of cemented clay. A series of unconfined compression tests was performed on a cement admixed clay sample cured under pressure values of 0 kPa (atmospheric pressure), 25kPa, 50kPa and 100 kPa using a typical unconfined compression equipment. The test samples with values of cement content of 0.5, 1.0 and 2.0 percent were cured for 28 days.The stress-strain curves obtained from all tests show a peak value of stress. The unconfined compressive strength or peak stress obviously increased with increasing cement content for all curing pressure conditions. It can be observed that the strength of samples gradually increased with curing pressure for cement content of 0.5 percent. For cement contents of 1.0 and 2.0 percent, the strengths of samples cured under pressures of 25 kPa dramatically increased from the strength of samples cured without pressure (0 kPa), however, the strengths of samples for curing pressures of 25, 50 and 100 kPa were not clearly different.

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Laboratory Experimental Research on Mix Ratio Test of Cement Soil

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.438-439.197 ◽

2013 ◽

Vol 438-439 ◽

pp. 197-201

Author(s):

Xian Hua Yao ◽

Peng Li ◽

Jun Feng Guan

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Unconfined Compressive Strength ◽

Cement Content ◽

Ratio Test ◽

Curing Time ◽

Curing Conditions ◽

Cement Ratio ◽

Water Cement Ratio ◽

Cement Soil

Based on the generalization and analysis of laboratory experimental results on mix ratio, the effects of various factors such as cement content, water-cement ratio, curing time, curing conditions and types of cement on the mechanical properties of unconfined compressive strength of cement soil are presented. Results show that the unconfined compressive strength of cement soil increases with the growing curing time, and it is greatly affected by the cement content, water-cement ratio, cement types and curing time, while the effect of curing conditions is weak with a cement content of more than 10%. Moreover, the stress-strain of the cement soil responds with the cement content and curing time, increasing curing time and cement content makes the cement soil to be harder and brittle, and leads to a larger Young's modulus.

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Study on the Relationship between Soil-Cement Parameters and Unconfined Compressive Strength

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.255-260.4012 ◽

2011 ◽

Vol 255-260 ◽

pp. 4012-4016

Author(s):

Jun Qing Ma ◽

You Xi Wang

Keyword(s):

Tensile Strength ◽

Compressive Strength ◽

Shear Strength ◽

Unconfined Compressive Strength ◽

Deformation Modulus ◽

Soil Cement ◽

Strength And Deformation ◽

Cement Soil ◽

Relationship Of ◽

The Relationship

This paper studies relationship between soil-cement parameters and unconfined compressive strength. The research in tensile strength and deformation modulus of soil-cement is an important basis for soil-cement failure mechanism and intensity theory. They also impact cracks, deformation and durability of cement-soil structure. Shear strength and deformation of soil-cement is important to the destruction analysis and finite element calculations. Therefore it needs to study on tensile strength, shear strength and deformation modulus of soil-cement. Based on previous experiments, the relationship of tensile strength, shear strength, deformation modulus and unconfined compressive strength of soil-cement are quantitatively studied.

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Effect of Sodium Aluminate Dosage as a Solid Alkaline Activator on the Properties of Alkali-Activated Slag Paste

Advances in Materials Science and Engineering ◽

10.1155/2021/6658588 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Bin Chen ◽

Jun Wang ◽

Jinyou Zhao

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Setting Time ◽

Sodium Aluminate ◽

Hydration Reaction ◽

Hydration Products ◽

Alkali Activated Slag ◽

Alkaline Activator ◽

Activated Slag ◽

Alkali Activated

Extensive research into alkali-activated slag as a green gel material to substitute for cement has been done because of the advantages of low-carbon dioxide emissions and recycling of industrial solid waste. Alkali-activated slag usually has good mechanical properties, but the too fast setting time restricted its application and promotion. Changing the composition of alkaline activator could optimize setting time, usually making it by adding sodium carbonate or sodium sulfate but this would cause insufficient hydration reaction power and hinder compressive strength growth. In this paper, the effect of sodium aluminate dosage as an alkaline activator on the setting time, fluidity, compressive strength, hydration products, and microstructures was studied through experiments. It is fair to say that an appropriate amount of sodium aluminate could obtain a suitable setting time and better compressive strength. Sodium aluminate provided enough hydroxyl ions for the paste to promote the hydration reaction process that ensured obtaining high compressive strength and soluble aluminium formed precipitate wrapped on the surface of slag to inhibit the hydration reaction process in the early phase that prolonged setting time. The hydration mechanism research found that sodium aluminate played a key role in the formation of higher cross-linked gel hydration products in the late phase of the process. Preparing an alkali-activated slag with excellent mechanical properties and suitable setting time will significantly contribute to its application and promotion.

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Effect of the Alkalized Rice Straw Content on Strength Properties and Microstructure of Cemented Tailings Backfill

Frontiers in Materials ◽

10.3389/fmats.2021.727925 ◽

2021 ◽

Vol 8 ◽

Author(s):

Shi Wang ◽

Xuepeng Song ◽

Meiliang Wei ◽

Wu Liu ◽

Xiaojun Wang ◽

...

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Compressive Strength ◽

Rice Straw ◽

Low Cost ◽

Strength Properties ◽

Hydration Reaction ◽

Strength Increase ◽

Improvement Effect ◽

Naoh Solution

The tailings and rice straw are waste by-products, and the storage of tailings on the ground and the burning of rice straws will seriously damage the ecological environment. In this study, the effect of different contents of alkalized rice straw (ARS; rice straw was alkalized with 4% NaOH solution) on the mechanical properties and microstructure of cemented tailings backfill (CTB; ARSCTB) was studied through uniaxial compressive strength (UCS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) tests. The results indicated that 1) the UCS of ARSCTB could be improved by ARS. However, with the increase in the ARS content from 0.1 to 0.4 wt%, the UCS showed a monotonous decreasing trend. The UCS improvement effect was best when the ARS content was 0.1 wt%, and at 7, 14, and 28 days curing ages, the UCS increased rate was 6.0, 8.3, 14.7% respectively. 2) The tensile strength of ARSCTB was generally higher than that of CTB and positively correlated with the ARS content. The tensile strength increase rate was 24.1–34.2% at 28 days curing age. 3) The SEM test indicated that the ARS was wrapped by cement hydration products, which improves its connection with the ARSCTB matrix. ARS performed a bridging role, inhibited cracks propagation, and provided drag or pulling force for the block that is about to fall off. Therefore, the mechanical properties of ARSCTB were enhanced. However, under high ARS content, the inhibition of ARS on hydration reaction and the overlap between ARS were not conducive to the improvement of the UCS of ARSCTB. 4) The post-peak residual strength and integrity effect of ARSCTB were greater. It is recommended to add 0.1–0.2 wt% ARS to the backfill with high compressive strength requirements such as the empty field subsequent filling mining method and the artificial pillar. 0.3–0.4 wt% ARS is incorporated into backfill with high tensile strength requirements such as high-stage filling with lateral exposure and artificial roof. This study further makes up for the blank of the application of plant fiber in the field of mine filling and helps to improve the mechanical properties of backfill through low-cost materials.

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Effect of nano-silica as cementitious materials-reducing admixtures on the workability, mechanical properties and durability of concrete

Nanotechnology Reviews ◽

10.1515/ntrev-2021-0097 ◽

2021 ◽

Vol 10 (1) ◽

pp. 1395-1409

Author(s):

Changjiang Liu ◽

Xin Su ◽

Yuyou Wu ◽

Zhoulian Zheng ◽

Bo Yang ◽

...

Keyword(s):

Mechanical Properties ◽

Building Materials ◽

Setting Time ◽

Microscopic Analysis ◽

Chloride Ion ◽

Cementitious Materials ◽

Hydration Reaction ◽

Ion Permeability ◽

Nano Silica ◽

Durability Of Concrete

Abstract Nano-silica (NS) is one of the most important nanomaterials in recent years. It is used as a new cement-based composite reinforcement in building materials because of its high volcanic ash activity. In order to achieve the goal of carbon peaking and carbon neutralization, combined with the research idea of cementitious materials-reducing admixture for concrete, under the condition of reducing the amount of cement in concrete by 20%, the influence of different dosages of NS on the setting time and mechanical properties of concrete was analyzed. In addition, the shrinkage performance, impermeability, and resistance to chloride-ion permeability of concrete were also studied. The results show that under the same curing conditions and ages, when the NS dosage is 2.5%, the compressive strength and splitting tensile strength of the specimen after 28 days of curing are the highest, reaching 40.87 and 3.8 MPa, which show an increase by 6.6 and 15.15%. The shrinkage performance of concrete increases with the increase in NS dosage. In addition, when the NS dosage is 2.0%, the durability of concrete has also been greatly improved. The impermeability of concrete increased by 18.7% and the resistance to chloride-ion permeability increased by 14.7%. Through microscopic analysis it was found that NS can promote the hydration reaction, generate more hydration products such as calcium silicate hydrate (C–S–H), enhance the interfacial adhesion between the matrix and the aggregate, and form a closer interfacial transition zone. Moreover, the addition of NS also reduces the cumulative pore volume in concrete, refines the pore size, and makes the internal structure of concrete denser.

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