Strength Of Soil-cement Research Articles

The effect of steel fibres on the uniaxial compressive strength and tensile strength of soil-cement

ABSTRACT Soil-cement is gaining acceptance in the construction industry for use in the improvement of sandy soil, despite its low strength Research has attempted to increase the strength of this material by increasing the percentage of additives. The current study investigated the effect of steel fibre (SF) as a reinforcer on the performance, UCS and TS at different fibre contents, lengths, diameters and shapes. The results showed that the use of 2% straight fibre significantly increased the UCS and that the samples performed better than those containing hooked or crimped. A decrease in the SF length from 10 to 5 mm and increase in the diameter from 0.3 to 0.6 mm caused decreases in the UCS. The greatest increase in TS occurred with the addition of 2% hooked fibres and was 4.6 times the increase in strength without fibres. The reason for the increase in the strength of the samples was bridge-like performance of the SFs in the soil-cement. The use of SFs together with cement to improve sandy soil is a new and effective way of improving the mechanical behaviour of the soil. This indicates that the addition of SFs can be a step towards more optimal use of soil-cement in engineering projects.

Experimental Investigation of the Axial Load Capacity of Bilateral Helix-Stiffened Cement Mixing Piles in Soft Marine Soil

Bilateral helix-stiffened cement mixing piles (BHCMPs) are a new type of robust composite pile. In this paper, the influence of design parameters, such as the diameter of inner helix plates and the number and size of outer mixing helix plates, on the vertical bearing performance of the pile foundation and the behavior of the pile diameter are investigated through laboratory model tests. The results indicate that incorporating a reverse-mixing process in the pile formation of helix-stiffened cement mixing piles can enhance the overall ultimate bearing capacity and strengthen the soil-cement of the piles. In the case of the same double-blade inner drill pipe, for every 22 mm increase in the blades, its ultimate compressive load-bearing capacity was increased by 10% to 25%, and its pullout load-bearing capacity was increased by 15% to 45%. With further increases in the blades, the percentage increase in the compressive and pullout load-bearing capacity was reduced. With an increase in the number of external mixing blades, its compressive load capacity increased in the range of 5% to 20%, and the elevation load capacity increased in the range of 10% to 25%. Increasing the number of reverse-mixing helix plates on the outer casing enhances the soil-cement strength of the pile body by approximately 15–20% for each additional plate. The average strength of the pile-body soil-cement for each additional plate is estimated to be 1 to 1.4 times that of the previous set, indicating that increased mixing iterations can enhance the perimeter soil-cement strength of the pile. The average bond diameter of soil-cement piles with double-blade internal drilling rods could be seen from the diameter of the piles formed, which was 1.02 to 1.21 times the diameter of the blades.

A Numerical Study of Reinforcement Structure in Shaft Construction Using Vertical Shaft Sinking Machine (VSM)

Using the Vertical Shaft Sinking Machine (VSM) for shaft construction is an emerging modern technology, which is also currently one of the most advanced techniques in the field of shaft sinking. Current research on VSM technology primarily focuses on mechanical and technical issues, neglecting the impact of the construction on the surrounding soil and the structure itself. This oversight leaves structural design lacking a reliable foundation. Additionally, there is insufficient information on the role of reinforcement design during construction in soft soils. These engineering challenges have hindered the widespread implementation of this new technology. Therefore, a series of numerical models were used to analyse the mechanical behaviour of shaft and soil during or after the sinking process, with the aim of addressing these gaps by investigating the influence of shafts constructed using VSM technology, and providing a scientific basis for reinforcement design in soft soil. The case study shows that increasing the soil-cement strength does not have a significant effect on the overall deformation of the soil surrounding the shaft, but leads to a notable reduction in the plastic zone volume, subsequently enhancing the overall stability of the neighbouring soil. The ring bottom beam design effectively reduces convergence deformation by about 50%, while also improving the horizontal internal force distribution near the cutting edge. However, this approach significantly escalates local vertical bending moments, necessitating thorough consideration in the design stage.

Performance of Ferronickel Slag Powder Soil Cement under Freshwater Curing Conditions

Ferronickel slag is the solid waste slag produced by smelting nickel–iron alloy. After grinding ferronickel slag into powder, it has potential chemical activity. It can partially replace cement and reduce the amount of cement, and is conducive to environmental protection. The mechanical properties of soil cement were investigated through the compressive strength test and inter-split tensile test of ferronickel slag powder soil cement with different dosages. To further study the mechanism of ferronickel slag powder’s action on soil cement microscopically, the microstructure of soil cement was analyzed by using a scanning electron microscope and nuclear magnetic resonance equipment. The results of the study show that the incorporation of ferronickel slag powder can enhance the compressive and tensile strength of soil cement. The best performance enhancement of ferronickel slag powder was achieved when it was doped with 45% of its mass. The hydration products of soil cement increased with the increase in the doping amount, but the excessive doping of ferronickel slag powder would lead to a weakening of the hydration reaction and a decrease in the strength of the soil cement. At the same time, ferronickel slag powder plays the role of filling the void of soil cement. With the increase in ferronickel slag powder, the large pores inside the soil cement are reduced and the structure is denser.

Seismic performance assessment of a retrofitted pile-supported wharf considering soil-cement uncertainties using artificial neural network

Seismic performance assessment of a retrofitted pile-supported wharf considering soil-cement uncertainties using artificial neural network

A Study on Mechanical Properties of Modified Soil–Cement Mixed with Ferronickel Slag Powder under Dry–Wet Cycles in Marine Environments

Soft soil foundations in marine environments are under coupling actions of seawater erosion and dry–wet cycles due to tides. Ferronickel slag is a solid waste produced in the smelting of ferronickel alloys. To recycle industrial solid waste and conserve energy, ferronickel slag is partially substituted for cement to solidify the soft soil foundations in marine environments. Unconfined compression tests were conducted for soil–cement mixed with ferronickel slag of various proportions to investigate its apparent erosion characteristics and mechanical characteristics under dry–wet cycles. In the tests, the corresponding numbers of cycles were set to 0, 6, 12, and 18. To further investigate the microscopic action mechanism of ferronickel slag on soil–cement, a nuclear magnetic resonance (NMR) device was utilized to analyze the microstructure of the soil–cement. According to the testing results, the unconfined compressive strength of soil–cement first increased and then decreased when the number of cycles of seawater erosion increased. With other conditions being the same, the addition of ferronickel slag can improve soil–cement strength, and changes in soil–cement strength were more significant than that with no ferronickel slag mixed. Moreover, the optimal amount of admixture was proved to be 45%. As the number of dry–wet cycles increased, the mass of soil–cement first increased and then decreased. With the same number of dry–wet cycles, soil–cement mixed with ferronickel slag had a smaller mass loss rate than that with no ferronickel slag added. After six dry–wet cycles, apparent erosion of soil–cement becomes increasingly serious, including the absence of edges and corners, deformation of surfaces, and even spalling and cracking. The NMR analysis revealed that dry–wet cycles can promote the evolution of small pores into larger ones within the soil–cement, thereby increasing the number of larger pores, leading to an increase in porosity, a decrease in the compactness of the soil–cement, and a reduction in strength.

Test research on flexural strength of soil-cement reinforced with carbon fibers

Test research on flexural strength of soil-cement reinforced with carbon fibers

Parametric Study on Analyzing the Effect of Soil–Cement Strength on the Uplifting Behavior of HSCM Piles Installed in Marine Soft Clay

The Helix-Stiffened Cement Mixing (HSCM) pile is a composite pile constructed by grouting the soil–cement during the installation of the helical pile. A series of 3-D Finite Element Method (FEM) models were developed to investigate the uplifting behavior of HSCM piles installed in marine soft clay. The uplifting behavior of HSCM piles was compared to the Stiffened Deep Cement Mixing (SDCM) piles and the difference was discussed. The FEM results showed that the uplifting ultimate bearing capacity of the HSCM piles and SDCM piles increased with the soil–cement-strength-to-clay-adhesion ratio (Cref/su) until the ratio reached 20 and 40, respectively. The failure mode influenced the uplifting behavior of HSCM piles. At Cref/su ∈ 40,80, the HSCM pile incurred damage at the pile–soil interface, which gradually shifted to the steel pipe and soil–cement interface as the Cref/su was further decreased. Based on the FEM results, the empirical formula for estimating the uplift ultimate bearing capacity of HSCM piles under different failure types was proposed, which provided reliable guidance for designing HSCM piles.

Soil-cement formation factor: methodological approach and relationship with unconfined compression strength

This study investigated the use of the Formation Factor of the material as an alternative way to estimate soil-cement strength involving no destructive tests. This factor is obtained from Archie’s Law and consists of the ratio of pore water electrical conductivity to saturated porous material electrical conductivity, being related to porosity by constant terms. In this study, the electrical conductivity of the pore solution was obtained from a soil-cement leaching test after curing, and the conductivity of the monolithic soil-cement, by applying continuous voltage between 12-35 V onto electrodes of 1 mm thick copper plates. The influence of cement content and dry density on the electrical properties and water absorption was studied and discussed for curing times of 7 and 28 days. The samples molded with higher dry densities and cement contents presented higher Formation Factor for Soil Cement and higher unconfined compression strength. The Formation Factor and the unconfined compression strength are linearly related. Due to the methodology adopted, the Formation Factor was predominantly influenced by the conductivity of the pore solution and was related to the open porosity by means of a power function. Therefore, the Archie’s Law can be applied to soil-cement. In this case, the cementation coefficient varies until 28 days of curing, tending to stabilize around 8 from that age onwards. The volumetric coefficient can be adopted as a constant with a value of 1012.

Effect of curing conditions on the strength of soil cement

An experimental program was directed to the evaluation of the strength of soil (ball clay)-cement, and soil (soft clay)-cement samples with different curing conditions; tap water, lime-saturated water, plastic wrapping, and open ambient air at 28 days. The compression, and the scanning electron microscopy results were used to describe the effect of curing conditions on the compressive strength of soil-cement samples. The compressive strength of soil-cement samples was ~ 50% that of the plain cement sample. The compressive strength of the soft clay-cement samples was slightly higher than the ball clay-cement samples because of the coarse particles of soft clay containing a high amount of quartz, allowing the water to react with cement powder and increased the strength of soil-cement samples. The tendency of compressive strength development in the soil-cement samples was similar to that of the cement sample. The highest compressive strength was obtained for the lime-saturated water cured samples, suggesting a higher rate of hydration process by the protection of CaCO 3 leaching from cement in the lime water. Thus, the compressive strength in soil-cement samples was enhanced by the binding of cement hydration products between the adjacent soil particles.

Analysis of Mechanical Properties of Loess with Cement Incorporation Ratio

Taking loess as the research object, the influence of cement content on mechanical properties of loess was studied. Firstly, the basic physical parameters of loess were obtained through laboratory physical index test, and improved by using Portland cement. Secondly, under different incorporation ratios (3%, 5%, 7%, 9%), heavy compaction test and liquid-plastic limit test were carried out respectively to obtain mechanical parameters of cement-improved loess. Finally, the shear strength parameters and compressive strength of the improved soil samples are obtained by unconsolidation undrained triaxial shear test and unconfined compressive strength test. The results show that the liquid limit, plastic limit and plastic index of loess improved by adding cement increase compared with the original soil sample, indicating that the binding force between soil particles is improved and the plasticity is enhanced. The variation range of dry density and water content has no obvious relationship with the content of cement. At the same time, the compressibility of soil is reduced and the collapsibility of soil is eliminated. With the increase of age, the strength of cement-modified soil also increases. Through unconsolidated and undrained triaxial shear tests and unconfined compressive strength tests, the strength of loess improved significantly after adding cement, and the strength of soil-cement increased with the increase of cement content, and water stability was obviously improved.

Sulfate Resistant Cement and Barium Components Effects on Soil-Cement Strength under Sulfate Attack –A Laboratory Study

Sulfate Resistant Cement and Barium Components Effects on Soil-Cement Strength under Sulfate Attack –A Laboratory Study

Mechanical Properties and Micro Mechanism of Nano-Clay-Modified Soil Cement Reinforced by Recycled Sand

To observe the effect of recycled sand and nano-clay on the improvement of the early strength of soil-cement (7d), 0%, 10%, 15% and 20% recycled sand were added. While maintaining a fixed moisture content of 30%, the ratios of each material are specified in terms of soil mass percentage. The shear strength of CSR (recycled sand blended soil-cement) was investigated by direct shear test and four groups of specimens (CSR-1, CSR-2, CSR-3 and CSR-4) were obtained. In addition, 8% nano-clay was added to four CSR groups to obtain the four groups of CSRN-1, CSRN-2, CSRN-3 and CSRN-4 (soil-cement mixed with recycled sand and nano-clay), which were also subjected to direct shear tests. A detailed analysis of the modification mechanism of soil-cement by recycled sand and nano-clay was carried out in combination with scanning electron microscopy (SEM) and IPP (ImagePro-Plus) software. The test results showed that: (1) CSR-3 has the highest shear strength due to the “concrete-like” effect of the incorporation of recycled sand. With the addition of 8% nano-clay, the overall shear strength of the cement was improved, with CSRN-2 having the best shear strength, thanks to the filling effect of the nano-clay and its high volcanic ash content. (2) When recycled sand and nano-clay were added to soil-cement, the improvement in shear strength was manifested in a more reasonable macroscopic internal structure distribution of soil-cement. (3) SEM test results showed that the shear strength was negatively correlated with the void ratio of its microstructure. The smaller the void ratio, the greater the shear strength. This shows that the use of reclaimed sand can improve the sustainable development of the environment, and at the same time, the new material of nano-clay has potential application value.

Variation in strength owing to solidification treatment of weathered granite soil

Recently, soil-cement is being increasingly used in various applications such as road pavements, slope protection, backfilling of earth walls, and improving soft ground, in order to increase the strength of the raw material soil. Therefore, in this study, the characteristics of changes in the unconfined compression strength of soil-cement were analyzed by adding a solidifying agent targeting granite soil, which is representatively distributed in Korea. Laboratory tests were conducted to analyze the changes in strength according to 1) curing conditions and fine contents, 2) inorganic solidifying agent, and 3) repeated effects of dry and wet conditions. The unconfined compression strength of soil-cement increased as the curing period and mixing ratio increased, and it was constant after 14 days of curing. In addition, weathered granite soil with relatively low fine contents showed a large increase in the unconfined compression strength. In addition, the strength increased with an increase in the solidifying agent added. X-ray-diffraction analysis showed that vermiculite was generated by adding cement and admixtures, and the strength was increased by filling the gap between the particles. Considering the results of this study, a relationship between the unconfined compression strength and the elastic modulus of soil-cement by treatment with a solidifying agent was proposed.

SOIL-CEMENT PILES FIBER REINFORCED

Problems and insufficient research of the issue of reinforcement of soil-cement piles are revealed. The use of fiber for reinforcing piles made by the deep soil mixing method is proposed. As a result, it is expected to increase the strength of soil cement, which will positively affect the bearing capacity of soil-cement piles on the material. Given the advantages for applications in the studies adopted steel fiber. The program of tests with the application of two-factor matrices of planning of experiment is made. The obtained results showed the degree of influence of fiber reinforcement on the strength of soil cement. Practical results have been obtained that can be used for implementation in the process of installation of soil-cement piles.

The use of incineration waste to improve the properties of the bases

Innovative ways of using furnace dust to improve the strength of soil-cement are analyzed. It is proposed to solve the environmental problem of utilization of this material, when using the addition of furnace dust during the construction of soil-cement elements. The samples were kept immersed in water for 28 days in order to gain strength, until laboratory tests. The removal ash before the experiment was sieved on a 4 mm sieve. Strength of soil-cement samples with the addition of furnace dust and pellet ash (with the main content of sunflower husk with a percentage of 5% by weight of cement) was studied. It is established that the average compressive strength of the samples with the addition of Mykolaiv CHP furnace dust with a fraction of inclusions up to 4 mm in the amount of 5 % increases the compressive strength by 30%. It was found that the content of organic matter (ash from burning sunflower husks) in soil-cement reduces its strength.

Experimental Investigation of the Effective Parameters on the Strength of Soil - Cement

Soil-cement is a mixture of Portland cement, soil and water, which are bonded together due to the cement hydration and compaction. It have durability, low permeability and resistance against wear. Water to cement ratio, cement content and type have been commonly investigated as the most effective factors on the compressive strength of soil-cement. This study aims at the investigation of the effects of some other factors, such as Sand Equivalent (SE), Plasticity Index (PI), and gradation of the soil on the compressive and flexural strength of soil-cement. Results show that the compressive and flexural strength of soil-cement increases with increasing the sand equivalent and decreasing the plasticity index of the soil.

Internal and External Effects of Sodium Sulfate on the Strength of Soil Cement

In coastal industrial zones with saturated loose soil, sulfate attack is an additional problem. The problem becomes more acute when using soil cement, because an undesirable sulfate content can enter the body of the element with the material used to create it. This research includes two parts. In the first part, the effects of internal and external sulfate attack are compared in simulation of four groups of elements: control, prefabricated, cast-in-place and soil–cement. In the second part, the effects of the sulfate-resistant cement content (100–400 kg/m3) and sulfate concentration (0–5%) on behavior of cement-stabilized sand specimens were examined. In both parts, the unconfined compressive strength of the cylindrical specimens was measured over the course of 362 days. The results of part one showed that internal attack had a significant effect on decreasing the strength of the soil–cement specimens (up to 70%) compared to prefabricated (about 40%) and cast-in-place (about 20%) specimens. The results of the second part showed a logarithmic trend in the variation of strength versus the cement factor and sulfate concentration over time.

Effect of Ferronickel Slag Powder on Strength of Soil in Marine Environment

Over the past few years, soil‐cement has been widely used in marine geotechnical engineering; meanwhile, the safety of soil‐cement in marine environment has attracted wide attention. In order to study the influence of composite ferronickel slag powder on the strength and micro morphology of soil‐cement in marine environment, the composite nickel iron slag powder was added into the soil‐cement in this paper. The unconfined compressive strength test, erosion resistance coefficient analysis, SEM, and EDS test analysis of soil‐cement were carried out.. Results showed that the marine environment had great influences on the strength of soil‐cement, and the addition of compound nickel‐iron slag powder can enhance the strength of soil‐cement, and the deterioration of the strength of soil‐cement is reduced. In addition, the compound ferronickel slag powder has microaggregate effect, morphological effect, and activation effect, which not only improves compaction rate of soil‐cement and prevents invasion of erosive ions in marine environment but also has positive effects on the performance of soil‐cement.

Experimental study on the strength of soil-cement with additions of mineral powder and ferronickel slag powder

With the rapid development of soil-cement application technology, soil-cement is widely applied in mine development, such as mine road construction, pit repair, stope reinforcement and mine backfill, etc. In this paper, ferronickel slag powder and mineral powder are applied in soil-cement to study the impact of their content on the strength performance of soil-cement. The results show that the addition of ferronickel slag powder has a greater impact on the strength of soil-cement at the early age. However, with the increase of age, the strength decrease rate of soil-cement with ferronickel slag powder reduces. When ferronickel slag powder and granulated blast furnace slag are mixed, the performance of soil-cement at the early age is better than that with ferronickel slag powder alone. The optimal combination is that ferronickel slag powder accounts for 20%, among which the mineral powder replaces 30% of the ferronickel slag powder mass.