Unconfined Compressive Strength Of Specimens Research Articles

Strength and durability characteristics of geopolymer treated pond ash as pavement material

This study evaluated the strength and durability characteristics of pond ash (PA) treated with geopolymer (3%, 6%, 9%, 12%, and 15%, by dry weight of PA) and compared them with Portland cement and hydrated lime stabilizations at same additive contents. Unconfined compressive strength of specimens was evaluated at curing durations of 1, 3, 7, 28, and 90 days. The durability of 28-day cured stabilised specimens against wet-dry cycles, freeze-thaw cycles, water slaking cycles, water immersion, capillary action, and dispersion was assessed. Geopolymer-stabilized PA achieved higher strength and durability than cement and lime-stabilised PA. It is due to the formation of a dense microstructure with significant reaction products. PA stabilised with 3% geopolymer and 15% cement satisfies the strength properties of the cementitious subbase in flexible pavements. Whereas, 6% geopolymer content fulfils the requirements of the cementitious base in flexible pavements and the cementitious subbase in rigid pavements as per IRC: 37-2018 and IRC: 59-2015, respectively.

Influence of some factors on the mechanical properties of cement-treated clay for shallow mixing in Vietnam: A comparative study

The compressive strength of cement-treated soil is known as the most crucial factor, which governs the quality of cement-treated soils. Indeed, many factors affect the compressive strength of cement-treated soils, including cement types and contents, water/cement ratio, soil types, as well as curing conditions, etc. In which, curing conditions, cement types, and soil types are the most important factors that govern the compressive and durability of cement-treated clay. Three cement types and two types of clay were used to prepare the specimens of cement-treated clay with three cement dosages (100, 150, and 200 kg/m3 of soil). The specimens of cement-treated clay were cured under two conditions (sealed and drying). The results showed that drying conditions significantly increased the unconfined compressive strength of cement-treated soils regardless of cement types, cement contents, soil types, and ages as compared to those under sealed conditions. The unconfined compressive strength of specimens under drying conditions was approximately 1.3–2.5 times higher than that under sealed conditions. Cement type significantly affected the performance (compressive strength and elastic modulus) of cement-treated clay regardless of cement content. The cement-treated clay specimens under sealed conditions showed a ductile failure mode while those under drying conditions exhibited a brittle failure mode. Finally, soil type significantly influenced the compressive strength and elastic modulus of cement-treated clay regardless of cement content and curing condition.

Temperature effect of tungsten tailings activated by NaOH

The unconfined compressive strength of specimens with three moisture contents and three NaOH/TMG ratios (sodium hydroxide mass/solid mass, where solid contains tungsten tailings, metakaolin and commercial geopolymer) cured at 60–100 ℃ for seven days was conducted to investigate the temperature effect and action mechanism of tungsten tailings strength activated by NaOH. The test results of the scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were adopted to analyze the micro characteristics of the mixture under different curing temperatures. The test results indicate that the unconfined compressive strength of tungsten tailings activated by NaOH increases first and then decreases with the increase of curing temperature, and reaches the maximum at 90 ℃. C(N)-A-S-H gels mixed with poly-sialate (PS) and poly-sialate-siloxo (PSS) types are generated at different proportions at different temperatures activated by NaOH. The relative content of PS type gels increases when the curing temperature rises from 60 ℃ to 90 ℃, and decreases when the temperature continues to rise to 100 ℃. The greater the total amount of gel and the relative content of PS-type gel, the greater the strength of the specimens. In this study, the unconfined compressive strength is strongest in the temperature of 90 ℃. It was the optimal curing temperature. The minimum and the maximum strengths were 12.4 MPa and 42.8 MPa when the curing temperature is over or equal to 70 ℃, which meets the strength requirements of building bricks of MU10. In conclusion, the research results provide scientific basis and references for the resource utilization of tungsten tailings.

Strength and durability properties of expansive soil treated with geopolymer and conventional stabilizers

This paper reports the strength and durability properties of expansive soil treated with slag-based geopolymer, hydrated lime, and Portland cement. The slag content in the soil-slag mix is varied as 5%, 10%, and 20% by dry weight of soil and activated with NaOH solutions of 2 M, 6 M, and 8 M concentrations, respectively. Whereas cement and lime contents in the mix are varied as 4%, 12%, and 15%. The plasticity and compaction properties of the mixes are evaluated. Further, the unconfined compressive strength of specimens, compacted to their respective maximum dry density at optimum moisture content, is determined after 0, 3, 7, and 30 days of curing. Durability studies such as freezing-thawing, slaked durability, modified durability, and resistance to water immersion are determined on 30-days cured stabilized soil specimens. X-ray diffraction and scanning electron microscopic analysis are carried out for identifying the reaction products and microstructure of the stabilized specimens. The results indicate that the expansive soil can be effectively stabilized with slag-based geopolymer. The geopolymer stabilized soil has superior strength and durability compared to the conventional stabilizers. Geopolymer stabilized soil attains dense and compact structures with the better formation of cementitious products.

MICROSTRUCTURAL INVESTIGATION AND STRENGTH PROPERTIES OF CLAY STABILIZED WITH CEMENT, RICE HUSK ASH AND PROMOTER

A clay soil, classified as Clay of High plasticity (CH) according to Unified Soil Classification System (USCS) was stabilized with cement, Rice Husk Ash (RHA) and promoter. The mineralogy of the clay soil and the morphology of the clay and clay specimens admixed with varied composition of cement, RHA and promoter were evaluated in order to determine effect of the RHA on promoter stabilization of cement based clay soil. The promoter used in this study consists of calcium chloride and sodium hydroxide in the ratio of 1:1. The clay was remolded at standard Proctor compaction energy and the specimens were mixed with 0, 1.0, 2.0 and 3.0% cement, admixed with 1.0, 2.0, 3.0% RHA each, and 0.3, 0.6, 1.0% promoter each. The molded specimens were cured for 1, 7, 14, 28, 60 and 90days before testing for Unconfined Compressive Strength (UCS) and consequently the modulus of elasticity. The UCS of specimens without cement increased from 20 kN/m2 for the natural clay soil to 95 kN/m2 on addition of 3% RHA and 1.0% promoter after 28 days of curing, representing 475% increase in the UCS. This increase was confirmed by morphology of the clay soil mixed with RHA and promoter only, which showed presence of calcium silicate hydrate. Addition of 3.0% cement with 3 and 1.0% RHA and promoter respectively, increased the UCS from 220 to 375kN/m2 after 28 days of curing, which was also confirmed by the morphology of the specimens. The highest elastic modulus of 48.3 MPa was observed at specimens containing 3% cement, 3% RHA and 1.0% promoter.

Prediction of Unconfined Compression Strength for Saline‐Alkaline Soils Mixed with Cement and Wheat Straw

A series of unconfined compression tests were performed to investigate the influence of wheat straws on the unconfined compression strength for saline‐alkaline soils and saline‐alkaline soils mixed with cement. In unconfined compression tests, 20 groups of soil specimens were prepared at five different percentages of wheat straws content (i.e., 0.0%, 0.1%, 0.15%, 0.2%, and 0.25% by weight of saline‐alkaline soils) and four different percentages of cement content (i.e., 0%, 3%, 6%, and 9% by weight of saline‐alkaline soils), and unconfined compression tests were carried out after 3‐, 7‐, 14‐, 28‐, and 56‐day curing periods. Test results indicated that the inclusion of wheat straws within saline‐alkaline soils and saline‐alkaline soils mixed with cement leads to an increase in the unconfined compressive strength of specimens and also changed the brittle behavior to a more ductile one for specimens. In addition, based on the results from unconfined compression tests, a formula for predicting the unconfined compression strength of specimens related to cement content, wheat straw content, curing periods, etc., was determined, and comparing with the results from unconfined compression tests, it had higher precision in predicting the unconfined compression strength of specimens.

The Effect of the Depth of Cutter Soil Mixing on the Compressive Behavior of Soft Clay Treated by Alkali-Activated Slag

Cutter soil mixing (CSM) is a fairly new technique for shallow to deep soil stabilisation that mostly uses cement based slurry to improve the in-situ properties of soft soils. This research aims to experimentally investigate the effect of the depth of cutter soil mixing on the compressive strength of a saturated soft clay treated with alkali-activated slag slurry. Various percentages of additives were added to the saturated soft clay to increase the compressive strength and to make it suitable for constructing shallow to deep CSM panels as earth retaining walls that are used for excavations. Several high-pressure curing apparatuses were used to simulate insitu field stress due to the depth/weight of CSM panels. Then a set of compressive strength tests were conducted to investigate the effect of different curing pressures, additives content and curing time on the compressive behavior and strength of CSM panels. Microstructural studies were also performed to understand the reactions of the mixtures. The results showed that the compressive behavior of CSM panel changes significantly by increasing the mixing depth. Moreover the influence of curing pressure equivalent to the depth of CSM panels on increasing unconfined compressive strength of specimens is partially more than the effect of additives and considerably more than the effect of curing time. The microstructural studies also showed that the main hydration products are cementitious products such as calcium silicate hydrates (C-S-H) and the addition of alkali-activated slag in a treated clay results in production of the cementitious products in a faster rate.

Strength Characteristics of Cement-Rice Husk Ash Stabilised Sand-Clay Mixture Reinforced with Polypropylene Fibers

In this paper, stress-strain behaviour of sand-clay mixture stabilised with different cement and rice husk ash percentages, and reinforced with different polypropylene fibre lengths are evaluated. Mixtures are widely used in road construction for soil stabilisation. It is observed that replacing half of the cement percentage (in high cement contents) with rice husk ash will result in a higher unconfined compressive strength. In addition, the presence of 6 mm polypropylene fibres will help to increase the unconfined compressive strength of stabilised samples, while larger fibres cause reverse behaviour. In addition, introducing a new index for assessing the effect of curing days. Curing Improvement Index it is obtained that larger fibres show higher Curing Improvement Index values. Results gained for the effects of curing days, and fibre lengths are further discussed and interpreted using Scanning Electron Microscopy photos. Based on the conducted Unconfined Compressive Strength, Indirect Tensile Strength, and Flexural Strength tests and using evolutionary polynomial regression modelling, some simple relations for prediction of unconfined compressive strength, indirect tensile strength, and flexural strength of cement-rice husk ash stabilised, and fibre reinforced samples are presented. High coefficients of determination of developed equations with experimental data show the accuracy of proposed relationships. Moreover, using a sensitivity analysis based on Cosine Amplitude Method, cement percentage and the length of polypropylene fibres used to reinforce the stabilised samples are respectively reported as the most and the least effective parameters on the unconfined compressive strength of specimens.

Experimental Study on Electrical Resistivity of Cement-Stabilized Lead-Contaminated Soils

Geotechnical applications based on soil resistivity measurement are becoming more popular in recent years. In order to explore the potential application of the electrical resistivity method in stabilization/solidification of contaminated soils, two kinds of lead-contaminated soils stabilized with cement were prepared, and the electrical resistivity and unconfined compressive strength of specimens after curing for various periods were measured. The test results show that a high lead content leads to a low value of electrical resistivity of cement-stabilized soils, and increasing cement content and curing time result in a significant increase in electrical resistivity. The reduction in porosity and degree of saturation, as a result of the cement hydration process, leads to an increase in electrical resistivity. The ratio of porosity-lead content/cement content-curing time, combining together the effect of lead content, cement content, curing time, and porosity on electrical resistivity of stabilized soils, can be used as a fundamental parameter to assess electrical resistivity of cement-stabilized lead-contaminated soils. Archie’s law can be extended to apply to cement-stabilized lead-contaminated soils by using this ratio, replacing the porosity. The new resistivity formula obtained in this paper is just empirical. There is a power function correlation between unconfined compressive strength and electrical resistivity of lead-contaminated soils stabilized with cement. Electrical resistivity measurement can be used as an economical and time-effective method to assess the quality of cement-stabilized lead-contaminated soils in practice.

Marble powder to stabilise clayey soils in sub-bases for road construction

Marble, used extensively as construction materials, yields huge amount of marble powder waste from natural marble stone processing. Therefore, it is essential to utilise marble powder waste in order to eliminate its negative effect on environment and to obtain economic benefit from it. There are almost no studies in the literature concerning the use of marble waste in the stabilisation of clayey soil under freeze–thaw effects. In this study, a pioneer attempt is made to evaluate the effectiveness of using marble powder in the stabilisation of clayey soil in a road construction under freeze–thaw effects. Natural clay is mixed with marble powder at different percentages; then, strength in terms of the results of unconfined compressive tests and durability in terms of mass loss after freeze–thaw cycles are investigated. As the marble powder content in this study reaches 10% in the clayey soil, the unconfined compressive strength of specimens rises to a peak point; meanwhile, plasticity of mixtures decreases. Mass loss as criteria for durability behaviour in the marble powder-stabilised soils at the end of freeze–thaw cycles is almost 5%. Test results indicate that marble powder could be used as a stabilisation material for clayey-type soils in sub-bases in highway construction under freeze–thaw effect.

Experimental Study of Dredged Sediment Sample Analysis and Solidification in Waterway Regulation Engineering

How to treat dredged sediment is one of the main environmental problems and the recycling technique is the best way to deal with this problem. This paper deals with the feasibility of beach protection project alternative materials-dredged sand, applies cement and addition to solidify it. The components of dredged sediment and the physical properties were analyzed. Specimens with a designed mix ratio of the cement and dredged sediment were made by means of instant formation. The specimens were cured under standard condition and room temperature. The unconfined compressive strength of specimens were measured after curing for 7, 14 and 28 days. Using solidified dredged sediment as construction material has advantages of technology, economy and environment protection.

Experimental Study of the Relationship between Matric Suction and Strength of Unsaturated Residual Clay in Xiamen under Different Drying-Wetting Cycle Paths

To discuss the relationship between matric suction and strength under different drying-wetting cycle paths of residual clay, soil water characteristic curve was determined by the filter paper method. The shear strength, unconfined compressive strength and matric suction were obtained during desorption and adsorption at the drying and wetting cycle. The experimental results show that the matric suction of soil specimens subjected to different drying and wetting cycle paths are different although at the same water content. Contributions of internal friction angle and cohesion to shear strength are different at different matric suction. In the low matric suction stage, matric suction mainly contribute to shear strength by affecting the cohesion, yet in the high matric suction stage by increasing both the internal friction angle and cohesion; in the transition matric suction stage, the contribution of cohesion decreases while the contribution of internal friction angle increases. Furthermore, the unconfined compressive strength of specimens subjected to the drying and wetting cycle path of desorption first and then adsorption is reduced and increase with the opposite path.

Freezing–thawing behavior of fine-grained soils reinforced with polypropylene fibers

A number of studies have been conducted recently to investigate the influence of randomly oriented fibers on some engineering properties of cohesive and cohesionless soils. However, very few studies have been carried out on freezing–thawing behavior of soils reinforced with discrete fiber inclusions. This experimental study was performed to investigate the effect of randomly distributed polypropylene fibers on strength and durability behavior of a fine-grained soil subjected to freezing–thawing cycles. For strength behavior, a series of unconfined compression tests were conducted. Mass losses were also calculated after freezing–thawing cycles as criteria for durability behavior. The content of polypropylene fiber was varied between 0.25% and 2% by dry weight of soil in the tests. The test results for the reinforced specimens were compared with that for the unreinforced sample. It was observed that the mass loss in reinforced soils was almost 50% lower than that in the unreinforced soil. It was also found that the unconfined compressive strength of specimens subjected to freezing–thawing cycles generally increased with an increasing fiber content. On the other hand, the results indicated that the initial stiffness of the stress–strain curves was not affected significantly by the fiber reinforcement in the unconfined compression tests.

Stabilization treatment of soft subgrade soil by sewage sludge ash and cement

In this study, incinerated sewage sludge ash (ISSA) is mixed with cement in a fixed ratio of 4:1 for use as a stabilizer to improve the strength of soft, cohesive, subgrade soil. Five different ratios (in wt%: 0%, 2%, 4%, 8%, and 16%) of ISSA/cement admixture are mixed with cohesive soil to make soil samples. In order to understand the influences of admixtures on the soil properties, tests of the pH value, Atterberg limits, compaction, California bearing ratio (CBR), unconfined compressive strength, and triaxial compression were performed on those samples. The study shows that the unconfined compressive strength of specimens with the ISSA/cement addition was improved to approximately 3–7 times better than that of the untreated soil; furthermore, the swelling behavior was also effectively reduced as much as 10–60% for those samples. In some samples, the ISSA/cement additive improved the CBR values by up to 30 times that of untreated soil. This suggests that ISSA/cement has many potential applications in the field of geotechnical engineering.

Sludge ash/hydrated lime on the geotechnical properties of soft soil

In this study, an effort to improve the properties and strength of soil, sewage sludge ash (SSA) and hydrated lime are applied to stabilize soft cohesive subgrade soil. Five different ratios (in weight percentage), 0%, 2%, 4%, 8%, and 16%, of sludge ash/hydrated lime are proposed for mixture with cohesive soil. Then, the effects of the different proportions of SSA/hydrated lime on soft cohesive soil are studied. Test results indicate that the unconfined compressive strength of specimens with additives was raised from three to seven times better than that of the untreated soil, and swelling behaviors were also effectively reduced for those specimens. Results of triaxial compression test indicate that the shear strength parameter, c, rose with an increased amount of additives and improved from 30 to 50–70 kPa. On the whole, SSA/hydrated lime could particularly improve the geotechnical properties of cohesive subgrade soil.

砕石粉の土質安定処理への有効利用について

Recently how to utilize resources and how to preserve natural environment have become serious problems in Japan. The waste rock powder is an industrial by-product from crusher plants. Since almost no disposal has been done for it, it causes the pollution of air and water. It is significant to examine how to utilize the waste rock powder as a construction material. If this becomes possible, the problems of resource utilization and the environmental pollution can be solved simultaneously. One method to solve the problems is to use the waste rock powder for soil stabilization.The purpose of this study was to investigate the possibility of reutilizing the waste rock powder for a supplemental material of stabilization. Firstly the relationship between physical or chemical properties of the waste rock powder and the unconfined compressive strength of stabilized specimens was examined in detail. According to chemical analysis, it was clarified that the waste rock powder has fairly large specific surface area and contains a large amount of amorphous materials. The unconfined compressive strength of specimens stabilized with lime or cement was closely related to the specific surface area or the ratio of Al2O3/SiO2, even if the waste rock powder was used as a supplemental material.In conclusion, this rock powder is useful to increase the stabilizing effect on soils having a small amount of fine particles, and if it is used, it results in saving the cost by reducing the amount of lime or cement.

The relationship between compressive strength and age for soils stabilized with four types of cement

Summary: The relationships between unconfined compressive strength and age up to 28 days have been determined for soil-cement specimens made with a sand, a silty clay and a clay, stabilized with four different cements. A comparison has also been made of the effects on compressive strength of coating test specimens with wax and of placing them in a humid atmosphere during the curing period. High-alumina cement was found to give the highest strength after 24 hours, wirh all three soils, but afier 28 days it gave lower strengths than the other cements. Rapid-hardening cement was found to give strengths 20-40 lb per sq. in. greater than normal Portland cement with the two cohesive soils, while super-rapid-hardening cement generally gave strengths about 40 lb per sq. in. lower than those obtained with the other two Portland-type cements. The setting of normal Portland and rapid-hardening cement mixed with the sand was retarded for seven days, due to an organic impurity, but the setting of high-alumina cement was not affected. The addition of lime, or calcium chloride (e.g. in super-rapid-hardening cement) was found to reduce the retardation, the latter being the most effective. The action of calcium chloride in this respect was confirmed with three other soils containing deleterious organic matter. Coating test specimens with paraffin wax during the curing period was found to result in considerably smaller differences in moisture content among similar specimens in a batch than was obtained by storage in a humid atmosphere. This was accompanied by a reduction in the differences in the unconfined compressive strength of specimens only in the case of the sand-cement. The average limits of error of the mean compressive strengths based on ten independent measurements were calculated to be between ±10 and ±20 lb per sq. in. for strengths ranging between 200 and 400 lb per sq. in.