Stabilized Soil Mixtures Research Articles

Analysis of Novel Porosity-Water-to-Binder Index for Prediction of Strength, Stiffness and Durability for Cemented Soils.

The initial weight and volume relationships are crucial factors in determining the strength, stiffness, and durability of cement-stabilized soils. The porosity/binder ratio has been widely used as a control parameter for stabilized soil mixtures. However, this approach does not take into consideration the water content used during the stabilization process, which can impact the strength and durability of the final product. To address this issue, this paper introduces the porosity-water/binder relationship as a new parameter to predict the strength, stiffness (Go), and durability against wetting-drying cycles of artificially cemented soils. The strengths, Go, and accumulated losses of mass (ALM) of different stabilized soils were compared based on this new parameter, and the comprehensive results were analyzed to demonstrate its effectiveness. The findings indicate that the new parameter is a suitable design parameter for soil-lime, soil-cement, and geopolymerized soil mixtures. Furthermore, it was determined that the water content has no effect on the splitting tensile strength to compressive strength ratio. The results of this study offer valuable insights into the optimization of stabilized soils and the development of improved soil stabilization processes.

Experimental and numerical evaluation of a stackable compressed earth block masonry system: Characterization at cyclic shear loads

Soil is a traditional construction material that is currently experiencing a new boom as an eco-sustainable alternative for housing. In this article, a structural system made up of compressed earth blocks is analyzed as a construction alternative for seismic countries. This study evaluated the physical properties of base soil as well as an optimization process for the chemical stabilization of the mixture using cement and lime. The mechanical characterization of the blocks and of a masonry system designed to be stackable and dry joint was also performed, including the evaluation of its seismic response to cyclic shear wall tests. Results indicate that it is possible to improve the workability of the stabilized soil mixtures and the mechanical behavior of blocks in compression and tension, by using cement-lime additives in a ratio of 1:3 with respect to the dry weight of the materials. In addition, it was found that it is feasible to produce a stackable masonry system that has the capacity to dissipate energy due to friction between blocks. The parametric analysis and the calibration process of numerical models performed for the cyclic shear tests highlight the importance of using a micro-modeling approach to obtain representative models that correctly predict the experimental capacity curve in both maximum load and ductility. The use of those models in the present study allowed to adequately replicate the concentration of damage in the joints between blocks, corroborating what was observed through experimental testing.

Stiffness and Strength of Stabilized Organic Soils—Part II/II: Parametric Analysis and Modeling with Machine Learning

Predicting the range of achievable strength and stiffness from stabilized soil mixtures is critical for engineering design and construction, especially for organic soils, which are often considered “unsuitable” due to their high compressibility and the lack of knowledge about their mechanical behavior after stabilization. This study investigates the mechanical behavior of stabilized organic soils using machine learning (ML) methods. ML algorithms were developed and trained using a database from a comprehensive experimental study (see Part I), including more than one thousand unconfined compression tests on organic clay samples stabilized by wet soil mixing (WSM) technique. Three different ML methods were adopted and compared, including two artificial neural networks (ANN) and a linear regression method. ANN models proved reliable in the prediction of the stiffness and strength of stabilized organic soils, significantly outperforming linear regression models. Binder type, mixing ratio, soil organic and water content, sample size, aging, temperature, relative humidity, and carbonation were the control variables (input parameters) incorporated into the ML models. The impacts of these factors were evaluated through rigorous ANN-based parametric analyses. Additionally, the nonlinear relations of stiffness and strength with these parameters were developed, and their optimum ranges were identified through the ANN models. Overall, the robust ML approach presented in this paper can significantly improve the mixture design for organic soil stabilization and minimize the experimental cost for implementing WSM in engineering projects.

Performance of clay stabilized by cementitious materials and inclusion of zeolite/alkaline metals-based additive

RoadCem (RC) is an additive produced based on nanotechnology and comprises of synthetic zeolites and alkali earth metals as some of its components. The geotechnical properties of a soil stabilized by adding RC to partly replaced cementitious materials are studied. Various combinations of the additives were investigated with the objective of reducing the amount of OPC by 50% by an inclusion of RC and ground granulated blast furnace slag (GGBS) in the stabilized soil. Laboratory studies involving index property testing, oedometer swell-deformation, unconfined compression tests and microstructural examinations were carried out on both the natural and 7-& 28- day cured samples of the stabilized soil. The influence of RC on the mechanical properties of the stabilized soil was examined by comparing the performance of the stabilized soil mixtures that contain the RC and the mixtures without the RC added. Results indicated the positive effect of RC as noticed by the tremendous strength gain in 7 days with the OPC reduced by 50% in the stabilized soil. Swelling decreased significantly to 0% after 28 days curing with the settlement also reasonably reduced for nearly all the percentages of the OPC substituted. The stabilized soil’s microstructure revealed the mechanism of cementation observed as an encapsulation or “wrapping effect” as a result of the presence of RC. A comparison of the RC-modified soil containing the by-products GGBS and PFA indicated that GGBS was more effective in the enhancement of engineering properties than PFA. Overall, as well as meeting some of the standards set for road pavement applications, the results obtained from this research are very promising for the ongoing discussions on reducing carbon foot-printing by OPC replacement.

Potential of snail shell and palm kernel shell powders in improving engineering properties of clay

This research is aimed at using Snail Shell Powder (SSP) and Palm Kernel Shell Powder (PKSP) in stabilizing clay. Elemental and oxide compositions of the powders were determined and they revealed SSP is richer in CaO than PKSP. Sieve Analysis, Compaction, California Bearing Ratio (CBR) and Atterberg Limit were conducted on natural and stabilized soil mixture. The natural soil (A-7-6) was blended with SSP and PKSP at varying proportion of 2%, 4%, 6%, 8%, and 10% by dry weight of soil respectively and also combined at ratios not more than 10% total . Inclusion of additives increase the Maximum Dry Density (MDD) while it predominantly the Optimum Moisture Content (OMC) values of the stabilized soil mixture. Plasticity Index (PI) decrease with the addition of the powders with the best performance observed mostly with SSP blended soil. It was also found that the CBR values of soil increase with corresponding increase in dosage of the powders. Soil blended with 8% SSP offered the best result with increase in MDD from 1198 to 1300kg/m3 while the combined additives gave the best result at 2%SSP+8%PKSP addition with MDD increasing to 1266 kg/m3 and further reduction of OMC to 21%. The best results in PI were from Soil blended with 2% SSP and also 2%SSP+8PKSP with 6.25% and 9.2% respectively. For CBR, soil blended with 8% SSP and 2%SSP+8PKSP of combined ratio gave peak performances. The potential of these additives in improving soil properties and reducing construction cost of road are presented.Keywords: Palm kernel shell Powder, Snail shell powder, Clay stabilization, Geotechnical properties

Using Natural Pozzolan, Cement and Lime for Stabilizing Soil in Earth Dams

The paper has focused on studying the ability of using natural pozzolan to combine lime and cement in process of stabilized soil, implementing experimental contents for on-site soil including: grain composition, plastic limit, plasticity index, mineral parts and other common mechanical properties, standard compaction. Followed by experiments for soil, cement and pozzolan stabilized soil mixtures, including standard compaction, compressive strength. A suitable model of physical experiments to simulate and prove lime, cement and pozzolan stabilized soil meets the criteria for making waterproofing materials for earth dams in the Central Highlands

Sand and silty-sand soil stabilization using bacterial enzyme–induced calcite precipitation (BEICP)

This paper examines the bio-derived stabilization of sand-only or sand-plus-silt soils using an extracted bacterial enzyme application to achieve induced calcite precipitation (ICP). As compared to conventional microbial induced calcite precipitation (MICP) methods, which use intact bacterial cells, this strategy that uses free urease catalysts to secure bacterial enzyme–induced calcite precipitation (BEICP) appears to offer an improved means of bio-stabilizing silty-sand soils as compared to that of MICP processing. Several benefits may possibly be achieved with this BEICP approach, including bio-safety, environmental, and geotechnical improvements. Notably, the BEICP bio-stabilization results presented in this paper demonstrate (i) higher rates of catalytic urease activity, (ii) a wider range of application with sand-plus-silt soil applications bearing low-plasticity properties, and (iii) the ability to retain higher levels of soil permeability after BEICP processing. Comparative BEICP versus MICP results for sand-only systems are presented, along with BEICP-based results for stabilized soil mixtures at 90:10 and 80:20 percentile sand:silt ratios. This BEICP method’s ability to obtain unconfined compressive strength results in excess of 1000 kPa with sand-plus-silt soil mixtures is particularly noteworthy.

Improvement in CBR Value for Flexible Pavement Design Using Solid Waste:A Case Study

California Bearing Ratio (CBR) value is an important soil parameter for design of flexible pavements as per IRC recommendation. In this study, attempts have been made to improve the soil strength by the addition of various proportions of fly ash (FA) & rice husk ash (RHA) and correlate the CBR values for the flexible pavement design. A series of proctor tests and CBR tests (soaked for 96 hours) were conducted by adding different proportions of FA & RHA of soil samples collected from different places of Durgapur, India & its nearby areas and optimized proportion is arrived. As soils of different area are having different strength properties, different optimum values of FA & RHA can be obtained for different region. Developed stabilized soil mixtures showed satisfactory increase in CBR values up to a specific amount of addition of FA as well as RHA and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, FA and RHA in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

Stabilized soil incorporating combinations of rice husk ash, pond ash and cement

The paper presents the laboratory study of clayey soil stabilized with Pond ash (PA), Rice husk ash (RHA), cement and their combination used as stabilizers to develop and evaluate the performance of clayey soil. The effect of stabilizer types and dosage on fresh and mechanical properties is evaluated through compaction tests, unconfined compressive strength tests (UCS) and Split tensile strength tests (STS) performed on raw and stabilized soil. In addition SEM (scanning electron microscopy) and XRD (X-ray diffraction) tests were carried out on certain samples in order to study the surface morphological characteristics and hydraulic compounds, which were formed. Specimens were cured for 7, 14 and 28 days after which they were tested for unconfined compression tests and split tensile strength tests. The moisture and density curves indicate that addition of RHA and pond ash results in an increase in optimum moisture content (OMC) and decrease in maximum dry density (MDD). The replacement of clay with 40% PA, 10% RHA and 4% cement increased the strength (UCS and STS) of overall mix in comparison to the mixes where PA and RHA were used individually with cement. The improvement of 336% and 303% in UCS and STS respectively has been achieved with reference to clay only. Developed stabilized soil mixtures have shown satisfactory strength and can be used for low-cost construction to build road infrastructures.

Performance evaluation of cement-stabilized pond ash-rice husk ash-clay mixture as a highway construction material

This paper reports the results of an investigation carried out on clay soil stabilized with pond ash (PA), rice husk ash (RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio (CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%–45% and 5%–20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were carried out, respectively. The results obtained indicated a decrease in the maximum dry density (MDD) and a simultaneous increase in the optimum moisture content (OMC) with the addition of PA and RHA. Multiple linear regression analysis (MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

Applications of Air-Foamed Stabilized Soil as Potential Subgrade Material of Railway Track

In these days, use of proper soils for construction materials become more limited, but wasted soils are abundant; therefore, the method which can use wasted soil such as soft clay has been investigated. Air-foamed stabilized soil has been used widely, but never been used as a subgrade material. The aim of this study is to verify the use of airfoamed stabilized soil as the subgrade construction material. Several wasted soils such as soft clay was selected to make air-foamed stabilized soil mixtures. The air-foamed stabilized mixture design was conducted to find the optimum quantity of stabilizing agent (cement) and air-foamed, and the effect of cement quantity and air-foamed quantity on strength of air-foamed stabilized soil mixtures base on the test results of unconfined compression test was investigated. As the quantity of cement is increased, the strength is increased, but the quantity of air-foamed is increased and the strength is decreased. Elastic moduli based on unconfined compression strength were obtained to use as subgrade of railway track design.

Laboratory Investigation on the Strength Characteristics of Cement-Treated Base

Cement-Treated Base (CTB) is a non-conventional method used in road bases materials to improve its engineering properties due to the hardening of cement when moisture is present and extends the period of curing times. This study investigates the effects of cement additive on properties of base layer using laboratory mechanistic evaluation of stabilized soil mixtures. Laboratory tests conducted were Unconfined Compressive Strength (UCS), Indirect Tension test for Resilient Modulus (ITRM) and Flexure Strength (FS) tests. The results revealed that by adding Portland cement, the mechanical properties of the mixture have improved where the UCS is found to be an important quality indicator. In addition, the variables that influenced these tests, which are cement content, curing time, moisture content, and dry density, play important role to determine the performance of CTB. This paper presents the finding of a correlation conducted to analyse the influences of these variables using regression and ANOVA to establish significant models with the aim of predicting the strength base on mixture parameters. Keywords: Cement-Treated Base, Unconfined Compressive Strength, Indirect Tension test for Resilient Modulus, Flexure Strength, Moisture Content, Dry Density, Regression Analysis.

Stabilization of saline silty sand using lime and micro silica

Many construction and post-construction problems have been reported in the literature when saline soils have been used without understanding of their abnormal behavior, especially their inferior bearing capacity in the natural condition. The strength of these soils further decreases on soaking. Saline soil deposits cover extensive areas in central Iran and are associated with geotechnical problems such as excessive differential settlement, susceptibility to strength loss and collapse upon wetting. Because of these characteristics, some of the roads constructed on saline soils in Taleghan area have exhibited deterioration in the form of raveling, cracking and landslides. The main objective of this work is to improve the load-bearing capacity of pavements constructed on Taleghan saline soils using lime and micro silica. Soil samples from Hashtgerd-Taleghan road were collected and tested for improving their properties using lime and micro silica at different dosages ranging from 0 to 6%. The load-bearing capacity of stabilized soil mixtures was evaluated using California Bearing Ratio (CBR) and unconfined compressive strength tests. The test results indicate that the lime improves the performance of soil significantly. The addition of 2% lime with 3% micro silica has satisfied the strength-deformation requirements. Therefore, improved soil can be used as a good subbase in flexible pavements.

Some engineering properties of stabilized clayey soils incorporating natural pozzolans and industrial wastes

Clayey soils are stabilized with various dosages of cement kiln dust, volcanic ash and their combinations. The influence of stabilizers is evaluated through Atterberg limits, standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity and California bearing ratio (CBR) tests. The durability properties of 14 stabilized soil mixtures are also investigated by studying the influence of water immersion on strength, water sorptivity and drying shrinkage. Correlations between strength, modulus of elasticity and CBR are also established. Developed stabilized soil mixtures have shown satisfactory strength and durability characteristics and can be used for low-cost construction to build houses and road infrastructures. The use of stabilized soils with locally available soils, volcanic ash and cement kiln dust can provide sustainability to the local construction industry.

Stabilized Soils Incorporating Combinations of Rice Husk Ash and Cement Kiln Dust

Cement kiln dust, rice husk ash, and their combinations are used variously as stabilizers in different percentages (maximum up to 20%) to develop and evaluate stabilized clayey soils. The influence of stabilizer types and dosages on fresh and mechanical properties is evaluated through Atterberg limits, standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity, and California bearing ratio (CBR) tests. The durability characteristics of 19 developed stabilized soil mixtures are also investigated by studying the influence of water immersion on strength, water sorptivity, and drying shrinkage. Correlations between strength, modulus of elasticity, and CBR are also established. Developed stabilized soil mixtures have shown satisfactory strength and durability characteristics and can be used for low-cost construction to build houses and road infrastructures. The use of locally available soils, rice husk ash, and cement kiln dust (waste from the cement industry) in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

Combined Lime–Cement Stabilization for Longer Life of Low-Volume Roads

Low-volume roads are an important part of the world's transportation infrastructure and a direct cause of the socioeconomic development of small city and rural communities. Construction, maintenance, and rehabilitation of these roads are major tasks and require a major part of the public works budget. Better design and construction methods can prolong pavement service life and result in lower maintenance and rehabilitation costs. This paper presents a research study done for the city of Arlington in north Texas to stabilize road subsoils with a combined lime and cement stabilizer, which in turn is expected to enhance service life of the roads. Both laboratory tests on stabilized soil mixtures and field performance data are analyzed and presented.

Stabilized soils for construction applications incorporating natural resources of Papua new Guinea

Papua New Guinea clayey soils are stabilized with various percentages of volcanic ash (VA), finely ground natural lime (L), cement and their combinations. The influence of stabilizers and their combinations is evaluated through Atterberg limits, standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity and California bearing ratio (CBR) tests. The durability of 38 stabilized soil mixtures is also conducted by studying the influence of water immersion on strength, water sorptivity and drying shrinkage. Correlations between compressive strength, modulus of elasticity and CBR are also established. Theoretical analysis of pavements incorporating subgrades improved by stabilized soils under traffic loads shows technical benefits compared with conventional flexible pavements without improved subgrades. Suitable stabilized soil mixtures using VA, L, cement and their combinations are proposed which can be used for the construction of road pavements, airfields, earth dams and low-cost housing. The use of locally available soils, VA and lime in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

Development of Damage Model to Analyze Stabilized Soil Layers Subjected to Repetitive Aircraft Loadings

The U.S. Army Engineering Research and Development Center is developing methods to construct a contingency airfield within a short time that can support C-17 aircraft loadings. The proposed approach is to construct the runway site surface by chemically stabilizing the in-place top soil layer. To develop an optimal stabilized soil mixture, a suite of soil–chemical mixture combinations was examined. Because of the complexity and expense of full-scale testing, a numerical approach is being developed to predict stabilized soil response at contingency airfields. Results from the numerical approach will then be used to supplement data obtained from full-scale tests. Three stabilized soil mixtures were investigated by using stabilizing agents of 6% cement, 4% cement, and 4% cement plus 1.5-in. (38-mm) polypropylene fibers. These three mixtures were evaluated for strength and durability from unconfined compression and repeated load tests. A total of 33 unconfined compression load tests and 48 unconfined repeated load tests were conducted. A numerical model using damage is presented to predict stabilized soil behavior in response to repetitive loading. The damage model is calibrated by using only two material properties and two damage parameters. Results of this study indicate that stabilized soil exhibits plastic behavior and therefore a numerical model for stabilized soil must consider both damage and plastic behavior.

Characteristics of volcanic ash and natural lime based stabilized clayey soils

Clayey soils are stabilized with various percentages of volcanic ash (VA), finely ground natural lime (NL), Portland cement, and their combinations. The influence of stabilizers and their combinations is evaluated through standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity, and California bearing ratio (CBR) tests. The durability of stabilized soil mixtures is judged based on drying shrinkage and the influence of water immersion on strength. Correlations between compressive strength, modulus of elasticity, and CBR are also established. Stabilized soil mixtures can be used in various constructions, including road pavements and low-cost housing.Key words: soil stabilization, volcanic ash, natural lime, mechanical properties, durability.