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This study uses fly-ash-based superplasticized geopolymer by adding a naphthalene-centered superplasticizer to the geopolymerized soil. Alkali-binder ratios and alkali-activator ratios are varied simultaneously with a molarity of 10M. The optimum dosages of binder, geopolymer, and superplasticized geopolymer are found from unconfined compression tests. California Bearing Ratio (CBR), pH, consolidation, water-holding capacity, and microstructure tests were performed on optimum dosages. The clayey soil's undrained shear strength and CBR value increased as the geopolymer was superplasticized. The 28-day undrained shear strength of geopolymerized clay was around 300 kPa, attained within three days of the curing period with superplasticized geopolymer. This is because adding a superplasticizer increases the polymerization reaction rate and improves the geopolymer's performance. The maximum undrained shear strength was attained within seven days of the curing period for both cases. The undrained shear strength after a curing period of 7, 14, and 28 days for geopolymer and superplasticized geopolymer was found to be almost the same value, which shows that after seven days, curing has little role in strength improvement. The hydraulic conductivity and coefficient of consolidation of geopolymerized soil increased with the addition of superplasticizer due to the reduction in fine particles and plasticity of the residual soil. Microstructural studies using scanning electron microscope and x-ray diffraction techniques showed an interaction between soil, geopolymer, and superplasticizer, thus confirming the formation of geopolymer gel and increased polymerization rate with the superplasticizer. [ABSTRACT FROM AUTHOR]

Enhancing the dynamic properties of expansive soils using cementitious materials has attracted the attention of many researchers over the past few decades. Supplementary cementitious materials (SCMs) can be used as partial substitutes for cement owing to their pozzolanic activity that further improves the mechanical performance of cement-stabilized soils upon curing. In this study, the effect of cement and zeolite incorporation on the mechanical behavior of expansive clay was quantified using the pressure wave velocity (Vp) indicator obtained from ultrasonic pulse velocity tests performed at different curing times. Furthermore, a polynomial model was developed to establish the relationship between Vp and zeolite replacement levels at specific curing times and cement contents. The results show that a polynomial function captured the decreasing trend of Vp upon the increase in zeolite at curing times below 14 days. Additionally, the developed equation explained the upward trend of Vp owing to the pozzolanic activity of zeolite at later curing times with an accuracy of over 92%. The coefficients of the polynomial model also increased with the increment of the cement percentage which conformed to the consecutive rise in Vp. Ultimately, the polynomial coefficients were expressed in terms of cement content and curing time using the Volterra series. Using this model, the optimum percentage of cement replaced with zeolite (Zopt), the efficiency of using Zopt instead of cement, and the percentage of zeolite replacement to achieve equivalent Vp of cemented clay samples (ZC) were estimated. The findings of this study contribute to promoting geotechnical sustainability by replacing cement with zeolite that has a considerably lower environmental footprint. Clay is a type of soil that can be found in many construction projects. For instance, many roads and buildings' foundations are constructed on clay soils. To ensure the necessary strength of the clay under the main structure, the soil should often be stabilized using adhesive construction materials such as cement. Interestingly, a portion of the cement could be replaced with other minerals not only to improve engineering performance but also to promote sustainability by lowering cement consumption. In this study, the effect of zeolite as a partial replacement for cement on the strength of clay soils was experimentally evaluated. The effect of various design parameters, such as cement replacement level and curing time, on the stability of clays was investigated using an advanced technique called the ultrasonic pulse velocity (UPV) test. Furthermore, a simple mathematical model was proposed based on the experimental results to help engineers design the stabilization plan and timely decide about the next steps of the construction process. [ABSTRACT FROM AUTHOR]

Foam lightweight soil (FLS) has been widely used in geotechnical engineering because of their high strength, low density, and thermal insulation. However, few scholars have researched its application to subgrade engineering, especially roadbed widening. In this case, this special artificial soil can significantly reduce the differential settlement of subgrades due to its lightweight and high strength. In the research background, a series of laboratory experiments were conducted to investigate the effects of mixing ratio and fibers on the physical, mechanical, and microporous structural properties of clay-based foamed lightweight soils (CFLS), with clay and cement as the main raw materials. The experimental results indicate that preparing CFLS for road widening using clay soils from around highways as raw materials is an alternative treatment method. During the application process, one should select the optimal mixing ratio and fiber content considering the fluidity, stability, and mechanical strength of CFLS. In addition, the dynamic modulus of elasticity and cumulative plastic strain of CFLS samples also indicate that CFLS has superior dynamic properties compared with cohesive soils and can meet the criteria for road construction. [ABSTRACT FROM AUTHOR]

This document discusses a research paper that explores the use of alternative binders to ordinary portland cement (OPC) in soil stabilization. The authors conducted a study using a binder composed of ground-granulated blast furnace slag (GGBS) and carbide sludge (CS) to stabilize clayey slurries. They found that the GGBS-CS binder performed better than OPC and proposed a pH-based approach to predict the optimum CS content. The document provides information on the unit weight of different materials, calculation of soil mass, and determination of GGBS and CS masses. It also presents data on the unconfined compressive strength (UCS) of different types of soil and suggests using a normalization procedure to fit the data to a single equation. The authors' experimental procedures are also questioned. [Extracted from the article]

The use of bacteria-based self-healing concrete for substructures in ground conditions is an area of increasing interest for enhancing the durability and longevity of infrastructure. In line with this objective, the present study investigates the bio-self-healing performance of a cementitious material embedded in clay soil with varying chemical exposures and water saturation regimes. Laboratory experiments were conducted on pre-cracked mortar specimens with Bacillus subtilis encapsulated in perlite. The specimens were incubated in the soil with different pH and sulphate levels, representing three exposure classes (based on Eurocodes). The crack healing ratio was evaluated through visual inspection and capillary-water absorption—before and after soil incubation. Findings showed that all inoculated specimens exhibited healing ratios noticeably larger than those of the control specimens, which mainly experienced small autogenous healing. Of note, the best healing performance was observed when the soil was fully saturated and pH-neutral. From the design perspective of bio-concrete, this study emphasizes the consideration of groundwater regime as well as acidity and sulphate of the soil. [ABSTRACT FROM AUTHOR]

This document serves as a follow-up to a previous paper on the use of lime and rice husk ash (RHA) to stabilize clayey soil. The original paper found that the addition of lime and RHA increased the strength of the soil, with the highest strength observed in samples containing 7% lime and 12% RHA. The document also includes additional research studies that support the use of RHA to improve soil strength. These studies found that the inclusion of RHA increased the California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) values of the soil, with the maximum strength achieved at an optimal RHA content. The increase in strength was attributed to the formation of cementitious products and agglomeration of soil particles. The degree of strength development varied depending on the type of soil and RHA used. The article also suggests future research directions, such as considering the effect of dry density and evaluating the suction effect. [Extracted from the article]

This document is a discussion of a research paper titled "Probing the Stochastic Unconfined Compressive Strength of Lime–RHA Mix Treated Clayey Soil." The paper explores the use of lime and rice husk ash as binders to stabilize clayey soil. The authors conducted tests to measure the unconfined compressive strength of soil-binder specimens with varying amounts of rice husk ash and lime. They used artificial neural networks and Gaussian process regression to analyze and predict the data. The discussers raise questions about the influence of suction on the strength of the blends and the effect of dry density, suggesting further evaluation of these factors. [Extracted from the article]