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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]

New ways to apply sustainable materials, such as biomass components, are essential for reducing dependence on fossil fuels. This work investigated the engineering properties of unsaturated expansive subgrade soils stabilized by bio-based energy coproducts containing lignin. Lignin is a waste by-product of the paper and pulp industry that is frequently burned. Highway subgrade could consume lignin as an environmentally benign, low-cost, and energy-efficient chemical substance for soil stabilization. Swell and shrink behavior of expansive subgrade soils complicates highway construction and causes damage to existing highways. However, research on the hydromechanical properties and volume change behavior of lignin-stabilized expansive soil is limited, and better insight is required into its unsaturated behavior for safe and economical pavement design practices. In this research, a series of geotechnical laboratory tests were conducted to characterize expansive subgrade soils treated with lignin by determining the Atterberg limits, compaction and consolidation behaviors, swelling characteristics, and water retention properties. The mechanisms influencing the changes in engineering properties of lignin-treated expansive soils were further investigated using soil pH, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analysis. The study shows that the optimal lignin content contributed to an acceptable degree of soil stabilization. The lignin-based cementing material effectively bonds soil particles together and fills pores, thereby preventing water infiltration into the soil and reducing the swell–shrink potential of stabilized soils. [ABSTRACT FROM AUTHOR]

The low bearing capacity of expansive soils often results in serviceability issues and premature failures of infrastructure built upon them. Various studies have demonstrated the use of different soil treatment methods using mechanical or chemical approaches to stabilize the weak ground as a precaution. Most of the reported studies are limited to either lab-based investigations or field monitoring works without the scientific connection between theory and translation. This study aims to verify the field application of a novel soil stabilization method by conducting laboratory-controlled experiments and field performance testing as verification. Enzyme–based soil stabilization was adopted for in-situ clay soil in combination with ordinary portland cement as a sustainable stabilization approach. Soil samples were collected at different regions from the field to evaluate the effectiveness and the mechanism of soil stabilization in the field by the means of replicating stabilization at the laboratory scale using identical mixing proportions of the additives. The mechanical behavior of stabilized soil was assessed through the unconfined compression strength and California bearing ratio test methods. In addition, the changes in the chemical composition of the soil due to the additives were evaluated through the X-ray diffraction testing technique and microporosity test using 2D images translated to 3D profiles from X-ray micro CT tomography. The efficacy of field stabilization was evaluated by conducting the falling weight deflectometer test in the stabilized site. Results from the study are useful to understand the efficacy of field soil stabilization and enhance the reliability of enzyme–based stabilization in practice. [ABSTRACT FROM AUTHOR]

The present work aims to evaluate expansive soil stabilization using different additives. Twenty soil mixtures consisting of 10%, 20%, 25%, and 30% zeolitic tuff (ZT) with 2%, 4%, and 6% lime in various combinations were used to stabilize the soil for pavement subbase application. A comprehensive test program, including Atterberg's limits, compaction, unconfined compression strength (UCS), California Bearing Ratio (CBR), resilient modulus, and permanent deformation, was performed on natural and stabilized soil specimens. Scanning electron microscopy (SEM) supplied with energy-dispersive X-ray spectroscopy (SEM/EDX) was used to confirm the study findings. Adding ZT increases the availability of the silica and alumina needed for the pozzolanic reaction; test results revealed that adding ZT increases the maximum dry unit weight, CBR, UCS, resilient modulus, decreases plasticity, and permanent deformation. As such, ZT can improve the physical and mechanical properties of lime-stabilized soil as a pavement's subgrade and subbase layers. [ABSTRACT FROM AUTHOR]

This study investigated the different geotechnical characteristics of soil stabilization with the addition of lime and rice husk ash (RHA) in varying amounts (3%, 5%, 7%, and 9% lime, and 4%, 8%, 12%, and 16% RHA). A series of compaction, unconfined compressive strength (UCS), California bearing ratio (CBR), pH, and X-ray diffraction (XRD) tests were performed in the laboratory to assess the impact of the considered admixtures on the stabilized soil parameters. This study also proposes the successful integration of an artificial neural network (ANN) and a Gaussian process regression (GPR) with the experimental UCS observations. The lime concentration, RHA concentration, and curing period were considered as the input parameters, and UCS was considered as the response. The proposed framework was extended to analyze the compressive behavior of treated soil on the minuscule level. Such coupled machine learning-based experimental investigation can provide deep insight into the soil behavior which otherwise would have remained unexplored due to the prohibitive nature of performing laboratory experiments on a large scale. The findings demonstrated the effectiveness of RHA in addition to lime in stabilizing the considered expansive soil. With the addition of lime and RHA mix, the UCS and CBR values of the treated soil increased significantly. [ABSTRACT FROM AUTHOR]

Efficient utilization of problematic soils such as soft clay by imparting additional strength using various stabilization techniques is done to improve soil properties. The application of nanomaterials in the area of soil stabilization has great potential to create a stiff skeleton, especially when blended with cementitious materials. Using the response surface method, this study focused on studying the effects of single and blended cementitious systems, comprising cement (0% to 20%), slag (0% to 20%), and nanosilica (0% to 2.4%), on the properties of soft clay in wet conditions [water-to-soil ratio (w/s) of 53% to 87%]. The mechanical [California bearing ratio (CBR), unconfined compressive strength up to 91 days] and durability (freezing-thawing durability factor) properties of stabilized clay were investigated, and the bulk trends were corroborated by thermogravimetry and microscopy analyses. Based on statistical analysis, incremental addition of cement, slag, and nanosilica led to the systematic increase in the properties of soft clay, albeit to different extents and with different mechanisms. At the low w/s (53%), superior mechanical and durability properties were obtained for soft clay stabilized with the ternary binder comprising cement, slag, and nanosilica. Numerical optimization showed that stabilizing this weak type of soft/expansive clay is possible, but the results (proportions, performance, cost) varied based on the target design criteria and application. [ABSTRACT FROM AUTHOR]

Plastic clays in subgrade may cause major engineering defects such as excessive heave or settlement during the wet season that contribute to the formation of uneven geometry at the pavement surface. Soil stabilization is often a requisite to ameliorate the engineering properties of soft soils or reactive clays. This study investigates the application of nano-silica and nano-alumina to improve the California bearing ratio (CBR) of a local clay. The clay was treated with cement (2%–8%), with nano-additive (0.1%–1.5%) and with cement and nano-additive (3% cement + 0.1%–1.5% nano-additive). The compacted sample was cured for 7 days and subjected to soaked and unsoaked CBR tests. The soaked CBR of the nontreated clay increased by 49% and 27% for 1% nano-silica and 1% nano-alumina treated clay, respectively. Although 3% cement addition improved the CBR of the soaked clay by 28%, the combination of 3% cement with 1% nano-silica and nano-alumina resulted in 196% and 164% increase in the soaked CBR of the nontreated clay, respectively. The combination of nano-additives and cement yielded the same soaked CBR as if 6%–7% cement would have been used. Clay treated with 1% nano-silica and 3% cement achieved the highest CBR value within the tested samples and the sample treated with 1% nano-alumina and 3% cement achieved the lowest free swell potential. The scanning electron microscopy (SEM) micrographs of the treated clay showed the formation of uniform fabric with fewer pore spaces and calcium silicate hydrate (CSH)/calcium aluminate hydrate (CAH) products within the fabric of nano-additive treated clay. [ABSTRACT FROM AUTHOR]