Most gravel roads leading to rural areas in Ghana have soft spot sections as a result of weak lateritic subgrade layers. This study presents a laboratory investigation on a typical weak lateritic subgrade soil reinforced with non-woven fibers. The objective was to investigate the strength characteristic of the soil reinforced with non-woven fibers. The California Bearing Ratio and Unconfined Compressive Strength tests were conducted by placing the fibers in single layer and also in multiple layers. The results showed an improved strength of the soil from a CBR value of 7%. The CBR recorded maximum values of 30% and 21% for coconut and palm fibers inclusion at a placement depth of H/5 from the compacted surface. Multiple fiber layer application at depths of H/5 & 2 h/5 yielded CBR values of 38% and 31% for coconut and palm fibers respectively. The Giroud and Noiray design method and the Indian Road Congress design method recorded reduction in the thickness of pavement of 56% to 63% for coconut fiber inclusion and 45% to 55% for palm fiber inclusion. Two-way statistical analysis of variance (ANOVA) showed significant effect of depth of fiber placement and fiber type on the geotechnical characteristics considered. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic),CBR(sic)(sic)7%(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic)(sic)(sic)(sic)H/5(sic)(sic)(sic)(sic)(sic)(sic),CBR(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)30%(sic)21%. (sic)H/5(sic)2H/5(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)CBR(sic)(sic)(sic)(sic)38%(sic)31%. Giroud&Noiray(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)56%(sic)63%,(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)45%(sic)55%. (sic)(sic)(sic)(sic)(sic)(sic)(ANOVA)(sic)(sic),(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

Microbial-induced calcite precipitation (MICP) is an eco-friendly soil stabilization technology widely applied to the solidification of aeolian sand. To further enhance the effectiveness of MICP in cementing aeolian sand, this study introduced wheat straw powder (WSP) as a reinforcing material and conducted experimental research on WSP-enhanced microbial cemented aeolian sand. By combining macroscopic physical and mechanical tests with discrete element method (DEM) simulations, this study systematically investigated the mechanisms by which WSP enhances microbial cementation and the mesoscopic failure characteristics of the material. The results indicated that adding WSP significantly increased the calcium carbonate content, resulting in uniform calcite deposition and encapsulation of sand particles. This enhancement increased the compressive strength and deformation resistance of the cemented sand columns, with a notable increase in strain at failure. DEM simulations further revealed that as the calcium carbonate content increased, macroscopic cracks within the sand columns evolved from single to multiple pathways, eventually penetrating the entire sand column along the loading direction. The internal bonding failure process could be divided into compaction, expansion, and rapid growth stages. Additionally, the uniformity of particle bonding in WSP-reinforced sand columns significantly impacted their macroscopic mechanical behavior, with uneven interparticle bonding likely inducing microcrack accumulation, leading to severe fracture patterns. These findings provide valuable insights for optimizing microbial cementation techniques for aeolian sand.

This study delves into the mechanical properties and mechanisms of bentonite-modified cement soil, a reinforced material formed through the physicochemical reactions of cement, soil, and water. Recognizing the material's widespread application in foundation treatment, slope reinforcement, and seepage control, alongside the environmental pressures of cement production, this research explores the potential of bentonite as a partial cement substitute. Through indoor unconfined compressive strength and permeability tests, varied by curing age, bentonite type, and mix ratio, the study assesses the impact of these factors on the material's performance. Microscopic analyses further elucidate the intrinsic mechanisms at play. Key findings include: a non-linear relationship between bentonite content and modified cement soil strength, with sodium-based bentonite enhancing strength more effectively than calcium-based; a significant reduction in permeability coefficient with increased bentonite content, particularly with sodium-based bentonite; and a detailed examination of the material's microstructure, revealing the critical role of cement and bentonite content in pore reduction and strength enhancement. The study underscores the paramount influence of cement content on both strength and permeability, proposing a prioritized framework for optimizing modified cement soil's performance. (c) 2025 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Expansive soils, widely distributed in nature, often pose challenges to construction stability due to their low unconfined compressive strength (UCS), poor shear strength, and high expansibility. This study investigates the application of phosphoric acid (H3PO4) in modifying sodium bentonite, focusing on its effects on the mechanical properties and swelling behavior of bentonite, as well as the underlying mechanisms. H3PO4 was added to bentonite at mass ratios of 1% to 8%. Compared to unmodified bentonite, the plastic index of the modified bentonite decreased by 39.9%, and the UCS value increased by 92.24% when the H3PO4 dosage was 2%. Notably, at an H3PO4 dosage of 8%, the free swelling rate of the modified bentonite decreased by 38.1% relative to the control sample, and the cohesion increased by 165.35%, indicating significant improvements in both the expansibility and bearing capacity of modified bentonite. The results on the physical and chemical properties of modified bentonite revealed an ion exchange involving hydrogen ions from H3PO4 and metal cations in sodium bentonite. The zeta potential of bentonite decreased with H3PO4 addition, reflecting a reduction in the double electric layer thickness due to hydrogen ion exchange with metal cations. This enhanced the gravitational attraction between soil particles, leading to their closer proximity and a significant increase in the UCS value of the modified soil. Additionally, the XRD results confirmed that the addition of H3PO4 facilitated the formation of a new mineral, aluminum phosphate, which is hard and insoluble, filling soil pores, contributing to its densification. This study demonstrates that H3PO4 can effectively enhance the swelling resistance and strength of sodium bentonite, offering a promising method to improve its application performance.

This investigation addresses the reinforcement of rammed earth (RE) structures by integrating carpet polyacrylic yarn waste (CPYW) generated from the carpet production process and employing Ground Granulated Blast-Furnace Slag (GGBS) as a stabilizer, in conjunction with alkali activators potassium hydroxide (KOH), to enhance their mechanical properties. The study included conducting Unconfined Compressive Strength (UCS) tests and Brazilian Tensile Strength (BTS) tests on plain samples, GGBS-stabilized (SS) samples, CPYW-reinforced (CFS) samples, and samples reinforced with a combination of GGBS and CPYW (SCFS). The results showed that the mechanical and resistance properties of the CFS and SCFS samples were improved; these findings were confirmed by the presence of more cohesive GGBS gel and fibers as seen in FE-SEM and microscopic images. Therefore, the use of GGBS and CPYW, both separately and in combination, is suggested as a viable approach to enhance mechanical performance and reduce the brittle failure propensity of RE structures. This study achieved significant improvements in the mechanical behavior of RE structures by integrating CPYW and alkali-activated GGBS. Results showed a 370% improvement in UCS and a 638% increase in BTS than the plain sample. These enhancements demonstrate the potential for using industrial waste in eco-friendly, high-performance construction materials.

Dredged soil has the disadvantages of high moisture content and low strength, making it unsuitable for practical engineering application. However, a gelling agent system composed of ground granulated blast-furnace slag (GGBS) and carbide slag (CS) can enhance the strength of dredged soil. Additionally, phosphogypsum (PG) can react with the products of this system (calcium silicate hydrate) to form ettringite and improve strength. In this study, CS, GGBS, and PG were selected to solidify dredged soil with high moisture content. The flowability test, unconfined compression test, and direct shear test were employed to evaluate the engineering properties of the dredged soil, while the scanning electron microscope test (SEM), X-ray diffraction test (XRD), nuclear magnetic resonance test (NMR), and toxicity characteristic leaching procedure test (TCLP) to investigate the microstructure evolution of the cured dredged soil. The results indicated that the decreased flowability of cured dredged soil showed a decreasing trend with increased curing agent content. The strength of cured dredged soil increased first and then decreased, and increased finally with the increase of PG content. The optimum PG content was identified as 10 % when the GGBS content was set as 15 %. The internal friction angle of cured dredged soil increased with increased PG content. The change of pore structure and hydration reaction were identified as the main root cause for the change of sample strength. The new cementing material composed of CS, GGBS and PG can effectively resolve the insufficient strength and high water content problems of dredged soil, while having negligible impact on the environment. Moreover, since it is made up of industrial by-products, it has a lower carbon footprint than the traditional cementing materials of lime or cement.

In order to reduce the storage cost and avoid environmental hazards of feldspar powder waste from lithium extraction byproducts, this work investigated the feasibility of ordinary silicate cement-stabilized feldspar powder-lateritic clay (FP-LC) composite as road construction material. Firstly, preliminary mix design of the new material was conducted to determine the optimum moisture content and maximum dry density. Subsequently, the effects of ratio of FP to LC on the mechanical properties of the composite were investigated through unconfined compressive strength (UCS), California bearing ratio (CBR) and shear strength tests. Finally, the strength formation mechanism of the FP-LC mixture was analyzed in combination with SEM and XRD testing. The results indicate that the UCS after 14 d curing, CBR and cohesive strength of FP simply stabilized by 6 % cement is 0.95 MPa, 87.3 % and 140.64 kPa, respectively, which can meet the requirements for subgrade materials. The addition of LC significantly improves the mechanical properties of the composite. The mass ratio of 40 % FP to 60 % LC results in the optimal UCS after 14 d curing, CBR and cohesive strength with 1.6 MPa, 164.1 % and 250.16 kPa, respectively, which makes it applicable as subbase materials for medium-light traffic levels. The particle closest packing analysis and SEM and XRD characterization demonstrated that the enhancement of UCS, CBR and shear strength comes from compact arrangement of FP and LC particles and the bonding effect of cement hydration products between them. This work proposes an eco-friendly and sustainable utilization approach of feldspar powder from lithium extraction byproducts as road construction material, which are important to overcome the challenges of both waste management and resource shortage for new energy and highway industries, respectively.

This study investigated the physical and mechanical properties of Malaysian kaolin clay treated with cement using unconfined compression strength and Oedometer tests. The objective was to simulate the actual conditions of soil-cement column installation employing the deep soil mixing method with cement slurry over a 180-day period. Cement content varied between 5%, 10%, 15%, and 20%. To ensure homogeneous mixing and workability, water content was maintained between the liquid limit and twice the liquid limit. Results indicated that increasing cement content enhanced the unconfined shear strength and elasticity modulus of the stabilized soil while decreasing water content after curing. Consolidation tests revealed a diminishing slope of the void ratio curve with increasing cement content and curing time. This study further introduced precise correlations between the void ratio and compression characteristics of cement-stabilized clay, achieving high accuracy. Additionally, the research conclusively demonstrated a robust linear correlation (R2 = 0.99) between unconfined compressive strength and consolidation yield pressure.

Freeze-thaw (F-T) cycling poses a significant challenge in seasonally frozen zones, notably affecting the mechanical properties of soil, which is a critical consideration in subgrade engineering. Consequently, a series of unconfined compressive strength tests were conducted to evaluate the influence of various factors, including fiber content, fiber length, curing time, and F-T cycles on the unconfined compression strength (UCS) of fiber-reinforced cemented silty sand. In parallel, acoustic emission (AE) testing was conducted to assess the AE characteristic parameters (e.g., cumulative ring count, cumulative energy, energy, amplitude, RA, and AF) of the same material under F-T cycles, elucidating the progression of F-T-induced damage. The findings indicated that UCS initially increased and then declined as fiber content increased, with the optimal fiber content identified at 0.2%. UCS increased with prolonged curing time, while increases in fiber length and F-T cycles led to a reduction in UCS, which then stabilized after 6 to 10 cycles. Stable F-T cycles resulted in a strength loss of approximately 30% in fiber-reinforced cemented silty sand. Furthermore, AE characteristic parameters strongly correlated with the stages of damage. F-T damage was segmented into three stages using cumulative ring count and cumulative energy. An increase in cumulative ring count to 0.02 x 104 times and cumulative energy to 0.03 x 104 mvmu s marked the emergence of critical failure points. A sudden shift in AE amplitude indicated a transition in the damage stage, with an amplitude of 67 dB after 6 F-T cycles serving as an early warning of impending failure.

As a renewable energy source, biomass has the potential to replace non-renewable, fossil fuels. However, the disposal of the waste biomass ash (generated during energy generation) needs to be studied. While prior studies attempted to utilise composite additives containing biomass ash for soil, the introduction of other additives, such as cement, was an environmental burden. By employing biomass ash composition as the sole additive for strengthening purple soil under various curing conditions using high-temperature treatment, this study maximised its utilisation. The results showed that the unconfined compressive strength (UCS) varied across different curing conditions as the biomass ash content increased. After high temperature treatment at 800 degrees C, the biomass ash consistently reinforced purple soil under all the curing conditions. However, the biomass ash stabilisation mechanism differed between dry and humid curing conditions. Under dry curing conditions, the UCS increase depended on the cementing effect of soluble salt and/or insoluble calcite; under humid curing conditions, the UCS change was attributed to the damage to clay minerals, contact mode, and cementing effects of multiple components. Therefore, the 800 degrees C temperature-treated biomass ash can be used alone to reinforce purple soil, inhibiting the soil-water loss. This study presents a novel avenue for utilising waste, biomass ash, with considerable implications for environmental protection and soil stabilisation.