The paper investigates the effect of curing conditions on the properties of laterite soil-based geopolymer cement. In the experimental testing, calcined laterite soil was used as a solid precursor in the preparation of geopolymer cement. Standard size prismatic geopolymer specimens were prepared and subjected to four curing methods, including open air curing and courses of combined open-air curing and oven curing. The prisms were tested at 3, 7, and 28 days to determine the effect of curing methods on the flexural and compressive strengths. The crushed prisms were further pulverised and analysed to investigate the microstructure, elemental composition, mineralogical phases, chemical bonding, and thermal behaviour. The findings showed that the highest strength at 28 days was obtained with the air curing method. However, the curing methods involving an oven curing course resulted in the highest early strength at 3(early strength) and 7 days.

The socio-economic growth of a nation depends heavily on the availability of adequate infrastructure, which relies on essential materials like river sand (RS) and cement. However, the rising demand for RS, combined with its excessive extraction causing ecological damage, and its increasing cost, has raised significant concerns. At the same time, the production of cement contributes significantly to environmental damage, especially through CO2 emissions. In this scenario geopolymer technology has emerged as a sustainable alternative to cement, offering environmental benefits and reducing the carbon footprint of construction materials. This study investigates the impact of replacing RS with copper slag (CS) and laterite soil (LS) in geopolymer mortar (GM) on key properties such as setting time, flowability, compressive strength, and microstructure. The results showed that as LS content increased, setting time and flowability decreased considerably, while increasing CS content caused a reduction in these values. Unlike the other observed parameters, the compressive strength values showed no distinct upward or downward trend. Moreover, the microstructural analysis, including SEM, EDS, XRD, FTIR, TGA and BET, provided valuable insights to support the observed results across various mix designs. Overall, the findings highlight that optimised binary blends of CS, LS and RS not only improved the compressive strength but also enhanced the microstructural characteristics of geopolymer mortar, reinforcing their potential as sustainable and high-performance alternatives to conventional fine aggregates.

The Loess Plateau region of China has an anomalous climate and frequent geological disasters. Hipparion laterite in seasonally frozen regions exhibits heightened susceptibility to freeze-thaw (F-T) cycling, which induces progressive structural weakening and significantly elevates the risk of slope instability through mechanisms including pore water phase transitions, aggregate disintegration, and shear strength degradation. This study focuses on the slip zone Hipparion laterite from the Nao panliang landslide in Fugu County, Shaanxi Province. We innovatively integrated F-T cycling tests with ring-shear experiments to establish a hydro-thermal-mechanical coupled multi-scale evaluation framework for assessing F-T damage in the slip zone material. The microstructural evolution of soil architecture and pore characteristics was systematically analyzed through scanning electron microscopy (SEM) tests. Quantitative characterization of mechanical degradation mechanisms was achieved using advanced microstructural parameters including orientation frequency, probabilistic entropy, and fractal dimensions, revealing the intrinsic relationship between pore network anisotropy and macroscopic strength deterioration. The experimental results demonstrate that Hipparion laterite specimens undergo progressive deterioration with increasing F-T cycles and initial moisture content, predominantly exhibiting brittle deformation patterns. The soil exhibited substantial strength degradation, with total reduction rates of 51.54% and 43.67% for peak and residual strengths, respectively. The shear stress-displacement curves transitioned from strain-softening to strain-hardening behavior, indicating plastic deformation-dominated shear damage. Moisture content critically regulates pore microstructure evolution, reducing micropore proportion to 23.57-28.62% while promoting transformation to mesopores and macropores. At 24% moisture content, the areal porosity, probabilistic entropy, and fractal dimension increased by 0.2263, 0.0401, and 0.0589, respectively. Temperature-induced pore water phase transitions significantly amplified mechanical strength variability through cyclic damage accumulation. These findings advance the theoretical understanding of Hipparion laterite's engineering geological behavior while providing critical insights for slope stability assessment and landslide risk mitigation strategies in loess plateau regions.

Pavement inundation disrupts natural drainage, causing its structural damage and potential failure. This study investigates the impact of moisture fluctuations on pavement failure through four distinct approaches. Firstly, the critical strain at the top of the subgrade layer in unsaturated conditions was predicted using non-linear visco-elastic layer analysis. Secondly, structural number (SN) was established to evaluate the pavement strength under unsaturated conditions. Thirdly, the impact of rising groundwater levels on the structural strength of pavement layers was determined using maximum capillary height from soil suction. Finally, characteristic deflection and static moduli of the lateritic subgrade after a rainfall event were determined from field investigations with Benkelman beam deflectometer (BBD). Simulation in KENLAYER showed that the critical compressive vertical strain above subgrade due to different axle loading for bound and unbound granular layers varied with moisture fluctuation. Calculated SN values showed reduced capacity under saturated conditions compared to optimum moisture under the same traffic. BBD test revealed that the static moduli of the subgrade were lower due to increased moisture content, emphasizing the importance of moisture control and effective drainage for the structural integrity of pavements.

This study presents a comprehensive investigation into the mechanical properties of lime-stabilized lateritic soil, with a focus on developing an improved constitutive model that incorporates both curing time and strain-softening effects. Current constitutive models fail to accurately capture the stress-strain behavior of lime-stabilized soils, particularly over extended curing periods. To address this, unconfined compressive strength (UCS) tests were conducted using lime contents of 0%, 1%, 3%, 5%, 7%, 9%, and 11% revealing that 7% lime content optimally enhances the compressive strength of the soil by 1202.66% compared to untreated soil. Triaxial consolidated-drained tests were then performed with the optimal 7% lime content, considering curing times of 3, 7, 14, and 28 days under confining pressures of 100 kPa, 200 kPa, 300 kPa, and 400 kPa. The results demonstrated that the shear strength, cohesion, internal friction angle, and initial tangent modulus of lime-stabilized lateritic soil increased with longer curing times and higher confining pressures. These findings were integrated into a re-modified Duncan-Chang model, which incorporates both strain softening and curing time as key factors. The revised model was validated through comparisons with experimental data, achieving an average relative error of 2.12% at 7 days, 1.46% at 14 days, and 17.55% at 28 days. This validation demonstrates the model's ability to accurately predict the stress-strain behavior of lime-stabilized lateritic soil under different curing conditions. The novelty of this research lies in the successful integration of curing time and strain-softening effects into the Duncan-Chang model, providing a more accurate tool for predicting the long-term mechanical performance of stabilized soils. The findings have significant implications for engineering applications, particularly in the context of soil stabilization for infrastructure projects in tropical and subtropical regions.

In a consequence of climate change's adverse effects, Malaysia's road infrastructure faces significant challenges, particularly during both dry and rainy seasons, which weaken the natural bonds of the laterite soil. This research, therefore, outlines a laboratory study aimed at assessing the impact of cement stabilisation on the compressibility characteristics of laterite soil, subject to both saturated and unsaturated conditions. This study reveals that a 6% cement dosage is optimal for stabilising the laterite soil, proving the minimum 7-day strength requirement of 800 kPa, as specified by the Malaysia Public Works Department (MPWD) for stabilised subgrade material in low-volume roads. Consequently, the research involved conducting saturated tests (utilising a conventional oedometer) on soil specimens stabilised with 3%, 6%, 9%, and 12% cement dosages. Meanwhile, only the 6% cement-stabilised soil is used in unsaturated tests with a modified suction-controlled oedometer. The findings of this study highlighted that cement-stabilised laterite soil exhibits significantly lower compressibility in comparison to unstabilised laterite soil. Furthermore, the unsaturated oedometer test demonstrated that soil's compressibility is notably decreased at higher suction levels (drying conditions) compared to lower suction levels (wetting conditions). In summary, this research contributes valuable insights, emphasising the potential of cement as an effective soil stabiliser by reducing soil settlement and enhancing the durability of Malaysia's roads in response to climate-related challenges.

This study investigated the combined effects of calcium carbide waste (CCW) and lateritic soil (LS) on sustainable concrete's fresh and mechanical properties as a construction material for infrastructure development. The study will explore the possibility of using easily accessible materials, such as lateritic soils and calcium carbide waste. Therefore, laterite soil was used to replace some portions of fine aggregate at 0% to 40% (interval of 10%) by weight, while CCW substituted the cement content at 0%, 5%, 10%, 15%, and 20% by weight. A response surface methodology/central composite design (RSM/CCD) tool was applied to design and develop statistical models for predicting and optimizing the properties of the sustainable concrete. The LS and CCW were input variables, and compressive strength and splitting tensile properties are response variables. The results indicated that the combined effects of CCW and LS improve workability by 18.2% compared to the control mixture. Regarding the mechanical properties, the synergic effects of CCW as a cementitious material and LS as a fine aggregate have improved the concrete's compressive and splitting tensile strengths. The contribution of LS is more pronounced than that of CCW. The established models have successfully predicted the mechanical behavior and fresh properties of sustainable concrete utilizing LS and CCW as the independent variables with high accuracy. The optimized responses can be achieved with 15% CCW and 10% lateritic soil as a substitute for fine aggregate weight. These optimization outcomes produced the most robust possible results, with a desirability of 81.3%.

Compacted soil layers effectively prevent the migration of radon gas from uranium tailings impoundments to the nearby environment. However, surface damage caused by wet and dry cycles (WDCs) weakens this phenomenon. In order to study the effect of crack network on radon exhalation under WDCs, a homemade uranium tailing pond model was developed to carry out radon exhalation tests under five WDCs. Based on image processing and morphological methods, the area, length, mean width and fractal dimension of the drying cracks were quantitatively analyzed, and multiple linear regression was used to establish the relationship between the geometric characteristics of the cracks and the radon exhalation rate under multiple WDCs. The results suggested that the radon release rate and crack network of the uranium tailings pond gradually stabilized as the water content decreased, following rapid development in a single WDC process. The radon release rate increased continuously after each cycle, with a cumulative increase of 25.9% over 5 cycles. The radon release rate and average crack width remained consistent in size, and a binary linear regression considering width and fractal dimension could explain the changes in radon release rate after multiple WDCs.

The experimental research elaborated by Rithy Domphoeun and Amin Eisazadeh (2024) delves into exploring the effect of Rice Husk Ash (RHA), Lime (L), and Coir Fiber (CF) on the engineering properties of laterite soil when used as reinforcement materials. They have used various tests, including Unconfined Compressive Strength (UCS), three-point bending flexural strength, direct shear, completely soaked durability, X-ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM), to analyze their effects. They found that the mixture of 20% RHA with 8% of lime exhibited highest UCS value after 56 days. Therefore, the mix of 20% RHA with 1% of coir fiber and 8% of Lime showed a tenfold increase in flexural strength compared to natural laterite soil after 28 days of curing. They reported also that the coir fiber and rice husk ash could be advantageous for structures like embankments and road layers exposed to significant tensile stresses. While recognizing the authors' dedication in crafting their paper, it's crucial to highlight that certain aspects demand additional clarification and assessment. This discussion piece aims to delve into and address these specific points for further understanding and evaluation.

Thailand is situated in the heart of Southeast Asia and is classified as having a tropical climate with high rainfall frequency and occurrence of floods. The weakening effect of water on laterite soil has led to different road damages such as potholes. Under these adverse environmental conditions, heavy traffic could also result in the formation of cracks and poor performance of roads. This study investigates the effects of Rice Husk Ash (RHA), Lime (L), and Coir Fiber (CF) as soil reinforcement material on the engineering properties of laterite soil. Several tests were conducted including the Unconfined Compressive Strength (UCS) test, three-point bending flexural strength, direct shear test, completely soaked durability test (to mimic flood conditions), X-ray Fluorescence (XRF), and Scanning Electron Microscopy (SEM) to observe the micro-structural changes of stabilized soil. The laterite soil was replaced by 10%, and 20% of RHA, 1% of CF, and 8% of L. The samples were cured for 7, 28, and 56 days before conducting the tests. The 20RHA8L mix designs showed the highest UCS value after 56 days curing period. In terms of the durability test results, the 20RHA8L mix design also exhibited the lowest reduction in compressive strength (3.8% drop) after undergoing 6 wetting-drying cycles. According to flexural strength, the 20RHA1CF8L (20%RHA, 1%CF, 8%L) mix design indicated a tenfold increase in flexural strength compared to the natural laterite soil after 28 days of curing. Based on the findings of this research, CF and RHA are beneficial for earth structures such as embankments and road layers that are subjected to significant tensile stresses. These waste materials can also reduce the brittleness of lime-stabilized soil.