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.
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%.
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.
Using biopolymers for soil stabilization is favorable compared to more conventional methods because they are more environmentally friendly, cost-effective, and long-lasting. This study analyzes the physical properties of guar gum and laterite soil mixes. A comprehensive engineering study of guar gum-treated soil was conducted with the help of a brief experimental program. This study examined the effects of soil-guar gum interactions on the strengthening behavior of guar gum-treated soil mixtures using a series of laboratory tests. The treated laterite soil's dry density increased marginally, while its optimum moisture content decreased as the guar gum increased. Treatment with guar gum significantly enhanced the strength of laterite soil mixtures. For laterite soil with 2% guar gum, the unsoaked CBR increased by 148% and the soaked CBR increased by 192.36%. The cohesiveness and internal friction angle increased by 93.33% and 31.52%, respectively. These results show that using guar gum dramatically improves the strength of laterite soil, offering a more environmentally friendly and sustainable alternative to traditional soil additives. Using guar gum in T8 subgrade soil requires a 1395 mm pavement depth and costs INR 3.83 crores, 1.52 times more than laterite soil. For T9 subgrade soil, the depth was 1495 mm, costing INR 4.42 crores, 1.72 times more than laterite soil. This study introduces a novel approach to soil stabilization by employing guar gum, a biopolymer, to enhance the physical and mechanical properties of laterite soil. Furthermore, this study provides a detailed cost-benefit analysis for pavement applications, revealing the financial feasibility of using guar gum despite it requiring a marginally higher initial investment.
Multiple-compaction demonstrates cyclic loading on laterite soils used in highway construction and its effects on engineering properties. The method determines the mechanical stability of derived soils from porphyritic granite, granite gneiss, and charnockite. Fifty-one soil samples were obtained from the horizons of the laterite soil profiles. Four sets of dynamic compactions were carried out on each sample. Index engineering properties such as specific gravity, Atterberg limits, and particle size distribution were investigated before and after multiple-compaction. The changes in engineering properties and moisture-density characteristics were investigated using the granulometric modulus and hardness index. Through multiple-compaction, larger grains in soils derived from granite gneiss and porphyritic granite disintegrated into smaller particles. The fine grains break down more easily than the large grains of quartz bound by clayey materials in charnockite-derived soils. Interestingly, the maximum dry density and optimum moisture content remain consistent in porphyritic and granite gneiss-derived soils after multiple compactions. Based on the densification and behaviour of the derived soils under multiple compaction in highway construction, porphyritic granite and granite gneiss-derived soils are more suitable as engineering materials than charnockite-derived soils.
Recently, the alkalization of various materials for solidifying vulnerable soil has become increasingly prevalent to improve their structural integrity and strength properties. However, the characterization of laterite soil solidified by alkalizing strong electrolytes has been limited. This research paper presents an innovative way of utilizing an alkaline activator and bischofite (MgCl2 center dot 6H2O) to initiate the activation of silica and alumina constituents and polymerization for the physio-chemical characterization of laterite soil and determine the optimal design mix. Standard compaction and uniaxial strength (UCS) were assessed for mechanical features, and mechanisms contributing to solidification were assessed using SEM, EDS, and FTIR. The alkalization of bischofite has significantly altered the mechanical characteristics of the sample. The UCS test findings at ambient room temperature revealed that a sample containing an alkaline activator proportion of 0.75, an activator-to-bischofite proportion of 0.9, and a 5% bischofite by dry soil weight of soil is the optimal mix to ameliorate the potency of the laterite soil. The development of hydroxyl groups on kaolinite edges and cation replacement decreased pH with the curing period, promoting structural modification in physiochemical analysis. The solidification methods created a bonding gel of hydrated magnesium silicate (M-S-H) compounds, as shown by SEM micrographs and EDS spectra. Additionally, the FTIR finding affirmed the formation of magnesium hydration products in the spectral range of 1600 to 450 cm-1 with silicate, aluminum, and magnesium chain polymerization evolution. Finally, the study demonstrated the potential of bischofite-alkalization to modify the physiochemical and micro-structural features of weak laterite soil to be utilized in various construction projects.