Due to the detrimental ecological impacts and the exorbitant expenses associated with the cement industry, researchers have sought to find natural, sustainable, low-carbon alternatives to Portland cement for weak soil stabilization. This research used geopolymer based on metakaolin (MK), a natural pozzolanic material with different activator concentrations (NaOH and Na2SiO3), to stabilize loose poorly graded sand soils. The research investigated the effect of different amounts of addition MK (5, 10, and 15 %) on the soil's mechanical properties. Furthermore, the effect of parameters such as the type and concentration of the alkaline solution and curing time (1, 3, and 7 days) on the unconfined compressive strength, failure strain, Young's modulus, California bearing ratio, and direct shear test were evaluated. This research also aims to measure the sub- grade reaction modulus (Ks) by developing and manufacturing a laboratory testing apparatus and steel mold to simulate the natural conditions of sandy subgrade soil obtained from performing nonrepetitive static plate load tests. Additionally, scanning electron microscopy images (SEM) and X-ray diffraction analysis (XRD) were also used to study the microstructural changes and the chemical composition of the stabilized soil samples. The results indicate that the soil samples that were stabilized with MK 10 % and NaOH had notably higher compressive strength (2936 kPa), indicating a denser and less porous structure (improved stiffness stabilized soil) in comparison to the soil samples stabilized with MK 10 % and Na2SiO3 which was (447 kPa). Ultimately, Microstructural analysis showed that, due to the addition of 10 % MK, stabilized soils have a denser and more homogeneous structure.

The soil packing, influenced by variations in grain size and the gradation pattern within the soil matrix, plays a crucial role in constituting the mechanical properties of sandy soils. However, previous modeling approaches have overlooked incorporating the full range of representative parameters to accurately predict the soaked California bearing ratio (CBRs) of sandy soils by precisely articulating soil packing in the modeling framework. This study presents an innovative artificial intelligence (AI)-based approach for modeling the CBRs of sandy soils, considering grain size variability meticulously. By synthesizing extensive data from multiple sources, i.e. extensive tailored testing program undertaking multiple tests and extant literature, various modeling techniques including genetic expression programming (GEP), multi-expression programming (MEP), support vector machine (SVM), and multi-linear regression (MLR) are utilized to develop models. The research explores two modeling strategies, namely simplified and composite, with the former incorporating only sieve analysis test parameters, while the latter includes compaction test parameters alongside sieve analysis data. The models' performance is assessed using statistical key performance indicators (KPIs). Results indicate that genetic AI-based algorithms, particularly GEP, outperform SVM and conventional regression techniques, effectively capturing complex relationships between input parameters and CBRs. Additionally, the study reveals insights into model performance concerning the number of input parameters, with GEP consistently outperforming other models. External validation and Taylor diagram analysis demonstrate the GEP models' superiority over existing literature models on an independent dataset from the literature. Parametric and sensitivity analyses highlight the intricate relationships between grain sizes and CBRs, further emphasizing GEP's efficacy in modeling such complexities. This study contributes to enhancing CBRs modeling accuracy for sandy soils, crucial for pertinent infrastructure design and construction rapidly and cost-effectively. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Concrete is one of the most widely used building materials due to its many advantages, which results in large amounts of concrete waste resulting from demolition. This study will be an attempt to produce an environmentally friendly road. In this research, recycled aggregates were used according to the class A and B, used in the Iraqi specifications for roads and bridges (SORB). Two methods were used, the first method was to use recycled aggregate of class A and B with different proportions of fine soil, as a binding material for the aggregate particles, and the second method was to use recycled aggregate of class A and B with different proportions of fly ash as a binding material for the aggregate particles. The physical and mechanical properties of the recycled aggregate were studied, the behaviour of road layers designed from recycled aggregate was also studied by determining the California bearing ratio in dry and wet conditions, as well as the unconfined compressive strength. The research showed that when using( 5%,10%,14%)of fine soil with recycled aggregate, the California bearing ratio fit gave high and acceptable values. However, when increasing the ratio to 16%, the values decreased from 41.0% to 38.7% for class A in the soaking state, but in the unsoakhng state, it decreased from44.6% to 42.0% and Also the class B values decreased in the soaking state from 41.4% to 39.3%, and in the un soaking state from 45.0% to 43.2%,Likewise The unconfined compressive strength decreased by 25% when the fine soil content increased to 16% while the values increased with increasing fly ash content. This study concluded that it is possible to use recycled aggregate in the design of road layers, especially since the values of the California bearing ratio of recycled aggregate are greater than the values of natural aggregate used in road works. Thus, this study achieved a major goal from an environmental and economic perspective.

Global economic growth leads to massive plastic waste increase, posing severe environmental challenges worldwide. Addressing it demands innovative solutions like repurposing plastics for construction. Extensive engineering and environmental assessments can accelerate their adoption. This study explores the potential incorporation of plastic waste (in flake and pellet forms) into a cement-treated fine-grained soil through a comprehensive geotechnical experimental testing program and Life Cycle Assessment (LCA) study to assess their environmental sustainability. Experimental investigations were conducted on four distinct plastic types, namely polypropylene (PP), high-density polyethylene (HDPE), polylactic acid (PLA), and polyethylene terephthalate (PET), with varying weight percent inclusions of 2 %, 4 %, and 6 %. Results revealed a decreasing trend in maximum dry densities and strength (both unconfined compressive strength (UCS) and split tensile strength (STS)) with increasing plastic content. Sorptivity of soil generally increased with plastic inclusions, yet in the case of PET, for plastic content > 4 %, a notable drop in the rate of increase was observed. California bearing ratio (CBR) test results indicated a reduction in the CBR values by up to 18.33 % for 6 % plastic inclusions. LCA study findings favoured plastic flakes over pellets as a more sustainable material choice, exhibiting a lower environmental impact across all assessed indicators. This research findings offer insights into the potential utilization of plastic waste and promote sustainable geomaterial choices in road pavement construction.

High plasticity clay soils have low bearing and high swelling potential, which can lead to major problems if used in embankment layers. In current study, recycled concrete aggregates (RCA) were used as the most important part of construction and demolition (C&D) wastes in order to reduce the swelling potential and improve the mechanical strenght of high plasticity clay soil, and to achieve these goals, granulated blast furnace slag (GBS) was used as chemical additive. A set of laboratory tests including standard proctor, unconfined compression strength (UCS) and CBR tests were conducted to investigate the mechanical properties of the treated soil. Laboratory observations showed that by adding of RCA wastes to high plasticity clay, the UCS value increased up to 20% RCA content and then decreased with further RCA. Also, adding GBS and prolonged curing time improves the UCS of the clay - RCA mixture, and addition of 9% GBS can be suggested as the optimal content to achieve the design criteria of the subbase and subgrade layers. The use of RCA improves the secant modulus of elasticity (E50) and reduces the deformability index (DI), and these parameters are improved more significantly in the presence of GBS additive.

The rapid growth of construction activities in India has led to a significant increase in the generation of construction and demolition waste (CDW). This waste poses a major environmental and economic challenge. One sustainable method to manage construction and demolition waste is to reuse the aggregates that are collected after the demolition of structures and damaged roads. In this study, a design mix of granular sub base (GSB) layer of close graded-grading II was considered. The GSB layer is a layer of compacted aggregate that is placed below the road surface to provide a stable base for the pavement. The design mix consisted of 40, 20, and 10 mm natural aggregates (NA), 20 mm of recycled aggregates (RA) collected from demolished buildings/concrete waste/damaged roads, and blended soil (BS). The properties of the clay with intermediate plasticity soil were enhanced with the addition of crusher dust for the preparation of BS. The RA were used to replace the NA in the design mix. The best combination of aggregates that met the specifications of the Ministry of Road Transport and Highways was selected. The results showed that up to 60% of the 20 mm natural aggregates could be replaced with recycled aggregates without compromising the performance of the GSB layer. The maximum dry density and optimum moisture content after replacement were found to be 2.00 g/cm3 and 10.37%, respectively. The California Bearing Ratio value at 2.5 mm penetration was also found to be 38.47. These results suggest that RA can be used as a sustainable alternative to NA in the construction of GSB layers. This can help to reduce the environmental issues of CDW and save natural resources.

Unconfined compressive strength (UCS) and California bearing ratio (CBR) are key indicators of soil strength, particularly in fine-grained soils that often fail to meet project standards for roads and embankments. This study investigates the effects of fly ash on UCS and CBR, demonstrating an increase in both, though not symmetrically, due to varying percentages of chemical oxides in the soil-fly ash matrix. The relationships between UCS, curing time, chemical oxides (silica, alumina, calcium, magnesia, ferric), maximum dry density, and optimum moisture content (OMC) were analyzed. Three mathematical models, pure quadratic (PQ), interaction (IA), and full quadratic (FQ), were used to model UCS for 111 fly ash-treated and 49 untreated soils. While FQ and IA offered excellent predictions, their complexity led to applying geochemical indices like the hydraulic index (HI) and lime modulus (LM) to simplify the equations, with FQ remaining the most accurate. Sensitivity analysis showed that curing time was the most influential factor on UCS, followed by calcium oxide (CaO). When geochemical indices were applied, the hydraulic index (HI) emerged as the most significant factor. These findings underscore the importance of grouped chemical oxides, particularly SiO2, Al2O3, and Fe2O3, in enhancing soil properties, providing valuable insights for geotechnical engineering applications.

Radish is a widely cultivated popular and economically important vegetable that can be consumed both as raw as well as in cooked form. However, its production is severely impacted by flea beetles almost round the year. The adults feed on leaves and larvae on roots. Numerous small shot holes on the leaves and dark stripes on the roots are the typical damage symptoms caused by beetle infestation. The biology, molecular taxonomy, damage severity and management of the Phyllotreta striolata along with economics have been studied. In the present study, an integrated organic pest management module was evaluated to control this nefarious pest in the present experiment which includes the following approaches: soil application of neem cake @ 500 kg/ha before radish seed sowing, inter-cropping with Indian mustard every alternate 8 rows as a trap crop 15 days before radish sowing, application of vermicompost enriched with Metarhizium anisopliae @ 10 g/kg of vermicompost during seed sowing; soil application of Heterorhabditis indica @ 10 kg/ha mixed with moist sand with light irrigation, need-based foliar spraying of Metarhizium anisopliae + Neem oil @ 2.5 g/lit + 2.5 ml/lit at 25 and 45 days after sowing (DAS) and Azadirachtin 300 ppm @ 5 ml/lit at 35 DAS were found significantly effective (P < 0.0001) in reducing number of shot holes (37.64/leaf), stripes on radish (7.37/root), population of adults (2.61/plant) and larvae (2.9 on radish root and rhizosphere) compared to farmers' practices (58.09, 16.48, 3.67 and 5.6, respectively) and untreated control plots (139.37, 32.46, 7.58 and 8.3, respectively) at 21 DAS. The organic IPM module had highest root yield (19.3 t/ha) accompanied by highest incremental cost benefit ratio (ICBR) of 1:2.81 followed by farmers' practices (13.9 t/ha and ICBR = 1:2.29) and untreated control (8.4 t/ha and ICBR = 1:1.92). The developed organic pest management module was found highly promising in management of radish flea beetle.

In this research, a combined method of chemical and physical stabilisation has been used to investigate the effect of using recycled concrete aggregate (RCA) and granulated blast furnace slag (GBS) in improving the strength properties of subgrade soil. A comprehensive series of compaction, uniaxial compressive strength (UCS) and California bearing ratio tests were performed on different mixtures. The results show that UCS values increased for clay subgrade with up to 20% RCA content and decreased after that. The subgrade soil with 20% RCA was treated with GBS to obtain the target uniaxial strength for stabilised subgrade soils. Also, the results obtained from investigating the effect of freeze-thaw cycle on the UCS of the optimum combination with different GBS content show that the F-T cycle reduces the value of the UCS from 32% to 53% after 12 F-T cycles.

Two common waste by-products in Thailand, rice husk ash (RHA) and coir fiber (CF), were used alongside lime (L) to stabilize laterite soil and create a sustainable subbase material for pavements. The mechanical properties of the laterite soil mixed with RHA, lime, and CF were evaluated through compaction characteristics, unconfined compressive strength (UCS), California bearing ratio (CBR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analyses. The dry soil mass was replaced with 10% and 20% RHA, and CF was added at 0.5%, 1%, and 1.5%. Additionally, based on the initial consumption of lime (ICL) test, 8% lime was incorporated into the mixture. The samples were cured for 7 days (short-term) and 56 days (long-term) before undergoing various tests. In terms of compaction, results showed that increasing the content of RHA, CF, and lime led to a decrease in maximum dry unit weight and an increase in optimum moisture content. The 10RHA8L and 20RHA8L mix designs demonstrated the highest UCS and CBR values after 56 and 7 days of curing, respectively. EDX analysis revealed the formation of calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) gels on the particle surfaces, leading to a denser and more cohesive structure. Based on these findings, the mixture containing 20% RHA and 8% lime exhibited the most favorable properties for use as a subbase material in road and embankment construction.