Search Results (133)

Rural roads are critical for connecting isolated communities to essential services such as education and health and administrative services, as well as production and market opportunities in low-income countries. More than 70% of movements of people and goods in Sub-Saharan Africa are heavily reliant on rural transport systems, using both motorised but mainly alternative means of transport. However, rural roads often suffer from poor construction due to the use of low-strength, in situ soils and limited financial resources, leading to premature failures and subsequent traffic disruptions with significant economic losses. This study investigates the use of rice husk ash (RHA), a waste byproduct from rice production, as a sustainable supplement to Ordinary Portland Cement (OPC) for soil stabilisation in order to increase durability and sustainability of rural roads, hence limit recurrent maintenance needs and associated transport costs and challenges. To conduct this study, soil samples collected from Mulungushi, Zambia, were treated with combinations of 6–10% OPC and 10–15% RHA by weight. Laboratory tests measured maximum dry density (MDD), optimum moisture content (OMC), and California Bearing Ratio (CBR) values; the main parameters assessed to ensure the quality of road construction soils. Results showed that while the MDD did not change significantly and varied between 1505 kg/m³ and 1519 kg/m³, the OMC increased hugely from 19.6% to as high as 26.2% after treatment with RHA. The CBR value improved significantly, with the 8% OPC + 10% RHA mixture achieving the highest resistance to deformation. These results suggest that RHA can enhance the durability and sustainability of rural roads and hence improve transport systems and subsequently improve socioeconomic factors in rural areas. Full article

Biodrying and composting are aerobic processes to treat and stabilize organic solid waste, but biodrying involves a shorter process time and does not require the addition of water. The resulting biodried material (BM) is mainly used as an energy source in cement production or in municipal solid waste incineration with energy recovery, but when obtained from agricultural or agroindustrial organic waste, it could also be used as a soil amendment, such as compost (CO). In this study, the phytotoxicity of BM compared to CO, both made from organic wastes (orange peel, mulch and grass), was evaluated on seed germination and growth (for 90 days) of lettuce (Lactuca sativa L.) seedlings on treatments prepared from mixtures of BM and soil, soil (100%) and a mixture of CO and soil. The germination index (GI%) was higher for BM extracts (200 g/L) than for CO extracts (68% vs. 53%, respectively). According to their dry weight, lettuce grew more on the CO mixture (16.5 g) than on the BM (5.4–7.4 g), but both materials far exceeded the soil values (0.15 g). The absence of phytotoxicity suggests that BM acts as a soil amendment, improving soil structure and providing nutrients to the soil. Therefore, biodrying is a quick and low-cost bioprocess to obtain a soil improver. Full article

Maintenance dredging produces large volumes of fine sediments that are commonly discarded, despite increasing pressure for beneficial reuse. Lime–cement stabilization offers one pathway, yet field performance is highly variable. This study juxtaposes two French marine dredged sediments—DS-F (low plasticity, organic matter (OM) ≈ 2 wt.%) and DS-M (high plasticity, OM ≈ 18 wt.%)—treated with practical hydraulic road binder (HRB) dosages. This is the first French study that directly contrasts two different DS types under identical HRB treatment and proposes practical boundary thresholds. Physical indexes (particle size, methylene-blue value, Atterberg limits, OM) were measured; mixtures were compacted (Modified Proctor) and tested for immediate bearing index (IBI). IBI, unconfined compressive strength, indirect tensile strength, and elastic modulus were determined. DS-F reached IBI ≈ 90–125%, UCS ≈ 4.7–5.9 MPa, and ITS ≈ 0.40–0.47 MPa with only 6–8 wt.% HRB, satisfying LCPC-SETRA class S2–S3 requirements for road subgrades. DS-M never exceeded IBI ≈ 8%, despite 3 wt.% lime + 6 wt.% cement. A decision matrix distilled from these cases and recent literature shows that successful stabilization requires MBV < 3 g/100 g, plastic index < 25%, OM < 7 wt.%, and fine particles < 35%. These thresholds permit rapid screening of dredged lots before costly treatment. Highlighting both positive and negative evidence clarifies the realistic performance envelope of soil–cement reuse and supports circular-economy management of DS. Full article

Considering the increasing requirements for the recovery of different natural and industrial waste materials, the application of volcanic ash as an alternative sustainable binder to traditionally employed lime and cement is proposed for soil stabilization for geotechnical engineering purposes, thus providing a reduction in carbon emissions. Soil stabilization was performed on natural clays with very high swelling potential, i.e. those classified as inadequate for reuse as a building material for geotechnical purposes. A mineralogical and chemical characterization of raw materials was carried out prior to the performance of different geotechnical laboratory tests, i.e., testing Atterberg limits, compaction, swelling potential, compressibility and resistance parameters over naturally remolded clay and soil mixtures with different binders. The swelling potential was reduced with an increase in the amount of applied binder, necessitating the addition of 10, 20, and 30% of volcanic ash compared to 3% lime, 3% cement and 5% lime, respectively, for a similar reduction in swelling potential. An investigation of the resistance parameters for soil mixture specimens that provided a suitable reduction in swelling potential for their reuse was performed, and a comparison to the parameters of naturally remolded clay was made. Full article

Soil stabilization with hydraulic binders like cement is widely used in road construction but significantly contributes to CO₂ emissions. This study investigates a more sustainable alternative involving the use of dispersed polypropylene fiber reinforcement to improve the mechanical properties of stabilized soils while reducing cement consumption. Nine clay sand mixtures with varying cement (2–6%) and fiber (0–0.5%) contents were tested using unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) methods. Fiber addition improved UCS by 5.59% in a mix with 2% cement and 0.25% fibers and by 25.45% in one with 4% cement and 0.25% fibers. This shows that fibers can improve strength at different cement levels. A novel reinforcement index ($R_i$) was introduced to predict UCS empirically. The model showed that using 0.5% fibers ($R_i=1.0\%$) enabled a 25.12% reduction in cement without compromising strength. However, this improvement came at the cost of stiffness: deformation modulus $E_{50}$ decreased by up to 67.51% at 0.5% fiber content. Statistical validation using MAE, RMSE, and MAPE confirmed the model’s accuracy. Although the results were based on a single soil type, they showed that polypropylene fibers can support decarbonization efforts by reducing cement demand and represent a technically feasible approach to more sustainable geotechnical engineering applications. Full article

The disposal of rice husk ash (RHA) in rice-producing regions poses critical environmental and public health challenges. However, RHA’s high amorphous silica content offers significant potential for soil stabilization, particularly in improving the mechanical properties of weak soils. This study investigates the shear strength of clay soil stabilized with rice husk ash (2%, 4%, 6%) and low cement dosages (2%, 4%, 6%) that incorporate layered subgrade systems (top, bottom, and dual-layer configurations). By optimizing rice husk ash incorporation with reduced cement content, this approach challenges conventional stabilization methods that rely heavily on cement. Sixteen soil-cement-RHA mixtures were evaluated through mechanical testing, supplemented by microstructural and elemental analyses using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Results demonstrated substantial improvements in shear strength across all subgrade layers. The dual-layer system with 2% RHA 6% cement (2%RHA6%C) achieved the highest cohesive strength (115 kN/m²) and maximum deviatoric stress (446 kN/m²). These findings highlight the viability of RHA as a sustainable, low-cement soil stabilizer, offering dual benefits: effective waste valorization and enhanced geotechnical performance. This study advances sustainable ground engineering practices by introducing a resource-efficient novel building material and provides a framework for layered stabilization systems in clay soils. Future investigations will focus on a broader range of soil types and extend the application of this approach to other sustainable ground engineering practices. Full article

In response to the need for sustainable soil stabilization alternatives, this study explores the use of waste materials and biopolymers to improve the mechanical behavior of clay from Cartagena, Colombia. Crushed limestone waste (CLW), ground glass powder (GG), recycled gypsum (GY), xanthan gum (XG), and the combination of XG with polypropylene fibers (XG–PPF) were used as stabilizing agents. Samples were compacted at different dry densities and cured for 28 days. Unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were conducted to assess the strength and stiffness of the treated mixtures. Results were normalized using the porosity/binder index ($\mathrm{\eta }/B_{iv}$), leading to predictive equations with high determination coefficients (R² = 0.94 for UCS and R² = 0.96 for stiffness). However, XG-treated mixtures exhibited distinct behavior that prevented their inclusion in a unified predictive model, as the fitted exponent x in the porosity/binder index ($\mathrm{\eta }/B_{iv}^x$) differed markedly from the others. While an exponent of 0.28 was suitable for blends with mineral binders, the optimal x values for XG and XG–PPF mixtures were significantly lower at 0.02 and 0.03, respectively, reflecting their unique gel-like and fiber-reinforced characteristics. The analysis of variance (ANOVA) identified cement content and compaction density as the most influential factors, while some interactions involving the residues were not statistically significant, despite aligning with experimental trends. The findings support the technical viability of using sustainable additives to enhance soil properties with reduced environmental impact. Full article

The stabilization of expansive soils is crucial for the construction projects to mitigate swelling, shrinkage, and bearing capacity issues. This study investigates the synergistic effects of cement and clinoptilolite zeolite on stabilizing high-plasticity clay (CH) soil from Kano State, Nigeria. A total of 30 admixture combinations—cement (0–8%) and zeolite (0–15%)—were tested via standardized laboratory methods to evaluate their free swell index (FSI), swell percentage, swell pressure, shrinkage, and California Bearing Ratio (CBR). Principal component (Lasso) “least absolute shrinkage and selection operator” regression modeled interactions between admixtures and soil properties. The key results include the following: (1) 6% cement + 12% zeolite reduced the FSI by 60% (45 → 18); (2) 8% cement + 15% zeolite decreased the swell percentage by 47.8% (22.5% → 11.75%); (3) 6% cement + 12% zeolite lowered swell pressure by 54.2% (240 kPa → 110 kPa); (4) 8% cement + 12% zeolite reduced shrinkage by 50% (5.6% → 2.8%); and (5) 6% cement + 9% zeolite achieved an unsoaked CBR of 80.01% and soaked CBR of 72.79% (resilience ratio: 0.8010). PCLR models explained 93.5% (unsoaked) and 75.0% (soaked) of the CBR variance, highlighting how zeolite’s mediation analysis indicates that zeolite improves the bearing capacity mainly by reducing the free swell index (path coefficient = −0.91429, p < 0.0001), while conditional process modeling provided greater explanatory power (R² = 0.745) compared to moderation-only analysis (R² = 0.618). This study demonstrates that zeolite–cement blends optimize strength and resilience in expansive soils, with implications for sustainable infrastructure in arid and semi-arid regions. Full article

Various stabilizers, such as jute, gypsum, rice-husk ash, fly ash, cement, lime, and discarded rubber tires, are commonly used to improve the shear strength and overall characteristics of clay subgrade soil. In this study, waste foundry sand (WFS) is utilized as a stabilizing material to enhance the properties of clay subgrade soil and strengthen the bond between clay subgrade soil and subbase material. The materials employed in this study include Type B subbase granular materials, clay subgrade soil, and 1100 Biaxial Geogrid for reinforcement. The clay subgrade soil was collected from the airport area in the Al-Muthanna region of Baghdad. To evaluate the effectiveness of WFS as a stabilizer, soil specimens were prepared with varying replacement levels of 0%, 5%, 10%, and 15%. This study conducted a Modified Proctor Test, a California Bearing Ratio test, and a large-scale direct shear test to determine key parameters, including the CBR value, maximum dry density, optimum moisture content, and the compressive strength of the soil mixture. A specially designed large-scale direct shear apparatus was manufactured and utilized for testing, which comprised an upper square box measuring 20 cm × 20 cm × 10 cm and a lower rectangular box with dimensions of 200 mm × 250 mm × 100 mm. The findings indicate that the interface shear strength and overall properties of the clay subgrade soil improve as the proportion of WFS increases. Full article

This investigation focused on the cementation mechanisms and mechanical properties of soil–rock mixtures–slurry cement (SRM–SC) to ensure the safety of tunnels during operation. SRM–SC specimens were prepared with different types of slurry and rock contents based on an actual slurry injection ratio. The macroscopic level analysis involved measuring the specimens’ uniaxial compressive strength and shear strength, determining the strength parameters, and analyzing the damage forms. At the microscopic level, the surface morphology and composition of the specimens were examined using scanning electron microscope imaging. This allowed for a comparative analysis of the cementation ability and mechanism of the slurry under different control conditions, providing a basis for determining the mechanical properties of SRM–SC. The results indicated that the rock content significantly impacts the macromechanical properties of SRM–SC. The compressive strength and stiffness of SRM–SC initially increase and then decrease with the increasing rock content, with an inflection point observed between a 20% and 60% rock content. On the other hand, the shear strength and stiffness both increase with the increasing rock content. Additionally, the macroscopic mechanical properties of SRM–SC formed by different types of grout exhibit noticeable differences. These findings serve as a reference for regulating the mechanical properties of SRM–SC. Full article

This study explores the stabilization of dredged sediments classified as lean clay (CL) using hydrated lime, type III Portland cement, and compaction. While quicklime is commonly used in practice, this research explores alternative calcium-based binders with the aim of valorizing sediments for civil engineering applications. The mechanical behavior of the treated materials was evaluated through an Unconfined Compressive Strength (UCS) test campaign, with the results interpreted using the porosity/volumetric cement content ($\eta /C_{iv}$) index. This relationship assesses the influence of apparent dry density and cement content on the strength improvement of sediments, aiming to evaluate the suitability of the dredged sediments for engineering applications. A key feature of this study is the extended curing period of up to 90 days, which goes beyond the typical 28-day evaluations commonly found in the literature. Interestingly, strength degradation occurred at advanced curing ages compared to shorter curing times. To understand the mechanisms underlying this resistance degradation, the mixtures were subjected to X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). These tests identified the presence of the expansive sulfate-based compound ettringite, which is associated with swelling and failure in soils stabilized with calcium-based stabilizers. This research contributes to the field by demonstrating the limitations of calcium-based binders in stabilizing sulfate-bearing dredged materials and emphasizing the importance of long-term curing in assessing the durability of treated sediments. Full article

Red-bed mudstone from civil excavation is often treated as waste due to its poor water stability and tendency to disintegrate. This study proposes a sustainable approach for its utilization in controlled low-strength material (CLSM) by blending it with cement and water. Laboratory tests evaluated the fresh properties (i.e., flowability, bleeding rate, setting time, and subsidence rate) and hardened properties (i.e., compressive strength, drying shrinkage, and wet–dry durability) of the CLSM. The analysis focused on two main parameters: cement-to-soil ratio (C/S) and water-to-solid ratio (W/S). The results show that increasing W/S significantly improves flowability, while increasing C/S also contributes positively. Flowability decreased exponentially over time, with an approximately 30% loss recorded after 3 h. Bleeding and subsidence rates rose sharply with higher W/S but were only marginally affected by C/S. To meet performance requirements, W/S should be kept below 52%. In addition, the setting times remained within 24 h for all mixtures tested. Compressive strength showed a negative correlation with W/S and a positive correlation with C/S. When C/S ranged from 8% to 16% and W/S from 44% to 56%, the compressive strengths ranged from 0.3 MPa to 1.22 MPa, meeting typical backfilling needs. Drying shrinkage was correlated positively with water loss, and it decreased with greater C/S. Notably, cement’s addition significantly enhanced water stability. At a C/S of 12%, the specimens remained intact after 13 wet–dry cycles, retaining over 80% of their initial strength. Based on these findings, predictive models for strength and flowability were developed, and a mix design procedure was proposed. This resulted in two optimized proportions suitable for confined backfilling. This study provides a scientific basis for the resource-oriented reuse of red-bed mudstone in civil engineering projects. Full article

Clay soils are known to have a high swelling pressure with an increase in water content. This behavior is considered a serious hazard to structures built upon them. Various mechanical and chemical treatments have historically been used to stabilize the swelling behavior of clay soils. This work investigates the potential use of shredded plastic waste to reduce the swelling pressure and compressibility of clay soils. Two types of highly plastic clay (CH) soils were selected. Three different dimensions of plastic waste pieces were used, namely lengths of 0.5 cm, 1.0 cm, and 1.5 cm, with a width of 1 mm. A blend of plastic–cement waste with a ratio of 1:5 by weight was prepared. Different fractions of the plastic–cement waste blend with a 2 wt.% increment were added to the clay soil, which was then remolded in a consolidometer ring at 95% relative compaction and 3.0% below the optimum. The zero swell test, as per ASTM D4546, was conducted on the remolded soil samples after three curing periods: 1, 2, and 7 days. This method ensures the accurate evaluation of swell potential and stabilization efficiency over time. The experimental results showed that the addition of 6.0–8.0% of the blend significantly reduced the swelling pressure, demonstrating the mixture’s effectiveness in soil stabilization. It also reduced the swell potential of the expansive clay soil and had a substantial effect on the reduction in its compressibility, especially with a higher aspect ratio. The compression index decreased, while the maximum past pressure increased with a higher plastic–cement ratio. The 7-day curing time is the optimum time to stabilize expansive clay soils with the plastic–cement waste mixture. This study provides strong evidence that plastic waste can enhance soil mechanical properties, making it a viable geotechnical solution. Full article

This study explores using natural rubber latex (NRL) as a sustainable polymeric additive to improve the mechanical performance of cement-stabilized soil–crushed limestone waste (CLW) mixtures for pavement base applications. The experimental program involved varying cement contents (3%, 6%, and 9% by weight of soil) and NRL replacement levels (10%, 15%, 20%, and 25% of an 18% optimum water content, as determined by the standard Proctor test) under two target dry unit weights (16.6 and 17.6 kN/m³) and curing periods of 7 and 28 days. Unconfined compressive strength (UCS) tests and stiffness (Go) measurements were performed, while microstructural developments were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results indicate that an optimal NRL replacement exists for each cement content, enhancing interparticle bonding through the formation of polymeric films that reduce porosity and improve the ductility of the matrix. However, excessive NRL was found to retard cement hydration and ultimately decrease strength. On average, a 28-day curing period produced a 38% increase in UCS over 7-day values, independent of the NRL dosage. Comparisons with literature standards, including the ASTM D4609 threshold of 345 kPa for field strength, confirm that the optimized mixtures meet and exceed the minimum performance requirements. These findings underscore the potential of NRL as a viable alternative to conventional synthetic latexes in sustainable pavement base materials. Full article

In recent decades, heavy industrial discharges have caused severe soil and groundwater pollution. Many areas previously occupied by industries are now represented by lands contaminated by the accumulation of toxic metals, which pose serious risks to human health, plants, animals, and surrounding ecosystems. Among the various potential solutions, the solidification and stabilization (S/S) technique represents one of the most effective technologies for treating and disposing of a wide range of contaminated wastes. This study focuses on the theoretical definition of a green material mix, which will subsequently be used in the solidification process of contaminated industrial soils, optimizing the mix to ensure treatment effectiveness. The mix design was developed through a literature analysis, representing a preliminary theoretical study. This paper explores the application of the S/S process using various additives, including Portland cement, fly ash (FA), ground granulated blast furnace slag (GGBFS), and other industrial waste materials, to create an innovative mix design for the treatment of contaminated soils. The main objective is to reduce the permeability and solubility of contaminants while simultaneously improving the mechanical properties of the treated materials. The properties of the studied soils are described along with those of the green materials used, providing a comprehensive overview of the optimization of the resulting mixtures. Full article