The recycling and reuse of construction and demolition materials offer significant environmental and economic benefits. This study investigated the performance of aggregates with varying proportions of recycled concrete aggregate (RCA) and natural aggregate (NA) as base materials. Key parameters, such as compaction behaviour, California bearing ratio (CBR), and resilient modulus, were evaluated. The findings revealed that the mixture with 50% RCA and 50% NA exhibited the highest CBR and resilient modulus values. Small-scale cyclic loading tests were then conducted on the samples of NA, RCA, and a 50% RCA-50% NA mixture to assess the suitability of RCA as a base material. Additionally, RCA and NA samples were reinforced with biaxial geogrids for material optimisation. The results showed that the 50% RCA-50% NA mixture exhibited the smallest permanent deformation, and the geogrid, placed at the middle depth of the base, significantly reduced rut depth. Findings of this experimental study suggest that RCA can be used as an alternative base material to partially replace NA in road construction. The results can help conserve natural resources, promote sustainability through the reuse of waste materials, and reduce the environmental impact associated with the use of NA in road construction.

The flexural behavior of geogrid-reinforced foamed lightweight soil (GRFL soil) is investigated in this study using unconfined compressive and four-point bending tests. The effects of wet density and reinforcement layers on flexural performance are analyzed using load-displacement curves, damage patterns, load characteristics, unconfined compressive strength, and flexural strength. A variance study demonstrates that increasing the wet density significantly increases unconfined compressive strength. Bond stress mechanisms enable geogrid integration, efficiently reroute stresses internally, and greatly increase flexural strength. With a maximum unconfined compressive strength of 3.16 MPa and a peak flexural strength increase of 166%, this reinforcement increases both strength and ductility by changing the damage pattern from brittle to ductile. The principal load is initially supported by the foamed lightweight soil, and in later phases, geogrids take over load-bearing responsibilities. Additionally, the work correlates the ratio of unconfined compressive to flexural strength with wet density and informs the development of predictive models for unconfined compressive strength as a function of reinforcing layers and wet density.

This study focuses on enhancing structural strength in flood-prone regions by utilizing industrial waste under varying temperature conditions. Industrial waste's increasing usage and its environmental implications require deeper comprehension. The escalating adoption of industrial waste as an alternative construction material underscores this shift. The research employs fly ash (F), ground-granulated blast-furnace slag (G), and lime (L) to augment geotechnical properties and bolster the flood resistance of stabilized soil. Various clay, lime, GGBS, and 2% fly ash mixtures are tested under optimal moisture and maximum dry density conditions. The curing spans 1, 7, 14, 28, 56, and 90 days at ambient temperature and 3 degrees C. Subsequent unconfined compressive strength (UCS), durability, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and field emission scanning electron microscopy (FE-SEM) analyses are conducted. Results highlight a 257% UCS increase at 14 days' curing for the 8% GGBS + 6% Lime + 2% Fly ash mixture at ambient temperature, while the mix of 6% GGBS + 8% Lime + 2% Fly ash records a 686% UCS enhancement after 90 days' curing at 3 degrees C. Lime concentration affects the plasticity index and maximum dry unit weight (MDU). Upon water immersion, durability testing indicates an 11-17% strength reduction for lime, GGBS, and fly ash samples. The microstructural evaluation identifies hydration products like calcium aluminate silicate-hydrate and calcium silicate hydrate. According to the findings, using industrial waste can be a promising solution to pavement sustainability, especially after the flood, and it can reduce related costs and decrease CO2 emissions.

The dynamic resilience characteristics of aeolian sand subgrade are influenced by salt content and water content, exhibiting significant stress dependence and anisotropy. The resilient modulus(MR) M R ) of aeolian sand represents the stress-strain nonlinearity under cyclic loading, serving as an important parameter for the design of aeolian sand subgrade in desert areas. In order to investigate the variation of M R of aeolian sand subgrade with salt content and water content under traffic loading, as well as the M R characteristics under these conditions, three types of aeolian sand samples with varying water content and four sulphate contents were prepared. The variation of M R of aeolian sand under different confining pressures and deviator stress levels, as well as the influences of water content and salt content, was studied through indoor dynamic triaxial testing. Based on the pattern of the fitting parameters of the benchmark model, a prediction model suitable for the M R of aeolian sand was constructed. The results indicate a rise in aeolian sand's M R with increasing deviator stress and confining pressure, with confining pressure having a more significant impact than deviator stress. With the increase in water content, the M R of aeolian sand decreases nonlinearly, and with the increase in salt content, it exhibits a wave-shaped trend of increasing-decreasing-increasing, which is related to the dissolution state of sodium sulfate in the soil. Based on the experimental results, a prediction model of the M R of aeolian sand was established, derived from the benchmark model, which can reflect the influence of salt content and water content on the M R , introducing them as variables within the model.

In this study, carbide slag (CS) and coal gangue (CG) powder were utilized to enhance the properties of the subgrade soil. CS-CG stabilized soil underwent lab experiments to assess its mechanical properties and durability. Tests included unconfined compressive strength (UCS), compressive resilient modulus (CRM), and California bearing ratio (CBR) at stabilizer dosages of 5 %, 10 %, and 15 %. Additional tests, such as dry-wet cycling, salt solution immersion, permeability, leaching, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP), were conducted specifically for the 10 % dosage. The mechanical properties and durability were comprehensively analyzed, with a microscopic investigation into pore size. Furthermore, the soil-water characteristic curve (SWCC) of CS-CG stabilized soil is derived through MIP, providing insights into its impact on the material's strength. Results showcased favorable bearing capacity and durability of CS-CG stabilized soil. The optimal mixing dosage is 10%, with the best ratio being CS: CG= 70: 30. After 6 dry-wet cycles, UCS loss rate was 18.6%, comparable to 4% Portland cement (PC) stabilized soil. Dry-wet cycle characteristics surpassed PC and Lime stabilized soils. Immersion in a 5 % NaCl solution for 30 days yielded a UCS of 3.8 MPa at 28-day age, while exposure to 5 % Na2SO4 solution led to an 11.6 % strength decrease compared to NaCl. Permeability coefficient indicated low permeability akin to PC and Lime stabilized soils. Heavy metal content met standards, with minimal increase during cycles. Hydration products mainly comprised C-S-H gel, Ca(OH)2 crystals, and carbonate modification. Analysis suggested capillary and transition pores predominantly, with minimal macropores presence. Dry-wet cycles induced a marginal increase in pore size, with negligible overall impact. SWCC predicted water content (theta s) ranged from 30 % to 32 %, with a slight increase in matrix suction during dry-wet cycles. CS-CG stabilized soil shows favorable mechanical properties, durability, and environmental sustainability, indicating its potential as a substitute for traditional cement and lime treatments in subgrade soil reinforcement.

The East Asia black cotton soil (BCS) cannot be used as embankment filling directly due to its high clay content, liquid limit, plasticity index, and low CBR strength (CBR < 3%). This study evaluates the effects of treating East Asia BCS with lime, volcanic ash, or a combination of both on its engineering properties. Experiments were conducted to analyze the basic physical properties, swelling characteristics, and mechanical properties of the treated soil. Results indicate that lime addition significantly reduces the free swelling rate, improves limit moisture content, increases optimum moisture content, decreases maximum dry density, and enhances CBR value. Although volcanic ash also improves BCS performance, its effects are less pronounced than those of lime. The combined treatment with lime and volcanic ash exhibits superior performance, greatly reducing expansion potential and significantly increasing soil strength. Specifically, a mixture of 3% lime and 15% volcanic ash optimizes the liquid limit, plasticity index, and CBR value to 49.2%, 23.8, and 24.7%, respectively, meeting the JTG D30-2015 requirements and reducing construction costs. The treatment mechanisms involve hydration exothermic reactions, volcanic ash reactions, and semipermeable membrane effects, which collectively enhance the soil's properties by producing dense, high-strength compounds.

Expansive soils exhibit directionally dependent swelling that traditional isotropic models fail to capture. This study investigates the anisotropic swelling characteristics of expansive soil with a medium swelling potential through the use of modified oedometric testing. Vertical swelling strains can reach up to 1.71 times that of the horizontal movements, confirming intrinsic anisotropy. A nonlinear elastic constitutive model incorporates vertical and horizontal elastic moduli with respect to matric suction to characterize anisotropy. Three elastic parameters were determined through the experiments, and predictive equations were developed to estimate the unsaturated moduli. The constitutive model and predictive techniques provide practical tools to better assess expansive soil pressures considering anisotropy, offering guidelines for utilization and design. The outcomes advance understanding of these soils' directionally dependent behavior and stress-strain-suction response.