This study evaluated lime-lignin composite stabilisers for clay enhancement. Results showed their synergistic effect significantly improved shear strength (S), cohesion (c), friction angle (phi), and maximum dynamic shear modulus (Gmax) of clay. Microstructural analysis revealed lime-induced granular crystals and lignin-generated cementitious products, enhancing soil structure. After 1 and 7 days curing, the clay stabilised with 6% lime and 2% lignin exhibited the highest S, c, phi and Gmax. After 14 days curing, the clay stabilised with 4% lime and 4% lignin exhibited the highest S, c, phi, and Gmax. A novel relative structural characterization method based on c and phi was proposed, alongside a modified Hardin's model integrating relative structural to predict Gmax. The study demonstrates that 6% lime + 2% lignin and 4% lime + 4% lignin ratios effectively enhance embankment clay properties, offering sustainable solutions for industrial byproduct utilization and soil stabilisation in geotechnical engineering.

In cold regions, the soil temperature gradient and depth of frost penetration can significantly affect roadway performance because of frost heave and thaw settlement of the subgrade soils. The severity of the damage depends on the soil index properties, temperature, and availability of water. While nominal expansion occurs with the phase change from pore water to ice, heaving is derived primarily from a continuous flow of water from the vadose zone to growing ice lenses. The temperature gradient within the soil influences water migration toward the freezing front, where ice nucleates, coalesces into lenses, and grows. This study evaluates the frost heave potential of frost-susceptible soils from Iowa (IA-PC) and North Carolina (NC-BO) under different temperature gradients. One-dimensional frost heave tests were conducted with a free water supply under three different temperature gradients of 0.26 degrees C/cm, 0.52 degrees C/cm, and 0.78 degrees C/cm. Time-dependent measurements of frost penetration, water intake, and frost heave were carried out. Results of the study suggested that frost heave and water intake are functions of the temperature gradient within the soil. A lower temperature gradient of 0.26 degrees C/cm leads to the maximum total heave of 18.28 mm (IA-PC) and 38.27 mm (NC-BO) for extended periods of freezing. The maximum frost penetration rate of 16.47 mm/hour was observed for a higher temperature gradient of 0.78 degrees C/cm and soil with higher thermal diffusivity of 0.684 mm(2)/s. The results of this study can be used to validate numerical models and develop engineered solutions that prevent frost damage.

Contaminant leaching from asphalt pavements poses a significant environmental concern, potentially damaging soil and groundwater quality. The growing interest in incorporating recycled materials in asphalt pavements has further raised concerns over the potential environmental hazards due to contaminant leaching. Consequently, this paper offers a comprehensive review of the literature over the past three decades structured into six sections: groundwater contamination via leaching, methodologies for evaluating leaching, analysis of contaminants, contaminants and leaching from road materials incorporating recycled waste, other factors affecting leaching of pollutants from asphalt pavements, and mathematical models to predict leaching from asphalt pavements. Despite the importance of addressing leaching issues, there is a lack of standardised leaching tests and guidelines specific to asphalt materials, limited attention to evaluating contaminants beyond heavy metals and PAHs in asphalt leachates, insufficient understanding of optimal instrument parameters for asphalt leachate analysis, and a scarcity of mathematical models to predict future leaching potential.

This study aimed to enhance the mechanical characteristics of the road subgrade layer by incorporating ground tile waste and lime as a soil stabiliser. The investigation on the effectiveness of tile waste as a supplementary additive to lime in subgrade stabilisation involved adding 7% of lime and varying percentages of 10%, 20%, 30% and 40% of tile waste. The study analysed the plasticity, compatibility, unconfined compressive strength, pH, the results of the indirect tensile test and microstructure of the soil samples. The results indicated that incorporating a mixture of lime and tile waste into the soil significantly enhanced soil strength. Adding higher percentages of tile waste to the soil-lime blend resulted in a proportional improvement in the soil's mechanical properties. In summary, using recycled tile waste for subgrade stabilisation can provide a sustainable and cost-effective solution for improving road and pavement performance and reducing the environmental impacts of road and pavement construction.

The plastic mold compaction device (PM Device) was developed in Mississippi to compact cementitiously stabilized soil inside plastic molds to improve soil-cement quality by adding value during design and construction activities. The PM Device has been incorporated as an AASHTO provisional standard (AASHTO PP92-19) and, to date, prevailing activities have been Mississippi Department of Transportation projects and have included controlled laboratory evaluations and field projects. This paper goes beyond previous efforts, to document a field study in which the PM Device was successfully used on an Alabama Department of Transportation project to evaluate its effectiveness within another state's construction specifications. The PM Device was capable of capturing quantifiable variation in mechanical properties over the duration of the construction project, as well as producing similar mechanical properties to cores taken from the compacted pavement surface. Additionally, molds described in AASHTO PP92-19 were compared with one another to evaluate their potential within the standard practice. AASHTO PP92-19 protocols were sufficient to produce viable, repeatable test specimens within another state department of transportation construction environment for quality control and quality assurance.

Utilizing natural expansive clays that are available on-site as sewer trench backfill can cause destructive deformations due to volume changes, which are caused by seasonal climatic changes. Such deformations result in manhole structures protruding from the surface, which cause damage to the surrounding infrastructure and generate potential trip hazards. In this study, mixtures of recycled materials with minor sensitivity to moisture variations and superior compactibility were investigated using geomechanics theories associated with granular materials as an alternative backfill material. Blends of recycled glass (RG), plastic (RP), and tire-derived aggregates (TDA) were mixed on-site, wetted to the required moisture content (MC), and used to backfill excavated trenches around two manhole structures and extended to approximately 11 m along the trench. A benchmark trial was constructed by backfilling with natural soils available on-site according to the normal procedure. The full-scale trial sites were instrumented using settlement plates and MC sensors at various locations and depths for performance monitoring. The results of approximately 17 months of field monitoring showed that settlements over both areas that were backfilled with recycled blends were <20% of those over areas backfilled with site-won soils. Approximately 82% of the settlements in the recycled blends occurred during construction. In contrast, trenches that were backfilled with site-won soils continued to exhibit deformation due to consolidation and swell-shrink cycles. The outcome of this study could contribute to the United Nations' Sustainable Development Goals, in particular, Goal 12, by improving the industry's confidence in the reuse of wastes in geotechnical applications.

The accumulation of waste tires is a global problem related to natural resources and the environment. The storage or burning of tires causes toxic chemicals to seep into the surrounding environment, which poses a serious ecological threat. Many previous studies have shown that waste tires can be used in geotechnical engineering. It was found that rubber reinforcement can increase the plasticity of sandy soil and improve its shear strength. It can control pore water pressure accumulation and improve dynamic properties. For cohesive soils, rubber additives can reduce dry density and improve compressive strength and soil stability. When mixed with soil with optimum content, waste tires can reduce various adverse effects of waste tire accumulation on the environment. The application of rubber has also a good impact on environmental protection and the promotion of green design. This paper presents the dynamic properties (shear modulus and damping ratio) of the RCA-RTW mixture for small, medium, and large ranges of shear strain levels (from about 1.5 center dot 10(-4)% to 1.3 center dot 10(-2)%). All specimens are constructed using different percentages of granulated tire rubber and concrete aggregate from curb crushing. A series of laboratory tests, resonant, and damping, are performed in the resonant column apparatus. The maximum shear modulus and minimum damping ratio are presented with the percentage of granulated rubber. The normalization is also applied to the G-modulus and D-ratio data set. Furthermore, a comparison is made between the results obtained for the tested geocomposites and a mixture of pure RCA.