This study investigates the viability of utilizing coal bottom ash (BA) as a replacement for natural fine aggregate (NFA) in concrete containing recycled coarse aggregates (RCA). Although recycled materials often diminish mechanical properties, BA’s potential as a fine aggregate in recycled aggregate concrete is under-researched. This study investigates various replacement levels (0

Fly ash (FA) is a hazardous industrial by-product of coal combustion that contains toxic metals and fine particles, posing serious environmental and health risks. Its utilization in geopolymer concrete (GPC) provides a sustainable alternative to ordinary portland cement concrete (OPCC), reducing the need for traditional cement. However, FA-GPC requires heat curing, which limits its practical use. The incorporation of ground granulated blast furnace slag (GGBFS) into FA-GPC addresses this limitation by facilitating the curing at ambient temperature. This study examines the age-dependent splitting tensile strength (fspt) and flexural tensile strength (fr) of GPC, incorporating varying proportions of FA and GGBFS ranging from 0% to 80%, with testing conducted up to 180 days. For comparison, an OPCC mix with the same binder content was prepared to evaluate the strength evolution in both concretes. The results showed continuous strength development in all GPC mixes, with GGBFS significantly improving both early and long-term tensile performance. GPC mixes with balanced FA and GGBFS content outperformed OPCC. Microstructural analysis confirmed that increased GGBFS content enhances matrix densification through the formation of additional calcium-alumino-silicate-hydrate gel alongside sodium aluminosilicate hydrate gel, leading to superior tensile properties. Furthermore, predictive models were developed to estimate fspt and fr of GPC based on age and GGBFS content. Overall, this study enhances understanding of the tensile and microstructural behavior of FA-GGBFS GPC, contributing to the advancement of sustainable concrete for construction applications.

Hazardous waste management is a critical environmental challenge, with sustainable solutions gaining prominence in the construction sector to reduce ecological impact. This study systematically investigates the effects of fly ash (FA), silica fume (SF), and chemical activators on enhancing the mechanical performance and sustainability of concrete. Eighteen concrete mixes were designed with a constant cementitious content of 400 kg/m3 and a 0.43 water-binder ratio. The experimental program consisted of three stages: (1) evaluating FA as a partial cement replacement at 35%, 50%, and 70% to assess its workability and strength effects; (2) incorporating SF at 5%, 10%, and 15% in combination with FA to study synergistic improvements in matrix densification; and (3) applying chemical activators-Na2SO4 and NaOH-at 5% of binder content to optimize early-age strength for FA-SF mixes. A total of 324 specimens were tested for slump, compressive strength (fc), and splitting tensile strength (ft) at 3, 7, and 28 days. Results indicate that high-volume fly ash (i.e., 50% and 70%) delayed early-age strength development, but the incorporation of SF and chemical activation significantly improved strength. SF additions enhanced both fc and ft, with 10% SF providing optimal performance. Further, microstructural analysis using scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed that chemical activation, particularly with Na2SO4, reduced porosity and enhanced C-S-H gel formation, contributing to strength improvements. Additionally, novel predictive models for fc and ft were developed, integrating the effects of curing age, FA, SF content, and chemical activation. These models demonstrated excellent predictive accuracy, offering practical tools for performance prediction and mix design optimization. Furthermore, a comprehensive cost analysis of all the mixes showed that the optimized mix with 50% FA, 10% SF, and 5% Na2SO4 was 4% more cost-effective than the control mix. These findings provide actionable strategies for engineers and researchers to optimize sustainable concrete mix designs, promote hazardous waste utilization, and advance circular economy objectives in construction.

The design of geosynthetic encased stone columns often relies on the conventional framework of saturated soil mechanics, neglecting the influence of in-situ unsaturated soil conditions. Such an approach results in unrealistic or overly conservative designs. For this purpose, this study evaluates the performance of stone columns with and without geosynthetic encasement under unsaturated soil conditions, focusing on the role of matric suction in the surrounding soil. A series of laboratory plate load tests were conducted to examine the mechanical behavior and load-carrying capacity of geosynthetic encased stone columns in saturated and unsaturated soils. The results indicate that matric suction in the surrounding soil significantly enhances the load-carrying capacity of stone columns. Geosynthetic encasement further improves performance by reducing radial deformation and promoting uniform stress distribution and effective load transfer. These improvements result in greater load-carrying capacity and structural stability of stone columns, particularly under varying unsaturated soil conditions. In summary, this study provides valuable insights into the interaction between unsaturated soils and geosynthetic encasement, offering a rational framework for designing stone columns in geotechnical applications where unsaturated soil behavior is critical.

Expansive soils, prone to volumetric changes in response to moisture content variations, pose challenges for infrastructure founded on them. In cold regions, these problems are further intensified by repeated freeze–thaw (F–T) cycles, which alter soil structure through ice lens formation, water migration, cracking, and pore redistribution. This paper critically reviews the effects of F–T cycles on the geotechnical properties of expansive soils, highlighting past research, current developments, and future directions for the design of durable infrastructure in colder regions. The reviewed studies observe that the greatest deterioration generally occurs during the initial F–T cycles, after which the rate of change often decreases toward a stable state. The severity of degradation depends on initial water content, degree of saturation, compaction state, freezing temperature, cycle duration, and clay mineralogy. Changes in pore structure and crack connectivity are closely associated with reductions in strength, resilient modulus, and ultrasonic pulse velocity, as well as increases in permeability, compressibility, and volumetric deformation. Although several traditional and emerging stabilizers have shown potential, their long-term performance under repeated F–T exposure remains insufficiently established. Important research gaps include open-system testing, coupled F–T and desiccation effects, suction and compressibility behavior, macro-micro correlations, and field-scale evaluation. Overall, this review provides directions for future research to advance understanding and improve stabilization strategies for durable infrastructure constructed on expansive soils in cold regions.

As environmental sustainability becomes increasingly critical, biopolymers offer a promising, eco-friendly solution for stabilizing industrial waste materials such as pond ash. Derived from natural sources, biopolymers present sustainable alternatives to traditional additives (such as lime, gypsum and cement) in geotechnical applications. This study investigates the potential of two biopolymers, xanthan gum and guar gum, to enhance the physical and mechanical properties of pond ash, a by-product of coal combustion that poses significant disposal challenges. Three types of pond ash were treated with varying biopolymer dosages and subjected to curing times ranging from 1 to 4 weeks. The results revealed significant improvements in compaction and Unconfined Compressive Strength (UCS) characteristics of treated specimens, with guar gum outperforming xanthan gum due to its higher viscosity and superior compressive strength. Statistical models were developed to predict UCS, enabling the optimization of biopolymer dosage and curing time for practical applications. The findings demonstrate that biopolymer-treated pond ash can serve as a sustainable construction material with enhanced engineering properties and reduced environmental impact. Overall, this research highlights the potential of biopolymers to transform industrial waste into valuable resources, supporting the development of greener materials for geotechnical applications, while advancing the principles of a circular economy.

This review article presents a comprehensive overview of the evolving landscape of road pavements, focusing on the critical need to improve existing practices in response to modern transportation demands. With projections estimating the construction of over 25 million kilometres of new roads by 2050, there is increasing pressure to develop roadway infrastructure that is more resilient and sustainable. The article highlights the key challenges facing modern road pavements, including the growing demands from increased vehicular loads, the impacts of extreme weather events, and the urgent need to address environmental concerns. Advancements in road construction materials, including the use of alternative binders and recycled components are discussed in the context of promoting sustainability and supporting circular economy principles in design and construction. The integration of smart technologies, including sensors and pavement digital twins (PDTs) is also deliberated discussed in terms of its capacity to enhance infrastructure management through performance monitoring, predictive maintenance, and data-driven decision-making. Sustainable design practices that reduce carbon emissions and optimise material use are becoming increasingly important in pavement engineering. These innovations collectively point toward the development of future pavements capable of supporting emerging transportation systems while significantly improving the environmental performance of road networks. Lastly, this review also introduces emerging research areas that facilitate the incorporation of innovative technologies and nature-inspired solutions in pavement design and maintenance.

Reclaimed asphalt pavement (RAP) has been widely incorporated into roadway base and surface courses, as they provide economic and environmental benefits that lead to sustainable construction practices. However, because of the increasing use of paving interlayers (e.g., geotextiles, geogrids, and geocomposites) during roadway rehabilitation, the likelihood of milling projects involving asphalt layers with paving interlayers (referred to as GRAP) has significantly increased. Consequently, the assessment of potential GRAP reuse in geotechnical and pavement applications becomes essential. This research study aims at evaluating the millability and recyclability of asphalt layers with paving interlayers. Specifically, sections with and without paving interlayers were first milled to evaluate the millability of asphalt layers with paving interlayers. Subsequently, the recyclability of GRAP for the base and surface course of pavements was assessed by quantifying the geotechnical characteristics of millings collected from asphalt layers with paving interlayers, referred herein as geosynthetic RAP or GRAP, and those without paving interlayers (RAP). The evaluation of RAP and GRAP materials for road base suitability included blending them with virgin aggregates and investigating these blends via determination of particle size distribution, binder content, compaction characteristics, abrasion resistance, hydraulic conductivity, and resilient modulus. The evaluation of RAP and GRAP materials for surface course suitability involved preparing asphalt mixtures that incorporated RAP and GRAP and quantifying their particle size distribution, indirect tensile strength, and moisture susceptibility. Comparison of the results obtained from five different base course blends and five different asphalt mixtures demonstrated that the base course blends and asphalt mixtures with GRAP exhibited properties similar to those with RAP. Also, the results of this investigation indicate that asphalt mixtures (surface course) and granular base courses can incorporate up to 30 % and 50 % GRAP, respectively, thus leading to sustainable roadway construction practices.

Expansive soils pose a serious challenge to civil engineering constructions due to their ability to swell and shrink upon wetting and drying. This phenomenon usually leads to damage of the structure when the soil is not treated properly. Moreover, the disposal and utilization of fly ash (FA) in both economical and eco-friendly ways has received high attention in the world. Thus, this study focuses on the improvement of the geotechnical properties of expansive soils stabilized with varying percentages of fly ash as an admixture. In the present study, low calcium fly ash in different proportions by weight (0%, 10%, 20%, 30%, and 40%) was added to a moderately expansive soil collected from Doharramafi Village, India. Laboratory tests performed on the prepared mixtures included the determination of moisture-density relationships, California bearing ratio (CBR), and shear strength parameters. Test results show that moisture-density relationships, CBR values, and shear strength parameters of fly ash-treated soil are significantly modified and improved compared to control specimens. Furthermore, based on all laboratory tests, 30% fly ash content is observed to be the optimum fly ash quantity required to improve the geotechnical properties of soil stabilized with fly ash.

The increasing cost of asphalt and environmental concerns have created a greater interest in exploring the possibility of incorporating higher percentages of reclaimed asphalt pavement (RAP) materials in asphalt mixtures. However, increasing the RAP content can adversely affect some of the properties of asphalt mixtures, including their cracking resistance potential. Consequently, finding a solution that accommodates incorporating higher RAP contents into the asphalt mixture is crucial. Moreover, geosynthetics has gained significant popularity as an anti-reflective cracking system in asphalt pavements, which may lead to the possibility of milling asphalt layers with geosynthetic interlayers. Thus, research studies need to be conducted to understand the characteristics and behaviour of RAP obtained from asphalt layers with geosynthetic interlayers (referred herein as GRAP). The objective of this study is to investigate the cracking characteristics of asphalt mixtures containing different percentages (0, 15, and 30%) of RAP and GRAP material using cross-shear tests. Results indicated that the addition of GRAP into the asphalt mixture by about 30% significantly improves the performance of asphalt mixtures against crack initiation and propagation compared to those asphalt mixtures containing only RAP. Overall, it can be inferred that the presence of geosynthetic fragments could increase the possibility of incorporating higher percentage of RAP in asphalt mixtures.

This study focuses on the essential task of monitoring the strength of structural concrete in construction and rehabilitation projects. The conventional non-destructive testing (NDT) approach offers an indirect estimation of concrete compressive strength. However, the existing models lack the ability to address the estimation of compressive strength in concrete mixtures containing bottom ash (BA) and recycled coarse aggregate (RCA). This study aims to bridge this gap by accurately estimating the compressive strength of such concrete using the ultrasonic pulse velocity (UPV) technique. To achieve this objective, various concrete specimens with different cement content, water–cement ratios (w/c), recycled coarse aggregate, and bottom ash contents through weight batching, were prepared. UPV and compressive strength measurements were taken on cylindrical concrete specimens after 28 and 90 days of curing. The analysis revealed an exponential relationship between the compressive strength and UPV, with a high correlation coefficient across the evaluated concrete mixes, independent of the curing time. Ultimately, two robust models were developed to predict the compressive strength of concrete mixes containing different percentages of RCA and BA, respectively, at 28 and 90 days of curing. These models offer valuable insights and practical tools for ensuring the structural integrity of concrete in construction and rehabilitation projects involving bottom ash and recycled coarse aggregate.

Improvement in geotechnical properties of coal ash is required for its better utilization in large infrastructure projects. Lime and cement are the most commonly used material to stabilize coal ash for railway and highway embankment construction. However, these admixtures have negative impact on the environment. This experimental study explores the viability of commercially available guar gum biopolymer, as an eco-friendly and cost-effective additive for coal ash stabilization. Guar gum biopolymer is chosen because of its pH stability, cold water dissolving characteristics and formation of hydrogen bonds along with being inexpensive. Different concentrations (1–5

The incorporation of geosynthetic interlayers during the asphalt overlay construction has proven successful in mitigating the reflective cracking and enhancing the pavement structural capacity. However, milling an asphalt layer reinforced with geosynthetic interlayer is a huge concern, since there is a possibility of geosynthetic interlayers compromising the reclaimed asphalt pavement (RAP) quality and characteristics. On the other hand, inclusion of RAP into the hot mix asphalt (HMA) is a common practice. Hence, it is important to understand the characteristics of RAP collected from geosynthetic-reinforced asphalt layers (referred herein as GRAP) and their influence on the performance of asphalt mixtures. The objective of this study is to understand the characteristics of GRAP and subsequently, investigate the performance of asphalt mixtures with 15% and 30% GRAP contents. Additionally, the performance of asphalt mixtures with 15% and 30% RAP contents, and 100% virgin aggregates (referred as control mixture) was evaluated for comparison with that of asphalt mixtures combining GRAP. The characterization of GRAP and RAP included particle size gradation and binder extraction tests, while the performance evaluation of the asphalt mixtures included indirect tensile strength, and moisture susceptibility tests. Comparison of binder extraction test results revealed that the GRAP samples had binder content slightly higher than that of the RAP samples. While the comparison of indirect tensile strength and moisture susceptibility test results indicated the performance of asphalt mixtures with GRAP similar to that with RAP, where both mixtures outperformed the asphalt mixtures made solely of virgin aggregates. This indicates the potential of incorporating GRAP and RAP up to 30% into the asphalt mixtures without compromising the performance of asphalt mixtures.

The incorporation of geosynthetic reinforcements during the rehabilitation of flexible pavements has significantly increased due to the ability of geosynthetic reinforcements to minimize reflective cracks. However, the performance of the geosynthetic-reinforced asphalt depends on the interface bond strength between the geosynthetic and the adjacent asphalt layers. Tack coat is generally used to maintain adequate bonding between the geosynthetic-reinforced asphalt layers. This study focusses on evaluating the influence of interface bond strength on the fracture resistance of geosynthetic-reinforced asphalt utilizing a new testing approach. The fracture resistance of geosynthetic-reinforced asphalt specimens was evaluated via cross-shear testing device, while interface bond strength was evaluated using interface shear strength testing. A Performance Grade (PG) 64-22 binder was applied as a tack coat at the geosynthetic-asphalt interface at four different rates that are relative to the asphalt retention capacity of the geosynthetic reinforcement. A fiberglass geocomposite was used as geosynthetic reinforcement in this study. The results indicate a correlation between interface shear strength tests and cross-shear tests, suggesting that the optimum tack coat rate is 125% of the asphalt retention capacity of the geosynthetic reinforcement to improve the fracture resistance as well as the interface bond strength of geosynthetic-reinforced asphalt layers.

The placement of geosynthetics between the asphalt layers has proved to enhance the pavement performance through functions including reinforcement, separation, and moisture barrier. Several experimental procedures have been adopted to quantify the performance of geosynthetic-reinforced asphalt pavements, including beam fatigue test, wheel tracking test, three- and four-point beam bending, and interface bond strength tests. The objective of this study is to evaluate the cracking resistance potential of geosynthetic-reinforced asphalt specimens using a monotonic cross-shear test. The unreinforced and geosynthetic-reinforced asphalt specimens tested in this study comprised of 19-mm-thick bottom asphalt layer, binder tack coat, geosynthetic interlayer (only in the reinforced specimens), and 19-mm-thick top asphalt layer. Three different types of geosynthetic interlayers, including polyester geogrid composite (PET-C), polyvinyl alcohol geogrid composite (PVA-C), and fiberglass geogrid composite (FG-C), were adopted in this study. Comparison of monotonic cross-shear test results from geosynthetic-reinforced and unreinforced specimens revealed that the geosynthetic interlayers enhanced the cracking resistance potential of the asphalt specimens. Among the reinforcements tested in this study, polymeric reinforcements exhibited a better performance over fiberglass reinforcement.

The present study investigates the rebound hammer number (RHN), ultrasonic pulse velocity (UPV), compressive strength, split tensile strength, and modulus of elasticity of concrete made with recycled coarse aggregate and bottom ash. The natural coarse aggregates (crushed rock aggregates) and fine aggregates (sand) are partially or fully replaced (0%, 50%, and 100%) with recycled coarse aggregates (RCA) and coal bottom ash (BA), respectively. Standard concrete specimens were then cast to determine the former properties at 28- and 90-days of curing. The experimentally obtained RCA and BA concrete properties are found comparable to conventional concrete. It has been observed that 100% RCA concrete properties at 90 days are similar to the 28 days of conventional concrete properties. Scanning electron microscope (SEM) analysis has also been performed to examine the mechanism behind the observed properties of RCA, BA, and RCA + BA (concrete containing both RCA and BA) concrete. Based on the experimentally obtained 28-day compressive strength, UPV, and RHN values, the analytical models for predicting the compressive strength, splitting tensile strength, and static modulus of elasticity of RCA, BA, and RCA + BA concrete at any age are also proposed. The values calculated from the proposed models are in good agreement with the experiments. The present study will be helpful for the designers and engineers in practice for fixing preliminary dimensions of concrete elements made with RCA, BA, and RCA + BA concrete mixes, thus leading to sustainable concrete construction.

Cement concrete and other cement-based composites find wide application in the construction industry. The manufacturing of cement releases a large amount of CO2, so the use of cement has become a major area of environmental concern. Attempts have been made to minimize the quantity of cement in con- crete by replacing it with supplementary cementitious materials. Geopolymer concrete is one of those potential candidates for alternative cementitious mate- rials. In today’s world, the production of Construction and Demolition (C&D) wastes has been increased worldwide which finds no suitable disposal and can- not be used in ordinary concrete due to potential deterioration of concrete quality. However, C&D waste can be safely used with geopolymer concrete with and without the usage of Supplementary Cementitious Materials (SCMs) and play a major role in improving the strength and durability properties of concrete.