Search Results (219)

Mining by-products present both an environmental challenge and a resource opportunity. This review investigates their potential application in road pavement construction, focusing on materials such as fly ash, slag, sulphur, red mud, tailings, and silica fume. Drawing from laboratory and field studies, the review examines their roles across pavement layers—subgrade, base, subbase, asphalt mixtures, and rigid pavements—emphasising mechanical properties, durability, moisture resistance, and ageing performance. When properly processed or stabilised, many of these wastes meet or exceed conventional performance standards, contributing to reduced use of virgin materials and greenhouse gas emissions. However, issues such as variability in composition, leaching risks, and a lack of standardised design protocols remain barriers to adoption. This review aims to consolidate current research, evaluate practical feasibility, and identify directions for future studies that would enable the responsible and effective reuse of mining waste in transportation infrastructure. Full article

To address the demands for resource utilization of Yellow River sediment and the durability requirements of engineering materials in cold regions, this study systematically investigates the mechanisms affecting the frost resistance of slag-Yellow River sediment geopolymers through the incorporation of mineral admixtures (silica fume and metakaolin) and fibers (steel fiber and PVA fiber). Through 400 freeze-thaw cycles combined with microscopic characterization techniques such as SEM, XRD, and MIP, the results indicate that the group with 20% silica fume content (SF20) exhibited optimal frost resistance, showing a 19.9% increase in compressive strength after 400 freeze-thaw cycles. The high pozzolanic reactivity of SiO₂ in SF20 promoted continuous secondary gel formation, producing low C/S ratio C-(A)-S-H gels and increasing the gel pore content from 24% to 27%, thereby refining the pore structure. Due to their high elastic deformation capacity (6.5% elongation rate), PVA fibers effectively mitigate frost heave stress. At the same dosage, the compressive strength loss rate (6.18%) and splitting tensile strength loss rate (21.79%) of the PVA fiber-reinforced group were significantly lower than those of the steel fiber-reinforced group (9.03% and 27.81%, respectively). During the freeze-thaw process, the matrix pore structure exhibited a typical two-stage evolution characteristic of “refinement followed by coarsening”: In the initial stage (0–100 cycles), secondary hydration products from mineral admixtures filled pores, reducing the proportion of macropores by 5–7% and enhancing matrix densification; In the later stage (100–400 cycles), due to frost heave pressure and differences in thermal expansion coefficients between matrix phases (e.g., C-(A)-S-H gel and fibers), interfacial microcracks propagated, causing the proportion of macropores to increase back to 35–37%. This study reveals the synergistic interaction between mineral admixtures and fibers in enhancing freeze–thaw performance. It provides theoretical support for the high-value application of Yellow River sediment in F400-grade geopolymer composites. The findings have significant implications for infrastructure in cold regions, including subgrade materials, hydraulic structures, and related engineering applications. Full article

Resource depletion and environmental degradation have resulted from the substantial increase in the use of natural aggregates and construction materials brought on by the growing demand for infrastructure development. Road building using mining waste has become a viable substitute that reduces the buildup of industrial waste while providing ecological and economic advantages. In order to assess the appropriateness of several mining waste materials for use in road building, this study investigates their engineering characteristics. These materials include slag, fly ash, tailings, waste rock, and overburden. To ensure long-term performance in pavement applications, this study evaluates their tensile and compressive strength, resistance to abrasion, durability under freeze–thaw cycles, and chemical stability. This review highlights the potential of mining waste materials as sustainable alternatives in road construction. Waste rock and slag exhibit excellent mechanical strength and durability, making them suitable for high-traffic pavements. Although fly ash and tailings require stabilization, their pozzolanic properties enhance subgrade reinforcement and soil stabilization. Properly processed overburden materials are viable for subbase and embankment applications. By promoting the reuse of mining waste, this study supports landfill reduction, carbon emission mitigation, and circular economy principles. Overall, mining byproducts present a cost-effective and environmentally responsible alternative to conventional construction materials. To support broader implementation, further efforts are needed to improve stabilization techniques, monitor long-term field performance, and establish effective policy frameworks. 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

Colloidal silica can seep through calcareous sand in the subgrade, forming colloidal-silica-cemented sand with self-sensing ability—that is, it is sensitive to stress changes caused by vehicle loading. Its self-sensing sensitivity is higher than that of traditional Portland-cement-based self-sensing materials. The self-sensing mechanism is attributed to the ionic conductive network formed by seawater. However, a change in tidal water level causes an unsaturated state, and foundation deformation leads to cracking of the roadbed. The effect of unsaturation and cracking on self-sensing remains unclear, and they have not been studied in the previous literature. The aim of this paper is to study the self-sensing ability of subgrades formed via colloidal-silica-cemented sand under unsaturated and cracked states, as well as to explore the underlying mechanisms. Specimens with different degrees of saturation and different levels of joint roughness in precracks were prepared; then, the self-sensing ability was tested using the four-electrode method for each specimen under cyclic stress loading. NMR (nuclear magnetic resonance) and an unsaturated triaxial apparatus were also used to investigate the underlying mechanisms. This paper discovers that (1) either unsaturation or crack alone can increase self-sensing, but their self-sensing sensitivities are on the same order; (2) under the coupled effect of unsaturation and cracking, the self-sensing sensitivity increases by one order of magnitude, which is higher than when only unsaturation or cracking exists; and (3) the joint roughness of precracks does not affect self-sensing in the saturated state, but it affects self-sensing dramatically in the unsaturated state. The NMR test demonstrated the conductive ionic water within nanopores, which forms the conductive network for self-sensing. Unsaturation causes suction-induced shrinkage based on the unsaturated triaxial apparatus, while unsaturation increases self-sensing sensitivity, indicating that shrinkage is accompanied by self-sensing improvement. This paper provides the effects of unsaturation and cracking on the self-sensing capabilities of colloidal-silica-cemented sand, and the findings can contribute to the knowledge of subgrades formed via colloidal-silica-cemented sand for stress-sensing under traffic loading. Full article

The application of construction and demolition waste (CDW) as roadbed filler faces challenges due to the variable mechanical properties caused by fragile recycled brick aggregates. This study elucidates the breakage mechanism of CDW fillers under compaction effort through a combination of standardized laboratory compaction tests and discrete element method (DEM) simulations. Furthermore, the breakage evolution patterns of mixed fills comprising recycled concrete and brick aggregates at various mixing ratios were revealed. A DEM model was developed to characterize recycled concrete and brick aggregates, adopting polygonal clumps for particles >4.75 mm and spherical clumps for finer fractions. The results indicate that particle breakage progresses through three distinct stages: linear fragment stage (0–200 kJ/m³, 50% of total breakage), deceleration growth stage (200–1000 kJ/m³, 38% of total breakage), and residual crushing stage (1000–2684.9 kJ/m³, 12% of total breakage). Recycled concrete aggregates form a skeleton restraining deep cracks, while brick aggregates enhance stability through energy dissipation and void filling. However, exceeding 30% brick content impedes skeleton development. Critically, a 30% brick content optimizes performance, achieving peak dry density with 25% lower compression deformation than concrete-only fillers, while limiting breakage index rise. These results provide a science-based strategy to optimize CDW roadbed design, improving recycling efficiency and supporting sustainable infrastructure. 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 study explores the influence of the water–cement ratio and fiber content in engineered cementitious composite (ECC) on the mechanical characteristics of foamed lightweight soil (FLS) through experimental analysis. Two types of cementitious materials—ECC and ordinary Portland cement (OPC)—were utilized to create FLS specimens under identical parameters to examine their mechanical performance. Results indicate that ECC-FLS exhibits superior toughness, plasticity, and ductility compared to OPC-FLS, validating the potential of ECC as a high-performance material for FLS. To assess the influence of the ECC water–cement ratio, specimens were constructed with varying ratios at 0.2, 0.25, and 0.3, while maintaining other parameters as constant. The experimental results indicate that as the water–cement ratio of ECC increases, the flexural strength, compressive strength, flexural toughness, and compressive elastic modulus of the lightweight ECC-FLS gradually increase, exhibiting a better mechanical performance. Moreover, this study investigates the effect of basalt fiber content in ECC on the mechanical properties of FLS. While keeping other parameters constant, the volume content of basalt fibers varied at 0.1%, 0.3%, and 0.5%, respectively. The experimental results demonstrate that within the range of 0 to 0.5%, the mechanical properties of FLS improved with increasing fiber content. The fibers in ECC effectively enhanced the strength of FLS. In conclusion, the adoption of ECC and appropriate fiber content can significantly optimize the mechanical performance of FLS, endowing it with broader application prospects in engineering practices. ECC-FLS, characterized by excellent ductility and crack resistance, demonstrates versatile engineering applications. It is particularly suitable for soft soil foundations or regions prone to frequent geological activities, where it enhances the seismic resilience of subgrade structures. This material also serves as an ideal construction solution for underground utility tunnels, as well as for the repair and reconstruction of pavement and bridge decks. Notably, ECC-FLS enables the resource utilization of industrial solid wastes such as fly ash and slag, thereby contributing to carbon emission reduction and the realization of a circular economy. These attributes collectively position HDFLS as a sustainable and high-performance construction material with significant potential for promoting environmentally friendly infrastructure development. Full article

In cold regions, the overlay effect often leads to pavement and subgrade distresses, severely compromising the functionality of roads and infrastructure. To address this issue, this study proposes a solution involving permeable pavements and roadbed structures. However, the application of permeable pavement materials in cold regions remains a significant challenge. Building on previous research, this paper introduces a novel pavement material with exceptional mechanical and temperature performance: terminal carboxylated nitrile rubber-modified epoxy asphalt. Specifically, the mechanical properties, viscosity, high-temperature rutting resistance, low-temperature cracking resistance, and modification mechanisms of five terminal carboxylated nitrile rubber-modified epoxy asphalt mixtures with varying terminal carboxylated nitrile rubber contents were investigated. Additionally, the high-temperature, low-temperature, and water stability properties of three types of porous asphalt concrete were compared. The results demonstrate that the incorporation of terminal carboxylated nitrile rubber significantly enhances the mechanical properties and low-temperature cracking resistance of the asphalt without altering the curing time. Although the high-temperature rutting resistance of the asphalt itself decreases, the high-temperature, low-temperature, and water stability properties of the porous asphalt concrete are improved. This improvement is attributed to the chemical reaction between terminal carboxylated nitrile rubber and epoxy resin, which generates a prepolymer containing new substances and forms a stable sea–island structure. This structure promotes a more homogeneous distribution of the asphalt matrix, thereby increasing the cohesive strength and toughness of the asphalt. Full article

Anthropization has significantly altered the natural water cycle by increasing impermeable surfaces, reducing evapotranspiration, and limiting groundwater recharge. Permeable Interlocking Concrete Pavements (PICPs) have emerged as a permeable pavement, effectively reducing runoff and improving water quality. This study investigates the base depth for PICPs regarding the strength and permeability. This study examines the hydraulic and structural performance of Permeable Interlocking Concrete Pavements (PICPs) for urban and industrial applications by evaluating the effects of subgrade conditions, traffic loads, and material properties. Using DesignPave and PermPave software, the optimal base layer thickness is determined to prevent rutting while ensuring effective stormwater infiltration beneath 110 mm-thick concrete pavers placed on a 30 mm-thick bedding course. The required base thickness for urban pavements ranges from 100 mm to 395 mm, whereas for industrial pavements, it varies between 580 mm and 1760 mm, depending on subgrade permeability, traffic volume, and loading conditions. The findings demonstrate that PICPs serve as a viable and environmentally sustainable alternative to conventional impermeable pavements, offering significant hydrological and ecological benefits. Full article

This study investigated the small-strain dynamic properties of expanded polystyrene (EPS) lightweight soil (ELS), a low-density geosynthetic material used to stabilize slopes and alleviate the subgrade settlement of soft soil. Resonant column tests were conducted to evaluate the effects of EPS’s granule content (20–60%), confining pressures (50 kPa, 100 kPa, and 200 kPa), and curing ages (3 days, 7 days, and 28 days) on the dynamic shear modulus (G) of ELS within a small strain range (10⁻⁶–10⁻⁴). The results indicate that ELS exhibits a high dynamic shear modulus under small strains, which increases with higher confining pressure and longer curing age but decreases with an increasing EPS granule content and dynamic shear strain, leading to mechanical property deterioration and structural degradation. The maximum shear modulus (G_max) ranges from 64 MPa to 280 MPa, with a 60% reduction in G_max observed as the EPS granule content increases and increases by 11% and 55% with higher confining pressure and longer curing ages, respectively. A damage model incorporating the EPS granule content (a_E) and confining pressure (P) was established, effectively describing the attenuation behavior of G in ELS under small strains with higher accuracy than the Hardin–Drnevich model. This study also developed an engineering testing experiment that integrates materials science, soil mechanics, and environmental protection principles, enhancing students’ interdisciplinary knowledge, innovation, and practical skills with implications for engineering construction, environmental protection, and experimental education. Full article

It is difficult to meet environmental requirements via the coarse treatment methods of landfilling and open-air storage of construction waste. At the same time, the consumption of building materials in highway engineering is enormous. Using construction waste as a filling material for proposed roads has become a research hotspot in recent years. This paper starts with basic performance tests of recycled construction waste materials, and then moves on to laboratory experiments conducted to obtain the road performance of the recycled materials, the testing of key indicators of post-construction filling quality of the roadbed, and analyses of the deformation pattern of roadbed filled with construction waste. Additionally, the ABAQUS finite element software was used to establish a numerical model for roadbed deformation and analyze the roadbed deformation under different compaction levels and vehicle load conditions. The experimental results show that the recycled material has a moisture content of 8.5%, water absorption of 11.73%, and an apparent density of 2.61 g/cm³, while the liquid limit of fine aggregates is 20% and the plasticity index is 5.4. Although the physical properties are slightly inferior to natural aggregates, its bearing ratio (25–55%) and low expansion characteristics meet the requirements for high-grade highway roadbed filling materials. The roadbed layer with a loose compaction of 250 mm, after eight passes of rolling, showed a settlement difference of less than 5 mm, with the loose compaction coefficient stabilizing between 1.15 and 1.20. Finite element simulations indicated that the total settlement of the roadbed stabilizes at 20–30 mm, and increasing the compaction level to 96% can reduce the settlement by 2–4%. Vehicle overload causes a positive correlation between the vertical displacement and shear stress in the base layer, suggesting the need to strengthen vehicle load control. The findings provide theoretical and technical support for the large-scale application of recycled construction waste materials in roadbed engineering. Full article

The resilient modulus (M_r) and permanent deformation of subgrade soils are key indicators for assessing pavement performance under repeated traffic loads. Although numerous studies have confirmed their importance in pavement design and performance prediction, a systematic review of empirical relationships and scientific knowledge is lacking, resulting in insufficient integration and application of current findings. To address these issues, this study systematically reviews laboratory and field-testing methods based on over 200 published papers, summarizes common empirical equations, and focuses on the feasibility and advantages of integrating AI to predict M_r. Meanwhile, by examining the main factors that influence M_r and permanent deformation, this study synthesizes and evaluates existing research to identify potential gaps. Findings indicate that laboratory and field tests effectively capture the mechanical behavior of pavement materials, and incorporating AI technology in modulus prediction enhances accuracy and efficiency while managing complex influencing factors. However, existing empirical equations have not been fully integrated with emerging technologies for validation and optimization, and some predictive models remain limited in terms of applicability and generalizability. This review highlights the need to refine empirical relationships for the resilient modulus using stochastic methods and AI techniques, thereby facilitating a more comprehensive integration of the latest testing technologies and computational tools. This research is of great significance for advancing sustainable pavement design, optimizing maintenance strategies, and guiding future research directions. Full article

Soil reinforcement using rice husk ash and cement is emerging as an effective method for enhancing geotechnical performance in subgrade layers, offering an environmentally friendly, stable, durable, and cost-efficient solution. This study investigates sustainable soil reinforcement by maximizing geotechnical performance by applying RHA in subgrade layers. Experimental evaluations were conducted using California Bearing Ratio tests, Scanning Electron Microscopy, and Energy-Dispersive X-ray Spectroscopy. The research focused on three subgrade configurations: upper, lower, and double subgrade layers, each treated with varying proportions of cement (2%, 4%, 6%) and RHA (2%, 4%, 6%). The findings demonstrated significant improvements in bearing capacity across all subgrade layers and combinations compared to untreated control specimens. Notably, the double subgrade layer with 6% RHA + 6% cement achieved the highest CBR value of 21.30 KPa, followed by the configuration with 2% RHA + 6% cement, which recorded a CBR value of 19.62 KPa. The specimen containing 4% RHA + 6% cement achieved a CBR value of 18.62 KPa. These results highlight the effectiveness of RHA as a sustainable material for enhancing geotechnical performance in soil enhancement applications. Full article

Sustainable construction and demolition waste (CDW) management have been widely discussed. For a city seeking urban renewal or transformation, aging houses are remodeled, which creates a large amount of CDW. Taiwan is located in an earthquake-prone area with many aging houses. Sustainable CDW management is extremely urgent for such cities or countries. This study presented the current CDW state in Taiwan and suggested possible management strategies. Material flow analysis was conducted to understand the use and distribution of the construction materials. This shows that 100% of the raw material of concrete is imported, whereas 100% of the raw material of brick is domestic. Half of recycled steel is used as a raw material in steel products. The predicted CDW from aging houses was calculated and could be a sustainable source for these materials. However, waste concrete and brick are currently mostly used as subgrade filling materials but are not recycled to produce new construction materials. There are three obvious challenges in CDW management: the lack of cost-effective recycling technology, the increasing quantity of CDW, and the limits of refilled land and landfill volume. However, three opportunities have also emerged: the high potential for reducing carbon emissions from CDW, improved recycling technology, and increasing awareness of the circular economy. This study concludes that reducing the amount of CDW, increasing the lifespan of buildings, increasing the use of reuse or recycled CDW, and proper management of final waste disposal help reduce waste and build a nearly zero-carbon-emission construction industry. Full article