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The mechanical performance of Masterbatch Natural Rubber (MNR)-modified asphalt concrete (MNR-AC) was investigated and is presented in this paper. When compared to conventional asphalt concrete (AC), MNR-AC exhibits significantly superior performance across key mechanical parameters, including Marshall stability, indirect tensile strength (ITS), resilient modulus (IT Mr), indirect tensile fatigue life (ITFL), and rutting resistance. The most pronounced enhancements are observed at the optimal dry rubber to asphalt cement (r/b) ratio of 3%, at which MNR-AC demonstrates peak performance in all evaluated tests. The fatigue distress models for MNR-AC and AC reveal distinct logarithmic relationships, with an intersection point occurring at an r/b ratio of approximately 3%. This suggests that MNR-AC with an r/b ratio of 3% or less exhibits a markedly superior fatigue life compared to conventional AC under equivalent applied-stress conditions. MNR offers significant practical advantages over liquid natural rubber, including more consistent mixing, and simplified storage and transportation, positioning it as a promising and sustainable advancement in pavement material technology. [ABSTRACT FROM AUTHOR]

This research delved into the mechanical and fatigue attributes of hemp fiber–reinforced concrete (HFRC) using both natural crushed aggregates (NCA) and recycled concrete aggregates (RCA) for sustainable rigid pavements. The additional hemp fiber ratios were 0%, 0.5%, 0.75%, and 1.0% by volume of concrete. The accelerated setting times were found due to hemp fibers facilitating rapid cement hydration. The compressive strengths were found to typically decrease with increasing hemp content. Mixes with 0.5% hemp (NCA-0.5H-FRC and RCA-0.5H-FRC) met the local road authority's rigid pavement standards, with enhanced energy absorption and ductility. Flexural strength was optimal at 0.5% hemp, with all mixes meeting the standard 4.2 MPa. The flexural fatigue test indicated that higher hemp content significantly improved the fatigue life of HFRC under repetitive loading. Scanning electron microscopy (SEM) analysis demonstrated hemp fibers' role in enhancing bond strength and interactions with cement matrix, thereby improving the concrete performance. While NCA mixes outperformed RCA ones, hemp fiber's reinforcing effect was consistent across both types of aggregates. The study indicated hemp fiber's potential in applications like pavements, highlighting 0.5% as the optimal hemp content for balancing enhanced mechanical properties while mitigating potential drawbacks. This research paves the way for the broader adoption of hemp fiber–reinforced concretes in sustainable construction endeavors. [ABSTRACT FROM AUTHOR]

The expansive development of infrastructure has led to increased consumption of virgin aggregates in road construction, resulting in significant environmental impacts. To address this issue, there is a pressing need for sustainable alternatives that utilize recycled materials in pavement applications. This paper presents a comprehensive review of a decade-long research program focused on the development and evaluation of sustainable pavement materials, such as recycled and waste aggregates, industrial by-products, and natural fibers. The research encompassed a wide range of innovative materials and technologies, such as geopolymer-stabilized recycled aggregates, cement-stabilized waste materials, natural additive-modified cement stabilization, and recycled aggregate-geogrid reinforcement systems. The experimental framework employed a combination of mechanical testing, durability assessment, microstructural analysis, and environmental safety evaluation to assess the performance and sustainability of these materials. The key findings demonstrated the superior mechanical properties, improved durability, and environmental suitability of the recycled materials compared to conventional virgin aggregates. The successful implementation of these sustainable solutions in real-world projects highlights their potential to reduce the environmental footprint of road infrastructure development. Furthermore, the paper discussed the practical implications of the research outcomes for pavement design and construction, as well as future research directions to further advance the field of sustainable pavement engineering. The findings of this research report can be used as guidance for researchers, practitioners, and policymakers seeking to upcycle the widespread adoption of recycled materials in road application and contribute to the development of a more sustainable and resilient transportation infrastructure. [ABSTRACT FROM AUTHOR]

This article investigates the viability of using natural rubber latex (NRL)-modified concrete with bottom ash (BA) as a partial replacement for river sand in sustainable rigid pavements. Concrete mixes with 10% and 20% BA replacement ratios and varying NRL dosages (0%, 1.0%, 1.5%, and 2.0% by weight of cement) were prepared and evaluated for their mechanical and microstructural characteristics. Results showed that BA substitution decreased the compressive strength of concrete. However, the addition of NRL at an optimal dosage of 1.0% significantly improved both the compressive and flexural strengths. The 10%BA+1.0%NRL and 20%BA+1.0%NRL mixes exhibited mechanical properties surpassing the control mix and meeting the minimum requirements for rigid pavement materials. However, excessive NRL content (1.5% and 2.0%) led to a reduction in mechanical strength. Scanning electron microscopy analysis exhibited a denser and more compact matrix in NRL-modified BA concrete, with NRL films enhancing the interfacial bonding and crack-bridging mechanism. Nonetheless, excessive NRL content resulted in the formation of abundant and thicker NRL films, which disrupted the continuity of the cement matrix and created weak zones. X-ray diffraction analysis confirmed the existence of crucial crystalline phases and their optimal balance in the 20%BA+1.0%NRL mix, contributing to its superior performance. Mixes with excessive NRL contents exhibited lower intensities of quartz, calcite, and portlandite peaks, indicating a disturbance in the proper formation and growth of essential crystalline phases. The findings demonstrated the potential of NRL-modified BA concrete as an eco-friendly and high-performance alternative for sustainable rigid pavements when using an optimal NRL dosage, promoting the employment of waste resources and reducing the environmental impact of the construction industry. [ABSTRACT FROM AUTHOR]

Porous asphalt concrete (PAC) is an open-graded asphalt concrete with a high air void, which functions as permeable pavement with high surface frictional resistance. PAC typically requires a high amount of coarse aggregate to provide the required porous structure. An expensive high-quality polymer-modified asphalt (PMA) is commonly required to prevent draindown issues and to improve the performance of PAC. Bottom ash (BA), a high-porosity byproduct from coal-fired power plants, is used as a greener product to improve the quality of traditional asphalt cement penetration grade 60/70 (AC 60/70) for producing low-cost PAC in this research. The effect of the BA replacement ratio (0%, 10%, 15%, 20%, and 25% by total weight of fine aggregate) on the draindown, loss of particle, Marshall properties, indirect tensile strength (ITS), indirect tensile resilient modulus (IT Mr), indirect tensile fatigue life (ITFL), permanent deformation (PD), rut depth, and skid resistance of BA-AC60/70-PAC were measured and compared with PMA-PAC. The draindown and particle loss values of BA-AC60/70-PAC were found to decrease with an increase in the BA replacement ratio. The BA replacement improved the Marshall properties, strength index, ITS, IT Mr , ITFL, PD, rut depth, and skid resistance of PAC up to the highest value at the optimum BA replacement ratio of 20%. The improved ITS is associated with the improved IT Mr in a linear relationship for all BA replacement ratios. The change in ITFL was found to be linearly related to IT Mr at a specific stress level. At the same design criteria, the 20% BA replacement ratio yields the reduction of total construction cost of BA-AC60/70-PAC surface course by 33% benchmarked to the conventional PMA-PAC surface course. [ABSTRACT FROM AUTHOR]

During the past few decades, the engineering and geotechnical properties of recycled concrete aggregate (RCA) has been investigated to evaluate its potential to use as a road construction material. This research studied the usage of polyvinyl alcohol (PVA) and cement for improving the mechanical strengths of RCA to be used as an alternative material in pavement base/subbase applications. The results showed that mixing PVA > 1.5% into the cement-stabilised RCA has a vital role in improving the compressive strength along with gaining a higher modulus of toughness. The unconfined compressive strength (UCS) value of stabilised RCA with 3% cement and RCA with 3% cement and 1.5% or 2% PVA met the minimum requirement for 7 days of curing. The addition of PVA reduced the resilient modulus (MR); however, the MR value of all blends was still higher than the minimum recommended value. The specimens with 28 days of curing had higher resilient modulus values than 7-day cured samples. The CBR value and swelling in soaked condition reduced with increasing the PVA content. The cement-PVA-stabilised RCA, as a supplementary material with up to 1.5% or 2% PVA content and 3% General Portland (GP) were found to have physical and strength properties, which comply with road authority requirements. [ABSTRACT FROM AUTHOR]