Addressing the global challenge of deteriorating infrastructure is amultifaceted task that requires collaboration among policymakers,researchers, industry professionals, and the public. Asphalt and conc-rete are indispensable to the construction and maintenance of criticalinfrastructure, such as roads, bridges, and buildings, which are essential for economic growth and maintaining quality of life. However,the rising demand for these materials necessitates a strong commitm-ent to sustainability, particularly in the face of pressing environ-mental concerns such as the depletion of natural resources and climate change. In response to these challenges, this issue showcases innovative research that leverages materials engineering to design, develop, and assess sustainable asphalt and concrete solutions.
The first paper, authored by Behera et al. (2024) from India, investigates the production of warm-mix asphalt (WMA) using a two-phase mixing process that combines bitumen–emulsion–coated aggregates at varying temperatures. The study incorporates 8% ground granulated blast-furnace slag filler, a proportion determined through hot-mix asphalt analysis, and explores different bitumen-to-emulsion ratios and mixing temperatures. Through a combination of experimental work and statistical modelling, the research thoroughly examines the impact of these variables on Marshall performance parameters. The WMA produced at 120°C with an 80:20 bitumen-to-emulsion ratio demonstrated superior performance across key metrics, including indirect tensile strength, tensile strength ratio, retained stability, rutting resistance, and raveling loss. However, the authors recommend further research on additional durability aspects to enhance the understanding of WMA’s long-term performance.
The second paper, an open-access and featured contribution from Canada by Yasien and Bassuoni (2024), provides a comprehensive review of the current state of knowledge on the challenges of cold-weather concreting. When concrete temperatures drop to −2.8°C, the hydration process of cementitious binders nearly halts due to the freezing of mixing water. This freezing generates pressures that exceed the tensile strength of the concrete, particularly in its early, immature stages, leading to compromised hardening, inadequate strength development, and potential irreversible damage. As a result, concrete applications in cold weather become highly challenging. The paper compiles key provisions from major codes and guidelines on cold-weather concreting and integrates the latest research on the subject, including mixture components and innovative methods for curing and protecting concrete at low temperatures. This review aims to be a valuable resource for the construction industry in cold regions, highlighting recent advancements that can reduce the need for heating operations, lower the carbon dioxide footprint, and encourage practical applications.
The third paper, by Ambily et al. (2024) from India, focuses on three-dimensional concrete printing (3DCP), a modern construction technique that has recently gained significant attention. This laboratory study aimed to determine optimal mix proportions and develop 3DPC mix designs using a trial-and-error approach to evaluate key properties such as flowability, buildability, extrudability, and open time. The research identified an ideal mix consisting of 19% ordinary Portland cement, 23% fly ash (FA), 7% silica fume, 13% ground granulated blast-furnace slag, 4% limestone, and 0.22% superplasticiser (by mass of the total binder). The proposed mix design and mixing protocol show promising potential for large-scale 3DCP applications.
The fourth paper, by Sinngu et al. (2024) from South Africa, examines the impact of natural zeolite (NZ) as a pozzolan on concrete properties, using durability indexes for evaluation. The study involved creating concrete mixtures with water/cementitious ratios of 0.50 and 0.70, using CEM I 52.5R cement blended with 0%, 10%, 20%, and 30% NZ. The performance of these NZ blends was compared with concrete containing 20% or 30% FA, a widely used pozzolan. Mechanical properties such as strength development were assessed alongside durability properties, including carbonation and a range of indexes – oxygen permeability, water sorptivity, and chloride conductivity. The results showed that NZ concretes demonstrated adequate to excellent durability index values and lower carbonation levels compared with FA concretes. Notably, the inclusion of 20% NZ in the concrete resulted in optimal performance, particularly with a significant reduction in carbonation, indicating its promising potential for producing blended cements.
These four papers present a broad spectrum of engineering and scientific topics, each with significant relevance for academic researchers and industry professionals alike. While the first paper focuses on the practical design of warm asphalt mixes, the remaining three explore advancements in materials aimed at enhancing the sustainability of concrete in response to industrial challenges, particularly in reducing the carbon footprint. I am confident that these papers will provide valuable insights to enrich your work and practices.
