ABSTRACT The transition toward sustainable construction necessitates the strategic reuse of demolition waste as a substitute for virgin aggregates. While environmental and economic benefits are clear, the challenge lies in the inferior mechanical properties typical of recycled materials compared to natural stone. This research addresses these limitations by exploring the synergy between Crushed Brick Aggregates (CBA) and Manufactured Sand (M-Sand). By optimizing these components, the study encourages denser matrix formation and improved interfacial bonding. The objective is to engineer a moderate-strength composite that balances environmental goals with structural requirements. Fresh and hardened state characterizations, specifically workability, density, and mechanical strengths, were conducted to assess the performance of the proposed concrete. The roles of CBA and M-Sand were scrutinized via experimental protocols and enhanced through statistical modelling. Mix optimization was achieved using RSM and CCD, with model reliability confirmed through ANOVA. The interaction of variables was graphically represented in 3D response surface plots, leading to the conclusion that a 40% CBA and 60% M-Sand configuration is optimal for cost-effectiveness and sustainability. Microstructural validation through thin-section analysis evidenced a robust aggregate–matrix bond, corroborating the measured mechanical improvements.
The construction sector is a major contributor to environmental degradation, with cement manufacturing accounting for a significant portion of global CO
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emissions. This study explores the partial replacement of cement with reclaimed asphalt pavement (RAP) powder as a sustainable alternative to conventional concrete production, a strategy that remains relatively underexplored in literature. Concrete mixes containing 2.5%, 5%, 7.5%, and 10% RAP powder replacing cement by volume were designed accordingly. The tarantula curve methodology was adopted to optimize aggregate gradation enhancing mix performance. Mechanical properties, including compressive, flexural, and tensile strengths, alongside workability and durability, were evaluated. Exploratory models were developed to examine the relationship between RAP content and compressive strength with flexural strength, tensile strength, and elastic modulus. Thermogravimetric analysis (TGA) indicated negligible pozzolanic activity of RAP powder of 8%. However, the results indicate that at 5% RAP replacement, the concrete achieved mechanical performance comparable to that of the control mix (0% RAP) suggesting a useful micro filler effect at his level. A Cradle-to-Gate Environmental Assessment using a 1 m
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concrete slab functional unit showed that replacing 5% and 10% of cement with RAP powder reduced CO
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emissions by 4.85% and 9.69%, and embodied energy by 4.72% and 9.29%, respectively. Environmental benefits stem mainly from reduced cement production emissions.
Firas Barraj, Georges Chalouhi, W. Arairo et al.· Frontiers in Built Environme...· 0 citations
The increasing generation of construction and demolition waste, along with the depletion of natural aggregates, has driven growing interest in recycled concrete aggregate (RCA) and reclaimed asphalt pavement (RAP) as sustainable alternatives in concrete production. However, a direct and systematic comparison between the two materials remains limited. This review addresses this gap by applying PRISMA guidelines to analyze 82 peer-reviewed studies published between 2010 and 2026. Both materials are evaluated across three key domains: physical properties, mechanical performance, and microstructural characteristics. The findings indicate that RCA can reduce compressive strength by up to 26%, mainly due to the presence of porous adhered mortar and a complex interfacial transition zone (ITZ). In contrast, RAP weakens bonding with cement paste because of its hydrophobic bituminous coating, leading to adhesive failure at the mortar asphalt interface. Despite these limitations, RCA and RAP exhibit distinct behaviors in terms of shear capacity, ductility, energy absorption, and durability. Enhancement techniques such as surface treatment, carbonation, supplementary cementitious materials, and fiber reinforcement show potential in improving performance. Additionally, life cycle and economic analyses reveal that RAP can reduce total costs and carbon emissions when efficiently processed. This study provides a unified comparative framework to support sustainable material selection and design optimization.
Ahmed M. Ashteyat, Aye Alkhalaileh, Mousa Shhabat et al.· Materials· 0 citations
The growing demand for construction materials has intensified concerns regarding natural sand depletion and the accumulation of industrial waste. Among these wastes, oil-contaminated sand (OCS) generated from petroleum-related activities presents environmental challenges while also offering potential for beneficial reuse. Previous studies have reported that low OCS contents can enhance workability and improve mechanical properties, highlighting its potential as a sustainable construction material. This study investigates the feasibility of incorporating OCS as a partial replacement for natural sand in 3D concrete printing (3DCP). Three mixes containing 0%, 0.5%, and 1% OCS were evaluated in terms of flowability, setting behaviour, printability, rheological response, hydration behaviour, mechanical performance, anisotropic response, and microstructural characteristics. The results showed that OCS incorporation had only a limited influence on flowability, while both the initial and final setting times exhibited noticeable delays. The maximum printable layers reached from 19 for the control mixture to 22 and 26 layers for the 0.5% and 1% OCS mixes, respectively, accompanied by reduced settlement and structural deformation. Rheological analysis revealed higher static yield stress and structuration rates for the OCS-modified mixes, contributing to enhanced buildability and geometric stability. Hydration calorimetry showed comparable heat-flow behaviour between the control and OCS-modified mixes, suggesting only a limited influence of OCS on cement hydration kinetics. The incorporation of OCS improved the compressive strength of the printed mixes and reduced compressive anisotropy, while SEM observations revealed a denser and more homogeneous microstructure, particularly for the 0.5% OCS mix. Thus, the findings indicate that low-level incorporation of oil-contaminated sand is a viable strategy for improving the printability and performance of 3D-printed concrete, promoting the sustainable reuse of contaminated industrial waste.
In response to growing concerns regarding construction waste management and the depletion of natural resources, this study investigates sustainable concrete mixtures incorporating crumb rubber, shredded rubber, fly ash, silica fume, and marble slurry powder. Twenty concrete mixtures were prepared to examine the combined effects of rubber aggregates and supplementary cementitious materials (SCMs) on mechanical properties, durability performance, and microstructural characteristics. The results show that, although rubber incorporation reduced strength, the use of SCMs partially offset this effect. Compressive, split tensile, and flexural strengths increased by up to 12%, 8%, and 10%, respectively, compared with their respective rubber-modified reference mixes. Durability indicators, including chloride migration and water absorption, were reduced by approximately 15–20%, indicating improved resistance to fluid ingress. These improvements are attributed to the pozzolanic activity and filler effects of the mineral additions, which promoted pore refinement and improved matrix continuity. Microstructural observations revealed denser interfacial transition zones and more uniform hydration products, supporting the observed trends in mechanical and transport behaviour. Regression-based analysis of variance (ANOVA) was used to evaluate the relative influence of the selected variables within the experimental domain, identifying crumb rubber content as the dominant factor affecting mechanical performance, with coefficients of determination ranging from 0.81 to 0.97. The findings demonstrate that carefully proportioned SCM systems combined with controlled rubber incorporation can produce durable and resource-efficient concrete suitable for non-structural and lightly loaded components where serviceability, durability, and waste utilisation are key design considerations.
Karan Moolchandani· Discover Concrete and Cement· 0 citations
The escalating demand for global infrastructure has intensified the depletion of natural resources and exacerbated environmental issues, particularly those associated with the disposal of fly ash (FA) from coal-based power plants and construction and demolition (C&D) waste from ageing structures. This study investigates the sustainable utilization of these waste materials by incorporating FA and 100% recycled concrete aggregates (RCA) in the production of solid masonry blocks (SMB). Specifically, FA is used as a filler material to replace 30% of fine recycled concrete aggregates (FRCA), and its effect on the physical and mechanical characteristics of SMB is evaluated across three different cement-to-aggregate (C:A) ratios ranging from 1:18F to 1:24F. The performance parameters examined include hardened density, compressive strength, flexural strength, and water absorption. The results reveal that replacing 30% of FRCA with FA enhances mechanical strength, increases density, and reduces water absorption compared to SMB made solely with RCA. Moreover, all SMB incorporating FA met the specifications outlined by Indian standards, confirming their structural reliability. The findings affirm that FA acts as a functional micro-scale filler, promoting improved particle packing and more efficient stress transfer in SMB produced from RCA. Rather than being limited to traditional cement substitution approaches, the present study provides new experimental insights into the performance-oriented contribution of FA in masonry systems. By integrating fundamental filler mechanisms with practical block manufacturing, the findings advance the state of the art in sustainable cementitious materials and support the development of structurally sound, environmentally responsible masonry blocks.
M. M. M. Dafedar, K. Rao, B. H. Venkataram Pai et al.· International Journal of Con...· 0 citations
manufacturing process contributes heavily to CO2 emission which is a challenge to the environment. Geopolymer with good physical and mechanical properties is a promising substitute for Portland limestone cement. This research investigates the microstructural and mechanical properties of geopolymer sandcrete blocks produced using fly ash, ground granulated blast furnace slag (GGBS), and alkaline solution as binder. The hollow sandcrete blocks were formed with a mould of dimensions 230 × 100 × 100 mm. The results indicate that geopolymer sandcrete blocks cured at a lower temperature of 60 °C had higher strength compared to those cured at 105 °C. Furthermore, the optimal combination of 8 mol sodium hydroxide solution and fly ash to GGBS ratio of 55 % to 45 % yielded the maximum compressive strength at both curing temperatures. While the findings highlight the environmental viability of geopolymer sandcrete blocks as low-carbon alternatives to Portland sandcrete blocks, their compressive strength remained lower under the tested curing conditions, indicating that further optimization is required to achieve mechanical performance comparable to conventional sandcrete blocks.
E. Abegunde, B. I. O. Dahunsi· Journal of the Ghana Institu...· 0 citations
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