HighlightsMetakaolin (10 wt%) restores the compressive strength of PET-modified mortars to reference levels.SEM analysis confirms that metakaolin densifies the ITZ and reduces interfacial debonding gaps.High cement replacement (50 wt%) may lead to strength loss, potentially associated with self-desiccation and autogenous shrinkage.Pozzolanic activity of MK improves stress transfer between PET flakes and the cementitious matrix.Matrix refinement is essential to mitigate the hydrophobic effects of recycled plastic aggregates.The incorporation of plastic waste into cement-based materials offers a promising strategy for improving sustainability; however, it is often associated with reduced mechanical performance due to weak interfacial bonding. This study investigates the effect of metakaolin on the interfacial transition zone (ITZ) and mechanical properties of cement mortars modified with polyethylene terephthalate (PET) flakes used for the partial replacement of natural sand. Mortars containing 10 and 50 wt% metakaolin (as cement replacement) and 5 vol.% PET flakes (as sand replacement) were prepared and tested after 28 days of curing. Compressive and flexural strength were evaluated, and microstructural analysis was conducted using scanning electron microscopy (SEM) with a focus on the ITZ. The results indicate that the incorporation of PET flakes leads to a reduction in mechanical properties due to the formation of a porous and weak ITZ. However, the addition of 10 wt% metakaolin significantly improved mechanical properties, enabling PET-modified mortars to achieve strength comparable to the reference mix. SEM observations revealed that metakaolin contributed to the refinement of the microstructure and reduction in ITZ porosity, which enhanced interfacial bonding and improved stress transfer between PET particles and the cement matrix. These findings demonstrate that metakaolin can effectively mitigate the negative effects associated with PET incorporation by improving the microstructural characteristics of the ITZ, thereby enhancing the performance of sustainable cement-based composites.

This study evaluated external rendering mortars with partial replacement of natural sand by açaí seed residual ash (ASRA). Initially, through a pilot study, mortars containing 0, 10, 20, and 30% ASRA were tested, analyzing their properties in both fresh and hardened states. Considering the demand for sustainable solutions for agro-industrial residues, this research aims to corroborate, with technical and scientific evidence, the feasibility of using ASRA as a substitute for sand in mortars. Based on the pilot study analysis, it was found that the mixture with 20% replacement (ASRA20) exhibited the best rheological and mechanical performance. Subsequently, an external rendering mortar with 20% ASRA was produced and compared, in terms of performance, with a reference mortar widely used in Brazil (plasticized mortar without ash). Both mortars (REF and ASRA20) were applied to vertical masonry panels built with ceramic blocks, where the following aspects were assessed: cracking, surface friability, permeability, and direct tensile bond strength. In addition, microstructural analyses were carried out using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results, analyzed through statistical methods, demonstrated that the ASRA20 mortar presented improved particle cohesion, higher plasticity, a lower cracking index, greater resistance to surface wear (scratch test), reduced permeability, and bond strength values exceeding the requirements established by standards. These findings indicate that ASRA has strong potential for application in cementitious matrices, contributing to the reuse of an abundant residue from the Amazon region and providing a sustainable alternative for construction materials.

Spent garnet (SG) wastes are generated in significant quantities by several industrial activities, including abrasive waterjet cutting (AWJ), abrasive blasting, and filtration and powdered media applications. These wastes represent a promising secondary raw material for the production of sustainable construction materials, particularly green mortars and concretes, through their partial replacement of natural sand in cementitious systems. Such applications are relevant to both hydraulically setting inorganic binders (cement-based materials) and alkali-activated cementitious materials (AACMs). The valorization of SG wastes offers multiple benefits, notably a dual environmental advantage: reducing the consumption of natural aggregates and diverting industrial waste from disposal by integrating it into a new life cycle as a value-added by-product. Additional potential advantages include reduced production costs and possible improvements in the overall performance of mortars and concretes. Despite these benefits, the use of SG as an aggregate replacement remains insufficiently explored, with existing studies providing only preliminary and fragmented evidence of its feasibility. This paper presents an overview of a comprehensive four-year research program investigating SG wastes derived from single-cycle AWJ processes and their incorporation into conventional mortars as partial fine aggregate replacement in cement-based construction composites. The validation stage of the performance assessment expands the range of SG sources by including new sampling from the original suppliers, enabling verification of the repeatability and reproducibility of earlier findings. A broad set of physical, mechanical, and durability properties—particularly resistance to freeze–thaw cycles—is evaluated to achieve a robust and comprehensive material characterization. These results are further correlated with chemical and microstructural analyses, providing critical insights to support the technological transfer of SG-based construction materials to industrial applications with reduced carbon footprint.

ABSTRACT This paper investigates the effect of recycled coarse aggregates as partial replacement of natural stone and recycled rubber particles as partial replacement of natural sand in concrete mix on the structural behaviour of concrete-filled steel tubular (CFST) members. Both experimental study and numerical simulations were conducted. Two types of concrete were employed: RA concrete with recycled coarse aggregates and RRA concrete with recycled rubber particles and recycled coarse aggregates. In total, eight CFST specimens made from square steel tubes and RA concrete or RRA concrete were tested under axial, eccentric and pure bending loading conditions. The material experimental results showed that the inclusion of 20% crumb rubber in concrete mix reduced the compressive strength of RA concrete by approximately 27%, while the steel composite effect effectively compensated this reduction, leading to only 9–19% lower ultimate loads in RRA-CFST components compared with RA-CFST specimens. Finite element (FE) models in ABAQUS accurately reproduced the observed load-displacement responses, with less than 10% deviation in ultimate load. Finally, prediction formulas for section compressive capacity and moment capacity were developed for RRA-CFST and RA CFST members. Good agreements were achieved among the results from experimental study, numerical simulation and prediction formulas.

The primary goal of the current paper is to evaluate the viability of the sustainable concrete (S.C) made of waste glass sand (WGS) and waste plastic sand (WPS). This paper looks at concrete mixtures as follow: the first group (5%, 10%, and 15%) WGS as the sand replacement and Group Two (5%, 10%, and 15%) WPS as a natural sand replacement, and finally, group three HRS where, (5%, 10%, and 15%) of WSP/WGS were evaluated as sand substitutes. Tests were done on the concrete to ensure that the tested concrete's behavior was within expectations. Among these tests are the slump test, compressive strength test, indirect tensile strength test, flexural strength, and elastic modulus test. The results showed that using WGS and WPS together improved the slump of the concrete mixtures. Adding WPS or HRS to concrete mixes enhanced the mechanical properties, and Compressive strength increased, reaching a maximum of 52.05 MPa after partially substituting natural sand with WGS-10% of sand. And finally, when replacement ratios were high, the results showed that the concrete's compressive strength decreased when WGS-15% and WPS-15 % were substituted at 9.85% and 14.45% respectively.

The paper identifies the compressive and flexural strength of concrete when foundry sand is used instead of natural sand. The proportion of mix ratios in the experiment was 1:2:4 and water-cement ratio 0.6 concrete cubes. Substitute 0, 20, 40, 60, and 100 percent of natural mass sand by foundry sand in compressive strength test and concrete beam flexural test. Compressive and flexural strength were boosted by the percentage composition of foundry sand. The compressive strength increased to 26.27 N/mm2 (60 percent replacement) after seven days as compared to 24.64 N/mm2 (0 percent replacement). The strength increased at 14 days noted to be 26.22 N/mm2 in 0% replacement to 29.10 in 60 replacement and 31.11 in 28 days. This resulted in compressive strength of 28.00 N/mm2 when foundry sand was used as a substitute of all natural sand. The flexural strength rose to 60 percent replacement level, and then decreased. At 0, 60, and 100 replacements, flexural strength was 2.20 N/mm2, 3.10 N/mm2, and 2.50 N/mm2, respectively. This indicates that the mild foundry sand enhances the tensile and bending strength of concrete with the enhancement of cement matrix-aggregate interfacial bonding. Analysis of sieves revealed that the two materials are within acceptable grading limits though, foundry sand exhibits a smaller particle spread in the pack and therefore is more efficient in packing density and less void at the optimum replacement level, making it a good partial replacement of natural sand in concrete manufacture.

ABSTRACT This study explores the impact of incorporating recycled brick sand as a partial replacement for natural sand on the mechanical and transport properties of roller-compacted concrete (RCC) for dam construction. RCC mixtures were prepared with varying brick sand replacement levels and two different water/cement (W/C) ratios with cement dosages. Workability was assessed using the Vebe apparatus, while compressive and tensile strengths were evaluated at different ages. Additionally, porosity, water permeability, capillary absorption, and thermal conductivity were measured over time. Microstructural was characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The results indicate that brick sand has minimal influence on the RCC Vebe time. Compressive strength improves with brick sand incorporation, particularly in the long term, with an optimal substitution level of 25%. However, porosity and sorptivity increase at higher replacement levels, negatively affecting durability. Water permeability and thermal conductivity decrease with greater brick sand content, enhancing RCC’s resistance to fluid penetration and thermal properties. Variations in cement dosage and W/C ratio had a limited impact on the brick sand RCC performance. These findings suggest that partial replacement of natural sand with brick sand can enhance RCC properties while promoting sustainable material reuse in dam construction.

Bottom ash as a partial replacement of natural sand in sustainable concrete production

Combined effect of iron ore waste and basalt fiber with high-volume supplementary cementitious materials on the workability, strength, and microstructure of sustainable concrete

Dumped non-biodegradable tires present a significant environmental threat, with overflowing landfills and associated health risks highlighting the urgency of tire waste disposal. Current disposal methods, such as stacking tires in open spaces, exacerbate the problem. The large-scale recycling of tire rubber waste offers environmental benefits. This study examines the effects of pre-treatment using NaOH and micro-silica as a mineral admixture on the mechanical strength of crumb rubber concrete (CRC) with partial replacement of natural sand. Samples of M20 and M30 grade were prepared with varying levels of crumb rubber (CR) replacement and evaluated at 28 days. CRC prepared with pre-treated NaOH solution and micro-silica showed improved workability and strength compared to conventional concrete and untreated CRC, with the highest strength observed for 5% CR replacement using micro-silica. Predictive models and micro-structural analysis validated these findings. Life Cycle Assessment (LCA) using OpenLCA v2.10 software and the ecoinvent database revealed that incorporating micro-silica into CRC did not significantly increase environmental impacts, compared to conventional concrete across different mixes.

There has been an increase in construction with three-dimensional (3D) printing technology but 3D printed (3DP) structures also require weight reduction similar to conventional reinforced concrete structures. In addition, the behaviour of this type of structure against fire needs to be investigated. The number of printed layers and the time gap between layers for the 3DP specimens were among the variables examined. The test results demonstrate that as the replacement percentage of natural sand (NS) with expanded perlite (EP) increased, at 25% volume of replacement, the interlayer bond strength increased on average by 18.6%, while at the highest replacement level, of 75%, the strength decreased on average by 5.8%. Additionally, by incorporating EP, the compressive and flexural strengths of 3DP specimens declined on average from 9% to 29.7%, and from 39.3% to 49.3%, respectively. As the replacement level of NS increased, residual compressive and flexural strengths increased after exposure to 800°C. Furthermore, it was demonstrated that exposure to high temperature had the least effect on interlayer bond strength, whereas it significantly reduced the compressive and flexural strength. The results show that increasing the time gap between layers reduced interlayer bond strength and flexural strength while negligibly affecting compressive strength.

Stabilized municipal solid waste as an alternative to natural sand in paver block construction

Pre- and post-heating mechanical properties of concrete containing recycled fine aggregate as partial replacement of natural sand and nano-silica as partial replacement of cement: experiments and predictions

Natural or River sand are weathered particles from rocks which are of various shapes and sizes depending upon the weathering action of rivers. In the present scenario, natural sand with required properties is not easily/locally available. In most situations, The natural sand is transported to the construction site from a distance. The cost of building will go up if river sand needs to be transported in this manner from a distance. These natural river sands are likewise becoming harder to find for a variety of reasons. Finding a different material that can partially or completely replace natural river sand is therefore crucial. Stone quarries can be found in great numbers and are widely dispersed throughout Tamil Nadu. They are a reliable supplier of both manufactured fine aggregate and coarse aggregate. The stockpiles of quarry fines produced by the crushers must be used. Consequently, in order to utilize this Manufactured sand in the building sector, It is necessary to conduct a thorough investigation on the use of Natural River sand in place of ordinary construction sand. This study presents experimental studies on the evaluation of the characteristics of M-sand acquired from various places (sources).by replacing natural sand from two sources. This study also includes experimental tests on the characteristics of freshly poured and cured concrete created with the developed mix proportions.

Heavy Mineral Sand as a Partial Replacement of Natural Sand in Ordinary and Standard Concretes

Abstract: Although fly ash as a partial replacement for cement has been utilized for many years, it has been almost exclusively used in low-volume percentages, such as 10 or 20% cement replacement. In this study partial replacement of Natural sand with Crushed stone waste for M 15 grade of concrete. The compressive strength of concrete of OPC concrete and with natural sand and Crushed stone waste is compared and it has been found that the strength of concrete got increased. Work may be extended with use of stone waste from different crushing plant. Different zones of stone waste can be formed from the result which will give better understanding of type of stone waste that can be replaced for each zone. Thus it can be concluded that use of stone dust can be effectively done for partial replacement of natural sand and better concrete can be achieved for structural use. Optimum replacement value is about 30 to 40 percent. Thus its use will also ensure less cost and use of waste material causing less environmental pollution.

Motivated by the multiple benefits of recycling plastic ingredients in cementitious materials, the present study focuses on the design of sustainable cement concrete incorporating recycled mixed plastic fine aggregate (MPFA) as a partial replacement of natural sand (NS). The MPFA produced in this work is composed of a combination of polymer types with similar concoctions to those observed in the postconsumer waste streams. This study approach is vastly different from past reported studies on the use of sorted, highly purified single-type recycled plastic aggregate in cement concrete. A multi-criteria decision-making technique, Best-Worst Method (BWM), was integrated with the Taguchi method to maximize the quality of MPFA concrete based on the Fuller–Thompson theory. More specifically, an L9 (34) Taguchi orthogonal array with four three-level design factors was adopted to optimize the fresh, durability, and mechanical properties of MPFA concrete. The results showed that MPFA concrete produced with 400 kg/m3 cement content, 0.43 water/cement ratio, 0.43 fine aggregate/total aggregate ratio, and 10 vol% MPFA content exhibited the highest quality. Findings from the present work also revealed that MPFA concrete produced with tailored particle size distribution of MPFA NS fine aggregate system achieved superior, if not comparable, qualities to those of conventional concrete.

Feasibility Analysis of Marble and Granite Waste as Partial Replacement of Natural Sand in Mortar Mix

The cement mortar in the building encounters a problem of curing due to covering mortar under finishing materials such as tiles, stones, and marble. Internal curing is one of the methods for solving this problem. This investigation highlights the impact of internal curing with lightweight pumice fine aggregate on cement mortar's mechanical properties, such as compressive and tensile strengths, and performance, such as density. Thus, the internal cured water-to-cement ratio was studied, which varied from 0 to 21.5%, and the partial replacement of natural sand with lightweight pumice fine aggregate varied from 0% to 16.63%. The results showed the mechanical properties improved with the increased internal water-to-cement ratio. Increasing the internal cured water-to-cement ratio up to 21.52% improves the compressive, split tensile, and flexural strengths of cement mortar up to 77.3%, 56.42%, and 28.71%, respectively. In addition, the partial replacement of natural sand with lightweight pumice aggregate up to 10.9% enhances the compressive, split tensile, and flexural strengths of cement mortar up to 24.2%, 6.1%, and 28.7%, respectively, due to a reduction in drying and autogenous shrinkage.

Introducing alternatives material on cement-based material manufacturing is the need for environmental sustainability due to the excessive mining of sand from quarry and river bed. At the same time, industrialization headed to an uncontrollable growth of waste. This fact encourages the researcher to enhance the utilization of recycled waste in construction practice. On one side, it affords a solution for waste management, and on the other hand, it contributes to an eco-friendly construction material that minimizes the environmental impact. This paper aims to investigate the usability of the iron waste obtained from the wrought iron industry, as natural fine aggregates replacement. In particular, it focused on studying the physical characteristic of waste aggregates and the effect of partial replacement of natural sand on mortar strength. Mortar cube specimen made with various levels of replacement (0%, 10%, 20% and 30 %) and also various cement-aggregates volumetric proportion, which are 1:3, 1:4, 1:5, 1:6, and 1:7. All of the measurement parameters are taken consecutively based on ASTM norms. The current work remarks that both waste aggregates and natural aggregates reveal complete fulfillment in the aggregate requirement of ASTM standard. Furthermore, the mortar cube test confirmed that the mortar passes the strength grade for N class and O class, which suitable for the above-grade and non-load bearing application.