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Significant construction and demolition waste (CDW) is produced by many useless concrete buildings, bridges, airports, highways, railways, industrial mining, etc. The rising need for new construction has increased the use of natural materials, impacting the ecosystem and incurring high costs from mining natural aggregates (NA) and processing CDW. The concept and implementation of recycled aggregate concrete (RAC) offer a sustainable solution for the concrete industry. Crushed concrete, made from recycled concrete, can be used instead of natural aggregates in structural concrete. This sustainable byproduct, recycled concrete aggregate (RCA), has the potential to replace natural aggregate. This paper examines the benefits of RAC from economic, social, environmental, and technological perspectives and discusses the replacement ratio (RR)—the weight percentage of natural aggregate replaced by recycled aggregate—which is crucial to RAC performance. A collection of used data on mechanical properties and economic performance, national specifications, standards, and guidelines is reviewed to determine the optimal replacement ratio for RCA, which was found to be 20%. Finally, we discuss the challenges and future of using RAC in structural concrete.

The application of recycled concrete aggregates (RCAs) has become increasingly popular for different types of structures, as presented in several studies. However, depending on the type of structure and the region, RCAs might have different properties. This study aims to investigate the application of RCAs of different origins for substructure layers of the cycle paths located in Central Europe, which was not analysed previously. Recycled aggregates from an airport, road overpass, and building demolition were tested according to European standards and used to produce concretes, in which compressive strength, density, water absorption, and frost resistance were tested. After 28 days, RCA concrete had compressive strengths from 5.9 to 17.3 MPa and frost resistance ratios close to 1.0. The concrete parameters indicate that RCAs might be used for the construction of cycle path substructural layers with the appropriate class of cement and W/C ratio. To meet the requirements of EN 12390-3 to achieve class C8/10, RCA concrete with CEM II B/V 32.5 should be used with a W/C ratio of 1. To meet the requirements of D-04.05.01v02, RCA concrete with CEM II B/V 32.5 and a W/C ratio smaller than 1.50 should be used. Applying recycled RCAs in various structures helps protect natural resources by reusing materials. However, the variability in RCA properties requires testing to guarantee quality.

This study focuses on exploring the potential of utilizing demolished concrete and promoting sustainable practices through the use of recycled concrete aggregate (RCA) as a substitute for natural aggregates, particularly in the context of Nepal. The region’s susceptibility to frequent earthquakes results in significant volumes of concrete rubble, posing challenges in waste disposal. To address this issue and mitigate resource depletion, the research focuses on concrete recycling. By conducting a thorough analysis of mechanical properties, crack patterns, strength variations, and specific gravity evaluations across different RCA compositions, the study emphasizes the ongoing endeavors toward sustainable concrete practices. A comparative examination of test results involving varying percentages of coarse recycled aggregate content (0%, 25%, 50%, 75%, and 100%) denoted as R0, R25, R50, R75 and R100, respectively, provides insights into the performance of different mixes. The compressive strength of cube for R25 increased by 20.13%, while R50 and R75 showed gains of 8.08% and 1.28%, respectively, while cylinder showed an increase of 25.86%, 18.88%, 9.54% and 2.65% for R25, R50, R75 and R100, respectively, compared to R0 concrete mix when tested at 28 days of curing. Tensile strength of concrete cylinder also improved, with R25 showing an 18.52% increase and R50 showing a 9.26% increase. Additionally, the RCA increased the flexural strength, with R25 leading with a 5% increase and R50 following with a 1.66% increase at 28 days of testing. The inclusion of numerical analysis in ABAQUS CAE using the Kent and Park Model serves to reinforce and support the experimental findings, establishing the credibility of both approaches. In essence, the study strongly advocates for the integration of recycled aggregate in concrete as a means to foster sustainable development and environmentally friendly construction methods.

The incorporation of a recycled concrete aggregate (RCA) as a replacement of natural aggregates (NA) in road construction has been the subject of recent research. This tendency promotes sustainability, but its use depends mainly on the final product’s properties, such as chemical stability. This study evaluates the physical and chemical properties of RCAs from two different sources in comparison with the performance of NA. One RCA was obtained from the demolition of a building (recycled concrete aggregate of a building—RCAB) and another RCA from the rehabilitation of a Portland cement concrete pavement (recycled concrete aggregate from a pavement—RCAP). Characterization techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), UV spectroscopy, and atomic absorption spectrometry were used to evaluate the RCAs’ coarse fractions for chemical potential effects on asphalt mixtures. NA was replaced with RCA at 15%, 30%, and 45% for each size of the coarse fractions (retained 19.0, 12.5, 9.5, and 4.75 sieves in mm). The mineralogical characterization results indicated the presence of quartz (SiO2) and calcite (CaCO3) as the most significant constituents of the aggregates. XFR showed that RCAs have lower levels of CaO and Al2O3 concerning NA. Potential reactions in asphalt mixtures by nitration, sulfonation, amination of organic compounds, and reactions by alkaline activation in the aggregates were discarded due to the minimum concentration of components such as NO2, (–SO3H), (–SO2Cl), and (Na) in the aggregates. Finally, this research concludes that studied RCAs might be used as replacements of coarse aggregate in asphalt mixtures since chemical properties do not affect the overall chemical stability of the asphalt mixture.

This systematic review and meta-analysis per PRISMA 2020 addresses the use of recycled concrete aggregates as a replacement for aggregates in self-consolidating concrete for structural and non-structural use. It provides a comprehensive evaluation of the available research and offers a synthesised overview of the potential use of recycled concrete aggregate in self-consolidating concrete beyond standardised replacement levels. A total of 256 research papers were obtained from different databases, and after a detailed content review, only 24 unique experimental research studies fulfilled the review criteria. Data were extracted on recycled concrete aggregate source, pre-treatment, replacement ratio, mix proportions, fresh properties, strength, stiffness, and durability. It was observed across all studies that the recycled concrete aggregates originated from precast concrete rejected elements with a low water-to-cement ratio, producing an equal or stronger concrete than the reference concrete in the studies; however, none of the studies included in this research resulted in a higher modulus of elasticity than the corresponding reference concrete. Additionally, moderate aggregate replacement (20–50%) preserved the workability, whereas high replacements (75–100%) affected fresh concrete properties as well as increased shrinkage and creep. The inclusion of fine recycled concrete aggregate in addition to coarse recycled concrete aggregate has a larger effect on lowering compressive strength and stiffness in the concrete. Overall, high-quality coarse recycled concrete aggregate (precast rejects or screened demolition waste)—an aggregate replacement level of around 50%—facilitates the production of sustainable self-consolidating concrete, whereas full replacement requires aggregate pre-treatment and a carefully optimised mix design.

Moisture is the basis of CO2 transport and carbonation reactions in the internal pores of cement-based materials. Too much or too little moisture influences the effect of the carbonation modification of CO2 on recycled concrete aggregate (RCA). During the carbonation reaction process of RCA, moisture is mainly derived from the environmental relative humidity (RH) and the initial water content (IWC) of the RCA itself. According to the available literature, most of the studies on the effect of moisture on the carbonation modification of RCA considered either RH or IWC. Further investigations of the synergistic effects of RH and IWC on the improvement in the properties of carbonated recycled concrete aggregate (CRCA) are needed. In this study, accelerated carbonation experiments were conducted for RCA samples with different IWCs under different environmental RHs. The results showed that the best moisture conditions for CRCA property improvement were confirmed as RH = 70% for the dry-state IWC and RH = 50% for the saturated-state IWC. When the RCAs were carbonized under the conditions of high RH with low IWC and low RH with high IWC, CO2 had good abilities to permeate and diffuse, with the improvement in CRCA properties achieving excellent levels of performance.

In the context of sustainable construction, recycled concrete aggregates (RCAs), including both fine and coarse fractions derived from construction and demolition waste (CDW), are gaining traction due to their potential to mitigate environmental impacts by reducing reliance on natural aggregates and minimizing waste. This paper provides a comprehensive review of the effects of RCAs on the mechanical and durability properties of concrete, including compressive and tensile strengths, modulus of elasticity, and resistance to environmental degradation. The review highlights that the presence of adhered mortar and higher porosity in RCAs generally leads to reduced mechanical performance and durability. However, pretreatment methods—mechanical, chemical, and thermal—along with optimized mix designs and the use of supplementary cementitious materials (SCMs) have shown to significantly improve the concrete properties of RCAs. Additionally, recent studies on carbon dioxide (CO2) capture through the accelerated carbonation of RCAs offer promising environmental benefits. Life cycle assessment (LCA) analyses reveal reductions in energy use, CO2 emissions, and material costs when RCAs are properly processed and locally sourced. Despite challenges related to RCA quality variability, the review identifies pathways for the effective use of RCAs in structural applications.

This study investigates the effect of vibration duration on the porosity, permeability, and compressive strength of pervious concrete incorporating 50% recycled concrete aggregate. Mixtures were prepared with Portland cement (CEM I) and blended cement (CEM II), and compacted by tamping or table vibration for durations ranging from 10 to 60 s. A refined falling-head permeability test was developed, using a novel circumferential heat-shrink sealing to eliminate lateral flow and ensure axial water penetration. Pore structure and connectivity were characterized using optical microscopy and X-ray micro-computed tomography. Increasing vibration duration reduced porosity and permeability while enhancing compressive strength. An optimal compaction window of approximately 30 s, corresponding to a normalized vibration dose of 226, provided the best balance between hydraulic and structural performance. Micro-computed tomography confirmed a highly interconnected pore network and strong agreement with effective porosity, demonstrating the value of three-dimensional metrics in mix design. The results show that combining recycled aggregate with low-carbon blended cements can meet functional performance targets while reducing cradle-to-gate carbon dioxide emissions by up to 25%. These findings offer practical guidance on compaction regimes and testing protocols, supporting reproducible and sustainable applications of pervious concrete in pavement infrastructure.

This study examines the strategic incorporation of various recycled materials into asphalt concrete, specifically focusing on municipal solid waste incineration bottom ash (MSWI BA), recycled asphalt shingle (RAS), and recycled concrete aggregate (RCA). Due to the high porosity of MSWI BA and RCA, and the significant asphalt binder content (30-40%) found in RAS, there is a need to increase the amount of liquid asphalt used. RAS is posited as an efficient substitute for the asphalt binder, helping to counterbalance the high absorption characteristics of MSWI BA and RCA. The research objective is to quantitatively evaluate the effect of the combined use of RAS, MSWI BA, and RCA in Hot Mix Asphalt (HMA). This study encompasses several laboratory evaluations (i.e., rutting and tensile strength tests) and a cost-benefit analysis, which is a life cycle cost analysis. The results indicate that the combined use of these materials results in a higher tensile strength and rut resistance when compared with the control (with virgin aggregate). According to the cost-benefit analysis result, when the three recycled materials are used for an HMA overlay over an existing aged pavement, it could be 60-80% more cost-effective compared to a conventional HMA overlay, thereby offering significant economical savings each year in the field of road construction.