Assessing life cycle sustainability: A comprehensive review of concrete produced from construction waste fine fractions.

This paper presents an overview of the scholarly works employing the life cycle assessment (LCA) approach to evaluate the environmental impact of construction and demolition waste (CDW) fine fractions derived from concrete elements throughout their life cycle. Unlike conventional studies, this work addresses the challenge of reducing the carbon footprint associated with CDW-based building materials, emphasizing environmental impact mitigation. The study highlights that approximately 30% of CDW is landfilled, 50% is recycled, and 20% is used as fill material, underscoring the potential for increasing recycling rates through improved processing techniques and management practices. In the reviewed studies, most research has been conducted in Europe, Asia, the USA, and China. The primary and secondary data sources for the life cycle inventory (LCI) vary depending on the study region and locality. By exploring innovative practices and critical stages in CDW fine fractions utilization for concrete components, the study aims to contribute to greener construction practices and sustainable resource management. The distinctive aspect of this research lies in its comprehensive review of CDW-based aggregates, binders, and alternative cementitious materials, highlighting the significance of sustainable energy resources and transportation strategies in enhancing the sustainability of CDW-derived concrete. Key findings highlight the necessity of sustainable energy for pretreatment and optimized transportation strategies, including route planning and vehicle selection, to produce greener CDW fine fraction-based building materials. Additionally, the study suggests key steps and parameters required for defining the system boundary and preparing the inventory for conducting an LCA of building materials based on CDW fine fractions. Through a detailed analysis of environmental burdens at each production stage, this study seeks to promote the adoption of greener concrete solutions worldwide. The use of CDW in concrete production promotes environmental sustainability and greener concrete regardless of the region.

Influence of the Addition of TiO2 Nanoparticles on the Self-Cleaning Capacity of Cementitious Composites.

This study evaluated the potential of incorporating TiO2 nanoparticles (NT) into cementitious composites to provide self-cleaning and self-sanitising properties, as well as the partial replacement of natural aggregates with recycled glass (RGA), ceramic brick (RBA), granulated blast furnace slag (GBA), and textolite waste (RTA) from electronic equipment on these properties. Based on the research results, the addition of NT to cementitious composites led to a significant reduction in contact angle, which means an increase in surface hydrophilicity. At the same time, Rhodamine B stain fading was highlighted, with the degree of whiteness recovery of NT composites exceeding that of the control by up to 11% for natural aggregate compositions, 10.6% for RGA compositions, 19.9% for RBA compositions, 15% for GBA compositions, and 13% for RTA compositions. In a mould-contaminated environment, it was shown that the introduction of NT allowed the material to develop a biocidal surface capacity which is also influenced by the nature of the aggregates used. Furthermore, the study revealed that, under controlled conditions, certain recycled waste aggregates, such as textolite, promoted mould growth, while others, such as brick and slag, inhibited it, highlighting not just the effect of the addition of NT, but also the significant influence of the aggregate type on the microbial resistance of cementitious composites. These improvements in the performance of cementitious composites are particularly advantageous when applied to prefabricated elements intended for the finishing and decorative surfaces of institutional (schools, administrative buildings, religious structures, etc.) or residential buildings.

Leaching characteristics of metals from recycled concrete aggregates (RCA) and reclaimed asphalt pavements (RAP).

Recycled concrete aggregates (RCA) and reclaimed asphalt pavements (RAP) are two construction waste products that are commonly used in the road construction industry. Besides many advantages, pollutants leaching from RCA and RAP are highlighted as the most concerning environmental issue. This study investigated metals leaching characteristics from RCA and RAP due to the variations in key influential factors of pH, dissolved organic carbon (DOC), compaction and liquid to solid ratio (L/S). The leaching tests for RCA and RAP were carried out separately and additionally, the standard leaching test was conducted as the benchmark for leaching investigations. Study outcomes revealed that the combined influences of factors are variable for RCA and RAP, while influences are also variable for individual metals. L/S ratios considerably affect the release of metals from RCA under saturated conditions, facilitating high metal concentrations in the leachate. On the other hand, acidic solutions are more favourable for leaching of metals from RAP. The influence of DOC in solution was minimal on the metal leachability. Interestingly, the increased degree of compaction with a higher density of materials presented the highest negative influence on metal leachability, suggesting that the metal leachability can significantly reduce, in particular when the RCA and RAP are used for the sub-base layers of road structure with a higher degree of compaction. However, the use of these recycled materials under field conditions should be further studied as there is an increasing concern of metal leaching from RCA and RAP with respect to recreational and drinking water thresholds.

Influence of TiO2 Nanoparticles on the Physical, Mechanical, and Structural Characteristics of Cementitious Composites with Recycled Aggregates.

The aim of this study is to analyze the effect of the addition of TiO2 nanoparticles (NTs) on the physical and mechanical properties, as well as the microstructural changes, of cementitious composites containing partially substituted natural aggregates (NAs) with aggregates derived from the following four recycled materials: glass (RGA), brick (RGB), blast-furnace slag (GBA), and recycled textolite waste with WEEE (waste from electrical and electronic equipment) as the primary source (RTA), in line with sustainable construction practices. The research methodology included the following phases: selection and characterization of raw materials, formulation design, experimental preparation and testing of specimens using standardized methods specific to cementitious composite mortars (including determination of apparent density in the hardened state, mechanical strength in compression, flexure, and abrasion, and water absorption by capillarity), and structural analysis using specialized techniques (scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS)). The analysis and interpretation of the results focused primarily on identifying the effects of NT addition on the composites. Results show a decrease in density resulting from replacing NAs with recycled aggregates, particularly in the case of RGB and RTA. Conversely, the introduction of TiO2 nanoparticles resulted in a slight increase in density, ranging from 0.2% for RTA to 7.4% for samples containing NAs. Additionally, the introduction of TiO2 contributes to improved compressive strength, especially in samples containing RTA, while flexural strength benefits from a 3-4% TiO2 addition in all composites. The compressive strength ranged from 35.19 to 70.13 N/mm2, while the flexural strength ranged from 8.4 to 10.47 N/mm2. The abrasion loss varied between 2.4% and 5.71%, and the water absorption coefficient varied between 0.03 and 0.37 kg/m2m0.5, the variations being influenced by both the nature of the aggregates and the amount of NTs added. Scanning electron microscopy (SEM) images and energy dispersive X-ray spectroscopy (EDS) analysis showed that TiO2 nanoparticles are uniformly distributed in the cementitious composites, mainly forming CSH gel. TiO2 nanoparticles act as nucleating agents during early hydration, as confirmed by EDS spectra after curing.

Study on Reducing Water Absorption of Recycled Aggregates (RAs) by Microbial Mineralization.

Crushing waste concrete and using it directly as RAs has the disadvantages of high porosity and high water absorption. To achieve the reuse of resources, the researchers use microbial mineralization methods to further reinforce RAs. In this paper, the effect of the microbial carbonic anhydrase mineralization method on the water absorption of RAs was investigated, and the macroscopic analysis was performed by determining the indexes of water absorption and apparent density of RAs before and after the modification, and the microscopic analysis of RAs by using the methods of SEM, XRD, DSC, and EDS as well. According to the microscopic analysis, the mineralization products of microorganisms are calcium carbonate crystals, and with the increase in microbial liquid concentration, the water absorption rate of RAs shows a trend of decreasing and then increasing, and it can be found through the microscopic morphology that abundant mineralization products attached to the surface of the aggregate lead to the surface of the aggregate becoming rougher and more porous. The method of soaking the RAs in 3% bacterial solution and 0.1 mol/L calcium acetate solution followed by carbonation with 20% CO2 resulted in a 4.85% reduction in water absorption.

Mechanical and Durability Characterization of Hybrid Recycled Aggregate Concrete.

The recycling of construction and demolition waste (CDW) for the extraction of recycled concrete aggregates (RCAs) to be used to produce recycled aggregate concrete (RAC) is widely acknowledged internationally. However, CDW not only contains concrete debris but may also contain burnt clay bricks. The recycling of such CDW without the segregation of different components would result in recycled aggregates having different proportions of concrete and brick aggregates. The utilization of these aggregates in concrete requires a detailed investigation of their mechanical and durability properties. In this regard, the present study focused on investigating the mechanical and durability properties of hybrid recycled aggregate concrete (HRAC) made by the 100% replacing of natural aggregates with recycled brick (RBAs) and RCA in hybrid form. The partial replacement of cement with fly ash was also considered to reduce the corban footprint of concrete. An extensive experimental program was designed and carried out in two phases. In the first phase, a total of 48 concrete mixes containing coarse RBA and RCA in mono and hybrid forms were prepared and tested for their compressive strength. The test results indicated that the compressive strength of HRAC is greatly affected by the proportion of coarse RBA and RCA. In the second phase, based on the results of the first phase, eight concrete mixes with the most critical proportions of RBA and RCA in hybrid form were selected to evaluate their mechanical and durability performance. In addition, four mixes with natural aggregates were also prepared for comparison purposes. To evaluate the mechanical properties of the concrete mixes, compressive strength and modulus of rupture (MOR) tests were performed, while for the evaluation of durability properties, water absorption and behavior after exposure to aggressive conditions of acidic and brine solutions were studied. The results revealed that a 20% replacement of cement with fly ash resulted in acceptable mechanical and durability properties of HRAC intended to be used for making concrete bricks or pavers.

Feasibility of Using New Sustainable Mineral Additions for the Manufacture of Eco-Cements.

Due to a continuously developing population, our consumption of one of the most widely used building materials, concrete, has increased. The production of concrete involves the use of cement whose production is one of the main sources of CO2 emissions; therefore, a challenge for today's society is to move towards a circular economy and develop building materials with a reduced environmental footprint. This study evaluates the possibility of using new sustainable supplementary cementitious materials (SCMs) from waste such as recycled concrete aggregates (RCAs) and mixed recycled aggregates (MRAs) from construction and demolition waste, as well as bottom ash from olive biomass (BBA-OL) and eucalyptus biomass ash (BBA-EU) derived from the production of electricity. A micronisation pre-treatment was carried out by mechanical methods to achieve a suitable fineness and increase the SCMs' specific surface area. Subsequently, an advanced characterisation of the new SCMs was carried out, and the acquired properties of the new cements manufactured with 25% cement substitution in the new SCMs were analysed in terms of pozzolanicity, mechanical behaviour, expansion and setting time tests. The results obtained demonstrate the feasibility of using these materials, which present a composition with potentially reactive hydraulic or pozzolanic elements, as well as the physical properties (fineness and grain size) that are ideal for SCMs. This implies the development of new eco-cements with suitable properties for possible use in the construction industry while reducing CO2 emissions and the industry's carbon footprint.

Characterization and Environmental Evaluation of Recycled Aggregates from Construction and Demolition Waste in Belgrade City Area (Serbia).

Sustainable consumption of construction materials is an important segment of sustainable development goals towards reducing climate change. Since the consumption of natural aggregates raises environmental concerns, there is an increasing demand for use of recycled aggregates (RAs), as it enhances social and environmental benefits and creates a market opportunity. This paper presents the practice of using recycled construction and demolition waste (CDW) in the Belgrade city area (Serbia) as a resource. Two groups of CDW from Vinca landfill site near Belgrade are analyzed: raw material before, and RAs after, construction of a recycling facility on site. Comprehensive characterization is performed (including particle size distribution, density, water and organic pollutants content, various mechanical resistances, flakiness index, etc.) and compilation of samples analyzed and compared to show a holistic overview. The test outputs in both groups show acceptable values and meet required standards, indicating that recycled CDW generated in the Belgrade area can be used as a substitute to natural aggregates. In addition to that, the environmental and economic benefits from this use as a substitute are analyzed and discussed, proving the substantial income from sold Ras and the landscaping benefits, as well as ecological and economic benefits from energy savings.

Investigation study data to develop sustainable concrete mix using waste materials as constituents.

Sustainable construction materials are those which contributes towards the carbon- negative process of manufacturing. Cement produced by raw materials from industrial wastes and non-fossil fuel sources is considered as green cement which has high potential in constructions due to high tensile strength and resistance to corrosion. Exploring replacement materials for conventional cement is an active area of research. This data investigation focused on development of novel concrete mix with various proportions of sustainable supplementary materials with cement, fine and coarse aggregate substances. Alccofine, Metakaolin, GGBFS, Foundry sand, Copper slag, Recycled aggregate and Sintered fly ash aggregate are suitable supplementary materials of the concrete mix. Data projected replacement of cement by 15 % Alccofine, 10% Metakaolin and 30% GGBFS substitution and Fine aggregates (50% Copper slag, 30% Foundry sand) and replacement of Coarse aggregate (20% Recycled and 30% Sintered Fly Ash aggregate) will produce sustainable concrete mixture. Compressive and split tensile strength examined at 7th, 14th and 28th day and compared with conventional concrete. This data shows that the concrete mixture CFACA 1234567 was outperformed among the five mixture studied.

Eco-Friendly Pavements Manufactured from Mixed Recycled Aggregates Obtained from Construction and Demolition Waste: An Industrial-Scale Validation.

This study aimed to validate that laboratory-scale results could be commercially replicated when manufacturing marketable precast concrete. Construction and demolition waste (CDW) was separated into two (fine and coarse) recycled aggregates (RAs). Precast paver and kerb units were fabricated by partial or total substitution of natural aggregates (NAs) by RAs. The study involved the comprehensive characterisation of raw materials, including particle size distribution, mineral composition, and elemental composition. Paver blocks and kerbs manufactured with up to 50% RAs showed mechanical resistance (T = 3.7 ± 0.2 and B = 5.3 ± 0.6 MPa, respectively), water absorption between 5.3-5.7%, and abrasion resistance (approximately 20.2 mm), which met the standard requirements (UNE-EN 1340:2004 and UNE-EN 1338:2004). Furthermore, industrial-scale precast pavement units demonstrated strength and durability suitable for heavy traffic areas. A reduction of 13% in cement content could maintain the requirements with a partial RA substitution of 25%, offering economic and environmental benefits. Therefore, it is feasible at an industrial level to replace NAs with RAs, promoting durability and technological properties with a positive environmental impact and considerably reducing CO2 emissions by up to 65%. Overall, pavers with RAs manufactured at the laboratory scale met mechanical standards, and the kerb stones showed improvements in abrasion resistance. On an industrial scale, kerb stones and precast blocks with specific substitutions can meet strength, water absorption, and abrasion requirements, allowing a reduction in cement content.

Hybrid Cements and Construction Elements Based on Alkaline Activation with Sodium Sulfates from Fly Ash and Construction and Demolition Waste.

This article demonstrates the possibility of producing hybrid cementitious materials (pastes, mortars, concretes, and precast elements) based on fly ash (FA) and construction and demolition wastes (CDW) using alkaline activation technology. Sodium sulfate was used as an activator and fine and coarse aggregates were obtained from CDW residues. An addition of Portland cement (OPC) (10 to 30%) allowed for improvement in the mechanical behavior of the hybrid cements and them to be cured at room temperature (25 °C). The FA and CDW cementitious materials obtained compressive strengths of 37 MPa and 32 MPa, respectively. The compressive strength of FA and CDW alkali-activated concretes at 28 days of curing was 22 MPa and 18 MPa, respectively, which identifies them as structural concretes according to NSR-10 title C in Colombia. The potential use of these concretes was validated by obtaining and classifying precast materials.

Towards a more sustainable environmentally production system for the treatment of recycled aggregates in the construction industry: An experimental study.

The reuse and recycling of construction and demolition waste is becoming an advisable choice to reduce the consumption of key raw materials and the environmental impact generated by the construction of new buildings. This study proposes the introduction of two new stages of recycled aggregate processing that allow redesigning the production process of recycled aggregates towards a more sustainable and eco-friendly system: sieving with secondary crushing and washing. Based on an experimental study, our findings show that the new stages reduce significantly the content of impurities and the water absorption of recycled aggregates, obtaining a better final product (i.e. cement mortar) for buildings. Moreover, the new final product made with treated recycled aggregates also experiences significant improvements in their physical and mechanical properties (i.e.: increased on average, 5% in flexural strength, 6% in compression strength and reduced shrinkage by 2%), in turn reducing both the costs associated with the manufacture of the new product and its environmental impact compared to other products that solely include untreated recycled aggregates. The potential economic and solid waste management implications for firms that choose to deploy the new production system depicted are also discussed.

Prediction of the Bending Strength of a Composite Steel Beam-Slab Member Filled with Recycled Concrete.

This study investigated the structural behavior of a beam-slab member fabricated using a steel C-Purlins beam carrying a profile steel sheet slab covered by a dry board sheet filled with recycled aggregate concrete, called a CBPDS member. This concept was developed to reduce the cost and self-weight of the composite beam-slab system; it replaces the hot-rolled steel I-beam with a steel C-Purlins section, which is easier to fabricate and weighs less. For this purpose, six full-scale CBPDS specimens were tested under four-point static bending. This study investigated the effect of using double C-Purlins beams face-to-face as connected or separated sections and the effect of using concrete material that contains different recycled aggregates to replace raw aggregates. Test results confirmed that using double C-Purlins beams with a face-to-face configuration achieved better concrete confinement behavior than a separate configuration did; specifically, a higher bending capacity and ductility index by about +10.7% and +15.7%, respectively. Generally, the overall bending behavior of the tested specimens was not significantly affected when the infill concrete's raw aggregates were replaced with 50% and 100% recycled aggregates; however, their bending capacities were reduced, at -8.0% and -11.6%, respectively, compared to the control specimen (0% recycled aggregates). Furthermore, a new theoretical model developed during this study to predict the nominal bending strength of the suggested CBPDS member showed acceptable mean value (0.970) and standard deviation (3.6%) compared with the corresponding test results.

Perspective on the Application of Machine Learning Algorithms for Flow Parameter Estimation in Recycled Concrete Aggregate.

The constantly expanding civilization and construction industry pose new challenges for a sustainable development economy. Aiming to protect the environment is often associated with waste management, thereby reducing the number of landfills. The management of recycled concrete aggregate (RCA) from building demolition and its reuse in construction perfectly fits into this trend. The characteristics of post-industrial and recycled materials are not homogeneous as is usually the case with natural materials. This leads to a search for solutions to determine the parameters in the simplest possible manner and with as few resources as possible, while eliminating estimation risks. This task can be solved using machine learning, whose algorithms are increasingly used and developed in many areas of life and industry. The research in this study is aimed at comparing the effectiveness of k-Nearest Neighbors (k-NN) and Artificial Neural Network (ANN) algorithms in determining the permeability coefficient to a linear regression model. This parameter has an important role from the perspective of the application of RCA in civil engineering, particularly in earth construction. Two different RCA materials with different origins and properties were used in the study. The filtration test for each sample was pre-prepared using different compaction energies of 0.17 and 0.59 J/cm3 and for loosely packed samples. Differences in the structures of the test results are presented for both materials. The lowest prediction errors were obtained for the k-NN model. This algorithm obtained for the training sample a coefficient of determination (R2) equal to 0.947 and for the test sample an R2 equal to 0.980. In the case of ANN, the coefficient of determination was in the range of 0.877-0.936. An important part of the study was the interpretation with SHAP of the obtained models, allowing insight into which parameters influenced the predictions. That is significant and novel, considering the heterogeneity of the materials studied, and provides a rationale for further research in this area.

Characterization of Three Types of Recycled Aggregates from Different Construction and Demolition Waste: An Experimental Study for Waste Management.

Achieving sustainable management and efficient use of natural resources stands out as one of the goals included in the Goals for Sustainable Development in the 2030 Agenda. The construction sector is currently far from presenting an efficient model in terms of treating waste generated by it. Variations in the physical and chemical properties of recycled aggregates coming from construction and demolition waste are one of the main reasons of their limited use in the production of construction materials. This research presents a physicochemical characterization of three different types of recycled aggregates coming from different types of waste: concrete, ceramic and mixed. Physical characterization shows that recycled concrete aggregate has better physical properties compared with mixed recycled aggregate and ceramic recycled aggregate, which makes it more suitable for use in masonry mortars and concrete, due to its higher dry density (2210.33 kg/m3), its lower content of fines (5.17%), its lower friability coefficient (24.60%), and its water absorption coefficient (6.70%). Chemical characterization shows that none of the tested recycled aggregates contains traces of harmful chemical agents that exceed the limits established by the reference regulations. Finally, the statistical analysis shows good homogeneity for these raw materials, obtaining low coefficients of variation and values within the recommended in each of the calculated confidence intervals.

Sustainable use of reclaimed asphalt pavement (RAP) in pavement applications-a review.

The purpose of this review is to examine the innovative usage of Reclaimed Asphalt Pavement (RAP) in flexible pavement applications. RAP is elucidated as isolated pavement earthly materials consisting of asphalt and aggregates. When the existing/old asphalt is removed for reconstruction, and resurfacing, these materials are generated. Now, it is highly required to classify the available RAP for further essential use in road construction. RAP addresses the issues regarding the diminishing of Virgin Aggregate (VA) sources, storage of material and disposal of RAP material nearby the site. The utilization of RAP includes social benefits like depletion of manufacturing waste, conservation of non-renewable natural stockpiles and low energy expenditure. The reviewed literature reveals that RAP has been utilized mainly for base and sub-base materials on the roads. To summarize, 100% replacement of VA by RAP possessed lesser strength and little resistance to creep and long-lasting deformations. Hence, RAP can be appended with natural aggregate or blended with cement or other admixtures like Fly ash (FA) or confined with geocell. It also accelerates the strength and stiffness of the base and sub-base of pavement as it degrades the failure like rutting and fatigue cracking of pavement due to dynamic loads.

Using sodium alginate aided bio-treatment for improving the uniformity of precipitates on recycled aggregates.

The recycled concrete aggregates have high porosity and water absorption, which hinders their utilization in concrete production. Microbial-induced calcium carbonate precipitation was regarded as a very promising method for strengthening recycled aggregates. However, the uneven distribution of CaCO3 on surface of aggregates encountered in the current bio-deposition treatment weakened the efficiency, especially in the aspect of the decrease of water absorption. Therefore, this study innovatively applied a sodium alginate aided bio-deposition treatment to improve the uniform distribution of biogenic CaCO3. The principle was that sodium alginate was used to uniformly "fix" the bio-agents (urea or bacterial cells) on the surface of recycled aggregates, which was supposed to promote the uniform in-situ precipitation of CaCO3 on the surface of aggregates, and hence effectively blocking surface pores, and reducing the water absorption of the aggregates. Two concentrations of sodium alginate (0.2w% and 0.5w%) and four sodium alginate aided bio-deposition treatments were studied. It was found that CaCO3 (a mass increase of 4.05%) was formed on the aggregates after the suitable sodium alginate aided bio-deposition treatment. The participation of sodium alginate made CaCO3 uniformly deposited on full surface of the aggregates, resulting in a significant decrease (42.10%) of water absorption. The biogenic CaCO3 showed limited mass loss under ultrasonic attack, indicated a strong cohesion and bonding strength with aggregates. The results demonstrated that sodium alginate-aided bio-deposition treatment can enhance the efficiency, which was beneficial to improve the quality of recycled aggregates and their utilization of recycled aggregates in concrete production. KEY POINTS: • The SA-aided bio-treatment promoted the distribution uniformity of CaCO3 on aggregates. • The water absorption of aggregates decreased by 42.10%. • The formed CaCO3 showed excellent cohesion and adhesion.

A succinct review on the durability of treated recycled concrete aggregates.

Building materials constitute a considerable portion of all the materials we use and about half the waste (in solid form) generated worldwide. Construction and demolishment (C&D) aggregates can be an invaluable source of construction material. If we measure the quantity of C&D waste in India, it will exceed the amount of all other types of hard solid wastes put together. Therefore, the use of recycled concrete aggregates (RCA) in new construction is being encouraged worldwide. But due to the inferior compressive, mechanical strengths and poor durability performance, it cannot be qualified for structural usage. Hence, there is a need to treat these aggregates and produce better quality aggregates suitable for good structural grade concrete. The present work focuses on the study and comparison of the effects on durability performance due to different treatment techniques of recycled aggregates. Effective treatment techniques can potentially separate or strengthen the weaker portions of the recycled aggregates like the old adhered mortar and the ITZs formed due to them. Effects of different RCA treatment methods along with their combinations such as immersing aggregate in acid solution and silicate solution impregnation, multistage-mixing techniques, biologically induced carbonate precipitation, modifier solution impregnation, ultrasonic cleaning, crushing aggregates at multiple levels, and mechanical grinding are considered for analyzing their effectiveness in improving RCA durability. The durability performance of treated RCA is evaluated based on the improvement in the parameters such as water absorption and resistance to acid attack, permeability, chloride attack, and carbonation.

Seismic Performance of Recycled Aggregate Geopolymer Concrete-Filled Double Skin Tubular Columns with Internal Steel and External FRP Tube.

The large production of cement is resulting in a high-carbon footprint, which is essential to minimize for sustainable concrete construction. Moreover, the large quantity of recycled coarse aggregate (RCA) from the demolition of old concrete structures is creating problems for landfill and disposal. The primary goal of this study is to investigate the seismic efficiency of innovative fiber-reinforced polymer (FRP)-recycled aggregate geopolymer concrete (RAGC) steel-tubed columns (FGSTCs) with an internal steel tube (STT), an external glass-FRP tube (GLT), and RAGC located between the two-tubed components to develop a serviceable structural element. To study their seismic functioning under axial load and lateral repeated load, five FGSTC specimens were manufactured and analyzed under quasi-static loads. The influence of three variables on the performance of FGSTC specimens, consisting of STT reinforcing ratio, compression ratio, and recycled coarse aggregate (RCA) replacement ratio, was investigated in this investigation. The produced specimens' ductility, hysteretic loops, strain distribution, skeleton curves, stiffness functioning, energy capacity dissipation, damaging functioning, and strength loss were all assessed and discussed. The results of this investigation revealed that percentage substitution of RCA had a minor impact on the seismic functioning of FGSTCs; however, the compression-load ratio depicted a substantial impact. The energy loss of the FGSTCs was 24.5% higher than that of their natural aggregate equivalents. FGSTCs may have a 16.9% lower cumulative failure rate than their natural aggregate counterparts.

Recycled Fine Aggregates from Mortar Debris and Red Clay Brick to Fabricate Masonry Mortars: Mechanical Analysis.

In this research, the mechanical behavior of masonry mortars made with partial substitution of sand by recycled fine aggregates (RFAs) of mortar (MT) and recycled clay brick (RCB) was compared. Mortar specimens were built in two groups (MT and RCB) considering different replacement proportions by dry weight. To reduce the water absorption of RFAs during mortar making, the prewetting method was utilized. All the mixtures were assembled with a volumetric cement-to-aggregate ratio of 1:4 and a consistency of 175 ± 5 mm. The properties in the fresh and hardening state of mortars were analyzed separately. The experimental results showed that the properties of mortars in a fresh state (bulk density and air content) were affected if RFA was added to the mixture; however, mortars assembled with up to 40% and 50% of MT and RCB, respectively, accomplished a compressive strength value of reference for new mixtures. Both mortar groups showed good results in adhesive strength values, with the RCB mortars standing up as they achieved greater adherence than the control mortar with substitution percentages of up to 30%. Therefore, the reutilization of both RFAs is feasible, notably in rendering and bonding functions.