Search Results (57)

This study investigates the impact of partially replacing cement with fly ash (FA) on the mechanical performance of fiber-reinforced rubberized concrete (FRRC) incorporating waste tyre rubber and recycled macro-synthetic fibers (MSF). FRRC mixtures were prepared with varying fly ash replacement levels (0%, 25%, and 50%), rubber aggregate contents (0%, 10%, and 20% by volume of fine aggregate), and macro-synthetic fiber dosages (0% to 1% by total volume). The fresh properties were evaluated through slump tests, while hardened properties including compressive strength, splitting tensile strength, and flexural strength were systematically assessed. Results demonstrated that fly ash substitution up to 25% improved the interfacial bonding between rubber particles, fibers, and the cementitious matrix, leading to enhanced tensile and flexural performance without significantly compromising compressive strength. However, at 50% replacement, strength reductions were more pronounced due to slower pozzolanic reactions and reduced cement content. The inclusion of MSF effectively mitigated strength loss induced by rubber aggregates, improving post-cracking behavior and toughness. Overall, an optimal balance was achieved at 25% fly ash replacement combined with 10% rubber and 0.5% fiber content, producing a more sustainable composite with favorable mechanical properties while reducing carbon and ecological footprints. These findings highlight the potential of integrating industrial by-products and waste materials to develop eco-friendly, high-performance FRRC for structural applications, supporting circular economy principles and reducing the carbon footprint of concrete infrastructure. Full article

Ceramic tiles classified as non-biodegradable are made from fired clay, silica, and other natural materials for several construction applications. Waste ceramic tiles (WCTs) are produced from several sources, including manufacturing defects; surplus, broken, or damaged tiles resulting from handling; and construction and demolition debris. WCTs do not decompose easily, leading to long-term accumulation in landfills and occupying a significant amount of landfill space, which has substantial environmental impacts. Recycling WCTs offers several critical ecological benefits, including reducing landfill waste and pollution, conserving natural resources, lowering energy consumption, and supporting the circular economy, which in turn contributes to sustainable construction and waste management practices. In green concrete manufacturing, WCTs are widely utilized as replacements for cement, fine, and coarse aggregates, and the recycling level in the concrete industry is an increasingly explored practice aimed at promoting sustainability and reducing construction waste. From this view, this paper reports the innovative technologies, advancements in green concrete performance, and development trends in the reuse of WCTs in the production of systems. The effects of WCTs on fresh, engineering, microstructural, and durable properties, as well as their environmental performance, are reviewed. In conclusion, the use of technologies for recycling WCTs has demonstrated potential in promoting sustainability and supporting the transition toward a more environmentally friendly construction industry. This approach offers a practical contribution to sustainable development and represents significant progress in closing the recycling loop within the construction sector. Full article

The aim of this work is to determine the short-term and long-term mechanical properties of lightweight concrete with relatively new sintered aggregate, as knowledge of these parameters is essential to the design of prestressed structures. The problem can be placed in a broader ecological context, because the aggregate comes from recycled power plant ash. This research study was planned based on two concrete mixtures that were already used in previous publications, as the aim of this work was to conduct comparative research by using other methods. In particular, the aim was to investigate the long-term properties of lightweight concrete by using standard methods and appropriate equipment, such as creep-testing machines. As a result of these studies, the secant modulus of elasticity, cylindrical strength, cubic strength, axial tensile strength, splitting tensile strength, bending strength, and shrinkage and creep strain were determined. This study confirmed the short-term properties of concrete obtained in previous studies but did not confirm the results regarding shrinkage and creep. These results turned out to be much higher, which means that these values should not be tested by non-standard methods. An unusual process of development of the elastic modulus and axial tensile strength was observed, and the reasons for these phenomena were described. Full article

Compressive strength tests of concrete using core samples are used to determine the strength of concrete elements in building structures. Due to ecology, the use of recycled aggregate in concrete is common. There are more and more concrete structures with recycled aggregate, in which the technical condition must be checked. It is difficult to find scientific studies concerning changes in compressive strength (using core samples of different sizes and using concrete with the addition of recycled aggregates) across the entire thickness of concrete elements. Therefore, studies of the compressive strength of core samples taken across the thickness (top layer, middle layer, bottom layer) of horizontally formed concrete elements with recycled aggregate and clean natural aggregate were conducted. The obtained test results allowed for the determination of the conversion coefficients that enable the compressive strength of the core samples (of different diameters: 59 mm, 74.5 mm, 114 mm, samples taken from different layers of a concrete element with a thickness of 260 mm) to be converted into the compressive strength of the core sample with a diameter of 94 mm and compared with a standard cubic sample with an edge length of 150 mm. The conversion coefficients can be used to determine the quality of the concrete produced or the technical condition of the building (mechanical damage, building reconstruction, building fire). The obtained results of the tests of the concrete samples, which had a compressive strength equal to 40 MPa and were prepared with the addition of recycled aggregate, indicate that there is a decrease of 17% in the strength value in the top layer of the concrete element when compared to its bottom layer. The concrete with a compressive strength of 20 MPa had a lower strength value of its top layer by 33% when compared to its bottom layer. Similar relationships were obtained for concrete with pure natural aggregate. Full article

The use of mineral waste for the production of lightweight artificial aggregate is an important element of activities for sustainable development in construction and the implementation of the objectives of the circular economy. The article presents the physical, mechanical, and ecological properties of an innovative artificial aggregate produced from bottom sediments, concrete dust, and municipal solid waste incineration fly ash. The obtained research results confirm that the developed material achieves technological properties comparable to artificial aggregates available on the market, both commercial and those derived from recycling. However, the increased leachability of chlorides and sulphates remains a significant challenge, which may limit the scope of its applications. Despite this, the material shows the potential for use, among others, in the production of lightweight concrete. The analyses carried out have shown that the thermal hardening processes (200–400 °C) and autoclaving do not guarantee full immobilization of harmful substances contained in the raw materials for the production of this type of aggregate. Full article

Concrete has a significant impact on the environment and efforts are being made to replace it with more environmentally friendly alternatives. One possibility is to replace all or part of the conventional components (i.e., cement, water, sand and gravel) with recyclable solutions. Several studies have already demonstrated the mechanical and ecological suitability of the new eco-concretes, but the safety of structures built with them is not considered in the literature, which indicates a lack of knowledge. The purpose of this study is to evaluate the fire safety of reinforced concrete beams built with eco-friendly concretes and compare them to conventional concretes. The analysis was performed numerically and solved with Abaqus software using the finite element method, assuming the thermal parameters previously proposed in the literature through experimental investigations. The thermal field generated in beams with eco-concrete is a maximum of 50% lower compared to conventional concrete and the temperatures of the reinforcement are reduced by a maximum of 260%. There is an interesting perspective for the use of these materials in terms of fire safety criteria. Full article

Recycled aggregate concrete (RAC), which is made by replacing all natural coarse and fine aggregates with recycled aggregate, plays a significant role in improving the recycling rate of construction materials, reducing carbon emissions from construction, and alleviating ecological degradation issues. However, due to its low strength and significant shrinkage and deformation problems, RAC has limited application. The effort of fiber type, fiber admixture, and fiber hybridization on autogenous shrinkage were studied to improve the structural safety of building materials and broaden the application of RAC. Test results indicate that the shrinkage of RAC decreases with an increase in fiber admixture, and steel fiber-reinforced RAC is more resistant to shrinkage deformation than polypropylene fiber-reinforced RAC. The shrinkage deformation of the hybrid fiber group is smaller than that of the single fiber group, and the inhibition of shrinkage deformation is most effective when the volume fraction of steel fiber is 0.5% and the polypropylene fiber content is 1.5 kg/m³. At 120 days, the PF15SF05 mixture showed a 65.3% reduction in shrinkage compared with ordinary RAC. By merging the shrinkage deformation characteristics of fiber-reinforced RAC and introducing the fiber influence coefficient, three theoretical calculation models for autogenous shrinkage applicable to single and hybrid fiber-reinforced RAC were established based on the experimental data. Full article

The excessive use of materials that are generally difficult to discard, such as stone materials, has caused growing ecological concern. Among these, marble is extracted from quarries, but when the raw material is exhausted, these places are deserted. For this reason, several measures have been adopted in recent years to requalify these areas. In addition, recent technological developments involve the creation of innovative green materials that privilege the circular economy and waste recycling. This research presents the development of innovative, sustainable filaments for the fused filament fabrication (FFF) printing technique from recycled marble waste (MW) and biocompostable and biodegradable polylactic acid (PLA) matrix. MW was added to the polymer in concentrations of 10 wt.%, 20 wt.%, and 30 wt.%, and the blends were extruded to develop innovative green filaments. The chemical/structural properties of the raw materials and the thermal and mechanical features of the new composites were investigated. Composites containing 10 and 20 wt.% of MW showed good printability. In contrast, extrusion and printing difficulties were observed with 30 wt.% of MW. Finally, this paper proposes a project to renaturalize and requalify a disused marble quarry located in Trani (Apulia, Italy) with 3D printing devices using the newly produced eco-filaments, which have better features. The main purpose of this article is to propose a concrete, economic, and sustainable application of 3D printing involving processes such as waste and by-product recycling and renaturalization of disused quarries, with both economic and environmental benefits. Full article

This study explores how consumers in developed and developing countries perceive sustainable food consumption and how these perceptions are shaped by local contexts. Using the theory of social representations, which frames sustainability as a system of values, ideas, and practices, we conducted a mixed-methods analysis of data from online focus groups in ten countries. The results reveal significant differences between sustainability frontrunners in developed countries and consumers in developing countries. Consumers in developed countries focus on immanent representations, linking sustainability to concrete practices such as recycling, buying organic products, and brand awareness. In contrast, consumers in developing countries adopt more transcendent views, emphasizing moral responsibility, tradition, and collective well-being, and often expecting government regulation to drive change. Barriers such as high cost, lack of knowledge, and skepticism reflect underlying socio-economic inequalities, particularly in developing contexts. The study highlights how global sustainability norms interact with local realities, revealing mismatches that limit the effectiveness of universal approaches. These findings underscore the need for context-sensitive policies and strategies that address local barriers while remaining consistent with global sustainability goals. More broadly, this research underscores the necessity of culturally tailored approaches to promote equitable and inclusive socio-ecological transformations. Full article

The construction industry is a major contributor to global greenhouse gas emissions, driven by the extensive use of conventional concrete in building activities. This study evaluates the environmental impacts of various concrete types, including innovative alternatives, using a computational life cycle assessment (LCA) model tailored to the Australian context. Key stages considered include raw material extraction, production, transportation, and end-of-life recycling. Results demonstrate that replacing 40% of cement with supplementary cementitious materials (SCMs) such as fly ash reduces global warming potential (GWP) by up to 25% compared to conventional concrete. Furthermore, carbonation curing technology shows a 15% reduction in ${\mathrm{C}\mathrm{O}}_2$ emissions during the production phase, underscoring its potential to significantly enhance sustainability in construction. High-strength concrete poses significant ecological challenges; however, incorporating SCMs such as fly ash, blast-furnace slag, and silica fume effectively mitigates these impacts. Recycling 60% of concrete demolition waste further decreases environmental impacts by over 20%, aligning with circular economy principles and supporting resource recovery. The findings provide actionable insights for engineers, architects, and policymakers, facilitating the design of sustainable concrete solutions that balance structural performance with reduced ecological footprints. Future research should explore dynamic modelling and broader socio-economic factors to refine sustainable practices. This study underscores the critical importance of adopting innovative materials and recycling practices to minimise the environmental impact of construction activities globally. Full article

Recycled concrete aggregate (RCA) has been widely adopted in construction and emerged as a sustainable alternative to conventional natural aggregates in the construction industry. However, the study of holistic perspectives in recent literature is lacking. This review paper aims to provide a comprehensive analysis of RCA, highlighting its properties, applications, and overall sustainability benefits to facilitate the comprehensive points of view of technology, ecology, and economics. This paper explores the manufacturing process of RCA, examines its mechanical and durability characteristics, and investigates its environmental impacts. Furthermore, it delves into the various applications of RCA, such as road construction materials, pavement bases, and concrete materials, considering their life cycle performance and economic considerations. This review reveals that there is a need for systemic data collection that could enable automated concrete mix design. The findings concerning various mix concrete designs suggest that increasing the 1% replacement level reduces the compressive strength by 0.1913% for coarse RCA and 0.2418% for fine RCA. The current critical research gaps are the durability of RCA concrete, feasibility analyses, and the implementation of treatment methods for RCA improvement. An effective life cycle assessment tool and digitalization technologies can be applied to enhance the circular economy, aligning with the United Nations’ sustainable development goals (UN-SDGs). The equivalent mortar volume method used to calculate the RCA concrete mix design, which can contain chemical additives, metakaolin, and fibers, needs further assessment. Full article

The extensive development of construction, in which cement concrete remains the key composite, enforces the need for particular environmental concerns. This applies to aspects, including ecological challenges in the cement industry and the rational use of natural construction aggregates. This review article focuses on new trends in the use of waste aggregate, with particular emphasis on concrete recycled aggregate and waste sands. The state of the art was analysed, including many years of own studies on modification of properties of waste aggregate and concrete composites made from it. It was assessed that among possible ways of quality improvement of RCA, the most promising for the macro scale seems to be carbonation, unlike biodeposition. The latter, novel and undoubtedly interesting from a scientific viewpoint, has not been studied sufficiently, and the real obstacle is the cost of its implementation in practice. Multi-recycling, the pioneering proposal of recycled concrete aggregate management, can be viewed only in the ecological context for the moment. The use of waste sands from hydroclassification combined with steel fibres is the closest to implementation for constructional purposes in engineering practice. Full article

Using construction and demolition (C&D) waste in concrete production is a promising step toward environmental resilience amid the construction industry’s ecological footprint. The extensive history of using bricks in the construction of buildings has resulted in a considerable amount of waste associated with this commonly used material. This study aimed to assess the quality of concrete by examining the effect of replacing cement with varying percentages of recycled brick powder (RBP—0% to 50%). The primary objectives include evaluating the mechanical properties of concrete and establishing the feasibility of using RBP as a partial cement substitute. The investigation of target concrete can be divided into two phases: (i) laboratory investigation, and (ii) numerical investigation. In the laboratory phase, the performance of concrete with RBP was assessed under short-term dynamic and various static loads. The drop-weight test recommended by the ACI 544 committee was used to assess the short-term dynamic behavior (352 concrete discs). Furthermore, the behavior under static load was analyzed through compressive, flexural, and tensile strength tests. During the numerical phase, artificial neural network models (ANN) and fuzzy logic models (FL) were used to predict the results of 28-day compressive strength. The impact life with different failure probabilities was predicted based on the impact resistance results, by combining the Weibull distribution model. Additionally, an impact damage evolution equation was presented for mixtures containing RBP. The results show that the use of RBP up to 15% caused a slight decrease in compressive, flexural, and tensile strength (about 3–5%). Also, by replacing RBP up to 15%, the first crack strength decreased by 7.15% and the failure strength decreased by 6.46%. The average error for predicting 28-day compressive strength by FL and ANN models was recorded as 4.66% and 0.87%, respectively. In addition, the results indicate that the impact data follow the two-parameter Weibull distribution, and the R² value for different mixtures was higher than 0.9275. The findings suggest that incorporating RBP in concrete can contribute to sustainable construction practices by reducing the reliance on cement and utilizing waste materials. This approach not only addresses environmental concerns but also enhances the quality assessment of concrete, offering potential cost savings and resource efficiency for the construction industry. Real-world applications include using RBP-enhanced concrete in non-structural elements, such as pavements, walkways, and landscaping features, where high strength is not the primary requirement. Full article

Water pollution intensifies water scarcity and poses a significant threat to ecosystems and human health. Construction waste generated by rapid urbanization also imposes a considerable burden on the environment. Fortunately, a large portion of this waste can be efficiently converted into recycled aggregates and reused in various fields including environmental remediation. In this study, three types of eco-recycled concretes (ERC) (Control-ERC, Biochar-ERC-1, and Biochar-ERC-2) were formulated by integrating shell-derived biochar with recycled aggregates. The porosity and water permeability of these concretes were characterized, and their efficacy evaluated in treating polluted water with six primary heavy metals (HMs), i.e., cadmium (Cd), chromium (Cr), arsenic (As), manganese (Mn), lead (Pb), and copper (Cu). Biochar addition significantly enhanced the continuous porosity and water permeability of the concrete, and substantially enhanced its adsorption capacity of HMs. Specifically, Biochar-ERCs removed over 90% of As, Cd, and Mn, and achieved a removal rate exceeding 60% for other HMs, surpassing the performance of Control-ERC. This study not only lays a solid foundation for the wide application of Biochar-ERCs in the field of environmental protection and remediation, but also provides strong technical support and practical examples for advancing the circular economy model of converting waste into resources while addressing the challenge of global water scarcity. Full article

Waste and its environmental impact have driven the search for sustainable solutions across various industries, including construction. This study explores the incorporation of solid waste in the production of eco-friendly structural concrete, aiming to reduce pollution and promote ecological and sustainable construction practices. In this context, two types of eco-friendly concrete were produced using marine shells and recycled rubber as waste materials and compared with conventional concrete through experimental and computational approaches. The results demonstrated that the concrete with marine shells achieved a compressive strength of 32.4 MPa, 26.5% higher than conventional concrete, and a 1% reduction in weight. In contrast, the recycled rubber concrete exhibited a compressive strength of 22.5 MPa, with a 2 MPa decrease compared to conventional concrete, but a 4.3% reduction in density. Computational analysis revealed that porosity affects Young’s modulus, directly resulting in a reduction in the maximum achievable strength. This work demonstrates that it is feasible to produce eco-friendly structural concrete through the proper integration of industrial waste, contributing to decarbonization and waste valorization. Full article