Eco-friendly Concrete Research Articles

High-Performance Concrete from Rubber and Shell Waste Materials: Experimental and Computational Analysis

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.

The impact of calcined mud on the rheological properties of eco-friendly concretes using the equivalent mortar method (CEM)

In order to harmonise technical and environmental aspects, people today focus not only on concrete's technical characteristics but also on environmental imperatives. Thus, the emphasis is on the development of concrete and cements that offer ecological and sustainable advantages. Commonly, people use various natural materials as cement additives, demonstrating their effectiveness by replacing a significant portion of the cement in the hardened state of concrete. This substitution leads to a substantial and remarkable reduction in carbon dioxide emissions. However, when it comes to the physical properties of the material in its fresh state, challenges may arise. Indeed, the rheological changes induced by these additives may hinder the on-site use of this eco-concrete. The main purpose of this study is to find out how adding minerals to environmentally friendly concrete changes its rheological parameters (yield stress, plastic viscosity) and fresh properties (slump, flow time). We will approach this using the concept of mortar equivalent to concrete (CEM). We developed five formulations of CEM’s by substituting cement with calcined mud (CM) in binary mixing systems at a temperature of 20 °C. The results showed that adding binary cements with calcined mud had a negative effect on the fresh properties and rheological parameters. However, when substitution happens at a low rate, it behaves almost like control mortar (OPC).

Eco-Friendly Concrete with Improved Properties and Structure, Modified with Banana Leaf Ash

The reduction of carbon footprint, the recycling of agricultural waste, and the development of novel environmentally friendly building materials are urgent matters that necessitate innovative solutions. The objective of this study is to explore the feasibility of utilizing banana leaf ash (BLA) as a partial substitute for cement in conventional density concrete technology. The BLA-modifying additive was produced under laboratory conditions. Its chemical, phase and granulometric composition was assessed. To determine the degree of effectiveness of BLA, eight concrete compositions were developed, where the BLA content varied from 0% to 14% with an interval of 2%. The properties of fresh concrete, such as density and slump, as well as compressive strength, flexural strength, water absorption, and microstructure of hardened concrete, were studied. It has been determined that the BLA additive exhibits pozzolanic activity, with a SiO2 content of 50.83%. It is recommended that the replacement of cement with BLA does not exceed 10% for optimal results. Concrete modified with 6% BLA had the best properties and structure. The study revealed a significant 7.42% increase in compressive strength, a 7.01% increase in flexural strength, and a notable 9.28% decrease in water absorption. Thus, the obtained result proves the possibility of using BLA as a modifying additive in the technology of cement composites. The developed concrete has improved properties and is a more environmentally friendly building material than conventional concrete.

Towards sustainable construction: Harnessing potential of pumice powder for eco-friendly concrete, augmented by hybrid fiber integration to elevate concrete performance

This study investigates the innovative use of industrial waste pozzolana, specifically pumice powder (PP), as a partial replacement for cement, combined with hybrid fibers in concrete. Seven formulations varying PP content from 10 % to 35 % were tested, identifying 15 % PP as optimal. PP improved porosity due to its fineness, leading to better homogeneity, a refined microstructure, and an optimum compressive strength of 28.8 MPa with reduced permeability, enhancing durability. Hybrid fibers, including steel fibers (SF) from waste tires and polypropylene fibers (PF), improved toughness, ductility, and resistance to brittle failure. Tests on hybrid fiber-reinforced concrete (HyFRC) mixes with 1 % and 2 % hybrid fibers showed up to an 18.09 % increase in compressive, tensile, and flexural strengths. Energy dissipation in compressive response improved by 544.20 %, while flexural and splitting responses increased by up to 299.65 % and 208.57 %. Durability assessments in hydrochloric (HCl) and sulfuric acid (H2SO4) exposure revealed the synergy of fibers and PP enhanced resistance to chemical degradation, with high PF mixes losing as little as 0.04 % strength. Scanning electron microscopy (SEM) confirmed a dense, well-bonded matrix with reduced porosity. Analytical characterizations of mixtures such as energy dispersive x-ray spectroscopy (EDX) were studied. Regression models developed using Popovic’s and Mander’s models, accurately predicted HyFRC stress-strain behavior, closely aligning with experimental results. The integration of PP and hybrid fibers not only improved mechanical properties but also extended service life in harsh environments, offering a cost-effective, sustainable concrete solution.

Eco-Friendly Concrete Solutions: The Role of Titanium Dioxide Nanoparticles in Enhancing Durability and Reducing Environmental Pollutants - A Review

Concrete is one of the key components of construction, which ensures durability and aesthetics of the building. In recent days, nanoparticles are playing an essential role in civil engineering research. The binding of nanoparticles into concrete significantly improves the mechanical and durable properties due to the nanostructure of the cementitious materials. This review paper represents the existing research data on titanium dioxide nanoparticles, when applied in the different types of concrete. The data influenced by the different research papers are presented in terms of strength and durable parameters. The most important property of titanium dioxide nanoparticle is its self-cleaning effect because of the photocatalytic reaction is also discussed. The inference from the papers shows the effect of titanium dioxide nanoparticles on correct proportion enhances the production of new material with good strength and durable properties in the construction industry. The photocatalytic action of nano titanium dioxide leads to the manufacture of self-cleaning concrete which shields the surface from environmental pollutants.

Calcined Clays as Concrete Additive in Structural Concrete: Workability, Mechanical Properties, Durability, and Sustainability Performance.

Calcined clays (CCs) as supplementary cementitious materials (SCMs) can be a promising option to reduce clinker content and CO2 emissions in eco-friendly concretes. Although CCs as components of composite cements in combination with Ordinary Portland Cement (OPC) and limestone powder (LSP) have attracted industry interest, their use as concrete additives is limited. This study investigates the effects of the addition of CCs on the fresh and hardened properties of industry-standard ready-mixed concretes. Four concrete mix designs, each with three superplasticizer dosages, were tested, resulting in 12 variations. The CCs used, which are typical of 2:1 bentonite clays with low metakaolin content, reflect the clays available in Germany. The results showed that CCs significantly influenced the workability, which could be controlled with a high superplasticizer dosage. Increased CC contents reduced bleeding tendencies, which was beneficial for certain structural applications. Early age strength decreased with CCs, but the 28-day strength exceeded that of pure OPC concretes up to 30 wt% CCs. Resistance to CO2-induced carbonation decreased with higher levels of CCs but was comparable up to 15 wt%. Freeze-thaw damage decreased, and chloride migration resistance improved due to a denser microstructure. The global warming potential (GWP) of the concretes tested is in line with that reported in the literature for concretes made from highly blended cements, suggesting that CCs can improve the sustainability of concrete production.

Experimental and Numerical Investigation of the Flexural Behavior of Reinforced-Concrete Beams Utilizing Waste Andesite Dust.

During the process of cutting andesite stones, the waste mud is kept in powder form once fully dried. It is difficult to store the waste that is produced as a consequence of the extensive utilization area and consumption of andesite. Thus, eliminating waste storage challenges and incorporating these wastes into the economy are crucial. For this reason, this study examined the effects of waste andesite dust (WAD) on the flexural behavior of reinforced-concrete beams (RCBs) using experimental testing and 3D finite-element modeling (FEM) via ANSYS. Thus, different rates of WAD up to 40% were used to investigate the influence of the WAD rate on the fracture and bending behavior of RCBs. While the RCB with 10% WAD had a slightly lower load-bearing and ductility capacities, ductility capacities significantly drop after 10% WAD. At 40% WAD, both the load-bearing capacity and ductility significantly reduced. Based on the experimental findings, using 10% WAD as a replacement for cement is a reasonable choice to obtain eco-friendly concrete. Moreover, the outcomes of 3D FEM were also compared with those of experiments conducted using ANSYS v19 software. The displacement values between the test and FEM findings are quite similar.

Effects of Volcanic Tuff Use on the Rheological and Mechanical Properties of Self-Compacting Concrete

The rise in demand of concrete products has led to overexploitation of river sand the main fine aggregate in concrete resulting in major environmental degradation. As a result, researchers have focused their efforts on developing eco-friendly concrete using alternative renewable materials like volcanic tuff and other natural pozzolana types. This study therefore, aims at investigating the use of Kenyan, Kitengela volcanic tuff as a partial replacement of river sand in self-compacting concrete, and determining the effects it will have on the rheological and mechanical properties of the self-compacting concrete. The study involved partially replacing river sand with volcanic tuff in percentages of 0%, 2.5%, 5%, 7.5% and 10% and carrying out rheological tests (V-funnel test, L-box test, T-500 test and J-ring test) on fresh concrete and mechanical tests (compressive strength and tensile strength tests) on hardened self-compacting concrete on days 7, 14, and 28 to determine the effects of volcanic tuff on properties of both fresh and hardened self-compacting concrete. There was a general decrease in rheological properties (flow and passing abilities) of self-compacting concrete with increase in volcanic tuff percentage replacement from 0 % to 10%, with least flow and passing abilities recorded at 10% replacement. Similarly, increase in volcanic tuff percentage replacement led to decrease in both compressive and tensile strength of self-compacting concrete with lowest values recorded at 10% volcanic tuff replacement.

Novel low-carbon eco-concrete filled-FRP tubes under axial compression: Experimental behavior and analytical model

Concrete is essential in global construction but significantly contributes to carbon emissions, primarily due to cement production. The cement industry is adopting low-carbon practices, such as using supplementary cementitious materials (SCMs) to reduce emissions. Concrete prepared with calcined clay can achieve a carbon reduction effect of approximately 30 % compared to ordinary cement. Current studies highlight the reuse of kaolin clay, the predominant constituent of engineering sediment in Shenzhen, China, providing raw materials for sustainable low-carbon and eco-friendly concrete. However, high substitution rates of calcined clay can compromise concrete strength, posing a challenge for the application in load-bearing structures. This study proposed a novel low-carbon eco-friendly concrete (i.e., using calcined clay as supplementary cementitious materials) filled into FRP tubes (i.e., Low-Carbon Eco-Concrete-Filled FRP Tubes, termed LCE-CFFTs) aiming to enhance substitution rates of calcined clay and to improve compressive strength and ductility. This paper provides a detailed description of the preparation method, chemical reaction process, chemical composition, and microstructure of calcined clay. Experimental tests investigated the axial compressive performance of LCE-CFFTs, considering calcined clay substitution rates and FRP thickness as key parameters. The experimental work and theoretical analysis indicated that: the inclusion of 10 % and 40 % calcined clay led to a reduction in carbon emissions, resulting in a decrement of 5.8 % and 23.3 %, respectively; confinement provided by FRP tubes mitigated the reduction in axial compressive strength resulting from calcined clay inclusion, particularly evident at higher substitution rates (40 %); the effect of FRP tube confinement in improving peak stress and axial performance of LCE-CFFTs became more pronounced with higher calcined clay substitution rates; to more accurately predict the axial compressive behavior of LCE-CFFTs of this study, it is essential to consider the biaxial stress-strain state of filament-wound FRP tubes.

Assessment of fracture toughness in fibrous concrete via Brazilian test: Experimental study with low-clinker cementitious binder

As the predominant and cost-effective material in the construction industry, concrete is susceptible to tension weaknesses, leading to significant flaws such as cracking and brittle fracturing. Recent advancements in fibrous concrete have emerged as a solution to mitigate these issues. Incorporating steel fibers in concrete has emerged as a promising solution to improve crack resistance and structural integrity. This study focuses on developing eco-friendly concrete using a low-clinker cementitious binder and short steel fibers to enhance fracture toughness and mitigate the environmental impact by effectively utilizing lime sludge. Concrete specimens were prepared with three binder types: treated lime sludge (TLS) at 15 % and 30 % and calcined clay (CC) at 15 % and 30 %, replacing conventional clinker. Short steel fibers were added at 1.5 % by volume to enhance mechanical properties. Fracture toughness was evaluated using notched Brazilian disc specimens, assessing mode I, II, and mixed-mode (I/II) fracture at multiple notch orientations (β = 0°, 15°, 28.83°, 45°, 60°, 75°, and 90°). Microstructural analysis during strength development was performed using scanning electron microscopy and X-ray diffraction. The findings revealed that specimens containing 15 % TLS, 30 % CC, and 1.5 % steel fibers exhibited the highest fracture toughness. Mode II fracture toughness exceeded mode I, indicating improved resistance to crack propagation. The addition of fibers to the specimens under mode II demonstrated improved fracture toughness, ranging from 0.44 to 0.53 MPa·m^1/2 compared to the corresponding non-fibrous specimens. The fibrous specimens showed significantly higher ultimate loads at β = 90° compared to β = 0°, indicating superior crack resistance and structural integrity under perpendicular loading conditions. The Brazilian disc specimens demonstrated variability in fracture toughness across different loading orientations, highlighting their suitability for mixed-mode fracture assessment.

Study on printability of 3D printing carbon fiber reinforced eco-friendly concrete: Characterized by fluidity and consistency

Carbon fibers have often been added to concrete as reinforcement. Eco-friendly concrete with industrial by-products has been widely studied and applied as green building materials. Studying the workability and printability of eco-friendly concrete with carbon fibers is worthwhile. The workability and printability of eco-friendly concrete are dominating factors that ensure that printing can be carried out smoothly. This study uses a combination of experiments and numerical simulations to study the printing performance of carbon fiber-reinforced eco-friendly concrete (CFREFC). The workability and printability of 9 mixes of 3D printing CFREFC under various combinations of different water-binder (w/b) ratio levels and superplasticizer (SP) dosages were tested. Two methods, namely the consistency and fluidity tests, were used to characterize the printability. After consistency and mortar fluidity tests, the 9 mixtures were printed to get the printing performance. Finally, the relationship between the workability and printability of 3D printing CFREFC was established. The condition numbered M7 (w/b = 0.4, SP = 0.5) in the selected experimental group was used as the source of its simulation parameter. The result shows that it is feasible to characterize printability using workability, i.e., consistency and fluidity, which increase with the increase of w/b and SP dosage. Under the printing parameters of the HC1008 printer were determined, i.e., 20 mm of nozzle size, 50 mm/s of printing speed, 30 rpm of material extrusion speed, and 14 mm layer height, the fresh CFREFC was not suitable for 3DP application when its consistency is less than 48.99 mm and more than 81.96 mm, or when its fluidity is less than 166.72 mm and more than 200.93 mm. When the consistency is from 56.34 to 65.61 mm, and the fluidity is from 172.18 to 183.30 mm, the printability of CFREFC is the best under the same printing parameters. The simulation results indicated that with the increased number of printing layers, the bottom of the printed model would be deformed by the gradual increase in pressure, and a specific height loss would occur, which was consistent with the experimental results.

Eco-Friendly Roller Compacted Concrete: A Review

Sustainable evolution is vital to address miscellaneous issues, and experts are currently exploring the possibilities of Eco-Friendly concrete (Green concrete). This type of concrete involves using environmentally and economically viable substances that can act as entire or partial replacements for conventional materials. By doing so, it can assist in reducing the consumption of natural resources and energy, as well as minimize pollution. For example, several researchers have performed on incorporating sustainable approaches in roller compacted concrete RCC by replacing certain substances with eco-friendly alternatives. That is a favorable step toward devising more sustainable construction practices. Therefore, this study resorted to reapplying recycled plastic garbage (sustainable plastic) to construct environmentally eco-friendly concrete (green concrete). First, examine the possibility of using plastic as a partial substitute for fine-aggregates in RCC mixtures. Second, examination of the possibility of using plastic as a partial substitute for coarse-aggregates in RCC mixtures to enhance the performance of RCC. In early periods, a suitable RCC mix was designed in the lab to test the concrete strength, freezing-thawing, permeability, durability, erosion, and porosity of set concrete. The findings confirmed that RCC can maintain the same properties as traditional concrete using the known mixtures. Trial tests were designed and organized to evaluate the quality of pouring and compaction operations, suitable mix composition, and void specimens to accomplish testing on the constructed RCC. It has shown that RCC with prime ingredients and proper ratios can be performed with similar strength and durability as conventional concrete. However, RCC differs from ordinary concrete pavements. This technology provides a favorable economical alternative for many branches of civil engineering installations.

Comparative analysis of selected machine learning techniques for predicting the pull-off strength of the surface layer of eco-friendly concrete

With recent trends reducing the carbon footprint of concrete, more novel materials are designed. It's mostly done by replacing cement with admixtures that are wastes in industrial processes. There is a need to provide reliable and accurate models to estimate the properties of the material. In this case the selected ML algorithms such as ANN, RF and DT were used for estimating the pull-off strength of the surface layer of cement mortar containing granite powder, fly ash and ground granulated blast furnace slag. The focus was on the cement-sand ratio of 1:3, replacing up to 30 % of the binder. Ultrasonic pulse velocity and pull-off strength of the surface layer. The analyses were performed in comparative manner and proved the accuracy of the designed models. The error values (MAPE, NRMSE and MAE) of the most effective model is below 3,5 %, indicating an extremely high success rate in prediction. An R2 ratio of 0.9436 confirms the very good fit of the model. Parametric tests were performed and SHAP analysis gave a better understanding of the models. The main conclusion of the study is to identify the possibility of replacing destructive testing with non-destructive testing supported by machine learning and material information to determine the pull-off strength of the subsurface layer at a selected depth for cement mortars containing waste materials. A particular advantage of the presented approach is the possibility of reducing the time to determine selected desired material parameters and the amount of testing required compared to the traditional approach.

Innovative Eco-Friendly Concrete Utilizing Coconut Shell Fibers and Coir Pith Ash for Sustainable Development

Concrete is the most commonly used and essential material in the construction industry, and it is also the most widely utilized product globally. The construction industry is a rapidly expanding industry. To improve the efficiency and strength properties of concrete, researchers from all over the world continue to search for supplementary cementitious materials (SCMs) and industrial by-products that can be incorporated as alternative materials. The current study aimed to determine the effects of partially substituting coir pith ash (CPA) for cement in coconut shell concrete, in addition to utilizing steel and coconut fibers. Various percentages of CPA were used to replace cement in the concrete mixes, ranging from 5% to 20% by cement weight. Steel fibers were utilized in this study at volume ratios of 0.25%, 0.5%, 0.75%, and 1.0%, and coconut fibers were utilized at volume ratios of 0.1% to 0.5% with an increment of 0.1% in the concrete to achieve the desired results. Various properties have been examined, such as workability, mechanical, durability, and morphological tests. The addition of coir pith ash to concrete increased its compressive, flexural, and tensile strengths by 10.36%, 8.75%, and 7.7% at 28 days compared to control concrete. The incorporation of coconut fiber and coconut shell in concrete production improves its performance and strength while also preserving natural resources and offering a solution to the problem of disposing of solid waste.

Push-out test of eco-friendly steel-concrete–steel composite sections enhanced by polypropylene fibers: An experimental study and statistical analysis

Steel-concrete-steel (SCS) structural element solutions are rising due to their advantages over conventional reinforced concrete in terms of cost and strength. The impact of SCS sections with various core materials on the structural performance of composites has not yet been fully explored experimentally, and in this work, both slag and polypropylene fibers were incorporated in producing eco-friendly steel-concrete-steel composite sections. This study examined the ductility, ultimate strength, failure modes, and energy absorption capacities of steel-concrete-steel filled with eco-friendly concrete, enhanced by polypropylene fiber (PPF) to understand its impact on modern structural projects. Eco-friendly concrete was produced by the partial replacement of cement with waste material such as ground granulated blast-furnace slag (GGBS) to reduce carbon dioxide emitted as one of the by-products of cement which harms the environment. A constant rate of cement replacement with GGBS was used. Polypropylene fibers were used as a fill material in the structural elements to enhance the performance. Seven specimens of SCS were analyzed for their mechanical properties using push-out monotonic loading. The control specimen was constructed with a conventional concrete core, even as testing specimens had different amounts of polypropylene fiber added to the core. The current investigation indicates that the impact of polypropylene fiber (PPF) material filling concrete on SCS performance is somewhat smaller than that of ordinary concrete (less than 10 percent). Applying PPF to concrete can increase its tensile strength, slow the spread of cracks, and strengthen the material overall. The compressive strengths of the samples were affected by the proportion of PPF, with the strength increasing from 47.6 MPa to 56.43 MPa as the PPF levels increased from 0 to 2 percent. Compared to the control sample, the PPF SCS specimens had an increased energy absorption. On the other hand, in comparison to PPF SCS specimens, the ductility level of the control sample was smaller.

Compressive behavior of eco-friendly concrete containing glass waste and recycled concrete aggregate using experimental investigation and machine learning techniques

This paper presents an experimental investigation on the compressive behavior of eco-friendly concrete containing glass waste (GW) and recycled concrete aggregate (RCA). In all mixtures, cement and water are stayed constant while fine and coarse aggregates were varied. The studied parameters are: utilizing fine recycled glass (FRG) instead of fine natural aggregate (FNA) at substitution levels of 0, 10, 25, 50 and 100 %, performing coarse recycled glass (CRG) instead of coarse natural aggregate (CNA) at replacement ratios of 0, 10, 20 and 40 %, conducting both CRG at constant ratio (20 %) as well as RCA at varied levels (0, 16, 40 and 80 %) and replacing CNA by RCA at varied levels (0, 16, 40 and 80 %). The experimental results showed that replacing 10, 25, 50 and 100 % of FNA by FRG declined the compressive strength of concrete by 12.8, 18.5, 24.5 and 49.8 %, respectively. Also, the compressive strength of concrete decreased by 18.5, 23.3, and 32.83 % when 10, 20, and 40 % of CNA were substituted by CRG, respectively. Additionally, the current study investigates the efficacy of machine learning (ML) techniques in evaluating the compressive strength of eco-friendly concrete containing GW and RCA separately. Four tree-based ensemble methods—decision trees, random forest, gradient boosted regression trees, and extreme gradient boosting—were trained and tested using 241 and 319 datasets to predict the compressive strength of eco-friendly concrete containing GW and RCA, respectively. The data employed in constructing the ML model were gathered from both the current experimental study and previous studies. The findings indicate that the XGBoost model demonstrates exceptional accuracy. The impact of each parameter on the predicted outcomes was discussed.

Innovative and Eco-Friendly Concrete Forming Sustainable and Resilient Structures Using Waste Marble Powder

Innovative and Eco-Friendly Concrete Forming Sustainable and Resilient Structures Using Waste Marble Powder

Structural Performance of Reinforced Concrete Slab with Sugarcane Bagasse Ash and Plastic Flakes as Partial Replacement

This research aims to reduce the weight of concrete structural members and promote the use of eco-friendly concrete. To achieve this, plastic flakes and sugarcane bagasse are used as additional materials in concrete production, which can partially replace fine aggregates and cement respectively. This makes structural members lighter, reducing the overall load transmitted to the foundation and the construction cost. The study investigates the effect of plastic flakes and sugarcane bagasse ash on the performance of a reinforced concrete slab. It includes workability, compressive, flexural, tensile strengths, and water absorption of different mix proportions in the fresh state. Various sugarcane and plastic flake percentage replacements of cement and fine aggregates are also investigated. The results show that the 5% SCBA and 5% plastic flake replacement ratio has better mechanical properties compared to the control concrete and other mix ratios. This ratio is used in casting the reinforced concrete slab, whose structural behavior is then investigated in terms of ultimate load, ultimate deflection, load-deflection relationship, and crack patterns. The study shows that the incorporation of sugarcane bagasse ash and plastic flakes as partial replacements improves the bearing of ultimate load capacity. Still, the slab portrays higher deflection than the control slab. The crack patterns appear in the tension zone of the slab, and the slab fails in flexion.

Experimenting with the Utilization of Recron3S Fiber and Steel Slag in Fresh Concrete for Analysis

Abstract: Concrete is well-known for being the most frequently utilized construction material due to its affordability, longevity, and adaptability. However, traditional concrete production requires a large amount of cement and aggregate, raising concerns about its environmental impact and depletion of natural resources. In order to address these issues and promote sustainability, we have been exploring alternative materials like Recron3s polyester fiber and steel slag. Recron3s fiber can enhance the flexibility of concrete, making it a valuable addition. On the other hand, the steel industry generates a byproduct known as steel slag, which presents environmental challenges and disposal issues. Nonetheless, when incorporated into concrete, steel slag can improve the mechanical and physical properties of the material, increasing its durability. Our research focuses on replacing OPC 53 grade cement and natural aggregate with Recron3s fiber and steel slag aggregate, respectively. Different percentages of steel slag aggregate (0%, 20%, 25%, 30%) and Recron3s fiber (0%, 1.25%) were used as substitutes for traditional materials in M30 grade concrete with a water-cement ratio of 0.44. We created concrete mixes by partially replacing OPC 53 with Recron3s fiber and substituting natural aggregate with steel slag aggregate to evaluate the performance of eco-friendly concrete. We then evaluated the performance of these mixes through workability tests such as slump cone, vee-bee consistometer, and compaction factor test. Overall, incorporating Recron3s fiber and steel slag aggregate into concrete has yielded positive results in enhancing mechanical properties and reducing environmental impact.

Effect of surface activity of recycled fine aggregates from clay bricks on the hydration, microstructure and chloride transport of concrete

Use of recycled fine aggregates from clay bricks (RFCB) in the preparation of eco-friendly concrete was proposed to tackle the river sand (RS) shortage and satisfy the construction demand. This study explored the surface activity of RFCB influenced by additional water and particle size distribution (PSD) on the hydration, microstructure and chloride transport of concrete. Compared to the RS, more silica and alumina released from RFCB depending on its PSD under alkaline environment was noted, which verified its appreciable surface activity. Overall, the presence of RFCB could hinder early hydration process because of the higher additional water, while the surface activity and nucleation effect supplied from finer RFCB were beneficial for the improvement of the hydration kinetics. Furthermore, inclusion of RFCB increased the total pore volume and porosity but performed better in refining the pore size distribution, thus decreased the average pore diameter. The surface activity of RFCB decreased CH content while increased chemical bond water and additional hydrates, thereby leading to enhancement of the compactness of interface, cement matrix and surface rim. More importantly, RFCB helped to decrease the chloride migration coefficient and electric flux. Though the surface activity of RFCB was beneficial in the strength development, it could not offset a deteriorated influence of porous RFCB with a higher replacement.