Natural Fine Aggregate Research Articles

Durability analysis of metakaolin recycled concrete under sulphate dry and wet cycle

This study aims to enhance the durability, cost-effectiveness, and sustainability of recycled fine aggregate concrete (RFAC) subjected to the combined effects of wet-dry cycles and sulfate erosion. Dry–wet cycle tests were conducted in RFAC with different admixtures of biotite metakaolin (MK) and 15% fly ash (FA) mix (M) under 5% sulfate erosion environment. The effect of 0%, 30%, 60% and 90% recycled fine aggregate (RFA) replacement of natural fine aggregate on mass loss, cubic compressive strength, relative dynamic modulus test of RFAC, damage modeling and prediction of damage life of concrete were investigated. The results showed that the concrete cubic compressive strength and relative dynamic modulus were optimal for recycled concrete at 15% MK biotite dosing and 60% RFA substitution, and its maximum service life was accurately predicted to be about 578 cycles under 5% sulfate dry–wet cycling using Weibull function model. This study is pioneering in addressing the durability of RFAC under sulfate attack combined with wet-dry cycling, employing a novel approach of incorporating MK and FA into RFAC. The findings highlight the practical application potential for using MK and FA in RFAC to produce durable and sustainable construction materials, particularly in sulfate-exposed environments. This research addresses a critical challenge in the construction industry, providing valuable insights for developing more durable and eco-friendly construction materials and contributing to long-term sustainability goals.

Production of sustainable GGBFS-based Self-Compacting Geopolymer Concrete containing E-waste aggregates under ambient temperature curing

Geopolymer concrete (GPC) has gained global attention due to its environmentally friendly composition and a reduction in the carbon footprint compared to conventional concrete. Self-compacting geopolymer concrete (SCGC) combines the environmental benefits of geopolymers with the convenience of self-compacting concrete (SCC), offering a sustainable solution that minimizes manual labor, reduces noise pollution, and ensures a high-quality finish in diverse construction locations. The rapid proliferation of electronic devices in contemporary society has substantially enhanced electronic waste (e-waste), creating significant environmental challenges. This study explores a sustainable approach in managing the menace created by e-waste through its partial replacement against natural aggregates in producing ground granulated blast furnace slag (GGBFS)-based SCGC under ambient temperature curing. The research methodology involves the preparation of eleven mixes, including the control SCGC mix (with no e-waste aggregate), utilizing printed circuit boards (PCBs) as partial replacement in natural fine and coarse aggregates at varying percentages, i.e., 10 %, 20 %, 30 %, 40 %, and 50 %. It is revealed through a detailed fresh property, mechanical property, durability property, and microstructural analysis that the optimal replacement levels with e-waste are 30 % NFA or 10 % NCA in producing a sustainable and workable SCGC comprising 28.2 % and 19.2 % of waste materials (GGBFS, EWF, and EWC) moving towards a sustainable concrete yield.

Incorporation of Silicone Mold Residues Influence on Acoustic Properties of Subfloor Mortars

The determination of minimum performance criteria for residential buildings has encouraged the development of new technologies by companies linked to the construction industry. In this context, the acoustic performance of floor systems is of great importance. One of the solutions to improve the performance of these systems is the incorporation of lightweight aggregates to replace natural fine aggregates in the subfloor mortars, with the aim of attenuating the noise caused by impact, thus improving acoustic performance. Therefore, the objective of this study was to analyze the properties of a subfloor mortar in a 1:4 ratio (cement:sand), with the incorporation of silicone mold residue, replacing natural fine aggregate, in proportions of 10%, 20%, and 30%. %, and a water/cement ratio (w/c) of 0.93. Tests were performed in the fresh and hardened state, such as incorporated air content, mass density, consistency index, flexural tensile strength, compressive strength, water absorption by capillarity, in addition to a specific test to determine the difference in sound pressure level between specimens. The results indicated that the mortar consistency was influenced by the incorporation of waste, increasing with its incorporation. The increase in consistency positively influenced the mechanical resistance of the mortars, which showed an increase with higher residue content, due to the reduction in the amount of voids. Consequently, densities also increased with high waste content. The acoustic test showed satisfactory results, with good attenuation of 10%, indicating an 8 dB improvement in the sound pressure level. The results presented show that the residue has great potential for acoustic attenuation.

Performance of fly ash/GGBFS based geopolymer concrete with recycled fine and coarse aggregates at hot and ambient curing

The incorporation of recycled aggregates in geopolymer concrete (GPC) exhibits higher environmental sustainability due to its ability to utilize industrial by-products and construction and demolition (C&D) waste. This study investigates the combined effect of fine and coarse recycled aggregates on the behavior of GPC. In this research, fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used as binder, whereas sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) were used as alkaline activators. Recycled fine aggregates (RFA) were used at 30%, 60% and 100% replacement of natural fine aggregates (NFA) and recycled coarse aggregates (RCA) were used at 0%, 50% and 100% replacement of natural coarse aggregates (NCA). To study the effect of curing temperature, two types of curing regimes, i.e. hot and ambient curing, were employed. Performance of developed GPC was evaluated in terms of workability, mechanical properties (compressive strength, splitting tensile strength, and flexural strength) and durability properties such as water absorption, sorptivity, resistance against acid attack, resistance against marine environment and electrical resistivity. It was found that the behavior of GPC is improved when the samples were cured at high temperature for 24 h, as compared to the samples cured under ambient curing conditions. Furthermore, NFA can be replaced up to 100% with NCA, and up to 60% in the presence of 50% RCA and up to 30% in the presence of 100% RCA. It was also found that with an increase in the percentage of recycled aggregates, durability performance gradually declined. The results showed that GPC can be developed with inclusion of both recycled fine and coarse aggregates, which can help to preserve valuable natural resources, reduce CO2 emission, and dispose C&D waste.

Axial compression performance of rubberized concrete-filled steel tubular stub columns after fire exposure: Experimental investigation and calculation models

Rubberized concrete (RuC) has emerged as a promising eco-friendly solution for structural elements, offering improved energy dissipation, damping characteristics, and ductility. Incorporating rubber particles into concrete-filled steel tubular (CFST) columns presents an environmentally conscious alternative for various structural applications. However, understanding its performance post-fire is crucial for safe design application, an area currently lacking comprehensive research. This study investigates the structural behavior of sixteen axially loaded circular RuCFST columns after exposure to fire. The columns, with diameters of 219 mm and 377 mm, are filled with normal concrete and RuC, containing 5 %, 15 %, and 30 % replacement of natural fine and coarse aggregate with rubber particles. Following ISO-834 fire standards, the specimens undergo elevated temperatures and subsequent application of compressive axial loads to determine their post-fire behavior. Analysis includes examination of failure modes, temperature-time relationships, axial load-deformation curves, and strain and stress development in the columns. Microstructural analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) is conducted to study internal morphology before and after exposure to high temperatures. Results indicate non-uniform and nonlinear distributions of maximum temperatures across cross-sections, with historical temperature affecting residual capacity more significantly with increased rubber content and decreased column size. Load-bearing capacities decrease by up to 30 % and 22 % for small and large RuCFST columns, respectively, after exposure to fire. Residual axial stiffness also declines, with reductions of nearly 55 % and 42 % for small and large columns, respectively. In contrast, ductility improves in fire-exposed specimens, with columns having a 30 % rubber replacement ratio showing the highest enhancement. A novel method for calculating post-fire residual load capacity based on the average historical maximum temperature is introduced, demonstrating high accuracy and offering a valuable tool for assessing and reinforcing RuCFST columns after fire exposure.

Manufacturing Environmentally Friendly Hollow Blocks using Different Aggregates: Effect on Mechanical Properties

Hollow concrete block (HCB) is one of the most fundamental materials in building and construction worldwide. Therefore, HCB has emerged as a viable alternative to traditional building materials likebrick. It is an excellent choice for constructing walls, pavements, and other masonry work construct a long-lasting structure. Today's new world requires a green, eco-friendly, and sustainable world, and HCB can play a significant role in achieving that goal. HCB has superior thermal and fire resistance properties, greater strength, cost-effectiveness, and eco-friendliness. Only a small amount of construction in Bangladesh is done using HCBs. However, as sustainable structural technology advances, more frequent use of HCBs will be required. As a result, this article will provide a brief overview of the various applications of HCBs in Bangladesh, including the manufacturing process and its benefits and drawbacks. Specifically, this work investigates and compares the effect of different natural fine aggregates collected from different areas of Bangladesh on the mechanical properties of HCB. The fine aggregates used in this study came from the Dharala, Patgram, Lalmonirhat, and Someshwari rivers in Durgapur, Netrokona, Bangladesh. HCBs were manufactured using a hydraulic press machine and were constructed using mix design ratios of 1: 5: 1: 3 (Cement: Gravel Sand: Sylhet Sand: Crushed Stone), 1: 4.17: 1.67: 1.5 (Cement: Gravel Sand: Sylhet Sand: Crushed Stone), 1: 2.33: 2: 1.33 (Cement: Gravel Sand: Stone Dust: Crushed Stone), 1: 3.33: 2.33 (Cement: Gravel Sand: Stone Dust) and 1: 2.5: 1: 0.50 (Cement: Gravel Sand: Stone Dust: Crushed Stone) with water cement (W/C) ratio of 0.37. The specimens' dimensions were chosen to be 390 mm x 190 mm x 100 mm. The specimens were tested for unit weight, water absorption, compressive strength, and tensile strength after 28 days of water curing. The results showed that HCBs made with different fine aggregates from the Dharala, Patgram, Lalmonirhat, and Someshwari rivers in Durgapur, Netrokona, Bangladesh, have different compressive strengths at 28 days, namely 978 PSI, 1604 PSI, 1267 PSI, 1162 PSI, and 2128 PSI. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 153-158

Integrating particle packing approach with ML techniques to optimise the compressive strength of RCA based concrete mixes

The present study focusses on predicting and optimizing the compressive strength of recycled concrete aggregate (RCA) based concrete mixes using machine learning algorithms. The issues with the gradation of irregular shape of recycled aggregates is leveraged using particle packing approach. Integration of the packing density into analysis of 466 data sets of RCA based concretes using ML techniques is the novelty of this work. Input variables water-to-binder ratio, binder content, natural fine aggregate, natural coarse aggregates, RCA percentage replacement (ranging from 0 % to 100 %), packing density, and output variable compressive strength (in MPa) are considered. Random Forest Regressor (RFR) algorithm demonstrated significant accuracy in predicting the RCA based concrete mixes. Validation through k-fold analysis reinforced robustness of the predictive model, revealing an average R2 of 0.99 with low predictive errors. Overall, ML-based regression analysis has come in handy to accurately predict the strength in RCA-based concrete mixes, offering a valuable alternative, avoiding, extensive laboratory experiments for strength optimization.

Synergistic effects of GGBFS and EAFS on rheology, mechanical properties, and durability of self-compacting concrete: Experiments, predictions, and life cycle assessment

With the aim of reducing the use of natural resources, this research evaluated the behavior of self-compacting concrete (SCC) containing granulated blast furnace slag (GGBFS) powder instead of limestone powder, GGBFS fine aggregate instead of natural fine aggregate, and electric arc furnace slag coarse aggregate (EAFS) instead of natural coarse aggregate. The evaluation included a comprehensive assessment of fresh concrete properties, compressive strength, flexural strength, ultrasonic pulse velocity (UPV), water absorption, and capillary water absorption. In addition, equations were proposed to predict the compressive strength of concrete in terms of the type and percentage of material replacement and curing time. Finally, the environmental effects of the concrete mixtures were studied, which fills a significant research gap. The results showed that with the optimal use of the mentioned substitute materials in concrete, the properties of fresh concrete, hardened concrete, and durability are improved. Using 45% GGBFS powder, 30% GGBFS fine aggregate, and 45% EAFS coarse aggregate, the concrete properties improved in comparison to the reference concrete. However, the results of the life cycle assessment showed that this mix design has more harmful effects on the environment than other designs of the present research. It should be noted that if these materials were not used in concrete, the same amount of damage would have been occurred due to their disposal.

Valorisation of bottom ash in concrete: serviceability, microstructural and sustainability characterisation

The present study investigated the synergistic influence of bottom ash as a Portland cement (PC) and natural fine aggregate (NFA) replacement in concrete. Coal bottom ash (CBA) is a heavy ash that settles at the bottom of the combustion chamber of a thermal power plant. It was ground (GCBA) for two hours prior to replacing 10–30% PC, while CBA was used in raw form to replace 25% and 50% NFA. The mechanical properties along with durability properties (accelerated carbonation and chloride penetration) were studied after 28 days and 90 days of curing. Non-destructive tests were also performed to check the quality of CBA-based concrete. Microstructural characterisation was conducted using various techniques, namely X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The concrete with 20% GCBA and 25% CBA (G20C25) reported the best performance in terms of parameters studied owing to the pozzolanic reactivity of GCBA and the filler effect of fine CBA. The microstructural investigations also validated the findings and trends observed in the experimental results. Well-fitted mathematical models were derived and optimisation was carried out using the desirability function approach. Multi-objective optimisation recommended 21.80% GCBA and 24.17% CBA as the optimum amount, resulting in a significant reduction of 19.19% and 18.19% in carbon footprint and eco-cost, respectively, compared to the control mix.

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.

Tailoring high ductility cementitious composite incorporating recycled fine aggregate based on shrinkage and mechanical properties

High ductility cementitious composite (HDCC) is recognized as an ideal structural bonding and repair material due to multiple steady-state cracking and strain-hardening properties. However， higher shrinkage strains and low economic and environmental friendliness limit its wide application. To promote the application of HDCC, recycled high ductility cementitious composite (R-HDCC) was prepared by using recycled fine aggregate (RFA) to replace natural fine aggregate (NFA), and the effects of RFA substitution rate and fly ash content on the mechanical and shrinkage properties of R-HDCC were thoroughly investigated. The results showed that the compressive strength of R-HDCC gradually decreased with the increase of RFA substitution, but its tensile strain was enhanced. R-HDCC, with 100 % RFA substitution, still maintained a tensile strength of 2.66 MPa and a tensile strain capacity of 2.46 %. The high fly ash content improved the matrix ductility, resulting in a 54.19 % increase in tensile strain over natural HDCC. In addition, the incorporation of RFA and fly ash reduced the autogenous shrinkage of R-HDCC due to the internal curing effect, but the total drying shrinkage of the matrix increased with increasing RFA substitution rate. R100-70 showed optimal environmental benefits and engineering application value through environmental impact assessment and economic analysis. Finally, this paper is expected to guide the design of ecological, economical, and high-performance R-HDCC.

Economic and Environmental Benefit Analysis between Crumb Rubber Concrete and Ordinary Portland Cement Concrete

Although manifold empirical studies have identified the mechanical properties of crumb rubber concrete (CRC), a comparative analysis of economic and environmental benefits between CRC and ordinary Portland cement concrete (OPCC) is not explored. In this paper, a quantitative meta-analysis between CRC and OPCC is conducted to explore optimized design strength, and a comparative analysis of the economic and environmental benefits of the two materials is undertaken. Considering cost price as the economic index and CO2 emissions per cubic meter of concrete as the environmental index in the materialization stage, CRC and OPCC were compared with different mix designs to achieve grades of similar strengths. Upon replacing less than 20% of natural fine aggregates in concrete with crumb rubber, while retaining the cement content, an increase of 6% in the cost price was achieved for CRC with 30–40 MPa strength grade. Apart from the aspect of mining and transportation of natural aggregates, the reduction of CO2 emissions by means of CRC adoption was verified in the treatment process of waste tire incineration. The results show that CO2 emissions from CRC decreased by 15–17% when compared with OPCC for 30~40 MPa grade concrete. The research conclusion can serve as a theoretical basis for the engineering application of CRC with the same strength, and make certain contributions to the industrial application of crumb rubber aggregates and the sustainable treatment of waste tires.

Sustainability Evaluation of a Paper and Pulp Industrial Waste Incorporation in Bituminous Pavements

The valorization of wastes as an alternative or secondary raw material in various products and processes has been a solution for the implementation of sustainability, a safer environment, and the concept of circular economy in the efficient use and management of natural resources. To promote sustainability through a circular economy approach, this work tries to demonstrate the environmental gains that are obtained by bringing together, in an industrial symbiosis action, two large industrial sectors (the pulp and paper and the road pavement sectors) responsible for generating large amounts of wastes. A sustainability assessment, based on a life cycle and circular economy approach, is presented here, and discussed using a simple case study carried out on a real scale. Two wastes (dregs and grits) from the pulp and paper industry (PPI) were used to partially replace natural fine aggregates in the production of bituminous mixtures used on the top surface of road pavements. The impacts at a technical, environmental, economic, and social level were assessed and it was shown that this simple waste valorization action is not only positive for the final product from a technical point of view, but also for the environment, causing positive impacts on the different sustainability dimensions that were evaluated.

Sustainable self-Compacting concrete with marble slurry and fly ash: Statistical modeling, microstructural investigations, and rheological characterization

The escalating generation of marble waste and the substantial carbon footprint associated with cement production pose significant environmental challenges. Thus, by substituting fly ash for supplementary cementitious material and using leftover marble waste for fine aggregate in concrete can reduce cost and carbon emissions that may lead to sustainable development. The presented paper aims to study the effect of partial substitution of marble slurry with natural fine aggregates and fly ash as supplementary cementitious material (SCM) on Self-Compacting Concrete (SCC). Polycarboxylate Ether (PCE) based superplasticizer (SP) was added in the concrete mix, to decrease the demand of higher water to binder (w/b) ratio. After developing SCC, fresh state properties and compressive strength (CS) at the curing age of 7 and 28 days were evaluated. To maximize the utilization of marble slurry and fly ash, mixture optimization was performed using the Box-Behnken Design (BBD), a robust technique within the response surface methodology (RSM) framework. Rheological analysis was performed to analyse the fresh state behaviour of the SCC with the help of the Bingham and Modified Bingham (MB) models. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) studies were also carried out to study the behaviour of the marble slurry and fly ash in the concrete. Carbon emission and cost analysis of SCC was evaluated at different replacement level of the marble slurry and fly ash. It was inferred that marble slurry and fly ash can be used in the certain percentages without compromising any strengthen and flowability properties of the SCC. The rheological behaviour also confirmed that linear and nonlinear behaviour of SCC in the certain mix proportion may results in the formation of the stable SCC. The analysis of cost and carbon emission confirmed that sustainable SCC mixture achieved substantial reductions of 21.44 % in cost and a remarkable 47.71 % decrease in carbon dioxide (CO2) emissions compared to conventional concrete.

Sustainable use of magnesite mine waste in self-compacting concrete and its study on strength, microstructure, cost and CO2 emission

Managing waste materials from mining is of universal interest owing to its massive volume, ecological impacts, health hazards, and disposal challenges despite high operational costs. Advancements advocate for recycling mine waste to sustainably support construction. As the construction sector heavily consumes resources, utilizing mine waste from magnesite mines (MMW) in concrete has gained attention. This experimental study assesses the viability of substituting MMW for natural fine and coarse aggregates in self-compacting concrete (SCC) at intervals of 10% up to 50% by weight. Evaluations were done on fresh (slump flow, T50 slump, V-funnel, J-ring, L-box) and hardened (compressive, splitting tensile, and flexural strength) properties, along with microstructural features, cost, and CO2 emissions. The findings unveil that nearly all mixtures exhibit commendable performance, where mine waste is replaced for fine and coarse aggregates showcasing superior fresh and hardened properties, respectively. Fresh property results reveal the SF1 flow category with VF1 and VF2 viscosity types for the SCC mixtures. Moreover, these SCC mixtures observed substantial strength enhancements of approximately 10% to 15% in compressive, splitting tensile and flexural test results at 28 and 90 days. Microstructural analysis corroborates the observed strength outcomes, indicating a denser concrete matrix. Significant environmental and economic benefits were observed, including a notable 20% reduction in CO2 emissions and 17% cost savings. These findings underscore the potential of integrating MMW into SCC mixtures as a sustainable approach towards construction materials, offering both performance and environmental advantages.

Influence on impact strength and chloride permeability of concrete made with cementitious material and artificial sand

The over usage of natural sand and cement has negative social and ecological effects. To address this, by-products of industrial wastes known as pozzolanic materials, including as fly ash, GGBFS, silica fume, and metakaolin, can be utilised with the manufactured sand in place of the natural fine aggregate and cement. As a result, the current research project discussed in this article examines the viability of replacing cement in concrete with pozzolana and crushed sand. Thus, this will address two issues at once: the large-scale use of pozzolanic materials and the preservation of natural sand quarries. The main objective of this experimental investigation is to find out the impact and durability properties of concrete produced by replacing natural sand by manufactured sand in varying percentages like 0, 10, 20, 30, 40, 50, 60 70, 80, 90, 100, and 20% cement replacing with pozzolanic materials. Cylindrical disc 150 mm diameter and 65 mm thick was tested for impact strength and chloride permeability 50 mm thick and 100 mm diameter samples were cast. The 28-day impact strength and chloride permeability of concrete mixed by partially substituting cement with pozzolan and partially substituting natural fine aggregate with artificial sand were tested. For the various concrete mix proportions, the findings for impact strength and chloride permeability were examined and contrasted with standard concrete. The results of this study show that substituting 20% of the cement with silica fume and 60% of the natural fine aggregate with M-sand results in concrete that has a maximum impact strength and a minimum chloride permeability. An ANN Model was developed using the experimental values. For design of model 400 result values where used, 20% results used for testing purpose and 80% results used for ANN model training. Calculated using the product of 25 input data. The ANN model’s results offer a precise elastic prediction of the impact strength and chloride iron pass ability of concrete mixed with substituting industrial cementitious waste for cement and artificial sand with naturally occurring fine aggregate. The findings of this study help to reduce the extraction of non-renewable natural recourses and the environmental impact of industrial waste by preparing more sustainable concrete.

Effect of Partial Replacement of Natural Fine Aggregate with Crushed Stone Dust: A Case Study of Makawanpur District

Effect of Partial Replacement of Natural Fine Aggregate with Crushed Stone Dust: A Case Study of Makawanpur District

Artificial neural network, machine learning modelling of compressive strength of recycled coarse aggregate based self-compacting concrete.

This research study aims to understand the application of Artificial Neural Networks (ANNs) to forecast the Self-Compacting Recycled Coarse Aggregate Concrete (SCRCAC) compressive strength. From different literature, 602 available data sets from SCRCAC mix designs are collected, and the data are rearranged, reconstructed, trained and tested for the ANN model development. The models were established using seven input variables: the mass of cementitious content, water, natural coarse aggregate content, natural fine aggregate content, recycled coarse aggregate content, chemical admixture and mineral admixture used in the SCRCAC mix designs. Two normalization techniques are used for data normalization to visualize the data distribution. For each normalization technique, three transfer functions are used for modelling. In total, six different types of models were run in MATLAB and used to estimate the 28th day SCRCAC compressive strength. Normalization technique 2 performs better than 1 and TANSING is the best transfer function. The best k-fold cross-validation fold is k = 7. The coefficient of determination for predicted and actual compressive strength is 0.78 for training and 0.86 for testing. The impact of the number of neurons and layers on the model was performed. Inputs from standards are used to forecast the 28th day compressive strength. Apart from ANN, Machine Learning (ML) techniques like random forest, extra trees, extreme boosting and light gradient boosting techniques are adopted to predict the 28th day compressive strength of SCRCAC. Compared to ML, ANN prediction shows better results in terms of sensitive analysis. The study also extended to determine 28th day compressive strength from experimental work and compared it with 28th day compressive strength from ANN best model. Standard and ANN mix designs have similar fresh and hardened properties. The average compressive strength from ANN model and experimental results are 39.067 and 38.36 MPa, respectively with correlation coefficient is 1. It appears that ANN can validly predict the compressive strength of concrete.

Influence of geometric shape, pore structure and surface modification of recycled fine aggregate on the rheology behaviour and strength development of mortar

The complex physical properties of recycled fine aggregate affect the rheological and mechanical properties of mortar, thereby limiting its application in cement-based materials. This paper evaluated the geometric shape and pore structure of natural fine aggregate (NFA), recycled fine aggregate (RFA), and recycled fine aggregate modified by water glass (MRFA), and studied its water absorption and bulk density. The influence of complex physical properties of RFA before and after modification on the rheological behavior, strength development, and microscopic properties of mortar was analyzed. The rheological tests were carried out on the fresh mortar with 7 mixes, and the compressive strength and flexural strength of hardened mortar after curing for 3, 7 and 28 days were tested. The results shown that the modification of water glass has improved the water absorption and geometric shape of RFA to some extent, resulting in a small increase in the apparent viscosity and yield stress of recycled mortar compared to NFA mortar. When the replacement level of RFA was less than 30 %, the compressive strength of recycled mortar was 13 % higher than that of NFA mortar. As the replacement level increased to 40 %, the incorporation of water glass also helped to improve the mortar strength. The irregular geometric shape and high water absorption of RFA were conducive to achieving dense mechanical bonding and reducing the Ca/Si ratio in the interface transition zone.

Performance of recycled refractory brick fine aggregate on diverse properties of Portland slag cement based heat resistant concrete

Utilization of industrial by-products generated through thermal processes is a critical approach in response to the industrialization and urbanization trends, may contribute to the creation of sustainable concrete, which might experience fire through its lifespan and its residual properties, are of specific interest. Hence, this innovation initiates a comprehensive experimental program to analyse the properties of novel heat resistant concrete, that blends Portland Slag Cement and Recycled Refractory Brick at distinct substitution levels (10,20,30,40,50,70, and 100 % of natural fine aggregate), including a control mix. The concrete samples are exposed to elevated temperatures (200,400,600,800, and 1000 °C) to assess the impact of Recycled Refractory Brick and develop a novel heat-resistant sustainable concrete, assuming the inherent heat resistance properties of Refractory Brick as it is prepared under high heating conditions. Subsequently, thermo-mechanical properties viz. weight loss, density loss, modulus of elasticity, ultrasonic pulse velocity, stress-strain behaviour, compressive strength, damage degree, failure pattern and Scanning Electron Microscopic analyses are executed. The experimental results displayed 1.01, 5.15, 6.01, 6.26 and 6.68 % of mass loss in the specimens after exposure to diverse elevated temperatures. The compressive strength significantly improved up to 29 %(10.57 MPa), 67 %(24.26 MPa) and 44 %(12.85 MPa) after exposure to 200, 400 and 600 °C temperature respectively compared to compressive strength at ambient temperature. The results pointedly indicate that higher substitution levels (70 and 100 %) have exhibited superior retention of mechanical properties compared to lower replacement levels after exposure to 800 and 1000 °C temperatures particularly. In authors’ view, substituting 10–40 % of natural fine aggregate with recycled refractory brick combining with Portland Slag Cement shows significant promise in the production of sustainable concrete intended for diverse applications under elevated temperature conditions.