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The study aims to investigate and find natural fiber as concrete reinforcement using the self-compacting concrete method. Methods of adding fiber and self-compacting concrete methods are exciting because these two methods have different characteristics and advantages. Therefore, the performance of the fresh-state flow capability of the self-compacting concrete method, which contains various fibers, was observed. Coconut fiber, pineapple leaf fiber, ijuk sugar palm fiber, and artificial polypropylene fiber were used with varying compositions of 0.3, 0.5, and 0.7% by mass of binder. The results show that coconut and pineapple fiber concrete met the European Guidelines for Self-Compacting Concrete standards. The coconut and pineapple fiber concrete performed admirably in all tests. [ABSTRACT FROM AUTHOR]

Geopolymer concrete (GPC) is a rising eco-conscious substitute for traditional cement-based concrete, bringing the construction industry closer to sustainability. Self-compacting geopolymer concrete (SCGC) enhances the concrete flowability and fills the congested reinforced areas without vibrators in concrete structures such as bridges, tunnels and canals. This study aims to analyze the impact of silicon dioxide nanoparticles (NS) on the rheological and mechanical properties of SCGC to optimize the dosage of NS in SCGC. For this purpose, NS (0–6%) blended in partially distributed binders of fly ash and ground granulated blast furnace slag (50:50) with 0.5 alkaline binder ratio, 2% superplasticizers (9 kg m−3) (MasterGlenium SKY 8233) and 12% extra water (54 kg m−3). Sodium silicate solution and sodium hydroxide ratio of 2.5 was used for this study. It is observed that SCGC with 3% NS replacement complied with the guidelines of EFNARC. According to the T50cm slump flow test, V-funnel test, and L-box test results meet the guidelines of up to 4% NS replacement, and 3% NS addition offers excellent mechanical properties in SCGC. This study concluded that the replacement of 3% of NS improved the fresh and hardened properties of SCGC, which can apply to construction. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is often used when compaction is difficult, requiring special attention to the curing process. However, traditional curing methods usually fail in practice. Despite taking precise measures to control water evaporation, surface water on vertical structure elements can still be problematic. To address these challenges, this study seeks to investigate the possibility of creating self-curing self-compacting concrete (SCSCC). Since the curing agent used has a significant impact on the production of SCSCC, this study examines the effects of using polyethylene glycol (PEG), a hydrophilic agent, at varying rates of 0.5%, 1%, 1.5%, and 2% on the fresh, hardened, and durability characteristics of the material. Additionally, to improve the sustainability properties of SCSCC, manufactured sand (M-sand) acquired from crushing rocks is used as a filler. Overall, the results indicate that the use of superplasticizer and M-sand is enough to achieve the required flowability for SCC mixtures without requiring specific fillers, and this method is effective in immediately controlling bleeding and segregation while maintaining the necessary compressive strength at all ages. The hardened properties of SCSCC were found to be improved by increasing the PEG content up to 1.5%, with an optimal range of 0.75% superplasticizer. Furthermore, the results demonstrate that the self-cured specimen, cured with PEG, has greater acid resistance than the conventionally cured one. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is a type of concrete that can be poured into complex geometries and dense reinforcement areas without the need for mechanical vibration, exhibiting excellent segregation resistance and flowability. Its adoption in the construction industry has surged in recent years due to its environmental, technical, and economic advantages, including reduced construction time and minimized occupational hazards. The performance of SCC is significantly influenced by the properties of the aggregates used. This study investigates the effects of variations in the coarse-to-fine aggregate ratio and water/binder (w/b) ratio on the fresh, hardened, and durability properties of SCC. A total of eight different SCC mixtures were prepared, utilizing two distinct s/b ratios and four varying fine-to-coarse aggregate ratios. The results indicated that increasing the s/b ratio enhanced fresh state performance but adversely affected mechanical strength and shrinkage behavior. Furthermore, the need for admixture and flow times improved with increasing coarse aggregate content, attributed to the reduction in cohesiveness and viscosity. However, this change did not significantly impact mechanical properties, while high-temperature resistance and shrinkage exhibited an upward trend. [ABSTRACT FROM AUTHOR]

Purpose: Recycled aggregate self-compacting concrete (RASCC) has the potential for sustainable resource utilization and has been widely applied. Predicting the compressive strength (CS) of RASCC is challenging due to its complex composite nature and nonlinear behavior. Design/methodology/approach: This study comprehensively evaluated commonly used machine learning (ML) techniques, including artificial neural networks (ANN), random trees (RT), bagging and random forests (RF) for predicting the CS of RASCC. The results indicate that RF and ANN models typically have advantages with higher R2 values, lower root mean square error (RMSE), mean square error (MSE) and mean absolute error (MAE) values. Findings: The combination of ML and Shapley additive explanation (SHAP) interpretable algorithms provides physical rationality, allowing engineers to adjust the proportion based on parameter analysis to predict and design RASCC. The sensitivity analysis of the ML model indicates that ANN's interpretation ability is weaker than tree-based algorithms (RT, BG and RF). ML regression technology has high accuracy, good interpretability and great potential for predicting the CS of RASCC. Originality/value: ML regression technology has high accuracy, good interpretability and great potential for predicting the CS of RASCC. [ABSTRACT FROM AUTHOR]

The production of raw-crushed wind-turbine blade (RCWTB) and its addition to conventionally designed self-compacting Concrete (SCC) enable us to provide a second life to wind-turbine blades. However, SCC containing RCWTB must show proper fresh behavior, an aspect evaluated in this paper both experimentally and through simulations based on computational fluid dynamics (CFD) for RCWTB additions up to 3.0% by volume. In experimental terms, RCWTB reduced the flowability and passing ability of SCC, and slowed SCC flow, although the performance of SCC with 1.5% RCWTB was adequate under free-flow conditions. In terms of modeling, RCWTB did not impact yield stress and increased plastic viscosity. CFD modeling under free flow, regardless of the presence or not of obstacles simulating concrete reinforcement, was successful, especially in the long term. Nevertheless, the modeling of the passing ability was not accurate; precision could be improved by simulating the effect of the individual GFRP fibers within the SCC flow. Finally, the mechanical properties of SCC were negatively impacted by RCWTB, the stitching effect of the GFRP fibers not being effective in an SCC with a conventional design. A specific SCC design when adding RCWTB is therefore needed to advance in the use of this waste in this concrete type. [ABSTRACT FROM AUTHOR]

Discarded medical face masks endanger the environment worldwide. In this study, experiments were conducted to investigate the effect of a shredded face mask (SFM) at 0% (control mix), 0.5%, 1.0%, and 2.0% by volume of concrete in the form of pieces that were 1 cm wide and 2 cm long on the properties of fresh and hardened concrete. After performing experimental testing on the materials, finite element masonry prisms with dimensions of 400 × 200 × 560 mm3 were modeled on the ANSYS platform. Four prisms with different fabric contents were numerically examined to study the compressive behavior, and 12 prisms with three different mortar joints were analyzed under an incremental horizontal load in the presence of four vertical displacements of 0.5, 1.0, 3.0, and 4.5 mm. The results revealed that increasing the SFM content in concrete led to a decrease in fresh and hardened concrete properties, including density, slump, split‐tensile strength, and compressive strength, by 9.5%, 20%, 24%, and 34%, respectively, compared with the control concrete at 0.5%. Moreover, the addition of 0.5% SFMs to the prism bricks reduced the maximum compressive load, deflection, and strain energy by 24%, 10%, and 39%, respectively. Altering the mortar type and vertical load affected the lateral cyclic behavior of the prisms. Compared with the M3 prism subjected to the same axial displacement, the M2 prism had 21.36%, 11%, 27.2%, and 10.48% higher lateral peak load, lateral peak displacement, equivalent stress, and strain energy, respectively. Furthermore, the lateral stiffness of the prism increases as the axial pressure increases. The lateral peak load of the M3 prism measured at 1.0, 3.0, and 4.5 mm axial displacement was raised by 60%, 142%, and 182%, respectively, as compared with the same prism at 0.5 mm axial displacement. The outcome provides a feasible concept for reusing masks in concrete construction with controllable strength deterioration on the masonry prism at 0.5% recycled SFM, resulting in attractive responses of these composites at the nonstructural scale [ABSTRACT FROM AUTHOR]

Self‐compacting concrete (SCC) is a specialized type of concrete that features excellent fresh properties, enabling it to flow uniformly and compact under its weight without vibration. SCC has been one of the most significant advancements in concrete technology over the past two decades. In efforts to reduce the environmental impact of cement production, a major source of CO2 emissions, silica fume (SF) is often used as a partial replacement for cement. SF‐modified SCC has become a common choice in construction. This study explores the effectiveness of soft computing models in predicting the compressive strength (CS) of SCC modified with varying amounts of silica fume. To achieve this, a comprehensive database was compiled from previous experimental studies, containing 240 data points related to CS. The compressive strength values in the database range from 21.1 to 106.6 MPa. The database includes seven independent variables: cement content (359.0–600.0 kg/m3), water‐to‐binder ratio (0.22–0.51), silica fume content (0.0–150.0 kg/m3), fine aggregate content (680.0–1166.0 kg/m3), coarse aggregate content (595.0–1000.0 kg/m3), superplasticizer content (1.5–15.0 kg/m3), and curing time (1–180 days). Four predictive models were developed based on this database: linear regression (LR), multi‐linear regression (MLR), full‐quadratic (FQ), and M5P‐tree models. The data were split, with two‐thirds used for training (160 data points) and one‐third for testing (80 data points). The performance of each model was evaluated using various statistical metrics, including the coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), objective value (OBJ), scatter index (SI), and a‐20 index. The results revealed that the M5P‐tree model was the most accurate and reliable in predicting the compressive strength of SF‐based SCC across a wide range of strength values. Additionally, sensitivity analysis indicated that curing time had the most significant impact on the mixture's properties. [ABSTRACT FROM AUTHOR]

AbstractThe transition of a material from macro- to Nano-scale brings about significant changes in electron conductivity, optical absorption, mechanical properties, chemical reactivity, and surface morphology. These changes present opportunities for creating innovative composite mixtures. As there is a growing need for improved infrastructure, it becomes crucial to develop new, high-performance materials. To enhance the performance of concrete mixtures, various methods have been explored, including the utilization of nanoparticles (NPs). Incorporating NPs aims to improve the fresh and mechanical properties of self-compacting concrete (SCC) while also enhancing the permeability and absorption capacity of the composite by introducing extremely fine particles to fill micro-pores and voids. Numerous initiatives have been implemented to explore the mechanical characteristics of SCC. Typically, compressive strength (CS) serves as a crucial mechanical parameter for assessing concrete quality. Conventional methods for determining SCC’s CS are costly, time-intensive, and restrictive due to the intricate interplay of various mixing proportions and curing processes. Thus, this investigation employs machine learning techniques, including artificial neural network (ANN), multi-expression programming (MEP), full quadratic (FQ), and linear regression (LR), to predict self-compacting mortar’s CS. Approximately 292 CS values from the literature were extracted and analyzed to facilitate model development. Six influential variables were used as input parameters and one as an output during the modeling process. Four statistical metrics gauged model performance, and sensitivity analysis was conducted. Results indicate that the ANN model outperformed other models in predicting self-compacting mortar’s CS. Meanwhile, the water-to-binder ratio, nanoparticle dosage, and concrete age significantly influence self-compacting mortar’s CS. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the self‐compacting alkali‐activated slag concrete‐filled cold‐formed steel tubes (SACFST) stub columns under axial compression. The innovative combination of alkali‐activated slag concrete (AASC) with concrete‐filled steel tubes (CFST) enhances both sustainability and structural performance. AASC, known for its eco‐friendly benefits compared to conventional concrete, was developed using industrial wastes, contributing to green construction practices. Based on Taguchi's L‐9 orthogonal array, nine mixes of self‐compacting alkali‐activated slag concrete (SASC) were developed, achieving impressive flowability exceeding 700 mm and compressive strengths ranging from 48 to 69 MPa. Additionally, split‐tensile strengths between 3.8 and 5.7 MPa, flexural strengths from 6.3 to 8.2 MPa, and a modulus of elasticity between 27.6 and 32.9 GPa were observed. Nine circular CFSTs containing SASC mixes were tested under axial compression, and a finite element model was developed to simulate their results. The experimental results were compared with standards from ACI 318, AIJ‐97, AISC‐360, AS 5100, and EC‐4, to evaluate the accuracy of axial capacity predictions. Among these standards, EC‐4 and AS 5100 provided the closest estimates, with mean PTest/PEC4 and PTest/P5100 ratios of 1.03 and 1.04, respectively, indicating a high level of accuracy. These findings highlight the potential of SACFST in advancing sustainable and resilient construction practices, laying the groundwork for future applications in structural engineering. [ABSTRACT FROM AUTHOR]

AbstractIn this research, masonry and concrete construction and demolition wastes (CDWs) were used as supplementary cementitious material (25% vol. residue of masonry, RM) and recycled coarse aggregate (RCA) in increasing levels (0%, 50% and 100% vol. residue of concrete), respectively, in the development of self-compacting concrete (SCC). The performance of SCC mixtures was evaluated in terms of fresh properties, compressive strength, resistance to both accelerated (1% CO2, 65% R.H. and 23 °C temperature) and natural carbonation as well as chloride penetration. Experimental results showed a monotonic workability reduction associated to the incorporation of increasing levels of RCA. In compressive strength, the SCC with RCA showed the greatest increase in this mechanical property after 28 days of accelerated exposure in the carbonation chamber, when compared to its water-cured counterpart. Yet, at 360 days of accelerated carbonation exposure, all SCCs showed compressive strength reductions compared to their water-cured counterparts. On the other hand, the chloride permeability resistance of the SCCs was low and very low at the ages evaluated. Thus, the findings of this study indicate that the use of CDW can generate SCCs with adequate fresh properties, compressive strength and carbonation and chloride penetration performance, which offers benefits for the environment. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is a specialized form of concrete known for its exceptional workability, high paste content, and incorporation of cement substitutes like silica fume, natural pozzolana, and slag. These cement alternatives offer various advantages including cost reduction, decreased carbon dioxide emissions, reduced depletion of natural resources, and enhanced properties in both fresh and hardened states. SCC finds application in diverse scenarios such as structures with densely packed reinforcement and tall shear walls, necessitating accurate performance prediction. This study aims to develop artificial neural network (ANN) models for forecasting the compressive strength, split tensile strength, and flexural strength of self-compacting concrete incorporating fly ash and waste copper slag, assessed at curing periods of 7, 28, 56, and 90 days. The ANN model comprises several input and output parameters, with model accuracy evaluated using Mean Squared Error (MSE) and R-squared (R2) metrics. Furthermore, the network's performance is evaluated through error histograms and regression network predictions using ANN. The Levenberg-Marquardt optimization method, implemented in MATLAB 2020a, is employed to effectively estimate the compression strength, split tensile strength, and flexural strength of self-compacting concrete, ensuring reliable results. [ABSTRACT FROM AUTHOR]

The research aims to investigate SCGC performance as a suitable alternative to the traditional concrete. The research will study the effect of LWCA, steel fiber and curing condition on the fresh and hardened properties of SCGC. The main materials will be used for SCGC are fly ash and slag. Curing will be performed using oven, and ambient temperature. Steel fibers SF will be incorporated into the mixture at 0%, 0.5%, 1% and 1.5% of binder content. While the natural coarse aggregate will be replaced by LWCA with 0%, 33.3%, 66.67% and 100% by weight. Analysis of this (SCGC) were done for both fresh and hardened state to assess the mechanical properties of (SCGC). This study finds that the addition of both LWCA and SF decreased the blend's L-Box ratio and slump flow value. All SCGC mixtures fulfilled the EFNARC guidelines and standards. Results reported that Mixes with a greater percentage of LWCA and SF became more cohesive and viscous. Results revealed that the SCGC exposed into ambient air curing condition had lower flexural strength, compressive strength, and tensile strength than of heating curing condition. The compressive strength CS of samples(M1-M9) exposed to heating conditions compared to the ambient ones increased about 36.09%, 26.32%, 17.88%, 23.87%, 27.96%, 27.69%, 38.94%, 27.91% and 24.53% respectively. The better CS values were 38.94% for M7 mix and 36.08% for M1 Mixtures. The FS of samples exposed to heating conditions compared to the ambient ones increased about 13.39%, 13.39%, 23.78%, 18.64%, 17.85%, 11.67%, 34.70%, 8.65% and 12.24% respectively the better flexural strength value was 34.70%, of M7 mix exposed to heating conditions. The better TS value was 26.22 Mpa for M3 Mixes at 1.5% of SF, While the TS reported dropping about 38.4% when applying LWCA as partially replacement of 66.67% with ambient curing condition. The study findings that the (CS) of mixes were proportional directly with steel fibers percentage till (1.0%). The CS, FS and TS of SCGC decreased when increasing LWCA. As a result, the SCGC that cured in oven showed enhancement in each fresh and mechanical properties, therefore, it is recommend to utilize the (SCGC) in hot areas and utilize wastes such as steel fibers and LWCA in SCGC as an economic, affordable and eco-friendly material. [ABSTRACT FROM AUTHOR]

The present study aims to determine the mix proportion of binder, heavyweight aggregates, water-to-binder ratio, and additives to develop self-compacting concrete with a bulk density higher than 2600 kg m−3. It also aims to evaluate the engineering properties, pore structure, and microstructure of established heavyweight self-compacting concrete. Barite (BA), magnetite (MAG) or their mix (MIX) were used as fillers, while binder was composed of Portland cement, blast furnace slag, metakaolin, and limestone at a ratio of 65:15:5:15. Based on text results of V-funnel, S-Cone diameter and S-Cone time, the proportion mix and binder: filler: binder to cement ration was optimized as follows: 1) BA 1: 3.5: 0.42, 2) MAG 1: 4: 0.42, and 3) MIX 1: 3.75: 0.42 with maximal aggregate size not exceeding 2 mm. Not only the bulk density was influenced by aggregate, but also, the mechanical properties, shrinkage, dynamic modulus of elasticity pore structure, and microstructure were also found to be dependent on fillers. [ABSTRACT FROM AUTHOR]

The present study aims to investigate how the use of high‐range water reducer (HRWR) and variations in water/cement (W/C) ratio affect the properties of self‐consolidating concrete (SCC) while taking into account different proportions of polypropylene fibers (PF) and natural zeolite (NZ). A total of 28 samples were cast and analyzed. PF fractions ranging from 0% to 1.5% by weight were added, along with a substitution of 10% NZ for cement (50 kg/m3). Four W/C ratios (0.30, 0.35, 0.40, and 0.45) were tested, in addition to seven HRWR contents ranging from 5 to 6.5 kg/m3. Various tests were conducted to assess slump, T500, V‐funnel, L‐box, modulus of elasticity, and compressive, tensile, and flexural strengths. Novel models were developed to predict the properties of hardened concrete based on W/C, HRWR, PF, and NZ content. Findings indicated that optimal performance of PF‐reinforced SCC with NZ was achieved when up to 0.75% PF was combined with an HRWR content equivalent to 1.25% of the cement fraction and NZ ratio. Furthermore, the proposed models offer accurate predictions of both fresh and hardened‐state properties of PF‐reinforced SCC with NZ based on W/C and HRWR ratios. [ABSTRACT FROM AUTHOR]

This study proposes a novel reduced beam section concrete‐filled double steel tube (RBS CFDST) beam‐to‐column joint and investigates the effect of RBS length and the beam moment of inertia on the plastic hinge formation in such joints. Therefore, a set of nine RBS CFDST connections were fabricated and cast with self‐consolidating concrete in the laboratory. Then, parameters including failure pattern, buckling mode, plastic hinge location, joint maximum load‐bearing capacity, and column rotation were inspected. The findings reveal that when the RBS length is equal to that of the beam dimension, the entire plastic hinge length is formed within the RBS zone. As such, the plastic hinge occurs away from the column face and brittle failure is avoided, while the joint column rotation is significantly reduced. It was also concluded that the maximum load‐bearing capacity is the highest when the RBS length is at its lowest. [ABSTRACT FROM AUTHOR]

Because the cement content is inexorably growing, CO2 emissions from the cement industry are becoming unavoidable. The use of rice husk ash (RHA) makes the system environmentally benign. This paper investigates the effect of RHA and manufactured sand (M-Sand) on the axial capacity of circular Concrete Filled Steel Tube (CFST) specimens subjected to axial compression. Thirty-two CFST specimens infilled with self-compacting concrete (SCC) with a replacement of RHA and M-Sand to cement and fine aggregate in 0%, 15%, 20% and 25% proportions are subjected to axial compression. Results show that use of RHA beyond 20% decreased the compressive strength of concrete and eventually decreased the axial capacity of CFST and occurred higher local buckling irrespective of their L/D ratios. Failure modes, strength index, confinement along with steel and concrete contribution on axial capacities of CFST specimens are studied. The axial capacities of the specimens were compared with various design code results such as: American concrete institute, Australian Standards, Chinese code, Eurocode, and Japanese code. Among all the codes, Chinese code overestimated the test results and hence, the axial capacity equation is altered and compared the results with test data along with 278 circular CFST data available from literature and found the results to be accurate. [ABSTRACT FROM AUTHOR]

The purpose of this study is to examine the influence of additives on estimating the useful service life of self-compacting concrete (SCC). For that, durability tests were performed on 43 SCC mix designs to estimating the service life of SCC based on the FIB model. The investigated supplementary materials included xanthan gum at concentrations of 0.2% and 0.25% by weight of cement, microsilica at concentrations of 5%, 7% and 10% by weight of cement, and nanosilica at concentrations of 2%, 3% and 4% by weight of cement. All 43 designs met the reliability index of the model, thereby obtaining the estimated service life for each design. The findings revealed that in chloride-rich environments, the control sample exhibited greater penetration depth compared to the concretes incorporating xanthan gum, microsilica and nanosilica additives. This observation suggests that the inclusion of xanthan gum extends the service life of SCC due to the formation of a denser and more cohesive structure in the hydration products of xanthan gum-modified concrete. Additionally, the investigations conducted indicate that the presence of nano and micro additives effectively reduces voids, while xanthan gum plays a significant role in minimising cracking and enhancing the thickening properties of the concrete. [ABSTRACT FROM AUTHOR]

Self-compacting concrete (SCC) is widely used in reinforced concrete buildings, owing to its ability to consolidate by weight and its lack of requirement for external vibration. Reinforced concrete buildings can be subjected to high strain rate loading during the early days of construction or in their service life. Thus, it is critical to understand the behaviour of concrete under high strain rate loadings at different ages. Minimal studies have previously focused on the early-age behaviour of concrete under high strain rates. This study tries to fill this gap. It focuses on the behaviour of M40 grade SCC under three levels of strain rate loading at ages of 1, 3, 7, 14 and 28 d. The split-Hopkinson pressure bar (SHPB) was used to test 45 SCC specimens of diameter 100 m and thickness 50 mm at high strain rates, ranging from 30 s−1 to 110 s−1, and the determined compressive strength, peak strain and elastic modulus results are compared with quasistatic test results of SCC specimens. The dynamic increase factor (DIF) determined in the SHPB experiment is compared with the CEB-fib code model. The results indicate that the DIF reduces as the concrete's strength and age increase. [ABSTRACT FROM AUTHOR]

In this paper, a novel pervious concrete (PC) has been proposed, which combines a high-strength self-compacting concrete matrix with artificial pore channels, to prepare a novel self-compacting recycled pervious concrete (NSRPC) with vertically and uniformly distributed pore channels. Then, an analysis was conducted to assess the flexural performance, permeability, and resilience to rainstorm of NSRPC after flexural fatigue load, which was carried out to ascertain the fluctuations in strength and drainage efficiency over the anticipated service life. The experimental results of NSRPC with porosity levels of 0.28%, 0.56%, 0.84%, and 1.12% show that the reduction in rainstorm will first decrease and then increase with the increase of fatigue cycles. After 2×105 fatigue cycles, the corresponding NSRPC flexural strength was 5.9, 5.6, 5.4, and 4.5 MPa, respectively, and the ultimate displacement decreased by 20.2%, 25.1%, 28.0%, and 33.1%, respectively. After 2×105 fatigue cycles, NSRPCs still demonstrate good storm waterlogging resistance under 20-, 50-, and 100-year rainstorms. The maximum water retention dissipation rate of NSRPC can reach 0.13 mm/min , and the maximum water retention depth is less than 2.5 mm. Additionally, the permeability coefficient of NSRPC remains almost unchanged with an increase in fatigue cycles. When the permeability coefficient is greater than 4.5 mm/s , the depth of stagnant water remains almost constant with the increase of the permeability coefficient. The research in this project provides a new material and direction for the study of pervious concrete to control rainstorms and waterlogging. [ABSTRACT FROM AUTHOR]

The effects of aggregate type and size on the fresh characteristics and strength gains of ambient-cured self-consolidating geopolymer concrete (SCGC) were investigated in the present study. SCGC was made from three different types of aggregates: crushed gravel, crushed marble, and a combination of both. In addition, several aggregate sizes (9 mm, 12 mm, and 16 mm) were also examined. The first group included 100% ground granulated blast furnace slag (GGBS), whereas the second group included 50% GGBS and 50% fly ash (FA). Slump flow, L-Box, and V-funnel tests were used to conduct fresh state tests, whereas compressive strength improvements were investigated at ages of 7 days, 14 days, 28 days, and 90 days. The results indicated that, regardless of aggregate type, aggregate size had a significant effect on fresh state characteristics. The optimal size of aggregate was 12 mm and crushed gravel showed optimum performance when compared to other types of aggregate and mixing. However, aggregate had a considerably lower effect on fresh characteristics than basic materials, and using fly ash significantly improved fresh properties. The improvement was about 5/, 10, and 60% respectively for both type/size of aggregate and the use of fly ash. Moreover, the base materials and aggregate types sufficiently affected the compressive strength of SCGC at different ages. The improvement was determined to be 8, 15, and 50% respectively for both the type/size of aggregate and the use of 100% GGBS. It was revealed that the compressive strength of SCGC in an ambient environment had a superior improvement at the age of 90 days in comparison to the age of 7, 14, and 28 days. [ABSTRACT FROM AUTHOR]

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This study explores the influence of different concentrations of recycled concrete aggregate (RCA) on the fresh and hardened properties of self-consolidating concrete (SCC) in order to assess the structural suitability of the use of RCA in a precast concrete plant. The study particularly emphasizes the early strength of the produced concrete. The RCA was sourced from crushed concrete used in roadway applications and was sieved to replicate the characteristics of natural aggregate. Five different SCC mixes were produced, with RCA substituting 0%, 10%, 30%, 50%, and 70% of the natural coarse aggregate (NCA) by weight. For each different mix design, the hardened properties tested were the compressive strength and tensile strength. The fresh properties investigated were the passing and filling ability. Additionally, aggregate properties including grain size distribution and absorption of coarse aggregate were studied. The selected mix design follows a typical well-graded self-consolidating concrete mix with 28-day strength of 8000 psi (55.16 MPa). It was found that replacing up to 50% of the NCA with RCA improves the early strength of concrete without a significant impact on the fresh and hardened concrete properties. [ABSTRACT FROM AUTHOR]

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transportation Science & Technolgy is the property of Transportation Science & Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Geopolymer concrete, a cement-free concrete with recycled concrete aggregate (RCA), offers an eco-friendly solution for reducing carbon emissions from cement production and reusing a significant amount of old concrete from construction and demolition waste. This research on self-compacted, ambient-cured, and low-carbon concrete demonstrates the superior performance of one-part geopolymer concrete made from recycled materials. It is achieved by optimally replacing treated RCA with a unique method that involves coating the recycled aggregates with a one-part geopolymer slurry composed of fly ash, micro fly ash, slag, and anhydrous sodium metasilicate. The research presented in this paper introduces predictive models to assist researchers in optimising concrete mix designs based on RCA rates and treatment methods, including the incorporation of coated recycled concrete aggregates and basalt fibres. This study addresses the knowledge gap regarding geopolymer concrete based on recycled aggregate, various RCA rates, and novel RCA treatments. The novelty of the paper also lies in presenting the effectiveness of Artificial Neural Network (ANN) models in accurately predicting the compressive strength, splitting tensile strength, and modulus of elasticity for self-compacting geopolymer concrete with various rates of RCA replacement. This addresses a knowledge gap in existing research on ANN models for the prediction of geopolymer concrete properties based on RCA rate and treatment. The ANN models developed in this research predict results that are more comparable to experimental outcomes, showcasing superior accuracy compared to linear regression models. [ABSTRACT FROM AUTHOR]

This study investigates mechanical properties, durability performance, non-destructive testing (NDT) characteristics, environmental impact evaluation, and advanced machine learning (ML) modelling techniques employed in the analysis of high-strength self-compacting concrete (HSSCC) incorporating varying supplementary cementitious materials (SCMs) to develop sustainable building construction. The findings from the fresh characteristics test indicate that mixes' optimal flowability and passing qualities can be achieved using different concentrations of marble powder (MP) alongside a consistent amount of silica fume (SF) and fly ash (FA). Moreover, the incorporation of 10% MP along with 10% FA and 20% SF in HSSCC significantly improved the compressive strength by 14.68%, while the splitting tensile strength increased by 15.59% compared to the reference mix at 56 days. While random forest (RF), gradient boosting (GB), and their ensemble models exhibit strong coefficient correlation (R2) values, the GB model demonstrates more precision, indicating reliable predicted outcomes of the mechanical properties. Following subsequent testing, it has been demonstrated that incorporating SCMs improves the NDT properties of HSSCC and enhances its durability. The finer MP, SF, and FA particles enhanced microstructural performance by minimizing voids and cracks while improving the C–H–S bond. As noticed by its lower CO2-eq per MPa for SCMs, the HSSCC mix with up to 15% MP inclusion increased mechanical strength while reducing the environmental footprint, making it an eco-friendly concrete alternative. [ABSTRACT FROM AUTHOR]

Steel fiber-reinforced self-compacting concrete (SCFRC) has been developed in recent decades to overcome the weak tensile performance of traditional concretes. As the flexural strength of SCFRC is dependent on the distribution of steel fibers, a numerical model based on Jeffery's equation was developed in this study for investigating the effects of the concrete flow on the fiber orientation and distribution in SCFRC. This numerical method shows higher computational efficiency than available particle-based methods like SPH and LBM. The influence of casting parameters like casting method, formwork size and casting velocity on the fiber orientation is investigated from the perspective of the flow field of fresh concrete during casting. The simulation results show that the fiber orientation is largely dominated by the concrete flow during the casting process. Importantly, during casting SCFRC beam, fibers tend to be oriented in parallel along the longitudinal direction at the middle section, while they stick up at the end of the formwork due to the upward concrete flow. In addition, the results from parametric studies show that the formwork size and casting method could significantly affect the concrete flow during the casting process, ultimately the orientation of fibers in a SCFRC beam. Furthermore, it indicates that the casting speed needs to be carefully chosen in order to achieve the optimal fiber alignment. [ABSTRACT FROM AUTHOR]

The effectiveness study results related to "soft" multi-stage crushing mode of concrete scrap are presented. During the research it was found that the processing of concrete scrap using this technology can significantly improve the characteristics of the secondary concrete aggregate, namely crushability, water absorption and voids. It is achieved by reducing the content of cement bound stones in the secondary crushed stone. Significant volumes of the dispersed material formed as a result of such processing can be used as a fine filler part at production technology of the self-compacting concrete. An optimum organic-mineral additive based on nanoparticle with a superplasticizer, which allows to obtain a homogeneous concrete mixture with additional stabilization properties was used for self-compacting concrete. The stability of the rheological characteristics of the modified cement systems will be insured if an optimum amount of organic-mineral additive is used. It was revealed that 28 days strength of a self-compacting concrete with concrete scrap crushing products content reaches more than 55,6 MPa, hardened under normal conditions and more than 75 MPa after one year under air-dry conditions. [ABSTRACT FROM AUTHOR]

This study focuses on the feasibility of using ground Acanthocardia tuberculate seashells as fine aggregates for self-compacting mortar production. The obtained results show a promising future for coastal industries as their use eliminates waste products and improves the durability of these materials. The use of Acanthocardia tuberculate recycled aggregate, in terms of durability, improves the performance of all mixes made with seashells compared to those made with natural sand, although it decreases workability and slightly reduces mechanical strength. Proper mix design has beneficial effects, as it improves compressive strength, especially when the powder/sand ratio is 0.7. Three replacement ratios based on the volume (0%, 50%, and 100%) of natural limestone sand with recycled fine aggregate from Acanthocardia tuberculate seashells, and three different dosages modifying the powder/sand ratio (0.6, 0.7, and 0.8), were tested. The fresh-state properties of each self-compacting mixture were evaluated based on workability. The mineralogical phases of the hardened mixtures were characterised using X-ray diffraction, thermogravimetry, and differential analyses. Subsequently, the mechanical and durability properties were evaluated based on the compressive and flexural strengths, dry bulk density, accessible porosity for water and water absorption, drying shrinkage, mercury intrusion porosimetry, and water absorption by capillarity. Therefore, the use of Acanthocardia tuberculate seashells in cement-based systems contributes to circular economy. [ABSTRACT FROM AUTHOR]

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400...D1600 based on hollow microspheres in comparison with heavy fine-grained D2200 concrete and to establish their structural and physico-mechanical characteristics. The study of the concrete mixtures was carried out using the slump flow test and the rotational viscometry method. The physical and mechanical properties were studied using standard methods for determining average density and flexural and compressive strength. According to the results of the research conducted, differences in the flow behaviors of concrete mixtures on dense and hollow aggregates were found. Lightweight concretes on hollow microspheres exhibited better mobility than heavy concretes. It was shown that the self-compacting coefficients of the lightweight D1400...D1600 concrete mixtures were comparable with that of the heavy D2200 concrete. The rheological curves described by the Ostwald–de Waele equation showed a dilatant flow behavior of the D1400 concrete mixtures, regardless of the ratio of quartz powder to fractionated sand. For D1500 and D1600, the dilatant flow behavior changed to pseudoplastic, with a ratio of quartz powder to fractional sand of 25/75. The studied compositions of lightweight concrete can be described as homogeneous at any ratio of quartz powder to fractional sand. It was shown that concrete mixtures with a pronounced dilatant flow character had higher resistance to segregation. The value of the ratio of quartz powder to fractional sand had a statistically insignificant effect on the average density of the studied concretes. However, the flexural and compressive strengths varied significantly more in heavy concretes (up to 38%) than in lightweight concretes (up to 18%) when this factor was varied. The specific strength of lightweight and heavy concrete compositions with a ratio of quartz powder to fractional sand of 0/100 had close values in the range of 20.4...22.9 MPa, and increasing the share of quartz powder increased the difference between compositions of different densities. [ABSTRACT FROM AUTHOR]

Concrete is used worldwide as a construction material in many projects. It exhibits a brittle nature, and fibers' addition to it improves its mechanical properties. Polypropylene (PP) fibers stand out as widely employed fibers in concrete. However, conventional micro-PP fibers pose challenges due to their smooth texture, affecting bonding within concrete and their propensity to clump during mixing due to their thin and soft nature. Addressing these concerns, a novel type of PP fiber is proposed by gluing thin fibers jointly and incorporating surface indentations to enhance mechanical anchorage. This study investigates the incorporation of macro-PP fibers into high-strength concrete, examining its fresh and mechanical properties. Three different concrete strengths 40 MPa, 45 MPa, and 50 MPa, were studied with fiber content of 0–1.5% v/f. ASTM specifications were utilized to test the fresh and mechanical properties, while the RILEM specifications were adopted to test the bond of bar reinforcements in concrete. Test results indicate a decrease in workability, increased air content, and no substantial shift in fresh concrete density. Hardened concrete tests, adding macro-PP fibers, show a significant increase in splitting tensile strength, bond strength, and flexural strength with a maximum increase of 34.5%, 35%, and 100%, respectively. Concrete exhibits strain-hardening behavior with 1% and 1.5% fiber content, and the flexural toughness increases remarkably from 2.2 to 47.1. Thus, macro PP fibers can effectively improve concrete's mechanical properties and resistance against crack initiation and spread. [ABSTRACT FROM AUTHOR]

AbstractIn order to study the seismic performance of Reinforced Concrete columns strengthened with Carbon Fiber Reinforced Polymer-steel tube self-compacting concrete, seven strengthened columns and one unstrengthened column were designed and manufactured with the main parameters of axial compression ratio, self-compact concrete strength, steel tube shape and steel tube thickness. The hysteresis curve, skeleton curve, ductility, energy dissipation capacity, stiffness, steel tube surface and steel bar strain variation of the specimens were analyzed. The test results show that the strengthened part of the specimen has good cooperative working ability with the RC column, and the failure process and failure mode of the specimen are similar to those of the concrete filled steel tube. Under the action of horizontal reciprocating load, the concrete at the bottom of the strengthened column is cracked; with the increase of horizontal displacement, the hysteresis curve becomes full and the energy dissipation capacity increases. The finite element software ABAQUS is used to model and analyze the specimens. The simulation results are in good agreement with the experimental results. It is proved that the simulation is reasonable and effective in unit selection, contact setting, meshing and material constitutive selection. The hysteresis curve, skeleton curve and failure mode of each specimen are obtained. [ABSTRACT FROM AUTHOR]

In this paper, the possibility of utilising coarse recycled concrete aggregate (CRCA) obtained from a construction and demolition waste (CDW) plant in Delhi to make 60 MPa self-compacted concrete (SCC) was evaluated. The CRCA was used in as-collected condition and was not processed any further. The aggregate packing (bulk) density (APD) method was adopted to prepare the SCC-CRCA mixture in order to obtain an aggregate mixture exhibiting maximum bulk density/least void content (45%). In addition, SCC was made using aggregate mixtures in which the natural coarse aggregate (NCA) was replaced with CRCA at 0%, 20% and 100% of the total coarse aggregate content by weight. The cement, fly ash, silica fume and water were kept constant for all SCC mixtures. The effects of CRCA on the flow behaviour, mechanical strength, shrinkage characteristics and microstructure properties of SCC mixtures were evaluated. The test results indicated that SCC mixtures made with up to 45% CRCA replacement can be used for structural concrete, which is higher than that recommended in Indian (20%) and international specifications (35%) for traditionally vibrated (conventional) concrete. [ABSTRACT FROM AUTHOR]

This article investigates the durability of recycled self-compacting concrete in relation to its resistance against freeze-thaw cycles and alkali-silica reactions. It explores the properties of fresh concrete, investigates the impact of various additives, and evaluates key factors such as spalling, weight loss, compressive strength, expansion rate, and ultrasonic properties in hardened concrete samples incorporating different levels of recycled aggregates. The findings illustrate the feasibility of achieving self-compacting recycled concrete by increasing the use of superplasticizers and adding 10% beach sand. Furthermore, incorporating 10% micro-silica and 7.5% wollastonite in the recycled mix enhances the strength of all samples, with the 25% recycled material sample demonstrating the highest strength and durability. Despite a decrease in strength and increased expansion as recycling percentages and freeze-thaw cycles rise, the recycled samples maintain acceptable durability. Additionally, this study employs the R programming language to elucidate the relationship between compressive strength and modulus of elasticity, offering valuable insights into recycled concrete performance and behavior. [ABSTRACT FROM AUTHOR]

Construction firms face considerable challenges in relation to finding cost-effective formwork solutions to meet increased construction demands. Project stakeholders have relied on self-consolidating concrete (SCC) to speed up the construction time because SCC is highly fluid and has numerous advantages compared to traditional concrete. To withstand SCC's high fluidity, formwork systems should be robust. Although previous research has experimentally examined various characteristics of SCC, few research studies have used machine-learning algorithms to estimate or predict the lateral pressure exerted by SCC on formwork systems. Hence, this study addressed this knowledge gap by proposing a machine-learning approach to predict the lateral pressure of SCC on vertical formwork systems. First, laboratory tests were performed to collect data on lateral pressure measurements, material factors, placement conditions, and formwork characteristics affecting the SCC lateral pressure on formwork systems. Second, four supervised machine-learning algorithms were considered in this study: k-nearest neighbor (KNN), artificial neural network (ANN), decision tree (DT), and random forest (RF). Third, the hyperparameters of the machine-learning algorithms were tuned, and their performance metrics were compared. Fourth, the most accurate predictive machine-learning model was verified on an unseen testing set. The results showed that the RF machine-learning algorithm was the best model for predicting the lateral pressure of SCC on formwork systems, with a mean percentage error of 0.8%, a mean absolute percentage error of 4.29%, and a coefficient of determination R2 of 0.9548. This study adds to the construction engineering and management body of knowledge by developing a machine-learning predictive model that can be used to accurately assess the lateral pressure exerted by SCC on formwork, which helps to ensure safe design of formwork systems and economic construction operations in formwork-related activities. [ABSTRACT FROM AUTHOR]

The accumulation of phosphogypsum (PG) has become a significant environmental and economic challenge, making PG reuse an urgent concern. This study aims to explore the potential of combining PG with steel slag (SS), ground granulated blast-furnace slag (GGBS), and cement clinker (CC) to create excessive-sulfate phosphogypsum slag cement (EPSC) for use in self-compacting concrete (SCC). However, residual acid and other impurities in PG can significantly slow down the setting time of EPSC. To optimize the setting time, different methods including wet grinding, washing, and the addition of pure gypsum, limestone powder (LP), and aluminum cement (AC) are used. Results show that the wet grinding method and washing method remove soluble phosphorus impurities and reduce fluorine ion levels by 64%. However, nonsoluble impurities that cannot be removed by wet grinding and washing continue to affect EPSC's setting time. Furthermore, the addition of LP shortens the setting time, but not enough. Using a 3% dosage of AC successfully reduces the setting time to a satisfactory level and EPSC SCC with a 28-day strength greater than 40 MPa is produced using the paste rheological threshold method. [ABSTRACT FROM AUTHOR]

Developing low-carbon and green self-compacting concrete (SCC) is essential for advancing sustainable building materials. In this study, recycled steel fibers (RSFs) and industrial by-products were combined for the production of SCC made with recycled aggregates (RSCC), with the aim of introducing multiple waste materials to improve the sustainability of SCC. 14 RSF-reinforced RSCC mixtures (RSF-RSCC) were prepared by replacing natural coarse aggregates (NCAs) with recycled coarse aggregates (RCAs) and cement with supplementary cementitious materials (SCMs) and reinforced with RSFs. The parameters studied in this paper include replacement levels of RCAs (75%), SCMs (50% and 75%), and RSFs (0.5%, 1.0%, and 1.5%). The influence of different content of RSFs and SCMs combinations on workability and mechanical properties was studied, and the synergistic influence of RSFs and SCMs was investigated in detail. The microstructure characteristic was investigated using a scanning electron microscope. The test results show that the addition of SCMs can compensate for the adverse effects of RSFs on the fresh properties, and all RSF-RSCC exhibited superior workability. Furthermore, the incorporation of RSFs enhanced the mechanical properties of RSCC, resulting in remarkable improvement in the compressive and flexural strengths. The combined incorporation of RSFs and SCMs led to an excellent synergistic effect, which resulted in significant enhancements in the mechanical properties. [ABSTRACT FROM AUTHOR]

This study investigates prestress loss measured on precast, prestressed concrete bridge beams for a bridge in Oklahoma. The research examines the effects of including mild reinforcing steel in the bottom flange of precast concrete girder and the alternative prestressing pattern on the prestressing losses of pretensioned bridge girders. Using solar powered batteries, a structural monitoring system has been providing an ongoing stream of data since beam fabrication and will continue through the service life of the bridge. In addition to the measured data, the prestress losses were predicted at the girder midspan using five different methods for computing prestress loss. Data show that current equations overestimate the concrete elastic modulus at early ages, leading to an underprediction of elastic shortening losses. Results show that prestress losses are reduced by incorporating a combination of fully tensioned top strand plus mild steel in the bottom flanges of the bridge girder. [ABSTRACT FROM AUTHOR]

The article discusses a research collaboration between PCI and Oak Ridge National Laboratory (ORNL) on next-generation materials for architectural precast insulated wall panels. The project aimed to develop lighter panels with higher thermal performance and a shorter production time. The research focused on developing a concrete mixture with reduced density and early tensile strength, as well as noncorroding inserts for the panels. The collaboration has led to further research opportunities in the precast concrete industry. [Extracted from the article]

This study investigated the effects of using bagasse ash (BA) and metakaolin (MK) together as substitutes for cement in self-compacting concrete (SCC), together with the addition of glass fiber (GF), on the physical and mechanical characteristics of concrete. Eighteen SCC mixes were created, each containing different proportions of BA (0%, 10%, 15%, and 20%), MK (0%, 10%, 15%, and 20%), and BA and MK collectively (10% + 5% and 10% + 10%) as cement replacements with and without 0.1% GF. Using the results of the slump flow, T500 slump flow, V-funnel, and L-box tests, the performance of fresh SCC was determined. Furthermore, this study evaluated the strength, durability, and microstructural properties of the SCC samples. The SCC mix blended with 10% BA and 5% MK revealed better flowability as the slump flow increased from 692 mm to 715 mm. A strong linear correlation was discovered between the slump flow values (mm) and V-funnel duration (sec) and blocking ratio (H2 /H1 ) with R² = 0.8876 and R² = 0.8467, respectively. Of all test mixes, the SCC mix blended with 10% BA, 5% MK, and 0.1% GF (SCC1B10M5) demonstrated the highest degree of strength. At 56 days, the 10% BA, 5% MK, and 0.1 GF mix had 12.8%, 25.7%, and 22.2% higher compressive, flexural, and splitting tensile strengths than the control mix, respectively. SCC, combined with BA, MK, and GF, outperformed the control mix. After immersion in a 3% H2SO4 solution, the SCC mix having 10% BA, 5% MK, and 0.1% GF experienced a minimum reduction in weight loss and ultrasonic pulse velocity of 1.01% and 3.1%, respectively. Additionally, there was a decrease of 29.4% in the percentage of charges passed. The ideal composition was achieved by incorporating 10% BA, 5% MK, and 0.1% GF into the SCC mixture, resulting in a dense structure without any visible pores or cracks during the microstructural analysis. [ABSTRACT FROM AUTHOR]

The production and servicing of cement-based building materials is a source of large amounts of carbon dioxide emissions globally. One of the ways to reduce its negative impact, is to reduce concrete consumption per cubic meter of building structure through the introduction of hollow concrete products. At the same time, to maintain the load-bearing capacity of the building structure, it is necessary to significantly increase the strength of the concrete used. However, an increase in strength should be achieved not by increasing cement consumption, but by increasing the efficiency of its use. This research is focused on the development of technology for the production of thin-walled hollow concrete blocks based on high-strength, self-compacting, dispersed, micro-reinforced, fine-grained concrete. The use of this concrete provides 2–2.5 times higher strength in the amount of Portland cement consumed in comparison with ordinary concrete. The formation of external contours and partitions of thin-walled hollow blocks is ensured through the use of disposable formwork or cores used as void formers obtained by FDM 3D printing. This design solution makes it possible to obtain products based on high-strength concrete with higher structural and thermal insulation properties compared to now existing lightweight concrete-based blocks. Another area of application of this technology could be the production of wall structures of free configuration and cross-section due to their division, at the digital modeling stage, into individual element-blocks, manufactured in a factory environment. [ABSTRACT FROM AUTHOR]