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Compared with the ground service environment, the evolution of concrete performance under a water pressure service environment is quite complex with variable conditions. Because of the coupling effect of load and pressure, water has a special impact on the strength and deformation of concrete. Meanwhile, harmful ions usually react with the cement matrix as pressure water seepages into concrete, resulting in the reduction of concrete durability. Based on this, this study provides a comprehensive review of the strength, deformation, and durability of concrete under water pressure environment. It is found that microcracks in concrete tend to propagate and connect after exposure to water pressure, leading to a decrease in strength and deformation performance. The average loss rate of strength and elastic modulus increased by 12.15% and 10.97%, respectively, when water pressure increased by 1 MPa. However, the loading process of water‐confining pressure makes concrete more compact, where the static and dynamic mechanical performance can be improved. Besides, due to the enhancement of excess pore water pressure, concrete strength under a high strain rate increases by 61.79% compared to static load. The effect of water pressure increases the ability of the liquid to penetrate concrete, and corrosive ions trapped within the liquid and freeze–thaw caused by external temperature changes would further reduce the concrete durability. This study points out that static and dynamic loading characteristics and durability of concrete under multi‐factor coupling in a water pressure environment will be the future research direction. The summarized contents can provide guidance for construction and research of concrete engineering under a water pressure environment. [ABSTRACT FROM AUTHOR]

Alleviating cracks induced by the temperature rise in mass concrete has always been a research hotspot and engineering problem. In this study, a type of energy storage phase change low‐temperature rising concrete was designed and prepared to reduce the cracking risk of mass concrete. First, a type of energy storage coarse aggregate (ESA) was prepared using a semi‐dry method with cement and fly ash as matrix materials, mixed with carbon black (CB), carbon fiber (CF), and phase change material (PCM). Furthermore, the influence of these materials on the mechanical properties, microstructure, and pore structure of the ESA was studied. Subsequently, ESA was used to prepare phase change low‐temperature rising concrete, and its mechanical properties, thermal conductivity (TC), and internal temperature rise were investigated. The research results show that, except for the compressive strength of PCM‐15‐ESA, which is only 7% lower than that of the control, PC‐P0, other samples have no mechanical property deterioration. The double‐layer protection measures can effectively avoid the mechanical property deterioration of concrete induced by PCM leakage. The maximum internal temperature rise of concrete is reduced by 9.8°C, which greatly reduces the risk of cracking of concrete. [ABSTRACT FROM AUTHOR]

Utilization of industrial by‐products in concrete is an effective way to reduce the exhaustion of raw materials for concrete production, but it can lead to degradation in concrete properties. Therefore, research efforts are required to achieve a balance between waste utilization and concrete performance. This study examined the strength and durability performance of geopolymer concrete (GPC) developed from fly ash (FA) and fine rice husk ash (FRHA) as main binders (50/50), with partial OPC substitution at different levels (0%–30%). Various properties like workability, compressive strength, water absorption, chloride penetration resistance, carbonation depth, electrical resistivity (ER), and acid attack resistance were experimentally investigated. Results indicated that there was a noticeable improvement in the workability with 20% OPC substitution, achieving the highest slump of 110 mm. The highest compressive strength (50 MPa) was attained with 15% OPC substitution after 90 days. Mix FR85C15 (15% OPC replacement) showed the highest durability performance at all ages through various indicators, that is, water absorption, charge passed, carbonation depth, and ER. Scanning electron microscopy and energy dispersive spectroscopy analyses also validated the enhanced microstructure of FR85C15 compared with other mixes. When exposed to sulfuric acid (H2SO4), Mix FR85C15 showed a minimal loss of 14% in compressive strength. It was concluded that GPC produced using FA and FRHA substituting OPC (up to 15%) can potentially be utilized for structural applications. [ABSTRACT FROM AUTHOR]

This report examines the strength of young and early age concrete that has been systematically exposed to horizontal, sinusoidal vibrations with varying vibration parameters. Specimens were subjected to vibrations of predefined vibration times (4–14 h) and the compressive strength was determined after a period of 28 days. It was found that the different parameters have no critical influence on compressive strength and that vibration prior to initial setting of the concrete can increase its strength. Additional information to examine the reasons for this increase was obtained by further investigations (nuclear magnetic resonance, x‐ray diffraction, and thermogravimetric analysis). [ABSTRACT FROM AUTHOR]

Experimental and numerical studies were conducted to investigate interaction between reinforced‐concrete grid frame (CGF) and ceramsite foam concrete (CFC) infill. In the experiments, compressive tests were performed on the CGF and RC grid frame filled with the CFC which forms a composite wall, namely CGFW. To investigate the mechanical properties of the CGFW and the interactions between the CGF and CFC infill, the failure modes, integral stiffness, local strains, and load distribution coefficients of the composite wall were analyzed. The experimental results indicated that the CFC infill could uniformly transmit loads and significantly improve the bearing capacity and vertical stiffness of the CGFW while reducing the ductility of the composite wall. The load distribution coefficients of the CFC infill were stable at 0.51 ± 0.06 before peak load and damage evolutions in concrete columns were effectively alleviated due to obvious interactions between the CGF and CFC infill. To evaluate the interaction mechanisms of the two, numerical analysis was carried out by changing the sizes of central grid, opening rates, and reinforcement ratios of the composite walls. The finite element model with plastic damage constitutive of concrete was calibrated by comparing the experimental results. The numerical results indicated that the interaction between the CGF and CFC infill was insensitive to changes in grid sizes, and the interaction between the two was significantly different with the same reinforcement method of frame beams and columns. In addition, the CFC infill played an important role in the stability of CGF as the opening rate significantly affected the mechanical properties of the CGFW, and a stable path of load transfer was the key factor to ensure the interaction between the CGF and CFC infill. [ABSTRACT FROM AUTHOR]

A novel posttensioning technique using nickel‐titanium‐niobium (NiTiNb) shape memory alloy (SMA) wires for the repair of reinforced concrete beams was evaluated numerically. A finite element model of a reinforced concrete beam was developed within a damage mechanics framework to simulate concrete cracking and subsequent posttensioning. The predicted yield and ultimate moment capacities of the simulated posttensioned beams were up to 14% less than the corresponding experimental results. Cumulative discrepancies in the assumed material models led to the conservative model results. The effects of concrete tensile damage, SMA reinforcement ratio, SMA‐concrete interaction (bonded vs. unbonded), and the effective prestress on the service and ultimate behavior of the posttensioned beam were evaluated. Partial loss of prestress in the SMA due to elastic shortening of the concrete was insignificant (<3%) because of the relatively low elastic modulus of the SMA. Increasing the SMA reinforcement ratio by three times increased the yield moment of the posttensioned beam by 99%. Reducing the effective SMA prestress to 80% of the initial prestress to account for the possible losses resulted in a decrease in the yield moment by up to 7.8%. [ABSTRACT FROM AUTHOR]

For the assessment of concrete structures in the new fib Model Code 2020 (fib MC 2020), three categories are distinguished: (1) the residual capacity of existing structures without damage, (2) the residual capacity of structures suffering deterioration, and (3) the residual capacity of structures with noncompliant details. In the accompanying paper by Walraven and Dieteren in this volume, the backgrounds for this subdivision have been explained, and indications for the assessment of existing concrete structures in those categories have been given. In the actual paper, examples are given how to perform an assessment of concrete structures for the categories mentioned above. These examples have contributed to the formulations of the recommendations proposed for fib MC 2020. [ABSTRACT FROM AUTHOR]

Sustainability is a global goal of sustainable development aimed at ensuring a quality life on the Earth for the future generations. Buildings, infrastructure and the entire built environment should be better prepared for the new conditions—they should be sustainable, resilient and adaptable to new situations. This requires new technical solutions for the construction, reconstruction, and modernization of buildings and all other engineering structures. Concrete is gradually becoming a building material with great potential for realizing technical solutions that meet new requirements, leading to the necessary reduction of environmental impacts and consequent improvement of social and economic conditions. The paper presents implementation of sustainability principles in the new fib Model Code 2020 (MC2020). This represents a contribution of the International Federation for Structural Concrete (fib) to the achievements of the Sustainable Development Goals (SDGs), set by the United Nations in 2015 as an action plan for the period up to 2030. [ABSTRACT FROM AUTHOR]

This paper introduces the conservation and intervention provisions included in the latest edition of the fib Model Code for Concrete Structures (MC2020). This is the first international code which addresses life‐cycle management issues for both new and existing concrete structures. Accordingly, the contents relating to conservation (maintenance and interventions) have been extensively enhanced compared with the provisions included in the previous MC2010, with these now including monitoring. Much of the contents on interventions are newly‐added provisions in MC2020. A new chapter (19) is introduced to show the available materials/systems and the properties necessary for these materials. The necessary properties required to make successful interventions also include consideration of the long‐term performance of materials/systems and compatibility with the substrate concrete. All the processes for interventions, including intervention strategies, selection of intervention methods, survey for interventions, design of interventions and execution of interventions are explained in chapter (38) on conservation and a new chapter (37) on execution of interventions. Selection of intervention methods should be made according to the intervention strategies and the causes and extent of deterioration/damage. In the future the issues of repairability and the standardization of intervention methods are expected to have greater importance. Repairability is the ability to physically repair a structure or structural element which has deteriorated or been damaged by the effects of the considered actions, thus restoring its functionality, but while incurring acceptably low economic cost, environmental burdens and societal disruption. [ABSTRACT FROM AUTHOR]

Reinforced concrete structures can experience various harsh environments during their service life, among which chloride ion exposure, especially in marine environments, can cause the durability reduction and deterioration of concrete structures. Artificial intelligence (AI)‐based modeling of the non‐steady‐state apparent chloride diffusion coefficient (DC) of concrete for a long exposure time using the experimental field results can assist in identifying the influential factors and better estimating the service life of a concrete structure. In this study, two novel extensions of ensemble AI algorithms, including genetic programming forest (GPF) and linear genetic programming forest (LGPF) algorithms, were proposed to model the DC of concrete. The experimental field data were gathered from the literature. Different structures of the proposed ensemble methods were developed and examined, and the best‐developed model was selected for further analysis, including sensitivity analysis and parametric study. In addition, the random forest (RF) method was used as the control ensemble technique to have a comparison. The results show that the best LGPF model possesses superior performance than the best‐developed GPF and RF models. In addition, the results show that silica fume‐to‐binder ratio, exposure time, and exposure conditions have the most significant impacts on the DC of concrete. This study contributes to the civil engineering practice by developing a new tool to model the DC of concrete that facilitates the durability assessment of concrete structures. [ABSTRACT FROM AUTHOR]

This study investigated the mechanical properties and stress–strain relationship of polypropylene fiber recycled aggregate concrete (PFRAC) subjected to uniaxial cyclic compression. A total of 78 cylindrical specimens were designed for uniaxial cyclic compression test with coarse aggregate replacement rate, polypropylene fiber volume fraction, and loading rate as variation parameters. The failure process of the specimens under cyclic loading was observed and recorded. The stress–strain curve of PFRAC was summarized. The important mechanical properties of PFRAC were obtained, such as plastic strain, accumulated energy dissipation. The microstructure of PFRAC was analyzed by scanning electron microscopy, and the crack resistance mechanism of PFRAC under cyclic loading was revealed. The results show that the PFRAC under cyclic loading appeared oblique splitting failure. The compressive stress–strain curve envelope of PFRAC subjected to cyclic loading exhibited similarity to the monotonic counterpart. The addition of polypropylene fibers can improve the peak stress, peak strain, residual stress, post‐peak ductility, and accumulated energy dissipation of the recycled concrete. In addition, a constitutive relation formula for the PFRAC stress–strain curve under cyclic loading is proposed, and the fitting result is good. [ABSTRACT FROM AUTHOR]

When considering the assessment of concrete structures, a consistent approach to assess the safety level of existing structures in an objective and well‐founded way is currently still lacking in practice. As such, fib TG3.1 has developed proposals for the quantification of adjusted partial factors for the assessment of existing structures and has harmonized these proposals with partial factors for design. This resulted in a set of equations and tabulated values for the determination of partial factors for the design of new structures as well as the assessment of existing structures, currently under consideration for the fib Model Code 2020 (MC2020). In this contribution, the equations and tabulated values for partial factors as proposed for MC2020 are briefly summarized and applied in a full‐probabilistic first order reliability method (FORM) analysis in order to assess the accuracy of the proposal with respect to reaching chosen target reliability levels. The proposals appear to lead to a consistent and adequate framework for both design and assessment, that enables targeted safety levels to be achieved. [ABSTRACT FROM AUTHOR]

The next edition of the fib Model Code for concrete structures, Model Code 2020 (MC2020), is under development with the aim of issuing a first partially harmonized draft for comment in early 2023. MC2020 is a single code dealing with both new and existing concrete structures, that is both the design of new structures and the various activities associated with the assessment, interventions upon and life‐cycle management (LCM) of existing concrete structures. The paper outlines the overarching sustainability framework and the performance‐based or outcomes‐based approaches (PBA) adopted by MC2020. There is a pressing need to reduce barriers to the evolution in concrete construction materials and the technical aspects of design and the LCM of existing structures, in order to meet pressing climate change drivers and the goal of achieving lower carbon construction. MC2020 also addresses significant advances made on a wide range of issues including those relating to structural design and analysis methods, seismic design and assessment procedures, durability, structural monitoring, service life design, structural assessment through‐life and making interventions to adapt existing structures or enhance their performance or extend their useful life. [ABSTRACT FROM AUTHOR]

The fib Model Code 2020 (MC2020) is developed to serve as the basis for future international codes and standards for the design of concrete structures by summarizing international research and experience and converting this knowledge into a practical document. The chapter "Concretes" contained therein provides a clear set of application rules in combination with sufficient background information and related references. This paper gives a concise overview of the contents of the Chapter 14 "Concretes" in the 2nd draft of MC2020. Instead of presenting numerous details on changes in the text and equations compared with the previous MC2010, major fundamentals on modeling concrete behavior are indicated. New sections in MC2020 on non‐conventional concretes, durability specifications and environmental performance are covered. Extended state‐of‐the‐art chapters on concrete transport properties and durability design conclude this contribution. [ABSTRACT FROM AUTHOR]

Despite their successful applications in practice for over a century, the design of concrete hinges still entails considerable modeling uncertainty. Their dimensioning still relies on semi‐empirical recommendations originally proposed for admissible stress design, based on limited experimental data and generalized with engineering judgment. This presumably results in overly conservative designs in many cases, particularly when applied with modern design codes based on partial safety factors. This paper addresses these issues by revisiting the analytical modeling for one‐way Freyssinet concrete hinges under general loading based on approaches compatible with current design codes. A cross‐sectional analysis with confined concrete properties is proposed for the behavior under axial forces and bending moments, where the strength of the triaxially compressed concrete in the hinge throat is determined with a discontinuous stress field. The hinge resistance to shear forces is investigated with failure mechanisms inspired by failure modes observed in experiments. Based on the shear strength, a simple approach to estimate the torsional resistance of the throat is proposed. Remarks are also made on the analysis of combined actions. The predictions of the proposed models are validated against a wide range of test data, including a series of recently conducted own experiments. Overall, the proposed models agree better with the available experimental data than the existing approaches, potentially allowing for a more efficient design of new and assessment of existing concrete hinges. [ABSTRACT FROM AUTHOR]

Fires are rare events, but in the case of their occurrence, they can have a significant effect on the structure. Concrete is a durable noncombustible material but can be damaged by fire. This damage does not often lead to structural collapse, but can significantly hinder the structure's future performance. A thorough post‐fire assessment of concrete structures is essential to determine the condition of the structure and select the best course of action to take. This paper reviews the current state of knowledge on the post‐fire assessment of concrete structures. The techniques that are commonly used are presented and discussed, highlighting their advantages and disadvantages. Furthermore, based on the literature case studies, an overview of different approaches and techniques is presented. Finally, the framework and goals of the post‐fire assessment are investigated. The paper concludes with a summary of the current state of knowledge and a list of key research needs. [ABSTRACT FROM AUTHOR]

In this experimental campaign, concrete‐to‐concrete interfaces were examined under cyclic actions, crossed by postinstalled reinforcing bars or industrial steel screws. In addition, the effect of the embedment length and the roughness was investigated. It was observed that different failure modes occur, depending on the different connector types and embedment depths. The positive effect of roughness on the interface resistance was confirmed, but the results indicate that, for very high roughness values, the resistance may be smaller than for moderate values. It was also noticed that the behavior of interfaces crossed by mechanical anchors was less stiff in the ascending branch and exhibited a less steep falling branch. The extension of the project on testing thin overlays showed that the resistance was significantly affected in case of cyclic loading, suggesting that the use of any type of anchor in seismic conditions needs to be supported by adequate experimental evidence. [ABSTRACT FROM AUTHOR]

Neither the shear transfer behavior of unreinforced hydraulic concrete structures nor experimental procedures for its determination have been standardized in recent building codes and regulations. This poses uncertainty for the assessment of the integrity of hydraulic structures. This paper adapts direct shear tests, which are an established method in rock mechanics, for the assessment of unreinforced concrete joints and expands the evaluation method through recognizing surface inclination as a contribution to the coefficient of friction. The evaluation is subsequently performed on direct shear test results performed on specimens taken from a lock built in the early 20th century. Based on the initial state of the concrete joints—intact or cracked bond—results for the basic friction angle and the inclination angle are discussed. Using entire shear stress‐deformation‐curves as opposed to singular values was found to yield more stable results of shear transfer parameters and additional insight on the validity of the test. [ABSTRACT FROM AUTHOR]

In this paper, the residual mechanical properties, mass loss, and cracking behavior of hybrid‐fiber‐reinforced high‐strength concrete (HFRHSC) containing 0%, 30%, and 60% ground granulated blast furnace slag (GGBFS) in normal and high temperatures have been investigated. Chopped aramid and steel fibers at 0%, 0.5%, and 1% by volume, either individually or in different combinations, were used to reinforce the HSC. In total, 24 different mix proportions were designed. The experimental results showed that the residual compressive strength of the majority of specimens increased at 400°C while this property of all of them decreased at 800°C. Also, the test indicated that the use of GGBFS did not reduce flexural and compressive strength of HSC significantly, and in some mixed designs, the presence of GGBFS slightly increases the strength. Moreover, another result that can be inferred is that although the utilization of hybrid fibers in concrete increases flexural strength, it may decrease its compressive strength. In addition, the residual flexural strength of most specimens was reduced at 400°C, but this property of all samples decreased at 800°C. The results showed that the simultaneous presence of GGBFS and hybrid fibers can improve the flexural strength of most specimens at different temperatures. [ABSTRACT FROM AUTHOR]

High‐performance fiber‐reinforced concrete (HPFRC) can be considered a promising material for the construction of precast concrete girders for road bridges. This paper presents conceptual considerations and numerical analysis to support this statement. The HPFRC is a compromised alternative between FRC and UHPFRC mixes. Specifically, a tailor‐made mix design of HPFRC jointly developed by ACCIONA and the authors is presented, and then compared with the other types of fiber‐reinforced concretes collected from the technical literature. In addition, some trends observed in the database are described. This material characterization is followed by a conceptual analysis of the advantages of the application of HPFRC to road bridges. Specifically, a proposed bridge for the case of a 60 m‐span box girder is analyzed. A comparison between alternatives based on the use of HPFRC and conventional reinforced concrete is discussed. The results shed light on the viability of this material for bridge application. Specifically, the main finding show potential significant material savings in structural elements of the superstructure. Finally, ongoing and future research for a wide application to the construction sector are briefly discussed. [ABSTRACT FROM AUTHOR]

For the last 20 years, carbon fiber reinforced polymers (CFRP) have been widely used in the retrofitting and strengthening of structures with inadequate earthquake performance. One of the most important design criteria in retrofitting and strengthening details developed with CFRP is delaying the debonding of CFRP strips from the surface. For this reason, the use of anchors in reinforcement details developed with CFRP has increased. In this study, available experimental data in the literature on bond‐slip research related to anchored CFRP strips were collected and a database was created. By using this database, it was aimed to create a generalized capacity equation and constitutive bond‐slip model for anchored strips via the artificial neural networks technique. The proposed NN models on the constitutive bond‐slip model are intended to be useful in design codes and finite element algorithms. [ABSTRACT FROM AUTHOR]

Concrete which is the most commercialized construction material and thus it plays a key role in this era of development and hence its evolution is of utmost importance and therefore the evolution of the quality of concrete to that of its highly evolved type namely, ultra‐high performance concrete (UHPC) is undeniably the boon to this sector. Though, the correlations between the technical characteristics of UHPC and the composition of its mixture are complicated, nonlinear, and complex to characterize using standard statistical techniques. This paper is intended to use both deep neural network and ensemble machine learning algorithms namely gradient boosting, extreme gradient boosting, random forest regressor, extra tree regressor, and voting regressor trained with an 810 UHPC mixture collections with 15 input variables to predict its compressive strength. After adjusting a regression model, the prediction efficiency and generalization ability of the developed models are validated using a number of performance parameters. It was established that all employed models performed better at forecasting result, the extra tree regressor was the most accurate followed by extreme gradient boosting. [ABSTRACT FROM AUTHOR]

With water scarcity posing an ever‐present worldwide crisis, treated wastewater usage as an alternative to fresh water could be a smart choice and contribute to a sustainable construction industry. Numerous studies have been conducted by using treated domestic or industrial wastewater in concrete production, providing a promising solution to the global water shortage and wastewater management. However, the effectiveness of wastewater on the concrete manufacturing in comparison to pure freshwater has been a concern due to its impurities and contaminants. The results derived from previously published studies on concrete manufacturing with wastewater vary as a consequence of considerate different additives, curing age, treatment method, or wastewater quality. This review compiles and compares the previous investigations on physical and mechanical properties, durability characteristics, and morphological assessments of manufactured concrete with treated wastewater, and discusses the reasons for similarities and differences. Research findings and conclusions from the literature are summarized, and future research directions based on the research gaps are also recommended. [ABSTRACT FROM AUTHOR]

Waste glass (WG) can be used as fine aggregate and powder in concrete mixtures, preventing pollution induced by this non‐biodegradable material. The properties of WG‐included concrete should be examined before its practical use. Compressive strength (CS) is one of the most crucial characteristics of concrete, and the measurement of which needs time‐consuming and expensive experiments. The use of machine learning (ML) methods for modeling the CS of concrete can help achieve more reliable and precise models. In this study, a comprehensive database of WG‐included concrete was collected from the literature. Next, four ML methods, including support vector regression (SVR), least‐square support vector regression (LSSVR), adaptive neuro‐fuzzy inference system (ANFIS), and multilayer perceptron neural network (MLP) were served in the CS modeling. A recently proposed metaheuristic method, called marine predators algorithm (MPA), was proposed to optimize the control parameters of the ML models to guarantee generalized accuracy. Results indicate that the hybrid LSSVR‐MPA model outperforms the other developed ML models comparing the error metrics with an RMSE = 2.447 MPa and R2 = 0.983. The sensitivity analysis reveals that replacing the cement with WG powder decreases the CS, whereas serving the WG as the replacement for natural fine aggregate improves the CS. [ABSTRACT FROM AUTHOR]

This project investigates the use of foamed glass aggregates in lightweight precast concrete. Precast mixes are evaluated for compression and split‐tension strength, and durability is assessed through rapid chloride permeability, thermal conductivity, alkali silica reactivity, and freeze–thaw performance. Mixes containing a 100% or 50% replacement of gravel with foamed glass aggregates are evaluated. The 100% mixes have a 28‐day compression strength = 23.3–27.89 MPa which is acceptable per structural lightweight concrete standards (ASTM C330), but the split‐tension strength falls short of ASTM C330 requirements. The 50% mixes have acceptable strength but exceed the maximum density allowed for lightweight concrete in ASTM C330. The mixes exhibited low–moderate permeability but poor freeze–thaw resistance. All of the proposed mixes with one exception have acceptable expansion due to alkali silica reactivity. The thermal conductivity of the mixes varies from typical lightweight to normal weight concrete ranges with respect to the aggregate replacement ratio. [ABSTRACT FROM AUTHOR]

This paper investigates high‐strength concrete (HSC) exposed to high temperatures using the full replacement of natural aggregates with steel slag. Polypropylene (PP) and steel fibers are used as reinforcements, and the effects of calcium aluminate cement and ordinary cement on the mechanical properties of this concrete are compared. A total of 81 cylindrical specimens of 100 × 200 mm and 81 prism specimens of 100 × 100 × 350 mm were made using different amounts of cementitious materials (cement and silica fume) of 450, 500, and 550 kg/m3, with constant water‐to‐cementitious materials ratio of 0.28. The present results revealed that the HSC made with steel slag aggregates and calcium aluminate cement reinforced with steel fibers, had the greatest compressive strength of 84 and 50 MPa at temperatures of 20°C and 800°C, respectively; and flexural strength of 7.9 and 4.5 MPa, respectively, at the same temperatures. Similar HSC specimens constructed with ordinary cement, on the other hand, performed better at 400°C. Moreover, the flexural strength of the samples placed at temperatures of 400°C and 800°C decreased by 28% and 48%, respectively, compared to the specimens at 20°C. Compared to specimens comprised of polypropylene fibers, the fracture energy and displacement of HSC with steel slag reinforced with steel fibers subjected to high temperatures were increased by approximately 100% and 60%, respectively. [ABSTRACT FROM AUTHOR]

The structural behavior of concrete hinges under general loading is far from being properly understood, which is to a large extent due to the lack of pertinent experimental data. This paper contributes to filling this knowledge gap by presenting and discussing the results of an experimental campaign on one‐way Freyssinet concrete hinges. Seven large‐scale concrete hinges were tested in the Large Universal Shell Element Tester, which allowed the investigation of their behavior under general loading by all six stress resultants. A combination of digital image correlation and distributed fiber optic measurements allowed a deeper insight into the structural behavior of the specimens. The tested hinges could sustain very high axial stresses exceeding 4.5 times the uniaxial concrete compressive strength, large rotations of over 60 mrad, and shear stresses in transverse and longitudinal directions up to 2.24 times the axial compressive stress. The resistance to bending moments about the strong axis and torques also proved to be significant. A moderate amount of reinforcement crossing the hinge throat considerably increased the shear resistance at low axial stresses and produced a ductile shear behavior. [ABSTRACT FROM AUTHOR]

The paper investigates the freeze–thaw resistance and sorptivity behavior of fine‐grained alkali‐activated concrete cured at ambient temperature. A blended binder system containing fly ash, ground granulated blast furnace slag, and silica fume was used. A combination of sodium hydroxide and sodium silicate was used as an activator. The freeze–thaw resistance was evaluated based on mass loss (scaling), and the extent of internal damage was assessed by testing the ultrasonic time at different cycles. Initial and secondary sorptivity coefficients were calculated based on the cumulative water absorption values at different time intervals. Alkali content, sodium silicate to sodium hydroxide ratio, and water to binder ratio were investigated. The experimental results showed that water to binder ratio is the most significant parameter for the scaling; higher ratios result in higher scaling. In terms of internal damage, alkali content is the most significant. The increase of alkali increased the amount of internal damage in the concrete. The initial sorptivity coefficient increased with the water and alkali content and decreased with the silicate content. The secondary sorptivity coefficient showed no significant change with the investigated parameters. [ABSTRACT FROM AUTHOR]

Crumb rubber (CR) concrete (CRC) characterized with high ductility and environment friendliness, has recently been studied widely in the field of green concrete. Generally, high volume fraction of CR in cementitious system leads to low strength. However, the effect of CR particle size has not been concluded yet. This paper focuses on the impact of CR size on the mechanical and microstructure properties of CRC. Two novel substitution approaches of CR for natural fine aggregate are adopted. In total, 10 groups are designed and experimentally tested for their workability in fresh state and mechanical properties in hardened state. Brittleness coefficient, fineness modulus, and micro‐morphology of CRC were analyzed and discussed. Results show that as size of CR decreases, workability improves significantly, apparent density and strength exhibit a firstly decrease and then increase trend, with the lowest value obtained around 1.18 mm CR size. The brittleness of concrete was significantly improved in the presence of CR, and the improvement was more significant for smaller‐sized CR. Weak ITZs between CR particles and interfacial porosity are the main reasons for the sharp strength deterioration. Crack arresting effect of CR makes the crack propagation path more tortuous, and smaller particle‐sized CR exhibits greater capability. [ABSTRACT FROM AUTHOR]

Internal curing (IC) process introduced via a water‐entraining agent using lightweight and porous aggregate has become an essential component in designing high and ultra‐high‐performance concrete (HPC/UHPC). This paper presents experimental results demonstrating the effectiveness of using recycled ceramic tile aggregates (RCTA) derived from waste ceramic tiles as an IC agent for high‐performance structural elements. Previous studies by the author have confirmed the efficiency of both the pre‐saturated recycled porous ceramic coarse aggregate (RPCA) as an IC and shrinkage compensating agents in mitigating autogenous shrinkage and the induced internal self‐stress in HPC mixtures. The main objective of this study is to investigate the effect of two different curing systems (internal curing using the waste ceramic aggregate combined with shrinkage compensating agents) on silica fume (SF) HPC behavior. The shrinkage compensating agents include a combination of shrinkage‐reducing agent (R) and expansive additive (E). The influence of this combined ternary curing system on the mechanical properties, including compressive, flexural, and splitting tensile strengths, modulus of elasticity, autogenous shrinkage, and internal self‐induced tensile stress, were investigated. The obtained results indicate a substantial reduction in the autogenous shrinkage strains magnitude and, consequently, the internal self‐induced tensile stress in the HPC mixtures designed with these two curing systems. It was also found that this combination of the two curing systems resulting in a hybrid curing system, performs much better than the single incorporation of shrinkage‐compensating agents. Besides, a long‐term strengths improvement was recorded for mixtures designed with the RPCA. Incorporating recycled aggregate in the design and production of HPC could further promote concrete sustainability by reducing the amount of virgin extracted non‐renewable minerals, reducing the energy required to extract and process natural aggregates and the CO2 generated, and also reducing solid waste materials disposal. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of multiwalled carbon nanotubes (MWCNTs) on the spalling and cracking behavior of concrete exposed to high temperatures, and also consider the mechanism of different cooling methods (including natural air cooling, spray cooling, and quench cooling) on its performance after high temperature. Meanwhile, the change rules of mechanical properties and pore structure of MWCNTs reinforced concrete during high temperature and cooling were explored by x‐ray computed tomography. The results demonstrated that spalling and cracking behavior of the concrete specimens exposed to high temperatures was effectively controlled by adding MWCNTs. Consequently, the thermal resistance and residual mechanical properties of concrete exposed to high temperatures were significantly improved. Moreover, the mesoscopic and microscopic observation showed that the MWCNTs have a favorable impact on reducing the porosity of the concrete specimens below 600°C. However, when the temperature exceeded 600°C, MWCNTs reached the burning point and lost the bridging effect. No trace of MWCNTs was observed in the concrete specimen, but the cumulative mitigation decreased the possibility of cracking and spalling of concrete at 800°C. Additionally, considering the influence of cooling methods, it is found that the spalling and cracking of the concrete specimens after high temperature caused by quench cooling were the most serious, while that of caused by spray cooling were the least. [ABSTRACT FROM AUTHOR]

The uniaxial compression test and dynamic compression test of C30, C50, and C80 concrete were carried out. The effects of strength grade and strain rate (ε′) on dynamic mechanical properties of concrete were analyzed in terms of dynamic compressive strength, dynamic increase factor (DIF), dynamic peak strain, and dynamic peak toughness. And the strain rate sensitivity of mechanical indexes and DIF fitting model of concrete with different strength grades were explored. The results show that the dynamic compressive strength, DIF and dynamic peak toughness of concrete with different strength grades all have obvious strain rate effects. With the increase of strength grade of concrete, the dynamic peak strain of concrete decreases continuously, and the strain rate sensitivity of dynamic compressive strength and dynamic peak toughness of concrete increases continuously. The mechanical indexes of C80 concrete have the strongest sensitivity to the strain rate. The DIF empirical formula of Comite Euro‐International du Beton (CEB) cannot fit the DIF of C30 and C80 concrete effectively. There is a critical strain rate beyond which the strain rate effect of DIF is significantly enhanced. With the increase of strength grade of concrete, the critical strain rate of concrete decreases continuously. The piecewise linear fitting of DIF and lgε′ of concrete with different strength grades shows good results. [ABSTRACT FROM AUTHOR]

Coal gangue concrete (CGC), a great low cost and environment‐friendly material, is considered to be the most effective substitute for normal concrete. The bond performance of steel bar embedded in CGC determines the feasibility of using CGC as structure material. So, this study presents an experimental program to investigate the bond strength of steel bar embedded in CGC compared to the one in normal‐aggregate concrete. The experimental program contains 75 specimens that are tested using the pull‐out test. In this study, coal gangue coarse aggregate replacement ratios (0%, 25%, 50%, 75%, and 100%), water–cement ratio (0.50, 0.45, and 0.40), and rebar diameters (14 mm, 16 mm, and 18 mm) were considered to analyze the variation law of bond strength. The test results show that the bond strength increased slightly with the decrease of water–cement ratio. The bond strength decreased slightly with the increase the aggregate replacement ratio if the replacement ratio was less than 50%. In contrast, the bond strength decreased significantly when the aggregate replacement ratio was more than 50%. In addition, the bond strength increases first and then reduces with increasing of bar diameters. Lastly, a new model of predicting the bond strength between the deformed steel bar and coal gangue concrete was proposed in this study because the widely used prediction models for the bond strength were not suitable for the coal gangue concrete. [ABSTRACT FROM AUTHOR]

The ordinary medium sand can no longer meet the increasing demands of engineering projects. Construction costs can be reduced and the natural environment can be protected by rational use of the local desert sand. To evaluate the spalling and fire resistance of the concrete, the desert sand concrete (DSC) is heated to 100–800°C and then cooled for splitting tensile strength test. The test results indicate that with the increment of desert sand replacement rate (DSRR), the compressive strength of DSC increases first and then decreases. The maximum value is reached when DSRR is up to 40%. The presence of fly ash slows down the loss of splitting strength of concrete with the temperature increasing. The regression model is established to predict the functional relationship between the concrete splitting strength and temperatures under heating and air cooling conditions. The result shows that the predictions calculated by the formula are consistent with the experimental results. The formula can be employed as a constitutive relation of the computer model to evaluate the spalling and fire resistance of the DSC structure. [ABSTRACT FROM AUTHOR]

Lichuan Bridge is the major bridge spanning the Dongguan Waterway with a major span of 138 m, located in the Dongcheng area of Dongguan City, Guangdong Province, China. In comparison to the reinforced concrete tower, the steel-shell concrete composite tower exhibits the following benefits: High bearing capacity: The bearing capacity of the steel-shell concrete composite tower is larger than that of the reinforced concrete tower due to the synergistic bearing and passive confinement effects of the steel shell. Convenient construction: The steel shell can be used as a concrete formwork during the tower's construction, eliminating the need for large-scale climbing formwork equipment and also making it easier to realize the alignment of the curve tower. [Extracted from the article]

As acknowledged explicitly or implicitly in most of current design codes, a high level of sustained loading has a detrimental effect on the concrete compressive strength. However, its beneficial effect in terms of deformation capacity is neglected in most cases. This latter topic and its practical consequences are addressed in the present paper on the basis of an experimental and theoretical investigation. In particular, the development of nonlinear creep strains in structural concrete members is investigated, clarifying the internal redistribution of forces between concrete and the reinforcement. The results of an experimental program with refined measurements are presented to better understand the phenomenon and to verify the predictions of a mechanical model developed by the authors on the time‐dependent response of concrete. The experimental program consists of 14 prismatic specimens with different reinforcement ratios tested under a wide range of uniaxial stress rates. The results allow clarifying the material response and validating the mechanical model, both in terms of strength reduction and enhancement of deformation capacity. Finally, the results of parametric analyses, performed considering different concrete ages, reinforcement ratios, and materials properties are presented to evaluate the practical implications of the findings. [ABSTRACT FROM AUTHOR]

Sustainable concrete is the demand of the present era to reduce carbon emissions. Fly‐ash‐based geopolymer (FLAG) concrete has been used in the construction industry for more than one and a half decades. The compressive strength (CS) of concrete plays a crucial role in the mechanical properties of concrete. Laboratory experiments take a huge amount of time and cost to estimate the CS of concrete. Although analytical methods exist to estimate the CS of concrete, but these models cannot forecast the CS of concrete with better precision due to the complexity of the design mixes. The machine learning (ML)‐based models have been helpful in estimating the CS of concrete with high accuracy and reliability. In this article, four ML algorithms (support vector machine [SVM], linear regression [LR], ensemble learning [EL], and Gaussian process regression [GPR]) and three optimized ML algorithms (EL, SVM, and GPR) have been used to estimate the CS of FLAG concrete. The R‐value of LR, EL, SVMR, GPR, optimized EL, optimized SVMR and optimized GPR models are 0.8916, 0.9172, 0.9313, 0.9529, 0.9459, 0.9348 and 0.9590, respectively. The accuracy of the optimized GPR model with an R‐value of 0.9590 and RMSE value of 1.7132 MPa outperformed all other ML models. The performances of all the developed models have been illustrated through Taylor diagram and error plot. The feature importance of the input parameters has been explained with the explainable ML technique. The developed, optimized GPR model can be reliable tool to estimate the CS with greater accuracy and also reducing time and cost. [ABSTRACT FROM AUTHOR]

Manufactured sand (MS) has been started utilizing as an alternative in constructions due to the escalated demand for river sand (RS). The microfine aggregate (MFA) is a salient constituent in manufactured sand, which is a crushed reactive form of parent rocks having particles less than 0.075 mm. This paper presents the effects of varying microfine aggregate levels on bleeding, plastic shrinkage cracking (PSC) and compressive strength of MS made concrete. Two types of MS were utilized: MS from Hornblende‐Gneiss rock (MH) and MS from Charnockite rock (MC) and the MFA level was ranged from 0% to 12% at 3% increments and the reference concrete was prepared with RS alone. With the MFA levels, the bleeding of MS concretes was reduced where, at 0% MFA level the maximum bleeding rates were observed for MC (1.63 kg/m2) and MH (0.84 kg/m2) concretes. PSC results were analyzed from an image processing technique, which revealed an increasing trend of mean and maximum crack widths, crack length and crack area with the MFA levels. At 0% MFA, the mean crack width of MC (0.19 mm) and MH (0.17 mm) concretes manifested marginally similar to RS concrete (0.17 mm). The decreasing bleeding with the MFA levels can be attributed to the increasing severity to PSC. Moreover, the optimum 28 days compressive strength of MC (57.5 MPa) and MH (56.1 MPa) concretes was achieved at 3% MFA level which are higher than RS concrete (51.5 MPa). Consequently, the MFA level should be limited to 3% for better plastic and hardened performance of MS made concrete. [ABSTRACT FROM AUTHOR]

Crystalline admixture (CA) has been extensively utilized as the commercial product for improving the performance associated with strengthening self‐sealing of cracks or decreasing the permeability of concrete. However, few researches characterizing the restrained shrinkage and cracking potential of concrete with CA at early age. This paper aimed to expand the limitation by means of the experiments including mechanical properties test and restrained ring test on high‐strength concrete (HSC) with CA from Xypex. The proportion of CA was 0%, 0.5%, 1.0%, and 1.5% by the mass of cement. The incorporation of CA enhanced the compressive and splitting tensile strength as well as modulus of elasticity tested in this paper. A significant increase was observed in free and restrained shrinkage of HSC with CA. Although incorporation of CA ameliorated the stress relaxation, residual stress in restrained concrete ring developed rapidly with the incorporation of CA due to the significant increase in restrained shrinkage at early age. Restrained concrete ring with CA demonstrated a higher stress rate, which implied a higher cracking potential. When CA proportion increased from 0% to 0.5%, 1.0%, and 1.5%, a higher cracking potential was revealed through calculation, and restrained concrete ring exhibited earlier cracking age. Caution should be exercised with the application of such CA in concrete mixtures under restrained conditions. [ABSTRACT FROM AUTHOR]

The dynamic compressive mechanical performance of coral aggregate concrete (CAC) has been studied by the servo‐controlled true triaxial testing machine (TAWZ‐5000/3000), the failure modes and the stress–strain curves were obtained under various loading conditions. The effect of strain rates and the constant lateral pressure on the strength, deformation capacity, and failure modes of CAC were analyzed according to the results obtained from the test. The results show that the lateral pressure significantly changes the failure mode while the strain rate only affects the degree. The strength and deformation capacity will improve with the increase of strain rate and lateral pressure, and the lateral pressure diminishes the strain rate effect on mechanical properties. A 5‐parameter empirical dynamic failure criterion was established based on the William‐Warnke criterion. Finally, a 2‐stage dynamic multiaxial compressive constitutive model obeying the Weibull and Lognormal statistical distributions was established, and the model had well‐fitting results with the experimental results. [ABSTRACT FROM AUTHOR]

Internal curing (IC) agents such as prewetted lightweight aggregates (LWAs) have been proved to be advantageous in reducing the autogenous shrinkage and early‐age cracking of concrete by introducing additional water. Quantitative analyses of internal relative humidity (IRH) of concrete are essential to better estimate the autogenous shrinkage of early‐age concrete. Existing studies investigate the IRH or autogenous shrinkage of early‐age concrete, respectively; however, the relevance between them of concrete containing prewetted LWAs remain lacking. Accordingly, the IRH, autogenous shrinkage, and the correlation between them for early‐age concrete with various LWAs replacement ratios were investigated. A noncontact device was utilized to measure the IRH and autogenous shrinkage of concrete simultaneously. Test results suggested that: (1) the absolute value of the maximum expansion increased from 0 με to 20, 50, and 96 με when the proportion of prewetted LWAs increased from 0% to 10%, 30%, and 50%, respectively; (2) compared with Mixture LWA00, the autogenous shrinkage at 28 days decreased by 14.7%, 36.3%, and 62.6% for Mixture LWA10, LWA30, and LWA50, respectively; (3) the IRH at 28 days or the critical time of IRH was 88.7%, 90.1%, 93.2%, and 95.9% RH or 5, 6, 8, and 10 days for Mixture LWA00, LWA10, LWA30, and LWA50, respectively; (4) a prediction model for the evaluation of the autogenous shrinkage was constructed based on IRH of early‐age concrete considering the quantity of IC water introduced by various replacement ratios of LWAs. [ABSTRACT FROM AUTHOR]

Despite offering several benefits in terms of environment and economics, few studies were conducted on the ground granulated blast furnace slag (GGBFS) based alkali‐activated concrete reinforced with recycled tire steel fibers (RTSFs). Therefore, this paper employed the Taguchi method to investigate and optimize the influence of GGBFS content, the alkaline solution to GGBFS content ratio, sodium hydroxide solution concentration, and RTSF volume fraction on splitting tensile strength (STS) of recycled tire steel fiber‐reinforced alkali‐activated slag concrete (RTSFR‐AASC). The microstructural evaluation was done through scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR) analyses. The results indicated that the fiber content, the most efficient parameter on STS, led to a considerable enhancement in the performance characteristic. Microstructural analysis proved the variations in formation of C–S–H gel. The results of the confirmation experiment on the proposed optimized RTSFR‐AASC mixture with the highest 28‐day STS (7.11 MPa) confirmed the effectiveness of the Taguchi method. [ABSTRACT FROM AUTHOR]

Bleeding is a common problem in concrete slabs, and may lead to serious damage. The goal of this article is to understand the impact of alternative binders and their properties on the bleeding of concrete. Therefore, the impact of the type of binder on the bleeding process is investigated. The results show that the addition of granite powder or fly ash allows for the increased control of the bleeding process. It was found that a finer particle size distribution (PSD), an increased specific surface area (SSA), and a higher bulk density may reduce the amount of dispensed water in the concrete mix. Furthermore, the use of additives with an increased SSA leads to even a 30% reduction of the bleeding rate of mixes. The utilization of additives with a finer PSD than cement enables a 37% reduction of the bleeding rate of mixes. The influence of bleeding on compressive strength was assessed using destructive and non‐destructive tests: Replacing 30% of cement with granite powder leads to a 30% reduction of concrete strength after 28 days of curing; on the other hand, replacing 30% of cement with siliceous fly ash leads to an 18% reduction of strength. Importantly, bleeding was also found to lead to the heterogeneity of the physical and mechanical properties across the concrete section. Consequently, the proper control of the bleeding process leads to more homogeneous properties of concrete across its cross‐section. [ABSTRACT FROM AUTHOR]

Triaxial compression tests were conducted on high ductile concrete (HDC) under three curing conditions to study its triaxial mechanical properties under different curing environments. The three different curing conditions are as follows: standard curing (temperature 20 ± 2°C, humidity ≥95%), water curing (temperature 15 ± 2°C, humidity ≥95%), and −20°C (−20 ± 2°C, humidity ≥85%). The variation laws of stress–strain response, peak stress, peak strain, and volume strain were analyzed for HDC under different environmental conditions. The mechanism of the effect of HDC mesostructure on strength under different curing conditions was revealed using ultrasonic and nuclear magnetic resonance detection technology. The relationship between HDC uniaxial compressive strength and ultrasonic speed was obtained by fitting the test data, and the relationship between the shear strength and temperature was provided. Results show that the peak stress of HDC under the same confining pressure increases with the rise in the curing temperature. The peak strain also decreases, and the HDC exhibits better ductility under −20°C curing. The peak stress and peak strain of HDC under the same curing conditions increase with the rise in confining pressure. HDC specimen fracture is in the composite failure mode of shear and splitting, and it cracks but does not disintegrate. The pore size is larger and the strength is lower when the pores are more harmful. [ABSTRACT FROM AUTHOR]

This article studied the mechanical properties and constitutive model of fiber‐reinforced coral aggregate concrete (FRCAC). The test results show that basalt fibers, carbon fibers, and polypropylene fibers (BFs, CFs, and PFs) can enhance the cube compressive strength and splitting tensile strength of coral aggregate concrete (CAC), but there are optimum contents. The optimal content of BFs, CFs, and PFs are 0.8%, 1.5%, and 0.3%, respectively. Fibers increase slightly the elastic modulus of FRCAC. The peak stress, peak strain, and ultimate strain of CAC can be improved by fibers, and the improvement effect is CFs, BFs, and PFs in descending order. According to the experimental results, a damage constitutive model suitable for FRCAC was proposed, which can efficiently indicate the stress–strain relationship of FRCAC. The damage parameter in the model can predict the damage evolution process of FRCAC. [ABSTRACT FROM AUTHOR]

Ultrahigh‐performance concrete (UHPC) is becoming increasingly frequent in several civil construction projects such as industries, buildings, and even infrastructure. The rheological and mechanical behaviors, coupled with durability, are the driving motives for this increase in use over the last few decades. However, the type of mixer used in UHPC production considerably affects the final composites performance due to variations in mixing velocity and the need to disperse particles with low granulometry. This study evaluated the effect of type of mixer in the properties of UHPC in the fresh and hardened states. This study evaluates three types of mixers: planetary vertical axis, horizontal axis, and drum. Results showed that the drum mixer was the least efficient in homogenizing the composite. It showed an average mixing time about 126% longer than planetary vertical or horizontal‐axis mixers to reach the same level of flowability. The composite from the drum mixer also had the most entrained air and void index. The planetary vertical‐axis mixer was the most efficient, with the resulting composite having a potential compression strength of 169.1 MPa, 19.3% higher than the composite from the horizontal‐axis mixer. [ABSTRACT FROM AUTHOR]

In order to comprehensively examine the influence of basalt fiber on the basic mechanical properties of concrete, the axial compression, axial tension and direct shear tests were carried out on basalt fiber reinforced concrete (BFRC) with different fiber contents and fiber lengths. The failure modes and stress–strain curves under different loading modes were obtained from the test data, and the basic mechanical parameters of BFRC were extracted from the curves. Based on the results, the following conclusions were drawn. With the increase of fiber content, both the compressive strength and tensile strength showed an upward trend first followed by a downward trend. In general, the shear strength of BFRC was lower than that of ordinary reinforced concrete with no fiber (RC). All BFRC specimens had an increased peak strain and significantly improved deformability compared to RC. Based on a comprehensive analysis, the specimen with a fiber content of 0.2% and a fiber length of 6 mm (BFRC‐0.2%‐6) exhibited the best mechanical properties. In addition, mathematical regression analysis was performed on the normalized stress–strain curves of BFRC, and the influencing parameters model of basalt fiber was proposed based on the fiber content and fiber length. Moreover, scanning electron microscopy (SEM) and computed tomography were utilized to analyze the influencing mechanism of basalt fiber content and fiber length on the mechanical properties of concrete from the microcosmic and mesoscopic perspectives. [ABSTRACT FROM AUTHOR]

An effort has been made to enhance the flexural fatigue lives of self compacting concrete (SCC) in which half of the natural aggregates (NA) were substituted with recycled concrete aggregates (RCA) by means of blended cements. Blended SCC mixes containing either silica fume (SF) or metakaolin (MK) along with cement, and fly ash (FA) was also adopted. Fatigue lives have been evaluated as mean value, design value life and theoretical value. The Weibull distribution parameters were utilized for the valuation of mean and design values of fatigue lives for different considered mixes. It has been observed that adding RCA in SCC causes degradation in the fatigue lives, which can be enhanced by adopting the blended mixture comprising of SF or MK, cement and FA. Both SF and MK established a promising result in improving fatigue lives. Still, the blend of MK in SCC contributed most effectively in enhancing the fatigue life of SCC comprising RCA. [ABSTRACT FROM AUTHOR]

High‐performance concrete (HPC) is a cement‐based material with excellent properties and durability which determines high‐level structural utilization. However, the necessity of high‐quality natural resources such as quartz powder and sand and a high amount of cement and silica fume and reinforcement by fibers causes a high environmental footprint and costs. One of the possible ways to reduce the environmental footprint and cost of the HPC/UHPC is to replace the powder or sand with secondary raw materials. In this study, the two types and three fractions of fine recycled concrete aggregate (fRCA) are used as supplementary materials in HPC. The reference mixture is based on the UHPC mixture without reinforcement to find out the influence of aggregate replacement. The properties of fresh and hardened concrete are examined. The results show a slight decline of mechanical properties however the autogenous shrinkage decrease with the replacement of natural aggregate by fRCA, which shows the possibilities of natural resources savings and thus leads to a lower environmental footprint of concrete structures as a contribution to the solution of sustainable development goals set by the United Nations in 2015 as an action plan up to 2030. [ABSTRACT FROM AUTHOR]