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Achieving traceability of concrete materials is a crucial step toward promoting sustainable concrete use. This includes creating accurate Environmental Product Declarations, minimizing mistakes during concrete placement, and improving understanding of the relationship between concrete constituents and performance. Despite these benefits, effective traceability for concrete materials has not yet been achieved in the laboratory environment or within wider practice. This work sets out a digital thread for concrete use and the functional requirements for a traceability framework for adoption in a laboratory environment. Traceable resource units (TRUs) are identified, and the primary critical tracking events for each TRU are described. A prototype traceability system is developed to link the necessary properties, constituent material data, production information, and performance results for concrete materials. The prototype system incorporates a novel inkjet printer QR code fingerprinting solution that is demonstrated to be highly effective for concrete specimens and for various media, including paper and metal, used to transport and store raw concrete constituent materials. A laboratory test series demonstrated a 100% readability rate with the proposed QR fingerprinting solution according to standard measures. This work advances knowledge of the appropriate traceable resource units and critical tracking events within concrete practice, develops effective marking procedures and forms a prototype constituent‐to‐product traceability system. [ABSTRACT FROM AUTHOR]

Improved utilization of coal mine overburden material (CMOB)‐incorporated concrete in the construction sector can contribute to developing a more sustainable built environment if the results of proven research on the behavior of structures constructed of CMOB‐incorporated concrete are applied. Even though there have only been a few studies on CMOB‐incorporated concrete, no research has been done on how this type of concrete can be used in structures. In particular, researchers have not paid much attention to the fact that the strength properties of CMOB‐incorporated concrete tend to be very variable, even though this variability is needed for a wide range of structural applications (such as limit state design formulation, reliability‐based structural analysis, etc.). For the first time, this research provides quantitative estimates of the variability in compressive‐, flexural‐, and splitting tensile strengths of cured concrete using varying amounts of a CMOB sample as fine aggregate. Taking into account the suggested distribution model, the research also provides a reliability‐based seismic risk assessment of a standard CMOB‐incorporated framed building. The failure probability and dispersion in the drift demand were found to be the same for the frames modeled with CMOB and standard concrete (natural sand); the results demonstrate that CMOB samples can be safely used for earthquake‐resistant constructions. [ABSTRACT FROM AUTHOR]

In an era flooded with a multitude of studies investigating the performance of concrete structures retrofitted using fiber‐reinforced polymer (FRP) materials, this review addresses the critical need for a comprehensive overview of the retrofitting of concrete members using near‐surface mounted (NSM)‐FRP composites, aiming to save time and effort while providing engineers and research community with valuable resources relevant to the field. This review focuses on the key factors influencing both the flexural and shear retrofitting processes of reinforced concrete (RC) beams, such as the percentage, type, size and geometry of NSM‐FRP reinforcement, as well as groove design, groove‐filling materials and beam depth. Moreover, the paper explores the failure modes associated with each retrofitting type, for example, debonding failures, shear/flexural failure and rupture of steel or NSM‐FRP reinforcement, to name a few. The review also delves into the bond behavior of NSM‐FRP‐bonded joints, examining factors, such as the bonded length, surface texture of NSM‐FRP reinforcement and type of bonding agent, which would affect the bond behavior and strength of the joints. The failure mechanisms associated with the bonded joints, such as interfacial bond failure, FRP rupture and splitting of the adhesive cover, are also highlighted. Finally, this compilation aims to guide engineers and researchers by offering a critical and comprehensive database for optimal designs, further development and suggesting future research directions. [ABSTRACT FROM AUTHOR]

The use of ultra‐high‐performance fiber reinforced concrete (UHPFRC) to repair or rehabilitate old concrete structures has been shown to be appropriate due to its properties, such as higher compressive strength, ductility, and durability than conventional concretes. One of the studied strengthening techniques is the reinforced concrete columns jacketing by UHPFRC. Some recent research evaluated some parameters, such as the repair thickness and the volumetric ratio of stirrups. However, other important parameters, such as UHPFRC jacketing thickness in different column cross‐sections and the concrete core compressive strength, need to be addressed. In addition, the analytical models presented in the literature are restricted to only one concrete grade. The present study aims to evaluate the behavior of short reinforced concrete columns strengthened with UHPFRC subjected to centered compression. Numerical analyses of three‐dimensional models were performed using the finite element method, validated, and calibrated using experimental results. The influence of the concrete core compressive strength, the UHPFRC jacketing thickness, and the shape of the cross‐section were evaluated. Numerical simulations concluded that the lower concrete core compressive strength columns showed the best relative increase performance. Moreover, the concrete core strength was inversely proportional to the resistance capacity of the repair system. In addition, the increase in repair thickness contributes to the axial strength of the column. Furthermore, the cross‐section influences the distribution of stresses and strains, showing the best performance for circular sections. Finally, regardless of cross‐section type, the proposed equations accurately predicted the numerical results. [ABSTRACT FROM AUTHOR]

Fly ash, river sand, and ordinary gravel, which are used in concrete as the admixture, fine aggregate, and coarse aggregate, respectively, were replaced by iron tailing powder, sand, and gravel. The influence of the iron tailings on the bond properties between concrete and steel bar was studied by conducting pull‐out tests on 16 groups and 48 specimens. At a curing age of 90 days, the splitting tensile strength of the iron tailing powder concrete (ITPC) for strength grades C25 and C30 was the lowest and was only 71.8% and 66.6% of the splitting tensile strength for the corresponding strength grade of conventional concrete (CC). The lower splitting tensile strength of ITPC caused the bond strength between the concrete and steel bar to be lower than that between the CC and steel bar, with a maximum difference of 14.67%. The bond strength between the iron tailing powder–sand concrete (ITPSC) and steel bar was slightly worse than that between the CC and steel bar, with a maximum difference of 6.88%, and better than that between the ITPC and steel bar. The bond strength between the full iron tailing concrete and steel bar was better than those between the CC and steel bar and between the ITPSC and steel bar. In addition, the bond slip characteristics were investigated. [ABSTRACT FROM AUTHOR]

The Metro Tunnel is a Victorian Government funded infrastructure project which will create a new end‐to‐end rail line from Sunbury in the west to Cranbourne/Pakenham in the south east, with bigger and better trains, next generation signaling technology and five new underground stations. This article provides a detailed summary of the structural fire testing requirements for the platform tunnel side wall and arch lining in the Metro Tunnel's State Library and Town Hall stations. Contrasted to building fires, tunnel fires are more significant within a few minutes due to the confined space which can cause concrete spalling and jeopardize the bearing capacity of the tunnel, which is a significant concern to designers. The catastrophic European tunnel fire events in 1999 and 2001 led to the development of innovative regulations and recommendations, including guidelines endorsed by the European Federation of National (EFNARC 132F r3:2006) and Efectis R0695:2020. This paper explains the methodology taken to design the fire rated concrete test for the platform tunnel side wall and arch lining in the State Library and Town Hall stations of Melbourne's Metro Tunnel Project for structural stability for the period of a serious fire event. For the first time, uniaxial loading (500T) was applied to five large‐scale flat concrete panels (1800 × 1800 × 400 mm) which are normally unloaded during fire exposure and exposed to the RABT ZTV (rail) fire curve. The first testing program investigated the influence of polypropylene dosage in the concrete mix design and its effect on the magnitude and severity of concrete spalling. The results indicated that the recommended 2.0 kg/m3 polypropylene dosage requirement as specified by Eurocode is conservative. Concrete mix designs with a stable aggregate and the correct curing regime can mitigate spalling at significantly lower polypropylene dosage rates. The water pooling effect was evident during the fire testing and the surface cracking that developed was vertical to the surface, allowing for the release of the pore water pressure build‐up. [ABSTRACT FROM AUTHOR]

The Annex D of the future EC2 draft gives guidance on the evaluation of early‐age cracking of large structures due to restraint. In case of restrained conditions, compressive stresses are firstly generated in massive structures due to temperature increase, then tensile stresses are generated due to temperature decrease and shrinkage. Due to these tensile stresses, there is a risk of cracking which may be evaluated by the simplified method in Annex D. This method is currently verified against laboratory tests performed in the temperature‐stress testing machine and field cases on restrained concrete elements. The laboratory verification consisted of five approaches to consider different available input (modeled, assumed, or measured). The field investigation focused on the relation between the calculated cracking risk and the observed damage. The results show that the method has very good accuracy and captures with reasonable simplicity the mechanisms and the relations between the parameters involved. [ABSTRACT FROM AUTHOR]

Exposure of concrete to elevated temperature affects its mechanical and physical properties. One of the important reasons for the use of fiber‐reinforced polymer (FRP) composite materials is because of its superior mechanical properties. These mechanical properties include impact resistance, strength, stiffness, flexibility, and also it is enhanced ability to carry loads. The high strength–weight ratio, and corrosion resistance of FRPs made them suitable for repair. For strengthening and retrofitting of concrete structures confinement with FRP has received considerable attention in recent years. Geopolymer concrete (GPC) can be expressed as “concrete without cement.” GPC is environmentally friendly and an inventive way to replace the conservative concrete which contributes 7%–8% of total CO2 production in the world. “The concrete which entails of the source materials and the alkaline solution.” The composite material made of fiber‐reinforced polymer (FRP) has recently gained attention as a potential repair method for concrete structures that have been damaged. This study investigates the performance of glass and basalt fiber‐reinforced polymer (GFRP and BFRP) laminates as a retrofit solution for fire‐damaged GPC specimens. The specimens were subjected to temperatures of 200°C, 400°C, 600°C, and 800°C for a period of 1, 2, and 3 h, followed by retrofitting with FRP laminates. The results indicated an increase in the ultimate load‐carrying capacity of GPC specimens when subjected to 200°C for 1 h, beyond which it decreased. However, a fall in ultimate load capacity was observed for higher ranges of temperature and duration of the fire. In this project, geopolymer specimens that had been damaged by fire are wrapped with GFRP and BFRP laminates to study the effect of confinement on the strength of GPC specimens. The fiber laminate used was bi‐directional glass and bi‐directional basalt. Based on the analysis of test data, there was the conclusion that the fire‐damaged GPC was strengthened when retrofitted with GFRP and BFRP laminates was attainable. [ABSTRACT FROM AUTHOR]

Increasing demand for energy globally, with the building sector being a significant contributor to energy consumption, is a major issue. To address this, efforts are being made to make buildings more energy efficient, including lowering the demand for heating, ventilation, and air conditioning to decrease energy demand. Phase change material (PCM) functions as a latent heat energy storage material that absorbs heat energy while transforming its phase from solid to liquid and then releases the heat energy when it transforms from liquid to solid state. Integrating PCM into building materials can considerably enhance their energy storage density. In this study, the potential of using fly ash cenosphere—capric acid (CeCA) composite PCM in concrete is evaluated. The mechanical, durability and thermal properties of the CeCA blended concrete were investigated. Furthermore, the CeCA‐concrete is enhanced with auxiliary cementitious substance, namely ground granulated blast furnace slag (GGBS). The optimal proportion of CeCA was determined to ensure a balance of compressive strength and thermal conductivity. The results indicated that the compressive strength of the CeCA blended concrete lowered with an increase in the percentage of CeCA. The thermal conductivity of the concrete specimen was lowered by 33.14% at a 25% incorporation of CeCA, resulting in improved thermal performance. The incorporation of GGBS has enhanced the mechanical and durability performance of CeCA‐Concrete. The optimal concrete specimen was found to be 25% CeCA +40% GGBS, which had greater thermal efficiency than the control specimen with similar strength performance. The findings were validated by field emission scanning electron microscopy analysis of the concrete specimen. [ABSTRACT FROM AUTHOR]

The concrete compressive strength is essential for the design and durability of concrete infrastructure. Silica fume (SF), as a cementitious material, has been shown to improve the durability and mechanical properties of concrete. This study aims to predict the compressive strength of concrete containing SF by dual‐objective optimization to determine the best balance between accurate prediction and model simplicity. A comprehensive dataset of 2995 concrete samples containing SF was collected from 36 peer‐reviewed studies ranging from 5% to 30% by cement weight. Input variables included curing time, SF content, water‐to‐cement ratio, aggregates, superplasticizer levels, and slump characteristics in the modeling process. The gray wolf optimization (GWO) algorithm was applied to create a model that balances parsimony with an acceptable error threshold. A determination coefficient (R2) of 0.973 demonstrated that the CatBoost algorithm emerged as a superior predictive tool within the boosting ensemble context. A sensitivity analysis confirmed the robustness of the model, identifying curing time as the predominant influence on the compressive strength of SF‐containing concrete. To further enhance the applicability of this research, the authors proposed a web application that facilitates users to estimate the compressive strength using the optimized CatBoost algorithm by following the link: https://sf-concrete-cs-prediction-by-javid-toufigh.streamlit.app/. [ABSTRACT FROM AUTHOR]

The utilization of recycled aggregate concrete (RAC) within the construction sector has the potential to prevent irreversible harm to the environment and reduce the depletion of natural resources. Nonetheless, it is essential to scrutinize the quality of RAC before utilizing it in practical applications. RAC's most significant design parameter is its elastic modulus, typically determined through time‐consuming and costly experiments. Machine learning (ML) techniques can be a feasible solution to reduce the number of experiments required and obtain accurate estimates. This article employs two robust ML techniques, namely Xtreme Gradient Boosting (XGB) and Adaptive Boosting regression, in three distinct modes, namely individual, hybrid, and ensemble‐hybrid methods. Furthermore, phasor particle swarm optimization (PPSO) and chaos game optimization (CGO) have been utilized in hybrid and ensemble‐hybrid modes to optimize final results, minimize errors, and obtain highly precise outcomes. As mentioned earlier, several evaluators were employed to identify the most appropriate model to compare the modes. The findings suggest that the relevant optimizers significantly contributed to achieving superior metric values. Specifically, the results indicated that PPSO exhibited greater efficacy than CGO in optimizing outputs and enhancing accuracy. The hybrid models, particularly XGB in conjunction with PPSO, yielded the most favorable correlation coefficient and root mean square error values equal to 0.996 and 0.336 and can serve as an effective ML method to determine elastic modulus of recycle aggregate concrete for time and energy storage. [ABSTRACT FROM AUTHOR]

Unsustainable development in the industry has increased the challenge of proper disposal of industrial by‐products and has caused environmental pollution on a large scale. Furthermore, minimizing the carbon dioxide emissions due to industrial and environmental activities is a crucial challenge to controlling the global warming crisis and climate change. The use of industrial by‐product‐based supplementary cementitious materials (SCMs) can reduce fossil fuel consumption through the reduction in cement production and contribute to suitable waste management. In this research, a meta‐model was developed using integration of the decision tree‐based method named reduced error pruning tree (REPtree) and ensemble approaches (boosting and bagging) to improve the pruning phase for strength simulation of concrete mixtures incorporating industrial by‐products. Then, ensemble multiple learning algorithms were applied to develop a meta‐model using the artificial neural network and Gaussian process regression. A comprehensive experimental‐based database incorporating 3836 records from short‐term to long‐term compressive strength (CS) was collected from the literature. Performance measures present that the proposed ensemble boosting‐REPtree model outperforms other benchmark and ensemble models with a correlation coefficient of 0.960 and root mean square error of 7.884 MPa. Also, uncertainty evaluation was done based on the Monte Carlo simulation algorithm in the modeling process. The FAST and SOBOL methods, as global sensitivity analysis, presented water‐to‐binder (W/B) ratio, curing time, and SCMs to binder ratio (SCM/B) as critical components to estimate the CS of concrete mixtures. The computational simulation of the influential parameters on concrete mixtures incorporating industrial by‐products revealed that the experimental factors yielding the highest CS of the mixtures were calculated as follows: cement content of 584 kg/m3, W/B ratio of 0.17, superplasticizer‐to‐cement ratio of 1.88%, and SCM/B ratio of 0.15. [ABSTRACT FROM AUTHOR]

The quantity of recycled concrete aggregates is increasing day by day due to the enhanced demolition rate of old infrastructures, which is dangerous to the environment's sustainability. Therefore, it is essential to handle these recycled aggregates for sustainable development. Furthermore, due to the low compressive strength (COS) of recycled aggregate concrete (RAC), it has always remained an active research area to ameliorate the mechanical performance of such concrete by either adding fibers and/or laterally confining with carbon fiber reinforced polymer (carbon‐FRP) wraps. The main objective of the current investigation is to improve the strength of hybrid fiber‐reinforced recycled aggregate concrete (HFRAC) transversely wrapped with carbon‐FRP wraps. The axial COS, axial strain, and compressive stress–strain graphs of the tested samples were assessed by manufacturing a total sum of 18 cylindrical samples wrapped with either one or two carbon‐FRP wraps. Two different grades of HFRAC were fabricated that is, 15 and 20 MPa containing hybrid fibers (steel and polypropylene fibers). The results showed that the transverse wrapping effectively ameliorated the axial strain, COS, and axial stiffness of HFRAC samples. By using a single layer of carbon‐FRP wraps, an enhancement of 115.7% was observed while using two layers of carbon‐FRP wraps, an enhancement of 130.7% was observed in the COS of 15 MPa group HFRAC samples. Similarly, by using a single layer of carbon‐FRP wraps, an enhancement of 37.4% occurred while using two layers of carbon‐FRP wraps, an enhancement of 112.6% occurred in the COS of 20 MPa group HFRAC samples. Hence, the lateral wrapping of low‐strength HFRAC is more efficient than the high‐strength HFRAC. A theoretical investigation based on the analysis of 11 different models was also performed to predict the COS of carbon‐FRP‐wrapped HFRAC samples. [ABSTRACT FROM AUTHOR]

This study seeks to present a sophisticated artificial intelligence (AI) framework to model the compressive strength (fc′) of concrete containing waste foundry sand (WFS), with the aim of minimizing the need for time‐consuming laboratory tests and skilled technicians. For this purpose, artificial neural network (ANN) is hybridized with two metaheuristic algorithms—particle swarm optimization (PSO) and ant colony optimization (ACO) to predict the fc′ of 340 samples containing WFS collected from the literature. Results indicated that the ACO + ANN model showed the best performance with the Pearson coefficient of 0.9971, mean absolute error of 0.0221 MPa, and root mean squared error of 0.7473 MPa. The values of prediction errors exhibited that more than 90% of them in the ACO + ANN model fall within the range of (−1.5 MPa, 1.5 MPa), while this range for the PSO + ANN and traditional ANN models was obtained as (−3 MPa, 3 MPa) and (−4 MPa, 4 MPa), respectively. Furthermore, the proposed ACO + ANN model predicted the fc′ in the range of 5.24–54.48 MPa. Besides, the results indicated that the water‐to‐cement ratio, cement strength class, and cement content had the most significant impact on the fc′ of WFS‐containing concrete. Finally, a comparison was made between the proposed ACO + ANN model and four other AI models recently proposed in the literature, in which the performance criteria demonstrated that the proposed ACO + ANN model outperformed the models in the literature. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop a systematic meso‐level theoretical modeling approach for analyzing the mode‐I fracture failure behaviors of concrete. Firstly, the crack model is developed in a way to be equivalent to the continuum model at the macro‐level. Secondly, an extended universal morphological model (XUMM) for concrete mode‐I fracture analysis is proposed at the meso‐level. Afterwards, both the mesoscopic fracture characteristics and the macroscopic mechanical parameters of concrete are theoretically deduced based on the proposed XUMM. Comparison with existing meso‐level test results shows that the predictions from the XUMM have good consistency, but offsets are obvious as well. At last, the XUMM is calibrated using the limit state method and preliminarily verified via mesoscale numerical simulations. [ABSTRACT FROM AUTHOR]

The paper describes the authors' contribution to the evolution of numerical simulation of concrete structures based on the nonlinear finite element method. The formulation of constitutive relations for concrete material is a keystone of this approach, whereas cracking is the dominant feature. Two distinct methods of crack modeling were developed, namely, the discrete and the smeared crack models. Blind prediction benchmarks of the experimental tests are used for model verification. Application of the numerical simulation in the design of concrete structures is supported by the global safety format, where the uncertainty sources, due to the material and the resistance model, are considered. A structural assessment of a prestressed reinforced concrete viaduct is shown as an example of application. [ABSTRACT FROM AUTHOR]

Raw coal gangue (RCG) as one of the solid wastes can result in serious ecological and environmental pollution. Utilization of RCG as coarse aggregates in concrete can mitigate the demand for natural aggregates in engineering construction to a certain extent. This study aims to assess the impact of utilizing raw coal gangue aggregates (RCGAs) on the mechanical behaviors and compressive stress–strain responses of concrete. For this purpose, a total of 90 concrete specimens were prepared, varying in RCGA replacement ratios of 0, 30%, 50%, 70%, and 100% and water‐to‐cement (w/c) ratios of 0.37 and 0.47. The slump, compressive and splitting tensile strengths in cubes, and complete compressive stress–strain curves of RCGA concrete were obtained and discussed. Results indicated that as RCGA was incorporated, the peak stress and elastic modulus of concretes with 0.37 and 0.47 w/c ratios decreased by 26%–51% and 23%–57%, respectively. In addition, the crack development and microstructural characteristics of RCGA concrete were analyzed by digital image correlation and scanning electron microscopy (SEM), respectively. The SEM analysis indicated that the interface transition zone between RCGAs and mortar was relatively thick and loose compared to that between coarse natural aggregates and mortar, indicating the poor mechanical properties of RCGA concrete. Finally, based on the test data, a normalized stress–strain model for RCGA concrete was proposed, taking into account the influence of RCGA replacement. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present the methodology used to validate the threshold levels of durability indicators from data acquired from existing reinforced concrete structures that may present corrosion problems resulting from carbonation or chloride ingress. This study was conducted in the framework of the French National Project PERFDUB in close collaboration with the MODEVIE ANR project. Durability tests form the basis of a performance‐based approach for the durability of concrete structures, and in order to set the threshold level for each of these durability indicators, it is important to take into account the experience feedback that can be obtained from the actual behavior of existing structures. This paper presents the investigations carried out on eight reinforced concrete structures, all of them having an age well in excess of 50 years, and the main data gathered on some relevant durability and lifetime indicators. Based on all these data, predictive models of carbonation and chloride penetration are applied in order to validate the threshold levels to be adopted for the durability indicators, and several other conclusions are drawn. [ABSTRACT FROM AUTHOR]

The carbon dioxide emissions associated with the production of conventional Portland cement may be mitigated through the utilization of ground granulated blast furnace slag (GGBFS). The consideration of compressive strength (fc) is essential in the design and construction of concrete structures, as it is an essential demand in concrete mixtures. The primary objective of this study is to establish an effective approach for conducting a comprehensive evaluation of machine learning algorithms in predicting the fc of concrete that incorporates GGBFS. The work focuses on using the adaptive neuro‐fuzzy inference system (ANFIS) to create predictive models for fc. The fc of the collected datasets ranged from 6.3 to 101.3 MPa. The study included the artificial rabbit optimization (ARO) and Bald Eagle search algorithm (BES) to improve the effectiveness of the ANFIS approaches. The novelty of this study is attributed to several factors, including the utilization of the ARO and BES methodologies, the incorporation of GGBFS in the evaluation of fc, the comparison with previous research findings, and the utilization of a substantial dataset encompassing multiple input variables. These factors offer a novel method for improving the effectiveness of prediction models and advance our understanding of forecasting the mechanical characteristics of concrete. The integrated ANF‐AR and ANF‐BA systems showed good estimating skills, according to the findings, which showed R2 values of 0.9961 and 0.9967 for the ANF‐AR's training and testing components and 0.9916 and 0.9946 for the ANF‐BA, respectively. Overall, the ANFIS optimized with ARO model is recognized as the outperformed system for prediction purposes. [ABSTRACT FROM AUTHOR]

There are several significant advantages to 3D concrete printing (3DCP) over conventional concreting techniques. Structures are built by printing them one layer at a time. This study aimed to improve the usability and accessibility of this technology to solve on‐site issues, such as those caused by chemical admixture. In order to construct concrete that can be printed in three dimensions, researchers added many chemical admixtures in controlled quantities. This experiment's main goals were to prepare 3D printable concrete (3DPC) without chemical admixture and to evaluate fresh and hardened properties. Slump, flow, extrudability, buildability, open time, and penetrometer tests were carried out for fresh properties. Compressive, flexural, splitting tensile strength, and modulus of elasticity were evaluated for hardened properties. The printed specimens in the longitudinal direction exhibited higher compressive strength than in the downward and lateral directions. Similarly, higher flexural and splitting tensile strength in the longitudinal direction of printed specimens than in the downward and lateral direction. The results of developing 3DPC without chemical admixtures demonstrated good performance in fresh and hardened properties. [ABSTRACT FROM AUTHOR]

The purpose of this study is to develop a systematic meso‐level theoretical modeling approach for analyzing the mode‐I fracture failure behaviors of concrete. Firstly, the eXtended Universal Morphological Model (XUMM) is briefly reviewed. Secondly, a normalized analysis method for the evaluation of effects of properties and scales of meso structures on the performance of concrete is proposed based on the XUMM. Afterwards, parametric studies regarding the aggregate strength effect, the aggregate volume effect, the maximum aggregate size (MAS) effect, the tortuosity of mesoscopic crack, the roughness of fracture surface and the characteristic length are conducted. At last, a case study on the MAS effect based on experimental tests is provided to verify the applicability of the XUMM. [ABSTRACT FROM AUTHOR]

Ultra‐high performance concrete (UHPC) offers superior tensile properties in comparison to normal and high‐strength concrete. This is known to largely depend on the fibers included in the UHPC mixtures. Among the available types of fiber, steel fibers have been commonly used in the current practice. However, given the price and availability issues associated with steel fibers, there has been growing interest in benefiting from synthetic fibers in UHPC. This was the motivation for the current study to investigate the potential of five synthetic fibers by evaluating how the tensile properties of the UHPC mixtures made with a hybrid of steel and synthetic fibers are influenced under direct tension. The synthetic fibers of choice consisted of nylon, polypropylene, polyvinyl alcohol, alkali‐resistant glass, and carbon fibers. By using a dog bone test setup, the main tensile properties of the developed mixtures (i.e., direct tensile strength, elastic modulus, and stress–strain relationship) were systematically determined. The results extracted from direct tension tests were then further processed in conjunction with digital image correlation analyses to investigate the formation and propagation of cracks, as well as the post‐cracking response. The original findings reported from this study are expected to pave the way to broaden the fiber types that can be considered for the structural applications of UHPC, especially where high tensile stresses/strains are anticipated. [ABSTRACT FROM AUTHOR]

Plasterboard, a commonly utilized construction material, comprises a gypsum core nestled between two paper layers. Gypsum after demolition of plasterboards is a recyclable waste that has been reused into new plasterboard or other purposes such as agricultural products. However, there is a lack of understanding on the potential for recycling the paper layers. This study investigates the use of wastepaper fibers, obtained from the paper layers, as a reinforcing material and metakaolin as a partial cement replacement material in concrete. This study demonstrates the ability of the paper from waste plasterboard for reinforcing concrete. Wastepaper fibers were used at different concentrations ranging from 0 to 2.5% by weight of binder. Bending test was conducted for assessing fracture behavior of concretes, including load bearing capacity, modulus of rupture, crack mouth opening displacement (CMOD) at the load bearing capacity, fracture toughness, and fracture energy. Slump, axial compression, and scanning electron microscopy (SEM) were also conducted on the concretes. It is found that incorporating wastepaper fiber by up to an optimum content of 1.5% results in an increase in the compressive strength (57%), flexural load bearing capacity and modulus of rupture (31%), CMOD displacement at load capacity (14%), fracture toughness (37%), and fracture energy (73%) of the metakaolin‐based concrete. However, further increase in the wastepaper fiber content results in decreased mechanical properties of the concrete, which is due to the fiber agglomeration and non‐uniform distribution within the concrete matrix. Based on the results, the concrete with 20% metakaolin and 1.5% wastepaper fiber experiences similar mechanical properties to the conventional concrete. The results of this study underscore the substantial potential of leveraging waste materials such as wastepaper and by‐products like metakaolin to diminish reliance on conventional cement. This approach not only enhances the mechanical properties of concrete but also fosters sustainable building practices by promoting the recycling of waste materials, reducing carbon footprint, and mitigating the environmental impacts inherent in traditional concrete production. [ABSTRACT FROM AUTHOR]

The concrete capacity design (CCD) method for the design of anchorages comes with a pre‐requisite that the base plate connecting the anchors of a group should be "sufficiently stiff." This article addresses a frequently and vastly discussed topic in fastening technology, namely "What a sufficiently stiff base plate actually means?" The qualitative definition used by the codes requires that the deformation of the base plate should be small compared to the anchor displacements, in addition to the requirement that the base plate should remain linear elastic. This requirement indirectly ensures that the forces among the anchors of the group are distributed in a linear manner, which is the primary requirement to apply the CCD method for design of anchorages. Such a qualitative definition has raised more questions than answers and haunts the fastening technology community. Perhaps the possible solution to this problem requires asking the question differently, that addresses the problem directly: How can it be ensured that the tension forces among the anchors of a group are distributed in a linear manner? This paper first discusses the problem in detail highlighting several issues in the current approach and later provides an overview of an assessment method in form of a set of criteria that can be used to evaluate whether the tension force distribution is linear for an anchorage with a given anchor pattern, baseplate, attachment, and load case. The principle of the approach is based on a combination of simple mathematical formulations and the evaluation of finite element calculations performed on anchorages modeled with base plate, attachment, and anchors. The proposed formulations are described, and it is explained why they are adequate to find practical and safe general solutions to the problems. The application of the set of criteria allows the calculation of an optimum base plate thickness, sufficient to distribute the forces linearly among the anchors, without being overly conservative. [ABSTRACT FROM AUTHOR]

Long‐term creep compliance is one of the most important mechanical properties for evaluating the long‐term behavior of concrete structures. This paper aims to optimize machine‐learning models to predict this viscoelastic property. The most relevant dataset available in the literature is considered, cleaned, and preprocessed to optimize the outcome. The advanced XGBoost model, which is to be the most effective shallow machine‐learning model for modeling tabular datasets, is employed in this study to maximize model accuracy. Short‐term creep compliances of a given sample at typical ages are used as input features to model the long‐term creep compliance of concrete. This approach outperforms standard machine‐learning approaches that do not include short‐term creep as an input feature. Indeed, the short‐term behavior of concrete strongly influents its long‐term one. The optimized machine model presented herein is accurate and useful for practical applications. It uses input features that are easy to obtain to predict long‐term creep compliance up to several decades, which is difficult and expensive to measure. [ABSTRACT FROM AUTHOR]

Fastenings in concrete are widely applicable in construction. A significant benefit of fastening technology lies in the fact that it can adapt to various geometries and construction sequences. As a result, the need to design and realize a fastening in structural elements with unconventional geometric configurations can be encountered. Existing design standards rely on the concrete capacity design (CCD) method for concrete‐related failures, which typically covers detailing situations with rectangular configurations of the fastenings and the concrete members. However, the lack of guidelines for a wider range of applications may lead to over‐conservative dimensioning or design constraints. This study investigates the influence of beveled concrete edges on the load‐bearing behavior of anchors. As part of the research, a series of experiments and numerical simulations were conducted. The results derived from the investigations are used to develop an analytical concept that extends the area of applicability of the CCD method and can be used for reliable dimensioning of fastenings close to non‐rectangular concrete edges and geometrical boundaries. [ABSTRACT FROM AUTHOR]

Digital fabrication with concrete (DFC) is fast becoming an attractive alternative for components (i.e., façades, urban furniture) and structural typologies (i.e., short‐span footbridges, columns, floor systems) for which complex geometries derived from particular aesthetical criteria and/or construction time constrictions are governing parameters. Additionally, some authors claim that this process allows improving the sustainability of structures, as less material is necessary compared to traditional concrete solutions, thus reducing greenhouse gas emissions linked to material consumption. Nonetheless, the environmental implications of DFC are still under scrutiny and remain objectively unquantified. In this study, a sustainability assessment model to allow decision‐makers to evaluate and compare concrete footbridge alternatives—from the sustainability perspective—including those constructed by means of 3D printed concrete (3DPC) techniques, is presented. The proposed approach is based on the MIVES method. For this purpose, the most representative criteria and indicators of sustainability identified are measured and weighted‐aggregated in a decision‐making tree. The sustainability index (SI) of each alternative is the outcome derived from the application of the model, and the SI was used as reference for evaluating the alternatives. The sustainability of 3D‐printed footbridges is quantified and compared to other concrete‐based solutions: traditional reinforced cast‐in‐place and precast concrete, as traditional solutions, and ultra‐high performance precast concrete and textile‐reinforced concrete, as innovative alternatives. The results of the analysis lead to conclude that 3D‐printed footbridges have positive impacts on environmental and social indicators, but economic indicators still need to be improved to attain a competitive solution. The approach proposed herein to assess the sustainability of footbridges can be extended to other cases and stakeholders' preferences by adapting the components of the method to sensitivities and particular boundary conditions of other scenarios. [ABSTRACT FROM AUTHOR]

High‐strength steel pipe joints are proposed for assembled composite columns. The steel pipe extends into the upper and lower prefabricated columns and is anchored by poured concrete or grout to realize the connection of the prefabricated columns. Bonding performance of high‐strength steel pipe and surrounding concrete/grout is critical to the joint reliability. Steel pipe push‐out test was carried out, considering parameters of steel pipe section specification, bonding length, bonding material, and outer wall treatment of the steel pipe. Comparative analysis of measured load–displacement/slip curves and calculated bond strength were conducted. Bonding length of 600 mm could provide sufficient bond strength. Increasing bonding length could delay the slippage, but the bond strength decreased. High‐strength grout significantly increased the peak load size. The slenderness ratio and diameter–thickness ratio of the steel pipe had no obvious influence on the bonding performance. Steel pipe with D114*25 section obtained higher bonding strength with smaller ratio of bonding area to cross‐sectional area. Spiral ribs welded to the outer wall of the steel pipe could effectively improve the bonding strength and delay the interface slip. With easy construction and reliable performance, spiral ribs were recommended to be applied in prRactical projects. [ABSTRACT FROM AUTHOR]

The durability of reinforced concrete structures exposed to aggressive environments is affected by corrosion of carbon steel reinforcement. For this reason, it is of great practical interest to look for alternative solutions guaranteeing durability through the incorporation of corrosion‐resistant materials, such as stainless steel rebars. This type of steel is specially recommended for structures with a long lifespan, located in aggressive environments, with chlorides or de‐icing salts, and for structures where repair, inspection and rehabilitation is complicated. This solution presents a challenge from the point of view of the materials themselves, the mechanical design and their durability. This article presents the material properties of stainless steel and their influence on concrete structures. Furthermore, it is explained how these properties have been taken into account in the latest draft of the second‐generation Eurocode 2. [ABSTRACT FROM AUTHOR]

In this paper, 2D and 3D meso‐models of concrete are developed numerically using different shapes of aggregate. For 2D model, circular and random polygon aggregate shapes are considered while for 3D model, spherical and convex hull aggregate shapes are adopted. Five different spatial distributions are employed in both circular and polygon shapes to get Circle1–Circle5 and Poly1–Poly5 geometrical model. Similarly, for 3D meso‐model, Spherical1–Spherical5 and one Convex hull geometrical models are developed. In all the numerical models, three different phases of concrete are considered, that is aggregate, mortar, and interfacial transition zone. Explicit analysis of the developed models has been performed using LS‐DYNA. All the developed models are verified by comparing the obtained results of stress–strain variations with the existing literature. The behavior of concrete is studied for both the loading conditions, that is quasi‐static and high strain loading rate. Added to this, the effect of spatial distribution of aggregates is also evaluated. Finally, the dynamic impact factors (DIF) are evaluated and compared for all the developed numerical models. Finally, cubic polynomial equations for DIF, for different shape aggregate 3D models, are obtained using regression analysis. [ABSTRACT FROM AUTHOR]

Silica, a principal component of waste glass powder (GP) reacts with calcium hydroxide to form the hydration products, and the process is affected by the fineness of GP and the percentage of cement replaced. This study investigates the structural behavior of concrete incorporating GP in reinforced concrete members by 0%–25% (by weight) replacement of cement with GP along with 0%–0.45% addition of glass fibers (GFs). The compressive and tensile strengths, strength activity index (SAI), and failure mode of treated concrete mixtures have revealed the optimum values as 15% replacement of cement with GP with 0.3% of GF. In the second stage of experiment, reinforced concrete beams were cast at various percentages of GP and GF to investigate the load–deflection response. It was observed that the beam specimen treated with GP exhibited considerably less mid‐span deflection (14.8 mm) at failure as compared to the control beam (with no GP and GF) which failed at 29.4 mm. The beam specimen treated with GP only showed significant degradation in stiffness after the peak load due to the fact that a part of GP remains unreacted and acts as a filler. Moreover, the beam specimen cast at optimum percentages of GP (15%) and GF (0.3%) showed large mid‐span deflection and higher failure load as compared to the control beam. These results suggest that the partial replacement of cement with GP should be accompanied by the addition of fibers to avoid unwanted brittle responses of GP concrete, with the additional advantage of reducing the non‐biodegradable waste. [ABSTRACT FROM AUTHOR]

Ultra‐high performance concrete (UHPC) prefabricated beams are competitive in accelerated bridge construction. However, their broader application has been hindered by limited large‐scale tests and inaccurate design methods. To fill this gap, the authors conducted an experimental investigation on the shear and flexural performance of UHPC pi‐beams using two full‐scale specimens. One specimen was a precast UHPC beam, while the other was a composite beam with a normal concrete slab on the UHPC beam. The primary focus was on crack propagation, ultimate capacities, and failure modes. To complement the experimental findings, the extended finite element method (XFEM) was developed as a numerical approach. Nevertheless, relying solely on XFEM to understand real structural behavior is prone to misinterpretations. Moreover, the shear and flexural capacities were evaluated using existing codes and compared with the experimental results. The comparisons revealed that the predictions of shear capacities were at least 15% lower than the experimental values, whereas the flexural capacities showed acceptable agreement. To address this, the authors introduced the limit equilibrium method, leading to a more accurate prediction of shear capacity for UHPC beams with a deviation of <2%. [ABSTRACT FROM AUTHOR]

The dynamic compression test was carried out on basalt fiber reinforced early strength concrete (BFRESC) with ages of 4–24 h by the split Hopkinson pressure bar (SHPB) test system. The effects of curing age and basalt fiber content on dynamic mechanical properties of ESC was analyzed. The result shows that the dynamic compressive strength and specific energy absorption of BFRESC at early ages increase continuously with the increase of fiber content. The dynamic compressive strength of concrete at the early ages increases exponentially with the strain rate. With the increase of curing age, the strain rate sensitivity of dynamic compressive strength of concrete increases gradually, and the strain rate sensitivity of dynamic compressive strength of BFRESC with fiber content of 0.1% is the strongest. The specific energy absorption of concrete at early ages increases linearly with the strain rate. With the increase of curing age, the strain rate sensitivity of specific energy absorption of concrete increases gradually, and basalt fiber can enhance the strain rate sensitivity of specific energy absorption of concrete. Based on the comparison with the formula for dynamic increase factor (DIF) calculation provided by Comite Euro‐International du Beton (CEB), etc., a model of DIF based on the increase of curing age is proposed. [ABSTRACT FROM AUTHOR]

The rise in temperature due to the heat of hydration in the high‐strength mass concrete poses serious issues such as thermal cracking and delayed ettringite formation. The present experimental investigation is to optimize the proportions of SCMs like fly ash (FA) and ground granulated blast‐furnace slag (GGBS) for the same grade of high‐strength mass concrete with a focus on controlling the peak temperature rise and improving sustainability. For this purpose, one 100% ordinary Portland cement (OPC)‐based sample (T1) and five SCMs‐based samples viz. T2, T3, T4, T5, and T6 in which OPC was replaced by 20% FA, 35% FA, 50% GGBS, 70% GGBS, and 33%FA + 33% GGBS, respectively, were cast in the insulated blocks having one cubic meter volume. Analyzing critically, it is observed that for the same grade of concrete, the right blend of SCMs greatly reduces the peak core temperature (~33.2% and ~ 39.4% for T5 and T6 samples, respectively) than the sample prepared with 100% OPC. This is due to the reduction in the total heat of hydration in the SCMs‐based system than that of the OPC‐based system at early age. The amount of hydration products formed at early age varies for different percentages of SCMs, which is investigated by X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and Field emission scanning electron microscopy (FESEM) analyses. Additionally, compressive strength analysis reveals that all the samples achieved almost similar strength (71.4, 74.6, 73.5, 71.5, 69.2, and 68.2 MPa, respectively, for T1 to T6 samples) at 56 days. Moreover, the rapid chloride permeability test (RCPT) values of the T2 to T5 samples are measured to be 597, 461, 672, 584, and 621 coulombs; while, the same is measured to be 2637, coulombs for the T1 sample, indicating higher durability of SCMs‐based samples. Finally, based on the analyses, a plausible model has been presented to explain the phenomenon, and industrial viability analysis is done to adjudge its suitability for an onsite application. [ABSTRACT FROM AUTHOR]

Slag is a by‐product of the steel industry that can be activated using alkali solutions to form concrete. This study presents new experimental results of basic and drying creep behavior of alkali‐activated slag (AAS) concrete. Different parameters affecting creep such as loading age, sample size and creep stress‐strength ratio were varied for experimental studies. The results show that the basic creep of AAS concrete is higher than that of ordinary Portland cement (OPC) concrete. The drying creep of AAS is lower than for OPC and this could be explained by a higher internal drying during the activation of slag. The experimental results were used to check the applicability of two existing engineering models, the fib MC 2010 and the B4s model, for AAS concrete. It was found that both models could be extended to predict the basic creep of AAS concrete. For drying creep, the B4s could better capture the creep behavior. For the fib MC 2010, a new formulation for drying creep would be required. [ABSTRACT FROM AUTHOR]

In order to study the size effect behavior of recycled concrete under dynamic compression load, a meso‐scale model of recycled concrete was established. The particle size of coarse aggregate, replacement ratio of recycled coarse aggregate, and section size were used as parameters to explore the mechanical properties of recycled concrete under uniaxial dynamic compression load, such as failure mode, compressive strength, peak strain, and residual strength. The effects of strain rate, particle size of recycled coarse aggregate, and replacement rate of recycled coarse aggregate on the size effect of dynamic compression of recycled concrete were further analyzed. The results showed that under uniaxial dynamic compression load, the damage degree of recycled concrete deep and along with the change of the strain rate change, recycled concrete dynamic compression strength and strain rate were positively correlated. There is the critical strain rate is 1/s, which weaken the influence of the size effect, when the strain rate reaches 10/s, the dynamic compressive strength of recycled concrete increases with the increase of section size. At the same time, when the strain rate is high, the particle size of recycled coarse aggregate and the replacement rate of recycled coarse aggregate have little effect on the size effect behavior of recycled concrete. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]