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Crack initiators in reinforced concrete structures can facilitate fulfilling the serviceability requirements. They can be used as a design parameter to diminish the minimum reinforcement for members subject to imposed deformation and exposed to the environment as they reduce the crack spacing and width when arranged close enough. While crack initiators in conventional concrete construction are cumbersome to provide (e.g., by construction joints or taperings), they are inherent to layered extrusion processes with digital fabrication technologies: the tensile strength is typically reduced locally in interfaces between layers. Rather than trying to avoid these weak interfaces, this paper discusses the potential of taking advantage of them to act as crack initiators reducing the minimum reinforcement content. A tension chord‐based model is developed to (i) account for the local strength reduction and (ii) predict the effect of weak interfaces on the expected crack spacing and width. As a key finding, the model predicts a reduction of the required minimum reinforcement ratio proportional to the locally decreased concrete tensile strength for a specified maximum crack width requirement under imposed deformations. An experimental campaign on five layered and three reference tension ties confirmed the clearly positive impact of weak interfaces on crack spacings and widths. [ABSTRACT FROM AUTHOR]

The main relevant difference between recycled concrete aggregates (RCAs) in comparison with the companion natural ones, is the presence of the Attached Mortar content which confers to the RCAs higher porosity and, consequently, higher water absorption capacity. In the last decades, several studies have been performed worldwide for unveiling the role of the employed RCAs on the resulting concrete mixture performances at both fresh and hardened states. On the other hand, the effects of RCA on the early‐age and/or long‐term concrete deformations (e.g., shrinkage) are still very limited. In this context, this article summarizes the results of a wide experimental campaign aimed at evaluating the influence of RCAs on the autogenous and drying shrinkage of normal (35 MPa) and high (60 MPa) strength recycled aggregate concrete (RAC) mixtures. A total of 10 mixtures were realized by considering the variation of both the original source and size of employed RCAs. The results showed a clear correlation between the intrinsic properties (i.e., Attached Mortar content) of the employed RCAs and the resulting concrete deformation. Moreover, although the drying shrinkage is higher for RAC mixtures, the presence of a more porous aggregates mitigates the observed autogenous shrinkage. Consequently, the overall total shrinkage result to be almost unaffected by the presence of the recycled particles. [ABSTRACT FROM AUTHOR]

Multiple initiatives advocate for reducing embodied carbon (i.e., greenhouse gas emissions) associated with concrete production. Even though readily implementable strategies exist, practitioners are concerned that reducing embodied carbon emissions may adversely affect concrete performance and durability, resulting in detrimental effects from a life cycle perspective. To address such concerns, this study investigated the correlations between embodied carbon of concrete mixtures, mixture design parameters, and experimentally measured mechanical and durability properties. The analyzed datasets included 145 mixtures, featuring a variety of mixture designs from laboratory and field studies. The results indicate that the cement content is the most significant predictor of global warming potential (GWP) and that considerable GWP savings can be achieved by reducing and replacing cement without compromising performance. Clear correlations of GWP with compressive strength were not identified, while the results demonstrated that reduced GWP and increased electrically based resistivity (the utilized durability indicator) often occur in synergy. [ABSTRACT FROM AUTHOR]

Cracked concrete members with fiber‐reinforced polymer (FRP) reinforcement generally suffer from increased deflections compared to steel‐reinforced members due to FRP reinforcements' lower modulus of elasticity. An approach to counteract this problem can be the prestressing of the FRP reinforcement, which can significantly reduce member deflections. However, time‐dependent prestress losses occur due creep and shrinkage of the concrete and relaxation of the prestressing tendons. Within the first part of this article, mathematical approaches to determine relaxation rates from creep tests are introduced. Subsequently, short‐term and long‐term tensile tests under sustained load on glass and basalt FRP reinforcement bars are presented. Based on the experimental data and the mathematical model, relaxation rates for the investigated specimens are derived. In addition, using an approach based on logarithmic extrapolation, the relaxation rates at 1 million hours (end of service life) are calculated, and the experimentally determined residual tensile properties are evaluated. [ABSTRACT FROM AUTHOR]

This paper introduces the key concepts of sustainability in the construction industry, together with a call for an urgent action to change the culture of all implied agents. The work presents an objective framework to evaluate sustainability through the analysis of the stages of the Integrated Life Cycle Assessment (ILCA). Such approach is applied to the global warming emissions indicator, and different aspects are investigated to support designers toward more sustainable designs. First, the principles for ILCA are introduced and sound values for the emissions of different structural materials are critically discussed and filtered taking into account the recently increased sensitivity to environmental aspects. On that basis, objective comparisons are presented for practical examples related to buildings and bridges. Specific design alternatives, based on the use of different materials and structural typologies, are also illustrated and compared to the original solution. The conclusions help the designer to identify which are the critical decisions leading to projects respectful of sustainability considerations. Specifically, material selection, structural efficiency, and a sound conceptual design are identified as the key aspects of sustainability. [ABSTRACT FROM AUTHOR]

The tensile creep of concrete with supplementary cementitious materials (SCMs) such as fly ash (FA) and ground granulated blast furnace slag (GGBFS) is investigated in this paper. A total of 21 series of tensile creep tests using dog‐bone specimens under uniaxial tensile loading have been carried out. The cement replacement rates considered were 30% fly ash, 40% and 60% GGBFS. The characteristic compressive strength of concrete was ranging from 25 to 100 MPa. The tests were conducted from the age of 2 days until 28 days. It is observed that the tensile creep of fly ash concretes was slightly lower than that of the reference mixtures without SCM. For GGBFS concrete, the higher the GGBFS content, the higher the tensile creep. Existing creep models, originally developed for creep in compression, could not predict the experimental tensile creep results. Thus, a new tensile creep model was proposed including creep prediction for concrete with fly ash and GGBFS. The new model was calibrated only for controlled environmental conditions (23°C and 50% RH) and has been validated by analyzing the development of concrete tensile stress in the restrained ring test. [ABSTRACT FROM AUTHOR]

Reusing industrial solid waste in cement‐based products is an economical and environmentally friendly solution. This study investigated the effect of steel slag on the mechanical properties of concrete mixtures, and development of damage constitutive relationship of steel slag concrete (SSC). Two steel slag aggregates, including fine steel slag aggregate (SSAF) and coarse steel slag aggregate (SSAC) were incorporated into the concrete mixtures to SSC. The portions of natural sand and coarse aggregate each were replaced with SSAF and SSAC at 10%–100% (interval of 20%) by weight. Therefore, effects of SSAF and SSAC on the mechanical properties of SSC mixtures were evaluated separately. Moreover, damage model of SSC mixtures was developed based on Lemaitre's equivalent strain principle and Weibull probability density function. The damage constitutive model was revised using the functional relationship between the toughness index, brittleness index, and distribution parameters. The results indicate that SSC's mechanical properties, crack resistance, and toughness have been significantly improved with increased steel slag content. However, reduction in strength was observed in the SSC specimens containing steel slag above 50% replacement. Nevertheless, these strengths are higher than that of normal concrete. The modified damage constitutive relationship fits better with the experimental results. [ABSTRACT FROM AUTHOR]

This study examines the use of steel fibers in enhancing the ductility of an economical ultra‐high strength concrete (UHSC). The addition of fibrous material with very small geometry in this mixture is an effective solution to improve its ductility and prevent its brittle failure which is a common characteristic of UHSC. Different mechanical properties of reinforced and unreinforced concrete (e.g., slump flow, compressive, splitting tensile strength tests, and failure modes) were taken into account to find out the efficiency of micro steel fibers. The test results showed that concrete containing 25 mm length and 0.20 mm diameter steel fibers at a volume fraction of 0.5% not only presented a reasonable improvement in ductility performance but also ensured cost‐effectiveness. The cost evaluation conducted on several existing mix designs is also introduced in this study to investigate the influence of various steel fiber contents on the total cost of concrete so that figure out the lowest budget solution. The evaluation shows the high price of fiber reinforcement in which an addition of steel fibers by 5% volume could increase 7% of the total concrete cost. [ABSTRACT FROM AUTHOR]

Deck caps of bridges—in Germany shortly known as "bridge caps"—are usually made of steel reinforced concrete to form the anchoring area for the guardrail of bridge deck edges on existing cantilever slabs. Combined with protective devices, the outside arranged deck caps provide safety against lateral breaking or crashes of vehicles. Due to their exposed position in the cross section of bridges and the particularly intensive stresses, the deck caps are considered as wear parts and have to be renewed several times during the service life of a bridge. The decisive factor here is the discrepancy between the frost resistance of the concrete and the crack width restriction. On the one hand, only very small cracks (<0.2 mm) can be accepted to prevent corrosion of the rebars under the strong exposure of these elements. To confine crack widths without applying an excessively high degree of reinforcement, a low concrete compressive strength is advantageous. On the other hand, a sufficient frost resistance requires a correspondingly high compressive strength. With carbon reinforcement, these contrary points could be defused and simultaneously the needed durability could be provided. Therefore, slightly modified deck cap concretes combined with a carbon reinforcement mesh were tested to examine the bond behavior with and without freeze–thaw attack. To prove the characteristics of this combined system, the crack formation and crack distribution were investigated experimentally. The test results were compared to calculated values from a mathematically tool to be able to develop different reinforcement concepts in future that can ensure an optimized crack formation and crack width for deck caps. [ABSTRACT FROM AUTHOR]

Understanding and predicting concrete carbonation are significant in designing durability and maintaining the service life of reinforced concrete structures. However, this purpose can hardly be reached because of complex carbonation mechanisms depending on various variables such as cement content (C), fly ash content (FA), water content (W), concentration of CO2, relative humidity (RH), temperature (T°C), and exposition time (Time). This investigation proposes a machine learning (ML) approach including eight ML algorithms such as four single ML models: XGB, GB, RF, and SVM, and four hybrid ML models: XGB_RRHC, GB_RRHC, RF_RRHC, and SVM_RRHC for investigating and predicting concrete carbonation depth containing fly ash. To achieve this purpose, a dedicated database consisting of 688 samples and seven input variables is built, and the performance of eight machine learning models is compared. Single ML model Extreme Gradient Boosting (XGB) using the default hyperparameters exhibited the highest performance with R2 = 0.9770, RMSE = 2.2725 and MAE = 1.5218. Shapley Additive exPlanations (SHAP) identifies the most influential feature and order of feature effect on concrete carbonation depth. The first four important features can be sorted in order: time of exposition > cement content > water content > CO2 concentration. Moreover, at a higher value of exposition time, water content, CO2 concentration, fly ash content, temperature and relative humidity, the carbonation depth of concrete increases. Using high content of cement can reduce the carbonation depth of concrete. [ABSTRACT FROM AUTHOR]

To investigate the influence of crack‐type defect and confining pressure on the mechanical properties of brittle materials, conventional triaxial compression tests were conducted on five types of prismatic samples with the same size of 41 mm × 70.7 mm × 175 mm at six confining pressures of 0, 5, 10, 20, 40, and 70 MPa, respectively. Among the five types of samples, one is intact, with uniaxial compressive strength of 140 MPa, and the other four are all defective and contain a single prefabricated crack with the length of 10 mm and the inclination angles of 0°, 30°, 60°, and 90°, respectively. All samples are made of reactive powder concrete with the same mix proportion. According to the test results, the following conclusions are obtained. (1) For any kind of defective sample and any confining pressure, relative values of the strength deviation that the defective samples deviating from the intact sample are all less than relative values of the strength range (max–min) of the five samples. (2) There exist two critical values p1 and p2 of the confining pressure p, the inclination angle of the prefabricated crack has significantly different impact on the compressive strength in the interval of 0 ≤ p < p1, p1 ≤ p < p2, and p ≥ p2, respectively. [ABSTRACT FROM AUTHOR]

Fracture energy (GF) represents the average total energy consumed in the whole process of crack propagation. Using one parameter of GF, it is not sufficient to describe the fracture behavior during crack stable and unstable propagation periods. In this study, the GF, stable fracture energy (GFS) and unstable fracture energy (GFU) of natural and recycled aggregate concrete (RAC) were investigated by using three‐point bending tests. Totally, 128 cubic specimens (100 mm × 100 mm × 100 mm) and 64 notched beams with size of 510 mm × 100 mm × 100 mm were manufactured to test the compressive strength (fcu), splitting tensile strength (ft), load–deflection (P‐δ), and load‐cracking mouth opening displacement (P‐CMOD) curves, considering different replacement levels (0%, 30%, 70%, and 100%) of recycled coarse aggregate (RA) and high temperatures exposure (20, 100, 200, and 300°C). The effects of RA substitutions and temperatures on basic mechanical properties, GF, GFS, and GFU were analyzed. The results demonstrated that the fcu, ft, and elastic modulus (E) decreased with the incremental temperature. The GFS of concrete with different RA substitutions first decreased and then increased, and the minimum value appeared at 200°C. The GF and GFU of concrete with different RA substitutions increased with the elevated temperature, and the increase rate decreased with RA substitutions. When the temperature is less than 100°C, the GF and GFU of concrete remained mostly unchanged with the increase of RA substitutions, while the temperature reached 200 and 300°C, the GF and GFU of concrete increased and decreased with the increase of RA substitutions, respectively. [ABSTRACT FROM AUTHOR]

The equivalent mortar volume (EMV) mixing method has been proposed to prepare recycled aggregate concrete (RAC) with comparable mechanical properties to those of reference natural aggregate concrete (NAC). Previous studies primarily focused on the mechanical properties of EMV concrete with a single replacement ratio of recycled coarse aggregate (RCA). This paper investigates how the mechanical properties of EMV concrete vary with the replacement ratios and particle size distributions of RCA. Five different RCA replacement ratios and two RCA particle size distributions were assessed. A material demand coefficient was principally proposed to quantify the contribution of the EMV mixing method to reduce the environmental impact; the maximum RCA replacement ratio was suggested to obtain sufficient workability of EMV concrete using an effective sand ratio; a drying shrinkage model was theoretically proposed for EMV concrete accounting for the drying shrinkage of residual mortar. The obtained results indicated that the compressive strength and elastic modulus properties of EMV concrete decreased with increasing RCA replacement ratios; using the effective sand ratio of EMV concrete, comparable mechanical properties to those of reference NAC could be obtained for EMV concrete; the proposed shrinkage model was consistent with the available experimental data. [ABSTRACT FROM AUTHOR]

The disposal of waste from coal plants and waste glass (WG) is causing significant environmental problems all around the planet. Currently, the amount of discarding of these wastes is increased. One possible option is to utilize fly ash (FA) from coal plants as a partial substitute for the cement and EG as a fractional substitute for sand in concrete, respectively. Besides, fibers can improve the strength and durability of concrete; explicitly speaking, using coconut fibers (CFs) is in trend due to their highest toughness among natural fibers making it suitable material as fiber reinforcement in concrete. This research studies the concrete behavior with 15% FA as a partial substitute of cement with 2% CFs and waste beverage glass as sand at various replacement levels (14%, 15%, 16%, 17%, 18%, 19%, and 20%). Mechanical and durability characteristics of concrete were assessed, such as compression strength, water absorption, flexural strength, density, workability, and water absorption. The current study results show that adding FA, CFs, and WG improved microstructure quality at 16% replacement of sand. The study showed that the M4 mix has enhanced the properties of concrete samples as compressive and flexural strength was improved to 47.2 and 6.2 MPa and improved apparent density by 20%. Adding more WGP than the optimal proportion (16%) led to detrimental effects on void ratio, permeability, and water absorption. Therefore, 16% of sand with WG and 15% of FA with cement can be substituted with 2% CFs to develop sustainable concrete. [ABSTRACT FROM AUTHOR]

The frost resistance of concrete is an essential evaluation index in cold areas; however, quantitative analyses of macroscopic mechanical properties and interfacial strength of concrete under freeze–thaw (F–T) action are scarce. Based on rapid F–T cycle tests of concrete, mortar, and interface specimens, with limestone, quartz, and basalt as variables, the internal damage and basic mechanical properties of specimens under F–T action were obtained. Furthermore, the quantitative relationship between the mechanical properties of the specimens, and between the internal damage and the basic mechanical properties of specimens under F–T action was established. The results showed that the properties of a coarse aggregate–mortar interface affected the mechanical properties and frost resistance of concrete specimens to a certain extent. After F–T action, the internal structure of the specimen tended to be loose, and the specimen was in a frozen state. The degree of damage on concrete specimens was more substantial than that on mortar ones. Quantitative analysis also indicated that the F–T erosion of concrete was mainly caused by the damage in the interface transition zone between the coarse aggregate and mortar. [ABSTRACT FROM AUTHOR]

With the growing usage of supplementary cementitious materials (silica fume, fly ash, and ground blast furnace slag, etc.) in concrete, accurate prediction of green concrete compressive strength (CS) has become an issue worth investigating. In this paper, a green concrete CS prediction model was developed using hybrid artificial neural network with genetic algorithm (GA‐ANN) based on 2479 green concrete CS experiment results. Also two prediction models based on support vector regression (SVR) and ANN algorithm were developed for comparison. Five new parameters were constructed based on the original nine influencing parameters of CS, taking all 14 parameters as input variables, the influence of the constructed parameters on the model performance was studied. Feature selection was then performed based on the maximum information correlation (MIC) and sensitivity analysis results, which could improve the model by deleting several parameters. The results showed that the prediction performance of the SVR, ANN, and GA‐ANN models were improved after adding new parameters, the GA‐ANN model has the best prediction performance. The accuracy and robustness of the GA‐ANN model were effectively improved by deleting the input variables with lower MIC and sensitivity values. [ABSTRACT FROM AUTHOR]

The paper presents integrated effects of concrete samples size and fibers amount on compressive strength of high‐ and ultra‐high strength concretes based on reactive powders. Ready to use the self ‐ compacting mix of high‐performance concrete, was applied. The main aim of the work was to determine compressive strength correlation coefficients for size of cubic samples and integrated compressive strength correlation coefficients for the size of cubic samples including fibers ratio. The article presents the results of experimental tests of compressive strength for 3 sizes of cubic samples, i.e. 40, 100, and 150 mm, with the application of the steel fibers ratio of 0%, 2%, 4% for each sample size. Concrete air content and cone flow test studies were performed for all research series. The obtained results show a diversified influence of the size of the samples and the amount of steel fibers on the results of concrete compressive strength of high‐ and ultra‐high strength concretes based on reactive powders. Namely, the compressive strength correlation coefficient for the size of cubic samples was determined in the range 1.0–1.3, while the integrated compressive strength correlation coefficient the for size of cubic samples including fibers ratio is in the range 1.0–1.47. [ABSTRACT FROM AUTHOR]

Post‐filling coarse aggregate concrete is a new type of green concrete that not only saves the cost of cementitious material, improves the strength, cracking resistance and durability of concrete, but also reduces the carbon footprint. In view of the lack of research on the seismic performance of post‐filling coarse aggregate concrete, this study designs eight interior beam‐column joint specimens made of post‐filling coarse aggregate concrete and three beam‐column joint specimens made of conventional concrete. It studies the influence of post‐filling coarse aggregate ratio, axial compression ratio and stirrup volume ratio of node area on the seismic performance of joint specimens. Through low cyclic reversed loading test, the failure process and the failure pattern, hysteresis curves, skeleton curves, ductility, stiffness degeneration, residual strength and residual displacement, and plastic hinge rotation of interior joints with post‐filling coarse aggregate concrete are analyzed. Test results show that the failure mode of post‐filling coarse aggregate concrete joints is similar to that of the conventional concrete joints. As the axial compression ratio increases, the seismic performance of the joints shows a trend of increasing first and then decreasing, and it reaches the peak when the axial compression ratio is 0.2. It also demonstrates that the seismic performance of the joints is increased by increasing the stirrup volume ratio of node area. Ultimately, under the same axial compression ratio, the seismic performance of the post‐filling coarse aggregate concrete is not significantly different from that of the conventional concrete. It proves that the reinforced beam‐column joint made of post‐filling coarse aggregate concrete could fulfill the comparable seismic performance as that of conventional concrete. [ABSTRACT FROM AUTHOR]

Corrosion and fatigue loading would inevitably degrade bond between rebar and concrete. However, there were only a few related test results available, and confinement of rebar was different from case to case. An experimental study was conducted to investigate the combined effects of corrosion and fatigue loading on bond behaviors between strong confined rebar and concrete. A total of 72 cube specimens with 13 target corrosion levels from 0% to 30% with a step of 2.5% were made and tested. Seven specimens were tested with monotonic pull‐out load. Sixty‐five specimens were tested with fatigue loads and divided into two groups according to corrosion level with two different loaded upper limits. Bond strength, corresponding slip value, residual slip value, and residual bond stress of tested specimens with different corrosion levels and stress levels are studied. Three typical failure modes were observed during fatigue loading processes: rebar fracture, bond fatigue failure, and pull‐out splitting failure, respectively. Test results indicated the residual slip continued to accumulate under fatigue load, and corrosion further increased the residual slip value. Specimens began to show bond fatigue failure when the actual stress level was >50%. The results of this study can provide reference for service life evaluation of reinforced concrete structures in coastal area under repeated loading. [ABSTRACT FROM AUTHOR]

The application potential of recycled aggregate concrete has been realized with the development and utilization of waste concrete. Fibers are added to concrete made with recycled coarse aggregate to enhance its mechanical properties and broaden its application possibilities. Additionally, in practical applications, parts of structural elements are frequently under compression‐shear stress. As a result, the normal stress ratio k (k = σ/fcu, where σ is axial compressive stress, and fcu is concrete cube compressive strength), coarse aggregate replacement rate, and carbon fiber content are used as design parameters to examine the compressive‐shear mechanical properties of carbon fiber recycled aggregate concrete in this paper. The results show that the normal stress ratio and fiber content affect the whole compression‐shear process curve, shear strength, peak shear displacement, and damage evolution. A compressive shear damage model that takes into account the aggregate replacement rate, normal stress ratio, and fiber content is established. And there is good agreement between the experimental findings and the calculation model. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) elements suffer continuous deterioration across their lifetime from in situ aggressive environmental factors. Chloride‐induced deterioration of the steel reinforcement presents significant repercussions on the mechanical and seismic behavior of affected RC members. This paper introduces and summarizes experimental work carried out at the University of Canterbury, investigating the long‐term implications of chloride‐induced deterioration on various mechanical properties. The impact of chloride corrosion on bond‐slip behavior, the cyclic flexural response of large‐scale RC piers, and the shear resistance of short RC columns, with particular focus on the latter, is reported. Results indicate that corrosion damage presents more severe consequences to the displacement ductility of RC columns than the load‐bearing capacity. Transverse reinforcement presents a much greater risk and vulnerability to deterioration, leading to a transition in failure mechanism from a ductile response to a brittle shear/shear‐bond failure. Reduced confinement negatively impacts the stress–strain response of the confined concrete and bond‐slip behavior in cracked members, where friction is relied upon as the primary load‐transfer mechanism once mechanical interlock is lost through the generation of rust by‐products and concrete splitting. [ABSTRACT FROM AUTHOR]

This paper presents the comparison of advanced semi‐probabilistic methods for the design and assessment of concrete structures represented by mathematical models solved by non‐linear finite element methods. The special attention is given to the advanced methods focused on the estimation of the coefficient of variation of structural resistance. Numerical examples represent a replication of laboratory experiments of beams with different failure modes. The obtained results are discussed with respect to the accuracy of the employed methods and the influence of the assumed statistical correlation among basic variables. Simplified methods give a good estimation of the design values, though their accuracy is dependent on the type of the failure mechanism. Moreover, it is shown that mutual correlations among random variables may significantly affect the design value of resistance, and they should be carefully defined and modeled. [ABSTRACT FROM AUTHOR]

This article proposes a new constitutive model for the cyclic behavior of rubberized concrete confined with fiber‐reinforced polymer (FRP) sheets. The model is calibrated with experimental results from 18 confined rubberized concrete (CRuC) cylinders tested in cyclic compression. The cylinders had 60% total aggregate volume replacement with recycled tyre rubber. Parameters investigated include the type of confining material (Carbon or Aramid FRP) and number of layers (two, three, or four). The results indicate that using FRP confinement leads to a strong (up to 100 MPa) and highly deformable (axial strains up to 7%) rubberized concrete that can be used in structural applications. The proposed constitutive model predicts accurately the material response under cyclic loading and can thus be used for design/analysis of highly deformable components made of FRP CRuC. This article contributes toward the development of advanced constitutive models for FRP CRuC, thus promoting the wider use of recycled materials in construction industry. [ABSTRACT FROM AUTHOR]

Buried pipelines in urban area are prone to corrosion defects for many years. Ensure the safety of buried corrosion pipelines is a key concern during tunnel blasting excavation. Based on the blasting engineering along Shenzhen Metro Line 12, the field test of full‐scale concrete pipeline adjacent blasting was implemented. The dynamic response of concrete pipeline induced by blasting vibration was analyzed by using the dynamic finite element numerical simulation method, and the reliability of numerical simulation was verified by the field monitoring data. On this basis, considering the corrosion defect morphology of pipeline, the distribution characteristics of peak particle velocity and peak effective stress of concrete pipeline with different corrosion depths, corrosion widths, and corrosion lengths induced by blasting vibration were discussed. The parameter analysis method was used to research the influence of corrosion morphology parameters on the dynamic response of the pipeline, and the corrosion depth of the inner‐wall of the pipeline was defined as the main control parameter of the dynamic response. According to the failure criteria of concrete materials, the safety criterion of corroded concrete pipelines with different service years subjected to blasting vibration was established. [ABSTRACT FROM AUTHOR]

To improve the tensile properties of steel fiber–reinforced reactive powder concrete (SFRPC), we prepared aligned steel fiber–reinforced reactive powder concrete (ASFRPC) members by controlling the fiber distribution under a magnetic field. Four‐point bending tests were carried out to examine the flexural tensile properties of the SFRPC and ASFRPC members. In comparison with SFRPC members under the same conditions, we found that the flexural capacity of ASFRPC members increased by 72.4%–149.5%. Moreover, the flexural toughness, residual strength coefficient, and residual load of ASFRPC members were greatly improved. The bearing capacity and toughness of both SFRPC and ASFRPC members were reduced to a certain extent with the increase in the water–binder ratio. The increase in the fiber length and content effectively improved the bending mechanical properties of the SFRPC and ASFRPC members; in particular, the increase in the fiber length significantly improved the deformation capacity of the members. [ABSTRACT FROM AUTHOR]

In this paper, concretes including three different fiber types (carbon steel fiber [CSF], forta ferro fiber [FFF], and polypropylene fiber [PPF]) with different percentages by volume (0.5%, 1%, and 1.5%) and crumb rubber (CR) as a replacement of fine aggregate by volume (5%, 10%, and 15%) are mechanically investigated. Compressive strength, flexural tensile strength, pull out strength, and elevated heat resistance tests are conducted 28 days after casting on the prepared concrete specimens. For the elevated heat resistance test, samples are exposed to 200, 400, and 600°C heat for 2 h and then compressive strength test is applied. According to the test results, fiber reinforcement limits compressive strength decrease and improves flexural tensile strength properties of the rubberized concretes. The positive effect of the fiber reinforcement is also observed on the samples conducted to pull out strength and elevated temperature resistance tests. CSF and PPF reinforced rubberized concretes perform better pull‐out resistance then the FFF reinforced rubberized concretes. Elevated heat resistance test is as expected since with elevation of the temperature strength of the concrete decreases. But according to the test results of the present study, the strength decrease seems to be limited with fiber reinforcement. As a result, incorporation of the fiber and CR could help to utilize more waste tire (CR) in concrete to produce sustainable eco‐friendly concrete. [ABSTRACT FROM AUTHOR]

This paper proposes a novel glass fiber‐reinforced polymer (GFRP)‐timber‐steel tube‐concrete composite column (GTSC) that combines an outer steel tube with GFRP fabric reinforcement, an inner timber core, and concrete for the rest of the space. The mechanical behavior of eight specimens of novel composite columns was investigated considering diameters of timber cores, layer numbers, and angles of GFRP laminates. The results showed that as the size of the timber core increased from 0 to 50 mm, the ductility and the energy dissipation capacity of the composite column maximum increased by 61.5% and 63.4%, respectively. Conversely, the ultimate load carrying capacity and stiffness decreased. It was also found that the timber core weakened the strength of the confined concrete. However, timber core reduced the weight of columns, which slowed down the reduction of the ultimate load carrying capacity of per unit GTSCs, with the stiffness remains unchanged. GFRP laminates with an angle of 60° provide the best stiffness and ductility, and the layer numbers of GFRP has a positive effect on GTSC's mechanical performance. In addition, an analytical model was proposed based on the ultimate equilibrium method, which accounts for the ultimate bearing capacity of GTSC based on the influence of timber. Analyses revealed a good correlation between analytical and experimental results. [ABSTRACT FROM AUTHOR]

Despite the many axial confinement models already proposed for the determination of the peak compressive strength of fiber‐reinforced polymer (FRP) confined concrete columns, they are, in general, applicable only to concrete columns of circular or square cross‐section, with full or partial confinement arrangements. In this study, by proposing a cross‐sectional and confining system unification approach, a new model is developed and calibrated based on a large test database. For the generalization of the cross‐section and FRP‐based confinement arrangement, the concept of confinement efficiency factor with a unified mathematical framework is adopted. By simulating experimental tests and comparing to the predictions of existing confinement models, the developed one demonstrates a very high reliability and suitable for design purposes by balancing the simplicity of the usage and accuracy. [ABSTRACT FROM AUTHOR]

Research in 3D concrete printing has gained an exponential increase in attention over the last decades. The automated production process can be beneficial to reduce material use and increase form freedom of produced elements. Disadvantages are the difficulty to apply reinforcement, the speed of execution if massive elements have to be made and the uncertain durability performance of the printed material. These aspects still lead to reticence in the concrete construction industry to use 3D printing at a large scale. To lower the threshold to move from the conventional toward the new construction technique, a combination of 3D printed and conventional concrete is proposed namely concrete elements with stay‐in‐place 3D printed formwork. In this paper, experimental research has been performed to investigate the behavior of 3D printed formwork during casting and curing of fresh material. Cylindrical formwork was printed on small scale and filled with self‐compacting concrete. During the experiments, strain development and temperature evolution were measured in and around the elements. The obtained data was analyzed taking in attention the material characteristics of both materials in order to separate the different mechanisms. Results showed that the formwork is subjected to the lateral pressure of the cast concrete, moisture warping and thermal curling. The strains in the formwork increase significantly after casting as a result of moisture warping and thermal curling. The peak strain of the concrete element is reached during the hydration phase of the cast concrete. As the cast concrete stiffened in a slightly deformed formwork, residual strains will be present after the element cooled down. [ABSTRACT FROM AUTHOR]

Probabilistic service life analyses for assessing the risk of chloride‐induced corrosion in uncracked concrete are often realized using the well‐known chloride ingress model of the fib Model Code for Service Life Design. In practice, however, concrete includes cracks, which alter the resistance of the concrete against the chloride ingress. In the past, different approaches to account for preexisting cracks, were developed. In this study, these modeling approaches are summarized and compared in context of the probabilistic service life prognosis. Furthermore, a new approach to account for cracks by theoretically adapting the convection zone is presented. This study demonstrates that the choice of model extension to account for cracks vastly influences the prediction results and shows the limits of application of the current extensions. [ABSTRACT FROM AUTHOR]

Connections in the assembled precast elements become essential locations for creating structural continuity. However, the construction challenges of conventional steel sleeve connections, such as rebar embedment length, rebar congestion, and formed grout defects (i.e., voids), are still a concern area for researchers and engineers. In this study, a proposed ultrahigh performance concrete (UHPC) grouted sleeve connection was presented for assembled precast elements, which might reduce defects, enhance durability, and accelerate structure construction. The tensile test of grouted sleeve connection with different grouting materials, rebar diameters, and anchoring lengths was conducted to determine an optimal anchoring length used in the flexural design. The precast specimens with the UHPC grouted sleeve connection were tested under flexural load. Also, strain changes in concrete, sleeve, and rebar were reported in tensile and flexural tests. The tensile test results showed two types of failure modes, the rebar rupture and bond failure between rebar and grouting. The recommended rebar anchoring length in the flexural design was six times the rebar diameter. The flexural test results showed that the precast specimen with or without the shear key has a similar failure mode as compared to the cast‐in‐place specimen, while their average cracking load, yield load, and ultimate load were 27.9%, 11.0%, and 7.4%, respectively, which is less than those of the cast‐in‐place specimen. Also, the flexural cracking resistance was the highest in the sleeve segment, followed by the joint region and the rebar segment. This study provides a reference for the design of the UHPC grouted sleeve connection for assembled precast elements. [ABSTRACT FROM AUTHOR]

Investigations on steel fiber reinforced concrete (RC) beams in torsion show, that the steel fibers positively influence the torsional load‐bearing behavior. Since a systematic evaluation of the previously known test results and the derivation of a generally valid design model were lacking until recently, current codes such as Model Code 2010 do not contain any design models for the consideration of the steel fiber load‐bearing effect in the torsion design. Due to this, the existing torsion tests on steel fiber RC were summarized in a database. Furthermore, on the basis of the test results and observations, the space truss model developed by Rausch and later refined by Lampert and Thürlimann, among others, was further developed and supplemented by additional longitudinal and transverse steel fiber tension struts. This modified space truss model was validated with the database and shows good to very good predictions to the torsion test data. [ABSTRACT FROM AUTHOR]

A comprehensive study focuses on the eccentric compressive behavior of steel‐fiber‐reinforced recycled concrete filled steel tube (SRCFST) columns. A total 39 stub columns are tested, and the variables include eccentricity ratio (e/r), steel fiber volume, quality replacement rate of recycled aggregate, concrete strength grade, and diameter–thickness ratio of steel tube. Failure mode, the load–lateral deflection behavior and the moment–curvature response are analyzed. The load–moment interaction relationships, the load–strain responds and the neutral axis position are researched. The results show that the use of recycled aggregate causes the little‐to‐no influence on the eccentric loaded performance of SRCFST columns with a relative smaller e/r. However, the ultimate load and deformability of the columns with higher e/r both decreases rapidly. Adding steel fibers can offset this adverse effect. The addition of steel fibers sustains a higher relative compression region height in the cross section. The ultimate load descent of SRCFST columns due to the increase of e/r is slower than ordinary concrete filled steel tube and recycled aggregate concrete filled steel tube columns. Moreover, on the basis of the unified theory, a calculation model is proposed to predict the ultimate capacity of SRCFST columns under combined loadings. The model captures well the compressive response of SRCFST columns. [ABSTRACT FROM AUTHOR]

As an important antiseepage structure of concrete face rockfill dam, the durability of concrete face slab is very important for the long‐term safe operation of the dam. Polypropylene fiber (PPF) and polyacrylonitrile fiber (PANF) are used as research objects to study the salt frost resistance of dual fiber Face slab concrete. The corrosion resistance of PPF and PANF concrete under different fiber volume was compared. The mass loss, residual compressive strength, relative dynamic modulus of elasticity and microstructure were evaluated in salt freezing environment. The results show that adding PPF and PANF to concrete can effectively improve the frost resistance of concrete, and the performance law is similar under the coupling failure of chloride and freeze–thaw cycles. Under the same volume, the effect of PPF concrete is more significant than PPF concrete, and the effect of adding two kinds of fibers at the same time is better than adding one fiber alone. Within the evaluation range, choosing 0.5% PPF and 0.5% PPF as additives is the best choice to improve the salt frost resistance. The results of scanning electron microscopy microstructure analysis of corrosion products are consistent with that of macro property analysis. [ABSTRACT FROM AUTHOR]

The bond performance of glass fiber‐reinforced polymer (GFRP) bars embedded in steel fiber–PVA hybrid fiber concrete plays an important role in their integration. In the present work, hybrid fiber concrete in different volume ratios of hybrid fibers with GFRP was investigated. Pullout tests with two amplitude regimes were conducted on hybrid fiber concrete specimens integrated with GFRP bars to investigate its ultimate bond strength, bond–slip curve, energy dissipation characteristics, and bond stiffness. The results indicate that when the total fiber volume ratio was fixed at 0.9%, the bond strength between the GFRP bars and hybrid fiber concrete increased gradually as the steel fiber volume increased, and the energy consumption increased gradually during the pullout. The slip corresponding to the ultimate bond strength under variable‐amplitude repeated loading is in good agreement with the experimental results under monotonic loading. The specimen P1S8 (0.1% PVA, 0.8% steel fiber) hybrid exhibited sufficient energy dissipation capacity and deformation capacity under repeated loads, and the bond stiffness is relatively higher and more stable during the loading and unloading stages. [ABSTRACT FROM AUTHOR]

Alkali‐activated slag is an alternative to ordinary Portland cement that has been studied for the past 20 years. One of the main challenges for its practical use is understanding and controlling its shrinkage behavior. In this study, new experimental results for two alkali‐activated slag concrete mixes are presented under both sealed and unsealed conditions. The results show that basic shrinkage increases with increased sodium silicate ratio. Under unsealed conditions, the age to exposure to drying has a most significant impact on the final drying shrinkage. Finally, the mechanisms explaining shrinkage of such materials are discussed and thefib Model Code 2010 is extended for alkali‐activated slag concrete using the new experimental results. The extended model consists of four parameters influencing the final values and the speed of both basic shrinkage and drying shrinkage. It is extensively compared with experimental datasets from the literature and improves significantly predictions compared with the original models for both basic and drying shrinkage. This demonstrates clearly the feasibility to extend it for predicting shrinkage of alkali‐activated slag concrete. [ABSTRACT FROM AUTHOR]

Soundless cracking technique has been widely applied in the demolition of rock and concrete structures because of its cleaner advantages compared with conventional explosive methods. However, the correlations between fracturing processes and characteristics of soundless cracking demolition agents (SCDAs) and the optimal use of SCDA in improving the efficiency of demolition are still poorly documented. In this concern, this study develops a reliable numerical model verified by experimental data to investigate the optimal use of SCDA in fragmentations of concrete based on the extended finite element method. The simulated results reveal that the minimum hole diameter is 26 mm required to break the concrete cube of 150 mm, and the crack process can be divided into three phases of initiation, propagation, and coalescence according to the energy release rate. Moreover, the proposed method is employed in simulating the crack process of meter‐scale concrete blocks with two predrilled holes, and the optimal hole spacing of 350 mm is then determined. This study provides some insights for improving the efficiency of SCDA in the field applications. [ABSTRACT FROM AUTHOR]

Strain and temperature measurements on reinforced concrete structures with Rayleigh‐based fiber optic sensors (FOS) promise dense data networks of crucial structural parameters. In this context, the measurement of temperature and mechanical strain is invariably intertwined, precipitating in a frequency shift recorded via FOS. Consecutive experiments were carried out on reinforced concrete beams under mechanical, thermal, and thermo‐mechanical loading. Basic analysis of fiber optics equations indicates the sensitivities toward both influences. These are quantified and juxtaposed in experiments, first separately and subsequently combined. As concerns temperature measurement, the slightest tensile forces exerted onto the FOS may engender distortions of several degrees Celsius. Conversely, strain measurements are affected by temperature changes to a lesser degree. Nevertheless, the level of strain to be sensed and the severity of corrupting temperature shifts must be carefully weighted. The article raises awareness for the coupling of temperature and strain and enables the practitioner to identify and assess perturbations. [ABSTRACT FROM AUTHOR]

Digital Image Correlation (DIC) technique is used to collect the whole‐field strain of concrete subjected to bending loads under different temperature change cycles, cooling rates, and water‐binder ratio. The bending damage behavior of concrete under large‐difference temperature circulation is analyzed with the whole‐field strain cloud map and data. In addition, with the whole‐field strain obtained by 3D‐DIC technology, the strain‐based damage variable is defined. Furthermore, the damage degree of concrete specimen in the bending process is quantified, and the bending damage evolution process of concrete under the action of temperature circulation is discussed. The results show that the damage of concrete in areas with large temperature differences is related to the number of temperature change cycles as well as the cooling rate. Moreover, the increase in the number of temperature change cycles and the cooling rate will aggravate the bending damage of the concrete. Additionally, the higher the water‐binder ratio, the more serious the adverse effect of temperature circulation on the concrete. This paper provide certain reference for the evaluation of concrete bending deformation damage in areas with a large temperature difference. [ABSTRACT FROM AUTHOR]

A 2D meso models of recycled concrete with different sizes is established using the base force element method. The specimens are loaded with different strain rates. The meso damage of recycled concrete is analyzed. In addition, the structural performance of specimens under the joint actions with strain rate and size are also studied. The simulation results find that the compressive strength has little difference when the values of strain rates are lower than 0.1 s−1. The greater the strain rates, the greater the difference of compressive strength between different sizes when strain rates are larger than 0.1 s−1. In addition, the Bažant statistical theory can be used to analysis the mechanical properties of recycled concrete. Besides, a modified formula in calculating the dynamic size effect of recycled concrete is also given based on the Bažant statistical size effect theory. [ABSTRACT FROM AUTHOR]

Nowadays, geopolymers, which are more environmentally friendly than cement due to the high energy requirements and high carbon dioxide (CO2) emissions of cement production, emerge as alternative binders. In this study, the mechanical and durability properties of geopolymer concrete (GC) based on ground granulated blast furnace slag (GGBS) (100GGBS), 50% fly ash (FA) and 50% GGBS (50FA50GGBS), and FA (100FA) with two different water/geopolymer solids ratios (W/GP) of 0.33 and 0.35 were investigated. Slump, compressive strength, splitting tensile strength, unit weight, water absorption, elevated temperature resistance, abrasion resistance, modulus of elasticity, and drying shrinkage tests were carried out. As the percentage of FA in the mixture increased, the slump of the concrete increased, while the cohesion of the concrete decreased and the setting time was delayed. The addition of GGBS increased the compressive strength and the splitting tensile strength of the GC by up to 377% and 278%, respectively. Under the effect of elevated temperature, the 100FA concrete showed less strength loss and weight loss than other concrete. After the abrasion test, 100GGBS concrete lost about 2.5 times less weight than 100FA concrete. The drying shrinkage of geopolymer mortar reached a maximum of 100 microstrains. Among all concrete, 50FA50GGBS‐0.33 showed the highest performance in terms of overall performance. [ABSTRACT FROM AUTHOR]

Pull‐out tests were conducted on 36 bond‐slip specimens with unslotted steel bars and 12 with slotted steel bars to analyze the effects of anchorage length and freeze–thaw damage on bond strength, and investigate the distributions of bond stress and slip between steel bar and recycled concrete at peak pull‐out load. The results show that, the bond strength decreases with the increase of freeze–thaw damage and anchorage length, and the effect of freeze–thaw damage on long‐anchored members is less than that on short‐anchored members. The presence of the arching effect changed the shape of the bond stress distribution curve, causing a second peak at the free end, and the arching effect was reduced accordingly after freeze–thaw damage. The calculated values using the modified softening sleeve theory proposed in this study are in good agreement with the experimental values. [ABSTRACT FROM AUTHOR]

Widely used by architects and builders for its many qualities: strength, durability and also for its great adaptability to shapes, the self‐compacting concrete (SCC) remains a material of great future both for major infrastructure works and for quality architectural achievements. Currently, to measure the rheological properties of the fresh concrete (plastic viscosity μp and yield stress τ0), the widely adopted test is the "concrete rheometer." However, the use of a rheometer on site is a very complex operation, because it is too expensive, and in addition, it requires a qualified person to move, handle or repair it. Hence, many laboratories use other empirical tests to predict the rheological behavior of concrete. Each of these tests characterizes only one of the two rheological parameters (μp or τ0) and depends on the operator. In several cases, these constraints lead to a false characterization of the concrete behavior. To remedy these problems, this work aims to develop another means of rheological characterization of SCCs. This test will represent total independence from the operator and will quantify both the plastic viscosity and the yield stress of the self‐compacting concrete. The proposed approach, verified both by experimental results and correlation studies, represents an economical and simple tool, that can be used efficiently on the building site, and it makes it possible to characterize the SCC rheology from its flow. [ABSTRACT FROM AUTHOR]

Ultrafine graded fly ash (UFGFA) is a well‐graded pozzolanic material among silica‐rich reactive pozzolans that contributes to the improvement of the early pozzolanic reactivity of cement paste, mortar, and concrete at early ages. The purpose of this article is to demonstrate the effect of UFGFA on the development of compressive strength in M20, M25, and M30 grade concretes with a partial replacement of cement ranging from 0% to 40% by weight at various water‐binder (W/B) ratios of 0.43–0.53. Compressive strength development was examined at ages 7, 14, 28, and 56 days. Additionally, three machine learning (ML) models (linear regression, ANN, and GEP) were used to predict the compressive strength of the concretes using different predictive classifications. According to the investigations, experimental studies indicate that a lower W/B ratio and a minimum amount of UFGFA replacement result in an increase in strength at an early age of 7 days. At 14, 28, and 56 days, higher strength results were obtained when 15%–30% UFGFA was replaced with a W/B ratio less than 0.5, whereas a reduction in strength was observed when more than 30% UFGFA was replaced with cement and with W/B ratio greater than 0.5. All machine learning models produced good predictions of compressive strength, with LR models having least performance and ANN has the more accurate fit. ANN models outperformed the other three machine learning models, but GEP models performed identically near to the ANN model, with expressions generated, that can be used for further development of predictive model. [ABSTRACT FROM AUTHOR]

Compressive strength is considered to be one of the most important mechanical properties of high‐strength concrete (HSC). In this study, three machine learning models, ELM, PSO‐ANN, and GS‐SVR were employed to predict the compressive strength of HSC using 681 data records. The five ingredients and the compressive strength of HSC were regarded as input variable features and output target, respectively. Results indicated that the GS‐SVR model showed the best performance in forecasting with the R of 0.992, MAPE of 0.016, RMSE of 1.241, MAE of 0.842, and RRMSE of 0.024, which could be an alternative candidate for strength prediction. Additionally, a sensitivity analysis was performed within the GS‐SVR model to achieve an in‐depth examination of the effect of each single input variable on the compressive strength. The sensitivity of input variables demonstrated that the water is the most sensitive parameter to the compressive strength of HSC, while the superplasticizer is less sensitive. The research of this paper can provide reference and guidance for concrete design and construction. [ABSTRACT FROM AUTHOR]

Sulfate attack is a major cause of the deterioration of concrete structures. Accurately predicting the temporal and spatial distribution of sulfate ions in concrete is the basis for revealing the mechanism of concrete performance deterioration caused by sulfate attack. In this article, based on the pore change caused by sulfate damage to cement mortar, a diffusion model of sulfate ions in cement mortar considering changes in surface concentration was established. Furthermore, a two‐dimensional mesoscopic concrete model composed of cement mortar, coarse aggregate, the intrafacial transition zone (ITZ) and macroscopic defects, which can reflect the real aggregate shape, was constructed to study the diffusion of sulfate ions in concrete. The correctness of the model is verified with existing experimental data, and the model is further studied. The results show the following. (1) The average value of the calculation results of multiple sets of models can be used to eliminate the influence of the randomness of the construction of the two‐dimensional mesoscopic concrete model. (2) With increasing stone content, the corrosion depth increases, but the average concentration at a given location decreases. (3) With increasing sulfate solution concentration and water‐cement ratio, the sulfate ion concentration and the corrosion depth in concrete increase. [ABSTRACT FROM AUTHOR]

Estimating delayed ettringite formation risks, early age cracking and/or early age strengths in concrete structures is still a complex task to achieve in construction projects. Indeed, numerous complex coupled phenomena occur during concrete hydration process, which must be finely described for accurate predictions of these different criteria. It requires the determination of various input data, which leads to various experimental tests (calorimetry, mechanical properties, temperature records, both chemical, and physical concrete constituent properties) which are not fully available for industrial practices. Therefore, since more than a decade Vinci Construction Grands Projets focuses on modeling and numerical simulations which allows transferring both construction project feedbacks and internal research investigations to our next industrial applications in the form of methodology and internal recommendations. Different representative examples from successful experienced projects illustrate this methodology and draw the main relevant key features to optimize construction processes. This paper shows that predicting the evolution of thermo‐physical properties of concrete from its mix design at the macroscopic scale allows an accurate temperature prediction in concrete structures when the used model correctly captures the key phenomena such as the thermo‐activation process based on the full detailed "Methodology." For the prediction of DEF and thermal cracks risks, the associated project requirements inherited from technical guides and relevant standards have been employed to help construction teams to optimize their construction options and associated planning in the most safely conditions. [ABSTRACT FROM AUTHOR]

This study explores the effects of mixture design parameters on the residual mechanical properties of lightweight expanded clay aggregate (LECA) concrete exposed to elevated temperatures. A total of 30 lightweight concrete mixtures were cast and exposed to three elevated temperatures, namely 250°C, 500°C, and 700°C. The test variables comprised the LECA percentage used as partial volume substitution for natural sand (0%, 25%, 50%, 75%, and 100%), silica fume partial replacement for cement by weight (5%, 7.5%, 10%, 12.5%, and 15%), cement content (300, 400, 500, 600, and 700 kg/m3), and different water‐to‐cement (W/C) ratios (0.25, 0.313, 0.375, 0.438, and 0.5). The compressive and indirect tensile strengths were measured before and after exposure to elevated temperatures. The results indicate that the lightweight concretes incorporating higher contents of cement and silica fume and made with lower W/C ratio exhibited higher initial mechanical properties yet incurred more significant drop in mechanical properties after exposure to 500°C and 750°C. [ABSTRACT FROM AUTHOR]

Using steel slag fine aggregate (SSFA) to replace river sand (RS) in making concrete offers a sustainable solution for mitigating the environmental issues owing to the large‐scale mining of RS and disposal of a large amount of steel slag. The mechanical behavior and chemical property of concrete made with SSFA at ambient temperature were investigated extensively. However, relatively few studies have been conducted to investigate the behavior of concrete with SSFA after exposure to elevated temperatures. To fill up this research gap, this paper studied the post‐fire behavior of five concrete mixes with SSFA replacing RS. The effect of SSFA replacement ratio by volume (0%, 25%, 50%, 75%, and 100%) on the heating temperature—time curve, color and appearance changes, weight loss, failure mode, and residual compressive strength of concrete under curing period of 28‐ and 91‐day, after exposure to 25 (ambient temperature), 400, 600, 800, and 1000°C was investigated. Besides, chemical composition at ambient and after exposure to elevated temperatures was analyzed with the aid of X‐ray diffraction. Test results showed that with SSFA partially or totally replacing RS, the heat insulation capability of concrete could be enhanced, especially at the replacement ratio of 75%. Moreover, concrete with RS replaced with SSFA presented larger or comparable residual strength after exposure to elevated temperatures from 600–800°C. Lastly, the design model by EC2 was adopted to predict the residual strength of concrete with and without SSFA. Comparing the design and measured residual strengths, it was concluded that EC2 was conservative. [ABSTRACT FROM AUTHOR]

The article describes measurements of strains of concrete, steel and textile reinforcement with distributed fiber optic sensors (DFOS). The technology of distributed strain measurements gains currently increasing attention within the civil engineering field and indeed the DFOS can be applied in various measurement scenarios providing results and insights which were not possible before. Within this article, the fibers and adhesives that are most commonly used are compared and several measurement scenarios and their results are described, including precise strain measurements with high resolution as well as measurements on large‐scale specimens. Concrete strains were measured in a multiaxial compression stress state and also during setting and hardening and in flexural tests. Strains of the steel and textile reinforcement were monitored along the bond zone and also in flexural tests. Finally, cracking patterns were observed and compared with digital image correlation methods. Validated examples of applications of DFOS in laboratory work are described. [ABSTRACT FROM AUTHOR]