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This paper investigates the behavior of reinforced concrete (RC) arch beams with shear weaknesses strengthened with fiber-reinforced polymer (FRP) composites, using two different methods: the externally bonded reinforcement (EBR) and grooving method (GM) in the form of externally bonded reinforcement on grooves (EBROG) method. Additionally, two different patterns of shear strengthening including two-sided and U-shaped were utilized. Nine arch beam specimens were tested, each having a square cross-section of 150 mm and a span length of 947 mm. Among these, two specimens were strengthened using the EBR method, while six specimens were strengthened using the EBROG method. The paper explores the impact of the strengthening method and pattern on the load-carrying capacity, failure mode, energy dissipation, and strain distribution of the specimens. The results indicate that the EBROG method significantly increased the load-carrying capacity of the arch beams compared to the EBR method in both patterns. The results also show that the U-shaped pattern was more effective than the two-sided pattern in increasing the load-carrying capacity of the specimens. The specimen with intermittent U-shaped FRP demonstrated 34.8% and 47.3% higher load-carrying capacity than the non-strengthened specimen when using the EBR and EBROG methods, respectively. The paper also introduces an analytical approach to estimating internal forces, such as flexural moment, axial force, and shear force, along the arch beam. The comparison between the experimental and theoretical results confirms the accuracy of the analytical approach. • The behavior of RC arch beam with shear weakness was investigated. • EBR and EBROG methods were adopted for strengthening of the arch beam. • PIV method was utilized to obtain the strain distribution, validate the displacements, etc. • An analytical procedure was conducted to validate the experimental results and investigate the performance of the strengthening methods. [ABSTRACT FROM AUTHOR]

To improve the fatigue behaviour of the concrete, this paper explored a potential innovative method: the joint addition of expansive agents (EA) and glass fibres (GF). It was envisaged that the addition of EA reduced additional defects caused by the addition of GF to the concrete, while the compressive prestress caused by EA enhanced the bonding between GF and the concrete, thereby improving the fatigue behaviour of the concrete. The test results indicated that the synergistic effect of EA and GF effectively improved the static bending strength, fatigue life, and deformation performance of the concrete. The synergistic effect of EA and GF on the fatigue life of the concrete was revealed qualitatively and quantitatively. The synergistic effect was further demonstrated from perspectives of the fatigue deformation and fatigue stiffness. Furthermore, P - S - N curves of EA and GF reinforced concrete were established, and the fatigue ultimate strength and conditional fatigue ultimate strength were provided as a design basis. This paper recommended adding an appropriate amount of EA to glass fibre reinforced concrete to achieve better concrete properties. • Joint addition of EA and Gf was a potential method for improving concrete. • Bending tests were used to elucidate fatigue bending performance of concrete. • Synergistic effect of EA and GF on fatigue performance of concrete was reveal. • Using two-paramater Weibull distribution, P - S - N curves were established. [ABSTRACT FROM AUTHOR]

High-strength steel reinforced concrete (HSRC) columns configured with T63E/E/G rebar (whose yield strength is 630 MPa) have significant advantages such as less steel consumption and higher load carrying capacity. However, the compressive strength level of T63E/E/G rebar in HSRC columns under eccentric compression with a large eccentricity (LEC-HSRC) and the eccentric load carrying capacity calculation model is not precisely determined yet. In this paper, 11 LEC-HSRC columns were tested, then the test results and sectional stress state are discussed in depth. The results show that the compressive strength of T63E/E/G rebar could be fully utilized in LEC-HSRC columns, thus the compressive strength design value of T63E/E/G rebar in Technical specification for application of new heat-treatment high-strength ribbed bar in concrete structures DBJ 61/T 157–2019 was revised to 545 MPa accordingly, to the same level as the tensile strength design value. It's conservative to calculate the eccentric load carrying capacity of LEC-HSRC columns according to Code for design of concrete structures GB 50010–2010. A new eccentric load carrying capacity calculation model, which satisfies both the static equilibrium and strain compatibility condition, was proposed based on stirrup confined concrete constitutive relation, and it has higher accuracy compared with currently used models. The assumption that the strain at the edge of the compression zone of core concrete reaches the peak under ultimate load can suitably calculate the compressive stress of T63E/E/G rebars in LEC-HSRC columns. This paper offers experiment and theory support for the revision of DBJ 61/T 157–2019 and the engineering application of T63E/E/G rebar in China. • T63E/E/G high-strength rebar's compressive strength level in LEC-HSRC columns is experimentally and theoretically studied. • An eccentric load carrying capacity calculation mode based on the stirrup confined concrete constitutive relation is proposed. • The compressive strength design value of T63E/E/G rebar is revised from 435 MPa to 545 MPa in standard DBJ 61/T 157-2019. • The strain at the edge of the compression zone of core concrete reaches the peak under ultimate load. [ABSTRACT FROM AUTHOR]

In this paper, the mechanism of chloride ion transport in unsaturated concrete considering the nonlinear seepage effect is investigated by indoor experiments and analytical modelling. The concrete sheet imbibition test is used to reveal the nonlinear characters of seepage including water convection and moisture capillary within the unsaturated concrete in case of various water-binder ratios. For modelling purpose, an exponential function is introduced to mathematically depict the nonlinear relation between the specific discharge and hydraulic gradient during both water convection and moisture capillary processes. Based on such nonlinear seepage models, new mathematical models are proposed for the problem of chloride invasion within the reinforced concrete structure. The solution for the mathematical model of chloride transport is resolved by Laplace transform and finite difference method, of which acceptability is verified by the comparison with the results from chloride ion invasion test. The result indicates that, compared with linear seepage law, the use of the proposed nonlinear seepage solution is preferred to depict the saturation-relative humidity curves from concrete sheet imbibition test. The consideration of nonlinear seepage can result in a slower chloride transport rate, which further makes a later flow start-up time and a smaller free chloride iron concentration within the concrete. Such effect can be enhanced with the increase of nonlinear flow degree. The paper provides an effective solution to evaluate the chloride invasion within the unsaturated concrete. • Pioneer proposes solutions considering nonlinear seepage effect on chloride transport within concrete. • Considering nonlinear seepage can better describe the relationship between saturation and relative humidity. • The start-up time of nonlinear flow obviously lags behind that of linear flow. • The occurrence of nonlinear convection-diffusion and capillary diffusion seepage can slow down the penetration of chloride ions. [ABSTRACT FROM AUTHOR]

Despite the substantial steps made in understanding the mechanics of reinforced concrete structures, effectively addressing, and mitigating inelastic buckling remains a complex and enduring challenge. Consequently, this paper provides a comprehensive review of all the previous studies on modelling the inelastic buckling of reinforcing bars, and the capability of current state-of-the-art numerical models to simulate the nonlinear stress-strain response of reinforcing bars with the effect of buckling under monotonic and cyclic loading. This review paper consists of four different clusters including: (i) inelastic buckling of reinforcing bars under monotonic loading with and without corrosion, (ii) inelastic buckling of reinforcing bars under cyclic loading with and without corrosion, (iii) influence of inelastic buckling on low-cycle fatigue life of reinforcing bars with and without corrosion, and (iv) influence of tie reinforcement on global stability of longitudinal bars and buckling length calculation. For each group, a summary and critical review of all the previous research is provided. A quantitative comparison between the most widely used uniaxial material models have been made and their performance have been assessed against experimental data. Finally, the current limitations in existing literature are examined, unresolved issues for future research are identified, and some recommendations for future research are suggested. ● Modelling inelastic buckling of reinforcing bars under monotonic and cyclic loading. ● Influence of corrosion on inelastic buckling of reinforcing bars. ● Influence of corrosion and buckling on low-cycle fatigue of reinforcing bars. ● Tie reinforcement, global stability of bars, and buckling length calculation. [ABSTRACT FROM AUTHOR]

The corrosion of reinforcement embedded in concrete caused by chloride attack is the main factor leading to the durability failure of reinforced concrete (RC) structures. A novel method of embedding diaphragm to effectively delay the corrosion of reinforcement is proposed in this paper. Furthermore, the mechanism of the diaphragm hindering chloride diffusion is revealed and the shape of the diaphragm is optimized and designed through numerical simulation. The results show that the diaphragm can effectively delay the accumulation of chloride on the surface of reinforcement, and the geometry of diaphragm has a great influence on the delay effect, and the best geometry is semicircular. Mover, the radius of diaphragm and the distance between diaphragm and reinforcement surface have nonlinear effects on the service life of reinforced concrete. The diaphragm configuration proposed in this paper provides a novel idea to solve the problem of reinforcement corrosion caused by chloride attack. • A novel method of embedding diaphragm is proposed to effectively delay the corrosion of reinforcement. • The mechanism of diaphragm blocking chloride transport is revealed through chloride transport streamline. • The geometry of each diaphragm is optimized to determine the best shape of the diaphragm. [ABSTRACT FROM AUTHOR]

Reinforcement corrosion caused by chloride attack is one of the main reasons for the degradation of reinforced concrete (RC) structures, especially those exposed to marine environment. To study the effect of chloride attack on the electrochemical corrosion behavior of reinforcement, a 2D meso-numerical model coupling ion transport and electrochemical corrosion was established by modifying the anode Tafel slope in this paper. More importantly, gaussian function model with clear physical meaning is proposed to describe the distribution of reinforcement corrosion layer. The reliability of the proposed model is further verified by compared with the third-party experiments data. Furthermore, the effects of electric field effect, meso-structure, maximum corrosion depth and corrosion rate on the distribution of reinforcement corrosion layer are investigated based on the proposed model. The numerical simulation results show that the influence of electric field effect and interfacial transition zone (ITZ) on corrosion morphology cannot be ignored. Moreover, the novel gaussian distribution model with physically meaningful parameters has wide applicability through comparison with experiments. Specially, a simulation of chloride diffusion trajectories in concrete meso-structures reveals how ITZ promotes chloride diffusion. The research of this paper provides theoretical support for the rust expansion cracking and service life prediction of reinforced concrete structures. [Display omitted] • A multiphysics numerical model is proposed to fully explore the mechanism of electrochemical corrosion of reinforcement. • Gaussian function model with clear physical meaning is proposed to describe the distribution of corrosion layer. • The mechanism of corrosion potential promoting non-uniform corrosion of reinforcement is revealed by numerical simulation. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of incorporating a hybrid combination of structural polypropylene fibers on the flexural behavior of concrete beams reinforced with steel, GFRP, and innovative hybrid bars. A new ductile hybrid bar with equivalent bilinear stress-strain characteristics has been developed to address steel corrosion and FRP ductility issues. Fourteen half-scale RC beams were fabricated and tested under four-point loading configuration to study the flexural response. The tensile reinforcement types (steel, GFRP, and hybrid), hybrid reinforcement ratios (0.85 %, 1.26 %, and 1.70 %), reinforcement hybridization schemes (hybrid-hybrid, hybrid-GFRP, and GFRP-steel), and hybrid fiber ratio (0.0 %, 1.0 %, and 2.0 %) are the major parameters studied. The test results were recorded and analyzed in terms of mid-span deflection, cracking load, flexural capacity, and failure mechanism. The results demonstrated that the addition of hybrid fibers and using hybrid bars significantly improved the peak strength, ductility index, and bending stiffness. Moreover, the hybrid-reinforced concrete beams exhibit large inelastic deformations similar to steel-reinforced concrete beams. The inclusion of hybrid fibers improves the post-peak response of the tested beam due to fiber bridging capabilities. For design purposes, a simplified formula proposed by ACI 544 for predicting the nominal flexural capacity of hybrid fiber concrete beams reinforced with hybrid bars was presented, compared with experimental results and validated with 44 specimens from other studies. The predicted and test results were in good agreement with a standard deviation of 0.12. Additionally, 3D nonlinear finite element analysis was developed to validate the test results, demonstrating reasonable accuracy in predicting the flexural behavior of the beams. • This paper investigates the effectiveness of adding a hybrid combination of structural polypropylene fibers on the flexural behavior of (steel, GFRP, and hybrid) reinforced concrete beams. • A new ductile hybrid bar with equivalent bilinear stress-strain characteristics has been developed to overcome traditional steel corrosion and FRP ductility problems. An experimental program of 14 half-scale RC beams was fabricated and tested under a four-point loading configuration. • The variables were: tensile reinforcement types, the addition of hybrid fibers, the hybrid fiber ratio, beam cross section, and the hybrid reinforcement ratio. • The test results were recorded and discussed in terms of mid-span deflection, cracking load, flexural capacity, and mode of failure. • To facilitate the design process, a simplified formula proposed by ACI 544 for predicting the nominal flexural capacity of hybrid fiber concrete beams with hybrid bars was presented. • A finite element analysis using ABAQUS/CAE6.14 was performed to verify the experimental outcomes. [ABSTRACT FROM AUTHOR]

• The numerical model's setup for the steel fibre reinforced concrete (SFRC) segment. • Numerical simulations of GPR detection for SFRC segment under different conditions. • Optimum frequency selection of the SFRC segment. • Validation of an SFRC segment detection based on a model test. • Calculation of the equivalent relative dielectric constant (ERDC) of SFRC segments. The SFRC segment is gaining attention in shield tunnels due to their better mechanical properties. However, the existence of steel fibres poses a greater difficulty when attempting to utilize ground penetrating radar (GPR) for nondestructive quality inspection compared to conventional reinforced concrete segments. This paper presented a refined numerical model of SFRC segments with gprMax software, to investigate the penetration characteristics of GPR. The numerical model incorporated four different steel fibre contents, namely 0%, 0.5%, 2.5%, and 5%. The model also included an internal void and a surface metal plate to compare and analyze the waveform characteristics of GPR with the normal sections of the segment. The orthogonal test of numerical simulation investigates the imaging characteristics, power attenuation patterns, and imaging features of three different GPR frequency gradients: 200 MHz, 500 MHz, and 1000 MHz. This analysis helps in selecting the appropriate detection frequency based on the observed energy attenuation patterns and imaging characteristics. Then, the model test was conducted at the selected frequency to study the penetration performance of GPR. The research results indicate that the numerical model established in this paper demonstrates good effectiveness in studying the waveform characteristics of steel fibre-reinforced concrete under various conditions. The numerical model established in this paper realized the study of the penetration characteristics and imaging features of different steel fibre contents, GPR frequencies, and detection targets. Analysis of waveform characteristics, power attenuation, and imaging results indicates that GPR at 500 MHz exhibits better detection performance for SFRC segments. The results of the numerical simulation were verified through model tests of real SFRC segments, demonstrating that 500 MHz has good penetration performance for SFRC segments. This paper also proposed a calculation method for equivalent relative dielectric constant (ERDC) based on the model test results and validated its rationality through the analysis of numerical simulation results and real GPR waveforms. [ABSTRACT FROM AUTHOR]

• 32 papers were collected on pull-out tests of deformed reinforcement bonded to concrete. • An experimental database containing 935 sets of deformed steel and concrete bond-slip test samples was established. • Some common formulas for calculating ultimate bond strength are compared. • The most important characteristic variables affecting the ultimate bond strength of the structure are selected according to the RF algorithm and correlation coefficients. • A prediction model for the ultimate bond strength of RC drawn specimens based on the GWO-SVR model was developed. Bond strength, as a mechanical property of reinforced concrete (RC) structures, is a crucial factor affecting the force characteristics of RC structures. In order to assess the load-bearing and deformation capacity of RC structures, it is essential to develop a model that can accurately predict the bond strength of RC structures. Therefore, a prediction model based on Random Forest (RF) feature selection and Grey Wolf algorithm optimized (GWO) support vector regression (GWO-SVR) is synthesized in this paper. An extensive database containing 1008 bonded slip test samples was first collected, and various feature parameters were finally preprocessed to filter 935 sets of test data. Next, the optimized support vector machine was trained using the training set data using the GWO-optimized SVR method. Meanwhile, the prediction accuracy of the model was evaluated using the integrated absolute error (IAE), the coefficient of determination (R2), and the mean absolute error (MAE). The model with a good prediction effect can predict the bond strength of unknown tests. When the sample size is small and the number of features is extensive, redundant features must be filtered out before the model prediction. The model prediction after feature selection is significantly better than that before training. The results show that the GWO-SVR model proposed in this study has a higher prediction accuracy than the existing bond strength model. The prediction results of the GWO-SVR model (Test set: R2 = 0.9547, MAE = 1.2487 MPa, IAE = 12.761%) outperform benchmark models such as the multilayer perceptron (MLP) and linear regression (LR). According to the training accuracy of the regression model, it can be found that the GWO-SVR model has good generalization performance (Training set: R2 = 0.9562, MAE = 1.1203 MPa, IAE = 12.182%). In addition, different optimization-seeking algorithms, kernel function types, and machine learning models have significant effects on the prediction results of the ultimate bond strength. In addition, the compressive strength of concrete was verified to be the most sensitive variable for the bond strength of RC structures using RF and Pearson correlation coefficients. The model presented in this study can also be extended to other regression issues. [ABSTRACT FROM AUTHOR]

• PVA fibres significantly improved tensile behaviour of foam concrete. • Pore structure dominated pre-crack behaviour of foam concrete. • Fibres dominated post-crack behaviour of foam concrete. • High bond strength of PVA fibres limited toughness and ductility of foam concrete. Fibre reinforcement is beneficial to control crack behaviour and the energy absorption ability of foam concrete. Several studies have investigated the flexural tensile behaviour of fibre-reinforced foam concrete to determine its ultimate peak strength gain. However, there remains a knowledge gap regarding the underlying mechanism of fibre influence on its tensile behaviour, as well as the impact of fibres on the pre and post-crack behaviour of foam concrete. This paper analysed and compared the flexural tensile behaviour and splitting tensile strength of PVA fibre-reinforced foam concrete. In addition, machine learning technology was used to develop regression models that described the importance of design parameters (foam concrete density, fibre length, diameter, and content), fibre distribution, and pore structure on foam concrete's tensile behaviour. The results show that the mechanism of fibre influence on pre-crack and post-crack flexural behaviour in foam concrete differs from that in normalweight concrete. In particular, contrary to the behaviour observed in normalweight concrete, PVA fibres noticeably enhanced the pre-crack flexural performance and splitting tensile strength of foam concrete. This paper found that this improvement is related to the effect of fibres on the pore structure in foam concrete, which in turn had a substantial impact on both pre-crack flexural behaviour and splitting tensile strength. Different from pre-crack behaviour (mainly influenced by pore structure), fibre content and size dominated post-crack behaviour of foam concrete. Optimising fibre size and content resulted in substantial improvements in splitting tensile strength (up to 75.3% for high-density foam concrete and 49.9% for low-density foam concrete) and flexural strength (up to 44.4% for high-density foam concrete and 117.9% for low-density foam concrete). [ABSTRACT FROM AUTHOR]

• Guiding principles to address deterioration due to corrosion are provided. • Available tests of determining the level of deterioration are culled from the literature. • A categorization of solution methods for protection, maintenance, and repair if offered. • A readily-available reference for practitioners and researchers on corrosion for coastal concrete structures. Deterioration due to corrosion is a key issue affecting the durability, safety, and sustainability of buildings and structures. Most cities are located in coastal areas and many reinforced concrete structures in these areas are exposed to aggressive marine environments. Therefore, it is important to provide protection and offer appropriate repair methods of buildings vulnerable to the degrading effects of corrosion. The first step of implementing recovery is determining the level of degradation undergone by exposed concrete structures. However, there is a lack of integrated guiding principles in this field. Thus, this review paper identifies the tests of determining the level of deterioration, with particular attention given to carbonation issues and chloride ion attacks. The paper also provides a categorization of solution methods for protection, maintenance, and repair, based on standards and codes culled from around the world. This research contributes to the field by providing a readily-available reference for practitioners and researchers, on the current state of knowledge on corrosion and repair strategies for coastal concrete structures. [ABSTRACT FROM AUTHOR]

• Development of a dual-functional intervention method for reinforced concrete beams. • Experimental programme on simply supported beams repaired by ICCP-SS method. • Analysis on the structural responses of simply supported beams with C-FRCM strengthening. • Comparison of test results with existing design methods. • Recommendation of changes on the design methods for cross-section capacity prediction. Chloride ions in marine environment can cause corrosion of steel reinforcement in reinforced concrete (RC) structures and result in structure deterioration. This study investigates a dual-functional intervention method, i.e. impressed current cathodic protection – structural strengthening (ICCP-SS) method, using carbon fibre reinforced polymer (CFRP) as both the anode material for impressed current cathodic protection and strengthening material for structural strengthening system. The effectiveness of the ICCP-SS method on the improvement of durability of RC structures is considered in a long-term timeframe. An experimental programme comprising nine simply supported beams is presented in this paper. The beams experienced 360-day accelerated corrosion and 180-day cathodic protection, followed by four-point bending tests. Flexural behaviour and capacities of the degraded beams repaired by using ICCP technology, structural strengthening technology and ICCP-SS technology were obtained. After the tests, the steel reinforcement bars inside concrete were taken out and cleaned to measure the section reduction due to corrosion. Results showed that the ICCP-SS technology can prevent the corrosion of the steel reinforcement effectively and increase the capacities of the beams at the same time. Finally, the appropriateness of existing design approaches for the intervened beams was also discussed in the paper. The ICCP-SS intervention method is found to be beneficial for the durability of RC structures in marine environment. [ABSTRACT FROM AUTHOR]

• This current research paper is focused on the toughness and impact resistance of hybrid fiber reinforced self-compacting concrete. • Compressive strength made this suitable for structural elements. • Using SEM images, the SCC's failure mechanisms were assessed and fibre-aggregate interface was evaluated. • In digital image processing, the cross sections inspected and fiber segregation coefficient values were evaluated. This research paper presents the results of extensive experimental investigations and analytical results on the fresh and hardened properties of self-compacting concrete reinforced with hybrid hooked end fiber (HF) and crimped steel fiber (CF) in different fiber volume fractions. In this present investigation, the mixes were reinforced with different fiber combinations of hooked end fiber (0.25, 0.5 and 0.75%) and crimped fiber (0.25 and 0.5%). The fresh state properties of the mixes were characterized by using slump flow diameter, T 50cm , and V-funnel test. The hardened properties of self-compacting concrete (SCC) mixes were assessed by using compressive strength, flexural strength and impact resistance test. Regression analysis was carried out in order to correlate the fresh and hardened state on the extensively large volume of collected experimental data. The results reported that adding hybrid hooked end-crimped steel fiber significantly improves the compressive strength, flexural strength and impact resistance. Addition of hooked end steel fiber led to improve the compressive strength when compared to crimped end fiber. Moreover, increasing the crimped fiber content decreased the effect of hooked end steel fiber in flexural strength improvement. [ABSTRACT FROM AUTHOR]

• Characterization of TM behaviour of TRC (F.GC2), refractory matrix, carbon textile. • Evolution of the stress-TM strain curve of F.GC2 as function of temperature. • Decrease of the F.GC2 rupture temperature with increase of the imposed load ratio. • Progressive reduction of efficiency coefficient of carbon textile in F.GC2. • Measurement of diffusivity coefficient of F.GC2 by thermal test. In comparison with carbon fiber reinforced polymer material, the carbon textile reinforced concrete (TRC) is usually coted to have a better fire behaviour. The aim of this paper is to analyse the elevated temperature behaviour of TRC. This paper presents the experimental results conducted on carbon TRC at mesoscale in the range of temperature from 25 °C to 700 °C. The carbon TRC consists of refractory matrix and carbon textile which has been treated with amorphous silica products for a good bond with the cement matrix. As a result, carbon TRC showed the strain-hardening behaviour with different phases and brittle behaviour depending on the temperature. The evolution of carbon TRC properties with elevated temperature (the ultimate stress, the crack stress, the initial stiffness) was experimentally identified. The mechanical property evolution of carbon textile and refractory concrete (the ultimate strength, the Young's modulus) depending on temperature was also presented. The thermal tests on carbon TRC cylinder specimens were also performed to identify the diffusivity coefficient of this composite. All results obtained were analyzed in order to find the contribution of carbon textile and refractory matrix to fire resistance of carbon TRC. Its ultimate strength has been improved about 2 times compared with non-reinforced matrix at elevated temperature ranging from 25 °C to 400 °C. The efficiency coefficient of carbon textile could be calculated in this study. [ABSTRACT FROM AUTHOR]

• Engineered cementitious composites (ECC) with PVA fibers is ductile but expensive. • The use of PVA-ECC is limited due to cost and absence of coarse aggregates. • PVA-FRC utilizes lesser cost and the use of large size aggregates in concrete. • The compressive stress–strain models are not available for PVA-FRC. • This paper suggests the compressive stress–strain models for PVA-FRC. Polyvinyl alcohol (PVA) fiber is limitedly investigated in the concrete containing large size coarse aggregates. Correspondingly, there is limited literature available related to the modeling of its mechanical properties. This paper suggests a model for the prediction of stress–strain behavior of fiber reinforced concrete (FRC) containing maximum size of coarse aggregate of 19 mm and reinforced with 1–3% PVA fiber volume. The compressive strength of FRC ranged from 72 to 86 MPa due to the incorporation of 10% silica fume and metakaolin as partial cement replacement. The suggested analytical model is found to be proficient of producing complete stress–strain curves for FRC containing PVA fibers and closely represents the realistic stress–strain curves when compared with the experimental data. Besides this, the accuracy of existing analytical models is also discussed. [ABSTRACT FROM AUTHOR]

Highlights • Efficiency methods can be applied as a decision-making tool for maintenance management. • An improvement in the formulation for the probability of damage detection is proposed. • MEA method seems to be more appropriate than SFA method for the inspection planning. Abstract Reinforced concrete is one of the most predominant materials used in constructed structures and infrastructures throughout the world. For this reason, the maintenance management of these structures is a frequent subject of study in material science and civil engineering. Thereby, several studies conclude that corrosion of reinforcement in concrete structures may become an expensive degradation mechanism whether a suitable intervention strategy throughout its service life is not applied. In this context, maintenance management is crucial to slow down the degradation process and to extend the lifespan, which can comprise two stages: inspection planning, and an assessment of repair probabilities according to the inspection results. The paper herein presented focuses on a decision-making model for the optimal inspection planning for concrete structures subject to carbonation-induced corrosion. A structured approach to optimise inspection times considering the uncertainty inherent in the corrosion-induced degradation and a trade-off between inspection costs and the structure serviceability is performed. The main objective of this work is to elaborate an efficiency analysis for a set of optimal inspection strategies that is conducted through two approaches: the Stochastic Frontier Analysis (SFA) and the Multi-direction Enveloping Analysis (MEA). This analysis provides an appraisal that reduces the number of inspection techniques necessary and the time gap between inspections to provide not only an optimal solution but the most efficient as well. Therefore, the outcome of this paper provides an inspection strategy that establishes the optimal solution for both the inspection times and the most suitable inspection technique to be applied considering the efficiency of the solution. [ABSTRACT FROM AUTHOR]

Highlights • NSM FRP system has gained considerable popularity worldwide. • This paper reviews current research on concrete members retrofitted by NSM FRP system. • The review focuses on the bond characteristics between NSM FRP, adhesive and concrete. Abstract The use of fibre reinforced polymer (FRP) in civil construction applications with near-surface mounted (NSM) method has gained considerable popularity worldwide and can produce confident strengthening and repairing systems for existing concrete structures. The response of concrete structural members rehabilitated using FRP with externally-bonded (EB) method under monotonic and fatigue loading has been well reported. On the other hand, the monotonic and fatigue response of NSM FRP-rehabilitated concrete structures is less known. This paper reviews current research on concrete members retrofitted by NSM FRP system and exposed to monotonic and fatigue loading. It provides an outline of FRP composites and the fatigue behaviour of concrete, steel and FRP materials. In addition, the review focuses on the bond characteristics between NSM FRP, adhesive and concrete substrate, and on the flexure behaviour of NSM FRP-strengthened and repaired reinforced concrete (RC) beams. Furthermore, the paper reviews the failure modes, factors affecting NSM FRP systems, guidelines and codes for the use of FRP in concrete structures, damage accumulation and residual strength, stress limits in steel reinforcement, and the limitations of using epoxy and polymer-based cementitious adhesives for the strengthening of concrete members. [ABSTRACT FROM AUTHOR]

• 184 papers are reviewed on the bond-slip properties of reinforced concrete. • The bond-slip mechanics model for concrete and reinforcement under corrosive, temperature, load and stress environments is outlined. • The principles and applications of stick–slip detection techniques for reinforced concrete structures are reviewed. • Research progress of bond-slip mechanical constitutive relationships and numerical simulations of reinforced concrete structures are discussed. • Research prospects for the performance and damage detection of reinforced concrete bonded slip structures are prospected. Based on a review of existing literature, this paper summarizes the research progress pertaining to the bond–slip in reinforced concrete (RC) structures. Specifically, considering the characteristics of bond–slip failures, constitutive relations, and experimental methods, the influences of reinforcement properties, concrete properties, stresses, loading modes, and temperature conditions on the bond–slip behaviors of RC structural members are summarized herein. Further, the main problems and future development trends of research on the bond–slip in RC structures are discussed. According to the bond–slip failure characteristics of RC structures, application scenarios of technologies for monitoring slip damage are determined, and the future research directions are also analyzed. Finally, theoretical analysis models and finite-element numerical analysis methods for RC structures are discussed; the advantages and disadvantages of each method are compared and analyzed as well. Considering the existing findings, research on the bond–slip failures of RC suffers from the following limitations: relatively few studies consider the coupling of stick–slip factors, previously proposed constitutive relationships are not widely applicable, and studies based on theoretical analyses are not comprehensive. Accordingly, this paper summarizes the test methods and research results of domestic and foreign research pertaining to the bonding performance of RC members; moreover, the limitations of existing research are also analyzed to provide a reference for further improvements in the basic theoretical system of RC. [ABSTRACT FROM AUTHOR]

Electrochemical kinetics of steel bar corrosion in concrete is of complex nature, especially when it is subjected to alternate wet and dry environments with changes in conditions of steel-concrete interface and rust properties. In this paper, a quantitative electrochemical mechanism was proposed based on thermodynamics and anodic polarisation kinetics to account for variations of microcell and macrocell current densities in reinforced concrete (RC) slabs subjected to periodic wetting and drying cycles. Effects of environmental conditions on corrosion process were incorporated into anodic Tafel slope through three quantifiable parameters, namely, corrosion potential, linear polarisation resistance and ferrous ion concentration at the steel bar surface. A numerical model was established based on the proposed mechanism to quantify microcell and macrocell current densities. An experimental programme of two RC slabs with multiple steel bars arranged at different layers was conducted to verify the numerical model. It shows that the model could reasonably predict variations of both microcell and macrocell corrosion under different wet and dry environments. When concrete was moistened, current density was substantially increased compared to that in dry concrete. Macrocell contribution from uncorroded steel bars at different layers was more significant than microcell corrosion on the corroded bar itself, especially in wet environments. • Quantitative mechanism to interpret variations of microcell and macrocell corrosion under repeated wetting and drying cycles. • Numerical model to quantify both microcell and macrocell current densities. • Corrosion rate in wet environment was larger than that in dry environment. • Macrocell contribution from uncorroded rebars was significant compared to microcell corrosion. • Corrosion rate increased when rebars were electrically connected by electric wires. [ABSTRACT FROM AUTHOR]

The thermal properties of recycled brick aggregate concrete 1 1 Recycled brick aggregate concrete: RBC (RBC) and recycled brick aggregate concrete structural walls 2 2 Recycled brick aggregate concrete structural walls: RBCW (RBCW) were investigated in this paper. The orthogonal test considering the effect of four factors including the water-cement ratio, sand ratio, water consumption per unit volume, and replacement rate of recycled brick aggregate 3 3 Recycled brick aggregate: RBA (RBA) was conducted to study the thermal conductivity and mechanical properties of RBC. Additionally, two RBCW specimens were prepared and their heat transfer coefficient was tested, and the finite element model of RBCW was established and validated. Moreover, the parametric analysis of the thermal properties of RBCW was carried out. The results show that the volumetric replacement rate of RBA has a significant effect on the thermal conductivity and dry density of RBC. The amount of water used per unit volume has a significant effect on the compressive strength of RBC. The thermal performance of RBCW is far better than that of traditional concrete structure wall, the thermal insulation performance of RBCW is slightly inferior to that of masonry wall and clay brick wall. • The factors influencing the mechanical and thermal properties of recycled brick aggregate concrete were tested. • The thermal conductivity of recycled brick aggregate concrete is much less than that of ordinary concrete. • The thermal performance of structural wall was tested. • A finite element analysis of the thermal performance of the structural walls was carried out. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) members are subject to map cracking owing to the delayed ettringite formation (DEF) by excessive core temperature during the first few days of hydration. Studies on the mechanical properties of concrete with DEF expansion have been conducted to identify the variation in moduli and strength of the material. This paper provides a comprehensive review of the mechanical properties of plain concrete with DEF expansion to examine the degradation characteristics compared to the experimental conditions. The dynamic moduli, static moduli, and compressive strength of the plain concrete decreased up to 60%, 85%, and 65%, respectively, owing to large swelling, where the damage process showed colossal expansion. The reduction amount depends on the aggregate-to-cement ratio, chemical composition of the cement, aggregate type, water-to-cement ratio, and the mix. The static moduli is more sensitive to expansion in the initial expansion stage than other mechanical properties. The structural performance of DEF-affected RC members was also investigated, reviewing the relevant studies to include the structural performance of alkali-silica reaction (ASR) affected structures. The structural performance cannot be appraised using the mechanical properties of plain concrete. It was indicated that the DEF expansion of concrete core can be significantly confined by surrounding reinforcement in RC members. This inhibits the reduction in mechanical properties of concrete and results in maintaining the load-carrying capacity of RC members. Chemical prestress developed in concrete due to the swelling restraint by reinforcement, and anisotropic damage improves the stiffness of the RC members. • Comprehensive review of mechanical properties of DEF-affected plain concrete. • Structural performance of DEF-deteriorated RC members was studied. • Structural performance depends on DEF- induced stress in reinforced concrete. • DEF expansion confinement should be considered to assess structural performance. [ABSTRACT FROM AUTHOR]

New-to-old concrete interfaces are commonly found in reinforced concrete (RC) structures due to precast splices, repairs, and construction joints. The interfaces provide access for chloride ions, oxygen, and water, which intrude on the concrete, reducing its durability with new-to-old concrete interfaces. Although the mechanical bonding properties of new-to-old concrete interfaces have been extensively studied, there is a notable gap in the durability of old-new concrete, particularly concerning chloride ion penetration resistance. This paper examined the interface bonding properties and the chloride ion penetration resistance of old-new concrete through ultrasonic nondestructive testing and rapid chloride migration (RCM) tests. Influences of water-cement ratio, casting interval, and interface treatment were considered. The test results indicated that the interface treatment has minimal effect on ultrasonic velocity while the w/c ratio is the primary factor influencing ultrasonic velocity. The bonding quality of the interface between new and old concrete is more accurately reflected by ultrasonic velocity than by the amplitude of the first wave. The chloride penetration in the old and new concrete specimens is primarily influenced by the water-cement ratio and curing age. As the casting interval increases, the difference in the chloride penetration between the new concrete area and the old concrete area becomes more pronounced. When the strength of new concrete exceeds that of old concrete, the chloride penetration at the interface is primarily influenced by the characteristics of the old concrete. The difference in chloride migration coefficients between the interface and new concrete ranges from 40% to 54%, while the difference between the interface and old concrete is only 4.5–22.2%. However, when the new and old concrete has the same strength, the chloride penetration at the interface tends to be closer to that of new concrete. The impact of interface treatment on the depth of chloride penetration is minimal. An influence coefficient was proposed to assess the effect of the interface on the chloride penetration resistance. With a shorter casting interval, the chloride ion penetration resistance is more affected by different interface treatments. As the casting interval increases, this influence gradually diminishes. • The water-cement ratio is the primary factor influencing ultrasonic velocity. • Chloride penetration in new and old concrete depends on the w/c ratio and curing age. • Whether Interface chloride migration is closer to old or new concrete was discussed. • Proposed an coefficient to evaluate the effect of interface on chloride penetration. [ABSTRACT FROM AUTHOR]

Steel rebar buckling is an important failure mode in reinforced concrete (RC) columns. Fiber-reinforced polymer (FRP) composites provide an effective mean that can restrain or delay longitudinal rebar buckling. To accurately predict the strength and ductility of FRP-strengthened rectangular RC columns, it is necessary to accurately evaluate the interactions between FRP confinement and steel reinforcement buckling behavior at as any loading levels as possible. This paper proposed a composite beam model and a tension-bending beam model to evaluate the lateral support stiffness of FRP-wrapped concrete cover on steel reinforcement in the corner regions and flat sides of rectangular columns. Then, the whole stress-strain curves for reinforcing bar buckling behavior considering the lateral support of FRP jackets can be obtained and validated with the existing test database. For FRP-strengthened rectangular RC columns under monotonic axial compression, the overall load-bearing capacity of RC columns can be determined by summarizing axial loads sustained by FRP-confined corresponding plain concrete (PC) columns and the load contribution of steel rebars considering FRP lateral support. The accuracy of the proposed method is demonstrated by comparing theoretical predictions with test results. This calculation method can accurately predict the strength and ductility of FRP-wrapped rectangular columns within a 20% variation margin, which provides a reliable basis for the design of concrete structures. • A composite beam model and a tension-bending beam model are developed to evaluate the spring stiffness. • A method is established to predict the overall behavior of FRP-confined rectangular RC columns considering bar buckling. • The factors affecting rebar buckling and the performance of FRP-confined rectangular RC columns are analyzed. [ABSTRACT FROM AUTHOR]

Highlights • This study uses both ICCP and SS techniques to strengthen sea-sand RC beams. • An experimental program consisting of 11 beams subjected to accelerated corrosion and ICCP was carried out. • The ICCP-SS retrofitting method is effective in retarding the corrosion and recovering the capacity of RC beams. • This proposed repairing method is beneficial for the durability of RC structures in coastal areas. • The existing design methods are found to be rather conservative for the flexural design of retrofitted beams. Abstract The popularity of reinforced concrete (RC) structures leads to increasing demand for sands, cement, aggregates and other raw materials. In the recent decades, river sand has been used to replace sea-in order to solve the resource shortages in many countries. However, sea-sand concrete might cause corrosion of steel re-bars and result in structure deterioration. Impressed current cathodic protection (ICCP) is an efficient method to prevent corrosion of re-bars, while bonding carbon fibre mesh to the RC structures can help improve the loading capacity of the deteriorated structures. This study proposes a new dual-functional intervention method, the impressed current cathodic protection – structural strengthening (ICCP-SS) method, to retrofit the deteriorated sea-sand RC structures by using the carbon – fabric reinforced cementitious matrix (C-FRCM). The C-FRCM composite, comprised of carbon fabric mesh and inorganic cementitious matrix, is both the anodic material for ICCP and the structural strengthening material. This paper presents an experimental program consisting of 11 simply supported beams, 9 of which were casted by simulated sea-sand and subjected to accelerated corrosion for 130 days. The specimens casted with simulated sea-sand were afterwards externally bonded with C-FRCM composite, exposed to ICCP for another 130 days, and finally tested. In this study, the loading capacity and deflection at midspan of the beams, as well as the open circuit potential (OCP) of re-bars were measured to assess the effectiveness of the intervention method. The proposed method has been shown to be effective in retarding the corrosion of steel re-bars and improving the loading capacity of the corroded specimens. In addition, this paper compares the experimental results with the capacity predictions set out in ACI 440.2R-08 for FRP strengthening system and ACI 549.4R-13 for FRCM strengthening system, which have been found to be rather conservative for the flexural design of retrofitted beams. [ABSTRACT FROM AUTHOR]

Highlights • Seismic behavior of different fiber-reinforced concrete columns was compared. • Nonlinear finite element models were built to present the behavior of columns. • Seismic capacity of columns was evaluated through the nonlinear pushover analysis. • Incremental dynamic analyses were conducted using 20 near-fault ground motions. • Seismic fragility curves were obtained based on the maximum drift of columns. Abstract Different fiber-reinforced concrete (FRC) has been widely used in the recent decades, which can improve the mechanical behavior and dynamic performance of reinforced concrete (RC) columns remarkably. This paper aims to compare the seismic behavior of columns constructed with different FRC material, namely steel fibers reinforced concrete (SFRC), polypropylene fibers reinforced concrete (PFRC) and steel-polypropylene hybrid fiber reinforced concrete (HySPFRC). 3-D nonlinear finite element models have been built to represent the seismic behavior of different FRC columns, which are calibrated with the available experimental results of quasi-static tests. The seismic capacity of bridge columns with different FRC material are assessed based on four flexural damage states through the nonlinear static pushover analysis, such as a) yielding of longitudinal steels; b) core concrete crushing; c) buckling and d) fracture of longitudinal of steels. Incremental dynamic analyses (IDA) are conducted using the selected suite of 20 near-fault as-recorded ground motions to evaluate the inelastic seismic responses of different bridge columns. IDA curves are generated based on the intensity measure, namely peak ground acceleration (PGA) in this paper and seismic demands (i.e. maximum drift, residual drift, displacement ductility and curvature ductility) through nonlinear dynamic time-history analysis. It can be concluded from the IDA results that the SFRC, PFRC and HySPFRC are all effective to enhance the seismic performance, thus reducing the anticipated damage of the bridge columns. Moreover, SFRC and HySPFRC are more effective to improve the seismic capacity of bridge columns for the slight and moderate damage states, while PFRC and HySPFRC are more effective at the extensive and complete damage states. [ABSTRACT FROM AUTHOR]

Highlights • Effect of wall-effect, and fibre orientation and content on tensile strength of SFRC. • MCST is a multi-axial cube splitting test used to get post-crack properties of SFRC. • An approach for the determination of fibre orientation using MCST is proposed. • MCST method was verified to be a good method of determining the orientation of fibre. Abstract The post-cracking behaviour of steel fibre reinforced concrete (SFRC) are significantly influenced by the distribution of steel fibre in the concrete, while steel fibre distribution is further affected by wall-effect and fibre content. A series of three-point bending tests, cube splitting tests, and Brazilian splitting tests were conducted to analyze the influence of wall-effect and fibre content on the post-cracking tensile strength of SFRC. Furthermore, the influence of wall-effect and fibre content on fibre distribution was determined by conducting inductive tests on cubic SFRC specimens. To directly determine the relationship between fibre content and orientation, and the post-cracking mechanical properties of SFRC, this paper proposes a multi-axial cube splitting test (MCST test). Furthermore, this paper also proposes a method which utilizes the MCST test to measure fibre orientation based on the relationship between post-cracking peak load and toughness, and steel fibre orientation. Therefore, MCST method can be adapted for using with any type of fibre reinforced concrete, while the inductive test can only be used for concrete that is reinforced with metallic fibre. The MCST method is verified by comparing the similarity of the fibre orientations that were obtained using the inductive tests and MCST tests. [ABSTRACT FROM AUTHOR]

Highlights • Fatigue loading tests on corroded RC beams are performed. • Load-deflection, fatigue crack of concrete, and failure modes are discussed. • A developed flexural stiffness deterioration model under fatigue is proposed. • Theoretical predictions agree well with the experimental observations. Abstract Corrosion of reinforcing bars accelerates the fatigue damage accumulation and significantly reduces the fatigue life of aging reinforced concrete (RC) bridges. This paper experimentally investigates the effects of corrosion on the fatigue behavior of reinforced concrete beams. An accelerated corrosion test is conducted in the laboratory conditions to obtain various corroded beam specimens. The initial crack width and the crack distribution are discussed. Based on the fatigue loading test, the load-deflection, fatigue crack propagation of concrete, fatigue life and the failure modes of RC beams after different fatigue cycles are investigated. Following that, a developed flexural stiffness calculation model for the corroded beams after fatigue is proposed. This model includes the effects of fatigue, corrosion-induced cracking and fatigue modulus degradation of concrete and other influential factors. The proposed method is validated with the experimental observations from various corroded RC beams of the current paper and available in open literature. [ABSTRACT FROM AUTHOR]

Textile-reinforced concrete (TRC) as a novel high performance composite material can be used as not only strengthening material but component bearing load alone. This paper aims to investigate the influences of the number of textile layers, prestress levels of textile, and volume contents of chopped steel fibers on the flexural behavior of basalt textile-reinforced concrete (BTRC) plate through four-point bending tests on 24 experimental cases. Flexural strength and toughness were observed to improve with the increase of the number of textile layers. Prestress on the textiles contributed to improving the first-crack flexural stress and pre-cracking flexural stiffness of the BTRC, but the flexural strength and toughness were found to decrease with the increase of the prestress level. The addition of chopped steel fibers in the matrix was revealed to positively affect the first-crack flexural stress, flexural strength, and post-cracking flexural stiffness and toughness. Moreover, the crack pattern, which features a high crack number and reduced crack spacing, was achieved with the increase of the number of textile layers and the volume content of chopped steel fibers. However, the crack number reduced and the average crack spacing increased with the increasing prestress level of the textiles. The prestress and chopped steel fibers significantly improved the flexural behaviors of BTRC, which contributes to the application of BTRC flexural components. The paper presents the formulas for calculating the flexural strength of non-prestressed BTRC without chopped steel fibers, and the calculation formulas can be used to guide the design of such BTRC flexural components. [ABSTRACT FROM AUTHOR]

This paper discusses masonry buildings constructed in Pernambuco and their relationship to several failures that have occurred, some of which included the death of inhabitants. Topics such as the main features of this building technique and its peculiarities that played an important role in its structural behaviour are discussed in detail. Additionally, the paper presents a large characterization of materials and components used constituting the most important current research on this topic in Brazil. Its content analyses in depth, experimentally, the behaviour of single bricks, prisms and wallets that allow the identification and quantification of the influence of several mortar rendering layers on the load capacity of elements tested. A critical analysis concerning the factors that contribute to the performance observed is presented from which it was possible to realize a significant variability of results. A summary with the main results of all experimental tests is presented. [ABSTRACT FROM AUTHOR]

Research on quantification of the size and porosity of the interface between the reinforcing steel and concrete is limited in the current published literature. This paper presents a reliable and accurate method for quantification of steel-concrete interface using the technique of Backscattered Electron (BSE) imaging. Details of sample preparation procedure designed to minimize the damage to the steel-concrete interface due to grinding and polishing are presented. A new thresholding method to separate porous band at the interface from steel and cement pastes is proposed. It is found that there is a relatively wide porous band with large pores and voids near the steel-concrete interface. It is also found that the size of porous band around the steel bar is not uniform, and that the water to cement ratio can significantly affect the size and distribution of porous band at the interface. Quantification of steel-concrete interface as proposed in this paper is of importance in crack prediction of corrosion-affected reinforced concrete structures. [ABSTRACT FROM AUTHOR]

• A rigid pavement structure called partially continuous reinforced concrete pavement (PCRCP) is proposed. • The early-age shrinkage cracking behavior of PCRCP is analyzed through experiment and numerical analysis. • The early-age behavior of PCRCP is improved than CRCP and ARCP. • There is a coupling relationship between temperature and humidity. • Active crack induction of PCRCP improves early-age cracking behavior significantly. As a form of durable pavement structure commonly used in the world, continuously reinforced concrete pavement (CRCP) has prominent problems caused by irregular crack distribution in the early stage. According to the characteristics of the discontinuous distribution of CRCP longitudinal steel bar stress and active crack control method, a rigid pavement structure called partially continuous reinforced concrete pavement (PCRCP) was proposed to simultaneously optimize the crack distribution pattern and reduce the longitudinal steel ratio in this paper. Since early-age shrinkage cracking behavior is a key factor affecting its durability. This paper purposes to assess the early-age shrinkage cracking behavior of PCRCP by comparing different reinforcement methods in laboratory experiments. Research results indicated that the early-age shrinkage behavior of PCRCP is basically the same as that of CRCP. The early-age shrinkage behavior of PCRCP is significantly improved than the advanced reinforced concrete pavement (ARCP). Restricted by the boundary and longitudinal steel bars system, the concrete beam produces a top-down nonlinear temperature and humidity gradient, resulting in various degrees of shrinkage deformation at different depths inside. The active crack control method can control the early-age concrete slab to form uniform crack pattern with straight lines or fewer bending cracks, which improves early-age cracking behavior significantly. This paper is to further deepen and develop the theory of CRCP early-age cracking behavior and provide basic theory support for the subsequent experimental section studies of PCRCP. [ABSTRACT FROM AUTHOR]

• In the paper, twenty-one specimens were designed and manufactured for pull-out tests to investigate the bond behavior of concrete reinforced with HSHT steel bar, considering the anchorage length, cover thickness, stirrup ratio, anchorage form, the diameter of HSHT steel bars, and the number of spiral grooves. • The bond strength of specimens reinforced with HSHT steel bars with six spiral grooves is higher than that of three spiral grooves, and it gradually decreases with an increase in the anchorage length. • The slip corresponding to bond strength increases linearly with an increase in the anchorage length and nonlinearly with an increase in the combined effect K. • The bond-slip model proposed in this paper can accurately calculate the bond-slip curves for the ascending and descending branches with different failure modes. To investigate the bond behavior between the ordinary concrete and high-strength and high-toughness (HSHT) steel bars with special spiral grooves on the surface, twenty-one specimens were tested by pull-out tests. The effects of test parameters, including anchorage length, the diameter of HSHT steel bars, cover thickness, stirrup ratio, anchorage form, and the number of spiral grooves, on failure modes, bond-slip curves, bond strength, the relative slip, and critical anchorage length were analyzed. The results show that increasing cover thickness and end-anchorage can significantly improve bond strength. The bond strength of specimens reinforced with HSHT steel bars with six spiral grooves is higher than that of three spiral grooves, and it gradually decreases with increasing the anchorage length. In addition, the decrease of the stirrup spacing can improve bond strength. The addition of stirrups can slow down the descending branches and make the failure modes of specimens change from splitting failure to splitting-pullout failure, indicating that the energy absorption capacity and the ductility of specimens have been improved. The models for bond strength and the slip corresponding to bond strength were established based on the existing models and experimental data. At the same time, coefficients B and D were established based on Wu's model. The evaluation shows that the proposed model can accurately calculate the bond-slip curves for ascending branches and descending branches, and it can also predict bond-slip curves corresponding to different failure modes. [ABSTRACT FROM AUTHOR]

• Australian standards AMBT and CPT correlate well with the long-term performance of field concrete. • CPT AS 1141.60.2 limit of 0.03% improves the correlation of AMBT, CPT and field data. • AMBT requires a similar or more conservative dosage of SCM than the CPT. • AS 1141.60.1 requires similar or more conservative dosage of SCM than ASTM C1567. • AS 1141.60.1 and 60.2 can be extended for the assessment of ASR mitigation using SCMs. This paper examines the reliability of the Australian Standards accelerated mortar bar test (AMBT) and concrete prism test (CPT), AS 1141.60.1 and 60.2, respectively, and the potential for extending these standard test methods to the determination of the type and dosage of supplementary cementitious materials (SCMs) required to mitigate deleterious alkali-silica reaction (ASR) in a similar manner to the corresponding ASTM C1567 and CSA A23.2-28A. Both AMBT and CPT have their strengths and limitations, however, their overwhelming value is in the availability of laboratory test results and their correlation with long-term performance (up to 20 years) of large concrete blocks and structural elements. Since Australia has no existing field exposure site, this paper uses reported data from CANMET's and Ontario Hydro's outdoor exposure sites in Ottawa and Kingston, respectively, in Canada and the 18-year exposure site data from the BRE site in the UK to demonstrate the efficacy of the AMBT and CPT approaches to evaluation of ASR reactivity and ASR mitigation using SCM blended cements. Good correlations are observed for moderately–reactive and highly reactive aggregates used with low-alkali cement and cement with alkali contents up to 0.9 % Na 2 O eq. The assessment of reported research demonstrates that both AMBT and CPT have the capacity to predict the long–term performance of structural concrete. In addition, AMBT and 2-year CPT test results for eight Australian reactive aggregates are reported showing the influence of SCMs (fly ash and slag) on mitigation of expansion. Whilst both AMBT and CPT demonstrated their potential for assessing SCMs in mitigation of ASR, AMBT was found to be more conservative than CPT and higher SCM dosages were required to achieve a non-reactive classification. The accelerated test data reported coupled with the correlation of AMBT and CPT to the prediction of long term performance of concretes strongly supports the extension of the Australian test methods AS 1141.60.1 and 60.2 for the assessment of ASR mitigation using SCMs. [ABSTRACT FROM AUTHOR]

Aiming to utilize coal gangue sand in structural concrete, this paper investigated the mechanical and environmental properties of the coal gangue sand concrete-filled steel tube (GSCFST) and reinforced gangue sand concrete (RGSC) stub columns. Axial compressive tests were conducted to study the effect of gangue sand replacement rate (r GS) on the mechanical performance and environmental impact of the stub columns. The results show that the failure patterns of GSCFST and RGSC are similar regardless of r GS. The reduction in the rigidity and ultimate bearing capacity of GSCFST is less than that of RGSC. When the replacement rate is 100%, the rigidity and ultimate bearing capacity of RGSC are reduced by 29.2% and 11.4% respectively, whilst those of GSCFST are 8.2% and 5.1% respectively. The ductility coefficient of RGSC shows no significant change under different gangue sand replacement rate. In contrast, the ductility of GSCFST is in an increasing trend with the increase of r GS , resulting from the stronger restraining effect of the steel tube on the core concrete of which compressive strength decreases with the increase in the replacement rate. Based on the tested results, a constitutive relationship of gangue sand concrete is used for numerical modelling. A design method of the ultimate bearing capacity for RGSC and GSCFSF is proposed by considering r GS. The predicted values differ from the tested and simulated values in the range of ± 10% and ± 6% for RGSC and GSCFST, respectively. The whole life cycle assessment (LCA) showed that r GS is positively correlated with willingness-to-pay (WTP) and negatively correlated with the axial strength of the two types of stub columns. The material strength and section diameter show the most positive effects on the mechanical-environmental (M-E) performance efficiency factor (k M-E). The k M-E of GSCFST is greater than that of RGSC under the same r GS. [Display omitted] • Gangue fine aggregate concrete is used in concrete-filled steel tube and reinforced concrete stubs. • The increase in r G S increases the ductility of the coal GSCFST. • Constitutive model of the gangue sand concrete is proposed. • Environmental impact of the GSCFST is less than that of the RGSC. [ABSTRACT FROM AUTHOR]

The application of fiber-reinforced polymer (FRP) composites has become a commonly-used technique for the strengthening/retrofitting of existing reinforced concrete (RC) columns. To date, extensive experimental studies have been conducted in this field, resulting in many stress-strain models of FRP-confined concrete for analysis or design use. Few models, however, are concerned with the concrete in FRP-confined RC columns, especially for the columns under partial FRP confinement. This paper first investigates the mechanical properties of the concrete under FRP strip-transverse steel reinforcement composite confinement via the assessment of existing analysis-oriented models (AOMs). Then, the peak stress of actively confined concrete and the dilation model in AOM are calibrated based on existing research, leading to a new AOM for FRP strip-steel confined concrete. Finally, a test database is assembled to evaluate the reliability of the new model in terms of the predictions of ultimate conditions and stress-strain curves. By comparing the experimental results and theoretical predictions, the proposed model exhibits higher accuracy for the FRP strip-steel confined concrete compared with the other existing models. • Hoop strain relationship between FRP strips and transverse steel reinforcement was investigated. • Parameters affecting the axial compressive behavior of partially FRP-confined reinforced concrete columns were discussed. • A new axial stress-strain model was developed for concrete in partially FRP-confined reinforced concrete columns. [ABSTRACT FROM AUTHOR]

Despite significant amount of research on Recycled Tyre Steel Fibres (RTSF – extracted from end-of-life tyres) as reinforcement in concrete slab applications, the potential of RTSF is not fully understood mainly due to their variability in length (and aspect ratio). This paper investigates the effect of fibre length on the mechanical properties of Steel Fibre Reinforced Concrete (SFRC) using Recycled Tyre Cord Filaments (RTCF - extracted from unvulcanised rubber tyre belt off-cuts) which have very similar mechanical properties to RTSF. The flexural behaviour of SFRC prisms is evaluated using fixed lengths of RTCF (6, 9, 12, 15, 18, 21 and 24 mm) at a dosage of 30 kg/m3. Based on the flexural results, inverse Finite Element analysis (FEA) is used to determine the uniaxial tensile behaviour of the SFRC mixes. Mixes with fibres longer than 15 mm control macro-cracks well whilst residual flexural tensile strength f R increases almost linearly with fibre length, up to fibre lengths of 21 mm. Fibres with a length of 21 mm are the optimum for the mixes examined in this study in terms of post-cracking flexural behaviour and energy dissipation. The relative contribution of various fibre lengths (aspect ratios) in an RTSF mix is predicted well by using an equivalent energy approach. This work will help determine the efficiency of RTSF and speed up their adoption by industry. • Comprehensive study on effects of varying fibre lengths (6 to 24 mm) in SFRC using RTCF. • RTCF longer than 15 mm significantly improve macro-crack control, with residual flexural tensile strength increasing up to fibre lengths of 21 mm. • Research identifies 21 mm as the optimal RTCF fibre length in SFRC mixes for enhanced post-cracking flexural behaviour and energy dissipation. • Simplified trilinear stress-strain model is proposed to predict the flexural behaviour of SFRC using RTCF. • Research provides both theoretical and practical insights for the construction industry, potentially accelerating the adoption of RTSF in concrete applications. [ABSTRACT FROM AUTHOR]

Internationally leading standards currently do not permit to consider the contribution of reinforcement made of fibre reinforced polymers (FRP) to a concrete member's compressive load-bearing capacity due to a lack of reliable knowledge regarding FRP's material properties in compression. Thus, there is a very high demand for carefully specifying an optimised test setup for FRP bar reinforcement that accounts for both theoretical considerations and established standards from other industry branches. This paper presents an extensive literature review on mechanical approaches to describe FRP material properties in compression, existing test setups from various industry branches as well as experimental studies that have been conducted in order to research the compressive material properties of FRP reinforcement. Based on experimental results from literature a database was compiled. Following a reasonable choice of a test setup based on the literature study, an experimental campaign was setup, in order to investigate the influence of different fibre materials (carbon, glass, basalt), polymer matrices and bar diameters on the compressive material properties of FRP reinforcement bars. In addition to the experimental determination of the material properties, the joint evaluation of the total sample size of n = 95 own experimental test results and the results from the database generated from literature allows for statistical investigations. Thus, the determination of material scatter and the estimation of the distribution type by means of a statistical analysis applying the Kolmogorov-Smirnov test provides the basis for further research towards the reliability of concrete structures reinforced with FRP bars in compression. • Experimental and statistical study of FRP reinforcement in compression. • Large compiled database based on literature/own tests for statistical analyses. • Recommendation of an optimum test slenderness of l test / d = 6.0 for FRP bars. • Comparison of compressive material behaviour of different FRP types. • Determination of the distribution type of FRP material properties in compression. [ABSTRACT FROM AUTHOR]

This paper presents a study on the compressive behavior of a novel type of highly deformable hybrid FRP tubular columns. The columns consist of an FRP tube filled with large-size recycled concrete lumps (RCLs) as aggregates and flowable grout as the binding material, and are thus termed FRP-RCL-Grout (F-R-G) columns. The use of large-size RCLs (e.g., up to 63 mm RCLs for 200 mm circular columns) leads to a relatively high recycling ratio and facilitates the manufacturing process. The flowable grout can be easily poured/pumped into the FRP tube, leading to ease of construction, while the FRP tube acts as an effective lateral confining device. The experimental part of the study involved compression tests on F-R-G columns and similar columns for comparison, with the main test variables being the FRP tube thickness, the size of the RCLs, the compressive strength of the concrete for producing RCLs and the WP ratio of the grout. The test results showed that F-R-G columns possess excellent structural behavior including ample ductility, and clarified the effects of the key parameters. In addition, based on the test results, a simple yet accurate model is proposed to predict the strength of F-R-G columns. • A novel FRP tubular column form incorporating recycled concrete lumps and flowable grout is investigated. • The novel column is highly deformable with ample ductility. • The novel column form provides an effective method of using recycled concrete lumps for structural applications. • The use of flowable grout highly eases the construction of the column. [ABSTRACT FROM AUTHOR]

Modeling an accurate bond-slip model between concrete and reinforcement is a significant challenge in fiber reinforced polymer (FRP) strengthened reinforced concrete (RC). This paper presents a novel method for developing and validating an accurate bond-slip model. By employing a numerical procedure based on the finite difference method and a metaheuristic optimization algorithm, this method eliminates the need for a specific bond-slip law shape. This unique feature enables the prediction of bond-slip laws for various strengthening methods, including EBR and NSM, as demonstrated in this study. Furthermore, the methodology allows for the prediction of bond-slip laws associated with premature failure. The numerical and experimental results obtained confirm the accuracy of the methodology. • Prediction of bond-slip laws of strengthening methods with general applicability. • Inverse analysis approach to determine the bond-slip law from load-slip curve. • Applicable to tests that experience premature failure. • Validation against synthetic data generated by Finite Element Model. • Exemplification on single-shear bond tests using EBR strengthening method. [ABSTRACT FROM AUTHOR]

Corrosion of steel in reinforced concrete (RC) structures has become a major problem worldwide, inevitably leading to very high maintenance and repair costs. Directly admixing corrosion inhibitors in cementitious materials when concrete casting or migrating them to RC structures at the later stage can delay or mitigate steel corrosion to a certain extent, which is a low-cost and high-efficient traditional strategy towards corrosion protection. However, it is also accompanied by several negative impacts on the hydration process of cementitious materials and the mechanical properties of RC structures. Therefore, based on the encapsulation of corrosion inhibitors in micro/nano-containers, the application of smart corrosion inhibitors provides a promising approach to delay the corrosion process of steel and extend the service life of RC structures. These smart corrosion inhibitors can be triggered to release as needed, offering responsive protection against corrosion. In this paper, a variety of environmental stimulations and active response mechanisms of smart corrosion inhibitors in cementitious materials and coated steels are reviewed. Furthermore, it also highlights the current challenges and unexplored possibilities in the design and synthesis of smart corrosion inhibitors, while future perspectives are provided for their engineering application in RC structures. • Recent trends in smart corrosion inihbitors in cemetitious materials are summarized. • Three main storage containers and their preparation methods for smart corrosion inihbitors are critically reviewed. • Different response mechanisms and their inhibtion mechanisms are systemically introduced. • Research gaps and recommendations for future investigations are proposed. [ABSTRACT FROM AUTHOR]

This paper studies the size effect on flexural fatigue in concrete. In particular, the main objective is to evaluate how the addition and content of steel fibers affect this size effect. For this purpose, four types of concrete have been produced: plain and reinforced concrete with fiber contents of 0.3%, 0.6% and 1%. Two prismatic specimen sizes were considered: 75×75×300 mm, named S, and 150×150×600 mm, named L. All specimens were subjected to 3-point bending fatigue at the same relative stress levels up to failure. The results reveal very interesting conclusions. The fibers mitigate the size effect on fatigue life, going from a difference of three orders of magnitude in PC, to practically zero in SFRC. Furthermore, it is observed that fibers do not necessarily improve fatigue life; in fact, the trend changes depending on specimen size. Finally, it is shown that the secondary crack opening rate dCMOD/dn has a good correlation with fatigue life, explaining the dispersion of N in general and the size effect in particular. • Small specimens have higher flexural strength, both in plain and steel-fiber reinforced concrete. • The addition of fibers significantly reduces the size effect in fatigue life. • Fiber-reinforced concrete does not necessarily have a longer fatigue life than plain concrete. • The secondary crack opening rate is a suitable parameter to explain the dispersion of fatigue life. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of the flexural performance of reinforced concrete (RC) beams externally bonded with hybrid fiber-reinforced polymer (FRP) laminates made of carbon and polyethylene terephthalate (PET) fibers. Ten beam specimens were subjected to four-point bending tests, with a focus on assessing the effects of the stacking sequence and the elastic modulus of hybrid carbon-PET FRP laminates on the flexural performance of the strengthened beams. The failure modes, load-bearing capacities, displacement ductility of the specimens and strain distributions in the FRP laminates were examined and discussed. The experimental results showed that the load-carrying capacities of the FRP-strengthened specimens were significantly increased by 10.18∼27.98%, while the displacement ductility decreased by 51.36∼77.85%. The peak load and ductility of the beam specimens strengthened with PC (i.e., PET-C FRP) and CPC (i.e., C-PET-C FRP) stacking sequences were higher than those of their counterparts strengthened with two or three layers of hybrid FRP laminates. The accuracy and reliability of the calculation methods specified in ACI 440.2R-17, CNR DT 200 R1/2014 and GB 50608–2020 for estimating the flexural strengths of the strengthened RC beams were evaluated through a comparison of theoretical predictions with experimental results. The average predicted-to-tested ratios for the flexural strengths of the strengthened beams using ACI 440.2R-17, CNR-DT 200 R1/2014 (based on PE debonding failure), CNR-DT 200 R1/2014 (based on IC debonding failure), and GB 50608–2020 are 0.994, 0.704, 0.946, and 0.930, respectively. • Flexural behavior of RC beams strengthened with hybrid carbon-PET FRP laminates was studied. • Effects of the stacking sequence and the elastic modulus of hybrid FRP laminates were examined and compared. • The hybrid FRPs achieved a significant increase in load-carrying capacity accompanying with a displacement ductility reduction. • The design methods specified in current guidelines reasonably predicted the flexural strengths of the tested specimens. [ABSTRACT FROM AUTHOR]

Polyurea (PU) coated reinforced concrete (RC) has been widely studied in structural strengthening under contact explosion, however, experimental investigations on dynamic response and failure mechanism of the coating during explosion remain scarce. In this paper, four contact explosion experiments are conducted on uncoated and rear side coated RC slabs. Dynamic strains and dynamic deformation of the coating are obtained by large-range strain gauges and a proposed measurement method based on a high-speed camera. Dynamic response characteristics of the coating are discussed and the blast resistance mechanism is further analyzed. Additionally, the effect of coating rebounding on the RC substrate and the effect of explosive placement on the coating are discussed. The results show that PU coating dissipates the blast energy through elastic deformation, plastic deformation, rupture and debonding. Glass transition at high strain rate may cause the rupture of the coating, and coating thickening significantly reduces the tensile strain rate under the same contact explosion conditions. With the development of breach and spalling of the RC substrate, PU coating on the rear side can be divided into four zones, and the blast resistance mechanism of the coating varies in different zones. Additionally, the elastic potential energy release of the coating may produce a secondary impact on the RC substrate. Coatings are more severely damaged when contact explosives are placed in locations that avoid rebars and should be considered as the most unfavorable load for the retrofitting of RC structures. • Transient deformation during contact explosion and dynamic strains were obtained. • Blast resistance mechanisms of the polyurea coating show zoning differences. • Polyurea coating dissipates the blast energy through elastic and plastic deformation, rupture and debonding. • Coating thickening significantly reduces the tensile strain rate. • The relative position of contact explosives and rebars has a significant effect on the damage of the coating. [ABSTRACT FROM AUTHOR]

• CFRP yarns in textile shear reinforcement transfer relevant loads by dowel action. • Dowel action is characterized by a three-branched dowel behaviour. • Pre-strain of the yarns has a significant influence on the dowel behaviour. • Dowel behaviour dowel forces depend on the inclination of the crack plane. Composite structures with textile CFRP (carbon fibre reinforced polymer) reinforcement are characterised by high compressive and tensile strength and have great potential for use in thin-walled structures such as shell structures or girder webs. However, the stress transfer mechanisms activated along cracks of carbon reinforced concrete (CRC) membranes have not been sufficiently investigated yet. Especially the potential of CFRP yarns to transfer shear across sliding crack surfaces has not been thoroughly understood. For steel reinforced concrete elements, dowel action has been studied for several decades and numerous constitutive laws for the shear contribution of dowel action have been developed. In contrast, the sensitivity to transverse pressure of CFRP reinforcement is expected to have a significant influence on the activation of dowel action in cracked CRC. Neither the damage and fracture of impregnated textiles due to transverse compression nor the shear-induced delamination of reinforcement in the vicinity of cracks have been investigated in detail. Therefore, suitable constitutive laws to describe the dowel effect of CFRP reinforcement are not available. This paper presents dowel tests with textile CFRP shear reinforcement and highlights the phenomenology of dowel behaviour in carbon reinforced concrete as well as the main factors influencing the dowel behaviour. [ABSTRACT FROM AUTHOR]

Concrete-to-concrete interfaces are common in new reinforced concrete structures with different casting stages and or with precast members with cast-in-place parts, as well as in rehabilitation of existing reinforced concrete structures. Their longitudinal shear strength has been studied in the last five decades. Today, it is established that this is ensured by a combination of adhesion, aggregate interlock, friction, and dowel action. Being all these resistant mechanisms, but mainly friction, highly dependent on the surface roughness, the quantification of the latter is of paramount importance. This paper investigates the correlation between the friction coefficient and the surface roughness of concrete-to-concrete interfaces. An experimental campaign of direct shear tests, performed on specimens with different surface treatments (smooth, rough and corrugated), was carried out. The surface's texture was analysed using a 2D Laser Scan and different roughness parameters (extreme, mean and segments) were calculated, then correlated with the corresponding shear strength and, lastly, based on the latter, correlated with the friction coefficient. Results showed that the extreme roughness parameters, as well as the peaks' height related parameters, have poor or no correlation with the magnitude of the friction coefficient. The average roughness of the profile, its mean square, the mean valley depth, and the mean peak-to-valley height turned out to have the strongest positive correlation with the friction coefficient. Based on these, a novel combined roughness parameter with an optimized correlation with the friction coefficient was derived and proposed. • Roughness and friction in concrete-to-concrete interfaces are investigated. • Concrete's surface roughness is analyzed using a 2D laser scan. • A novel roughness parameter for more precise estimation of friction is proposed. [ABSTRACT FROM AUTHOR]

• Combination of several industrial by-products produced highly porous alkaline cements, suitable for thermal applications. • The mechanical properties of these sustainable pastes is also adequate for applications such as façade panels. • The incorporation of damping materials, also originated from industrial disposal, increased porosity. • The most performing paste was classified as 'T1′, regarding their thermal performance. • Significant margin for development, which can increase effectiveness. Alkali activated cements (AAC) are becoming an increasingly promising alternative to traditional Portland cement. There are still some significant barriers which have yet to be addressed, by all the agents involved in the construction industry. However, it appears that some AAC applications can be introduced in current applications at a faster rate than, for instance, structural concrete. One of these applications are materials with thermal performance, based on the capacity of some types of AAC to expand during initial reactions. The present paper aims to assess the viability of producing porous AAC for application in thermally effective façade panels. A wide range of industrial by-products were activated with sodium hydroxide and sodium silicate. Two additional by-products were incorporated to increase the thermal damping of the pastes, with the intention of taking advantage of the large pore volume. Flexural and compressive strength and density was measured, and selected pastes were then submitted to microstructural characterisation (SEM/EDX), environmental behaviour (heavy metal leaching), porosity (SEM) and thermal performance (thermal coefficient). The results showed maximum compressive strengths of 2.5 MPa, while the majority of the pastes tested showed conductivity values below the threshold of 0.2 W/m.°C, which is the requirement for obtaining a classification of 'thermal'. Therefore, the production of panels for thermal insulation based on alkali activated industrial by-products is competitive with traditional materials based on current commercial solutions, and, given the non-structural nature of this application, can be very close to reach industrial production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Experimental and theoretical research on the fire resistance of reinforced concrete beams is summarized. • The important parameters are selected by parameter correlation analysis. • The fire resistance prediction equation is proposed by Machine Learning and regression analysis. Reinforced concrete (RC) beams are widely applied in building structures, and fire resistance performance becomes a focus of fire research with the high frequency of building fires. This paper aims to summarize the fire resistance performance of 216 specimens in 80 references and propose a fire resistance prediction equation. Firstly, the factors of fire resistance are considered in these specimens such as load ratio, concrete cover thickness and longitudinal reinforcement ratio. The influence rules of these factors are summarized. And the theoretical analysis, finite element simulation and fire resistance prediction equation of RC beams are also summarized. It is found that the parameters such as load ratio and concrete cover thickness have a great impact on fire resistance, while the parameters such as stirrup spacing have a minor impact on fire resistance. Secondly, the Pearson correlation analysis of 10 parameters is conducted in 216 specimens and 6 parameters with a correlation degree greater than 0.1 are identified as important parameters. The database is established by 4 Machine Learning (ML) algorithms. It is found that the database established by the Random Forest (RF) algorithm has high performance. Finally, the fire resistance prediction equation of RC beam is obtained by the database and nonlinear regression analysis. The prediction equation is compared with existing equations, and it is found that the proposed equation with R 2 of 0.935 has high precision in predicting fire resistance. The proposed equation can be adopted to guide the fire resistance design of RC beams. [ABSTRACT FROM AUTHOR]

• 2D model of embedded PZT-structure interaction inclusive of tensile/compressive stress. • Analytical interpretation of stress and damage identification using the proposed model. • Proof-of-concept experiment on an RC beam structure subjected to four-point bending test. • Comparative monitoring of stress/damage development via embedded and bonded sensors. • Flexural performance evaluation using electromechanical admittance and derived indicators. This paper proposed a real-time identification approach of flexure-critical stress and damage in reinforced concrete (RC) beam structure using embedded Piezoelectric lead Zirconate Titanate (PZT) transducers. Effect of structural stress and damage were theoretically incorporated into mechanical impedance to derive a novel two-dimensional (2D) embedded PZT-structure interaction model. Analytical analysis was conducted to calculably interpret the identification of tensile/compressive stress and damage based on the electromechanical admittance (inverse of impedance, EMA) signatures. The proposed approach was validated by experiment on an RC beam subjected to four-point bending test, which was continuously monitored by cement-embedded PZT (CEP) transducers. Analytical and experimental results showed that resonance peak and frequency shift of the EMA spectrums of CEPs exhibited converse behaviors when responding to tension and compression stresses, while typical frequency decrease and peak increase accurately indicated the occurrence of initial cracking. Comparative studies also revealed that CEPs were superior to visual inspection and bonded PZT transducer in identification of concrete cracking, and that located in compressive zone was more efficacious in prediction of the forthcoming yield and final failure of the RC beam. Results of this study cogently demonstrated the potentialities of CEP transducer as a means of on-line monitoring of stress/damage in flexure-critical RC infrastructures. [ABSTRACT FROM AUTHOR]

• New internal stiffening strategy with insertion of flexible bars was developed. • The insert-bar structure on mechanical performance of CC was investigated. • Vertical bar combination provided higher load-bearing capacity and toughness for CC during penetration. Concrete canvas (CC) is a promising composite based on a combination of three-dimensional fabric and cement-based powder, with the comprehensive advantages of easy storage and transport, convenient construction, rapid strength development, and low dust pollution. In civil and military engineering, interest and exploration work within the field of CC have been ongoing for many years. While external measures exist to enhance the mechanical properties of CC, substantial internal measures are still lacking. In this paper, an internal stiffening strategy was proposed by coupling warp-knitted spacer structure with a series of insert-bar structures, attempting to improve the mechanical performance of CC. The reinforcing effect of flexible bar stiffeners were investigated through quasi-static bursting test and impact test. Damage morphology analysis was then performed to reveal the progressive failure mechanism. The obtained results demonstrated that flexible bar stiffeners with low modulus were highly beneficial reinforcements for CC due to their favorable synergy and great stress dissipation capacity. The load-bearing capacity and toughness of CC were increased with the insertion height and groups of bar combination. The vertical combination could further enhance the penetration resistance by altering stress transfer. [ABSTRACT FROM AUTHOR]