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In this paper, for the first time, we investigate the inherent ionic conductivity of seawater-based cementitious composites containing marine sand aggregates, when air cured over 28 days with the objective of uncovering new functionalities. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and density functional theory (DFT) were employed to elucidate the ionic conduction mechanisms in this material system and characterize its stress self-sensing and electrochemical charge retention capabilities. The results revealed that the marine aggregates are not ionic conductive materials; however, they facilitate improved electrochemical response through enhanced formation of highly ion-exchanging calcium-silicate-hydrate (C-S-H) phases, coupled with integrated porous channels that enable sustained ion mobility despite drying. This synergistic ion transport yielded a bulk ionic resistivity around 25 kΩ⊡cm at room temperature, which lies in typical ranges seen in solid-state electrolytes for battery systems. Controlled compressive loading indicates appreciable self-sensing capacity at low-stress levels, suggesting applicability to detect the onset of mechanical damage. Negligible charge leakage upon 28 days of curing further demonstrates the electrical energy storage potential of the sea-based cement. By harnessing locally available seawater and marine sand resources to develop ionic conductive cementitious composites, this work provides the framework to optimize durable multifunctionality for sensing and electrical energy storage in reinforced concrete infrastructure. This in return improves the sustainability and energy efficiency of the built environment. • A new approach to induce self-sensing and energy storage in cementitious composites using marine sand. • Marine sand enhances ionic conductivity, electroactivity, charge storage capacity, and self-sensing composites. • Coupling between self-monitoring and energy storage enables multifunctional structural materials. • Marine sand valorizes this abundant waste for advanced cement composites. [ABSTRACT FROM AUTHOR]

Copper slag (CS) exhibits pozzolanic activity in alkaline cementitious systems, making it a suitable supplementary cementing material for cemented tailings backfill (CTB) with reduced carbon emissions. However, its utilization is constrained by the unacceptable cost of alkaline materials, e.g., NaOH and CaO. In this paper, the CTB bound by CS activated using red mud (RM) has been investigated through mechanical and microstructural analysis. The results show that RM content and curing time significantly affect UCS development throughout the CTB life cycle. The CTB containing 1.5 % RM and 3 % RM exhibit lower strength values at 28 d compared to the control group without RM, measuring 3.07 MPa and 2.65 MPa, respectively. Despite this reduction, the cost calculation confirms that using RM as a partial substitute for NaOH reduces the CTB cost by approximately 50 %. Microstructural analysis reveals that the RM particles in CTB were bonded together by gels, and the amounts of gels on the surface of the aggregated particles and other crystals increased with the increasing RM contents. Further, its strong alkalinity facilitates the decomposition of Al monomers from RM and partially replaces Si in the C-S-H gel to form C-A-S-H gel. This study corroborates the feasibility of preparing CTB bound by CS activated using RM, providing new insights into the application of RM and CS. • The cemented tailings backfill bound by copper slag activated using red mud is investigated. • The relationship between sample strength and red mud contents was evaluated. • The hydration products and microstructure of the samples were characterized. • Providing new insights into the application of red mud and copper slag in mines. [ABSTRACT FROM AUTHOR]

A pullout analytical model is introduced to simulate the Double Edge Wedge Splitting (DEWS) test to obtain the tensile post-peak response of steel fiber reinforced concretes. One of the main barriers to the widespread utilization of FRC as a structural system is the anisotropy of the material. This augments the uncertainty of the material behavior (fibers random distribution and orientation in the bulk concrete), increases the dispersion of the test results, and requires the performance of characterization tests to check the residual tensile stresses at specific crack opening intervals. The characterization tests proposed in the literature (e.g., Barcelona, Montevideo, Wedge Splitting Test, EN 14651) are time-consuming and relatively complex, demanding careful preparation and hydraulic presses with data acquisition systems. This paper aims to contribute to the discussion of alternatives for FRC characterization procedures by the introduction of a pullout analytical model to predict FRC constitutive law based on DEWS tests. The pullout analytical model is calibrated with pullout tests considering straight and hooked-end steel fibers with different strengths, embedment lengths, inclinations, and diameters. A 3D digital model reproducing the experimental DEWS samples is developed, considering the fibers' randomness distribution, orientation, and wall effect. The analyses are compared with four different experimental tests. The results define a linear post-peak tensile constitutive law, considering the mean residual stress values at different COD values. The model was able to reproduce the specimens' production procedures and the fibers' distribution and orientation correctly. The results demonstrated a good agreement with the experimental data. [Display omitted] • Pullout analytical model for straight and hooked-end steel fibers. • 3D parametric digital model considering fibers random distribution and wall effect. • Prediction of DEWS tests considering the manufacturing process. • Determination of FRC linear tensile post-peak constitutive model. [ABSTRACT FROM AUTHOR]

In the variable water level area, hydraulic concrete structures are susceptible to variable temperature and alternating dry-wet cycles, especially for thin-walled structures. To elucidate alterations in the microstructure and strength of hydraulic concrete subjected to variable temperature dry-wet cycles, this paper firstly conducted a durability test on hydraulic concrete. Subsequently, CT scan images of the specimens are acquired during the variable temperature dry-wet cycle. Secondly, in view of the shortcomings of existing threshold methods for CT image pore segmentation, a new image segmentation method (RASLPSO-TV-Top-hat) is proposed by using Tensor voting and Top-hat technology, combined with a Reverse Adaptive Particle Swarm Optimization algorithm with Self-Learning ability. The evolution process of pore structure (microcracks) of hydraulic concrete under the variable temperature dry-wet cycles is captured. Thirdly, an in-depth analysis is conducted on the compressive strength and acoustic emission characteristics. The analysis shows that with the number of cycles increases, there is a discernible interconnection among the pore structures. This interconnection leads to a noteworthy reduction in the compressive strength of the concrete. Additionally, the cumulative number of Acoustic Emission ringing events exhibits an initial rise followed by a subsequent decline. The study successfully identifies the patterns governing the deterioration of strength and microstructure evolution in hydraulic concrete. The mechanism underlying the decline in performance of hydraulic concrete under variable temperature dry-wet cycles is elucidated. It provides a reliable and valuable basis for the safety assessment of hydraulic concrete structures in the variable water level area. • We conduct a durability test of concrete under variable temperature dry-wet cycles. • We propose a new image segmentation method. • Pore structure, compressive strength and acoustic emission character are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, the fatigue failure of engineered cementitious composites (ECC) and concrete laminated structure was investigated by using a model based on the peridynamics (PD) method. The model enhances efficiency by incorporating "residual life" and "cyclic blocks," utilizing the fully discrete method for ECC interfaces and the energy-based PD model for bimaterial interfaces. Its effectiveness, accuracy, and versatility have been validated through various numerical examples. Furthermore, the study examines crack propagation in ECC pavement overlays under four-point bending and investigates the impact of ECC layer thickness and fiber content on the fatigue characteristics of laminated structures. • A fully discrete fatigue model of ECC is constructed based on PD. • The energy-based PD model for the interfaces in ECC-concrete laminated structures was built. • The established model simulated the fatigue failure of ECC-concrete laminated structures. [ABSTRACT FROM AUTHOR]

The incorporation of Graphene Oxide (GO) nanomaterial into concrete has gained significant attention due to its potential to enhance mechanical and durability properties. The addition of GO to concrete creates considerable changes in the morphology of the concrete matrix, creating a densified microstructure. Critical parameters significantly affect these microstructural enhancements and, consequently, the final performance in GO-added concrete. These parameters include GO material properties, superplasticiser (PS) type, and dispersion techniques. Therefore, this study investigates the influence of GO on the mechanical performance of concrete, focusing on these critical factors. Unlike existing studies concentrating on a single parameter's effect, this research comprehensively compares how these parameters impact GO-added concrete. Two commercially available GO types (GO-A and GO-B) and two PS types (PS-A and PS-B) are utilised. At the same time, three commonly used mixing techniques, such as mechanical, high-speed, and ultrasonic mixing techniques, are considered for GO dispersion. GO-A is added to concrete in percentages ranging from 0.02 % to 0.14 % by weight of cement (bwoc), while GO-B ranges from 0.04 % to 0.20 % bwoc. Based on compressive strength test results, the optimum GO dosages are 0.08 % for GO-A and 0.12 % for GO-B. The highest strength results are achieved for GO-B added concrete with PS-A addition and following the ultrasonic dispersion method, highlighting these parameters as optimal for maximising GO-added concrete performance. The optimum concrete mix exhibits 33 %, 24 %, 25 %, and 30 % increments for compressive strength, indirect tensile strength, flexural strength, and elastic modulus properties at 28 days. This paper provides a deep theoretical explanation of the effects of GO material properties, dispersion techniques, and PS type on GO-added concrete performance. The findings provide valuable insights into selecting suitable parameters for optimising the mechanical properties of GO-added concrete, contributing to the advancement and effectiveness of construction materials. • Addition of Graphene Oxide (GO) is effectively improved the mechanical properties of concrete. • Choosing right GO, superplasticiser, & dispersion method is vital for optimal mechanical properties in GO-concrete. • Performance of GO-added concrete is greatly influenced by its dispersion level. • GO-added concrete dispersibility accomplished via ultrasonic dispersion polycarboxylate-ether-based superplasticisers. [ABSTRACT FROM AUTHOR]

Reinforced concrete is a commonly used material for constructing basements in low-rise buildings or residential houses in Canada, and as the use of cross-laminated timber (CLT) advances, the door to think of an alternative basement material to offset greenhouse gas emissions associated with reinforced concrete is open. However, the evaluation of CLT durability in below-grade environments, specifically concerning moisture and mould development, remains an unexplored field in research. Hence, this paper aims to analyze CLT's moisture response and mould growth risk in below-grade environments using field and laboratory experiments. A laboratory experiment was carried out to test a waterproofing membrane solution selected to compose the wall assembly in the field experiment. A large-scale experimental CLT basement was built at a cohesive soil site in Edmonton, Canada. The field experiment involved monitoring the relative humidity, temperature, and soil volumetric water content of the CLT panels, which measure 3 m by 6 m in plan and 2 m deep. Data was collected for an extended period from June 2022 to July 2023. The VVT model, developed by Hukka and Viitanen (1999) and updated by Viitanen et al., 2011 to estimate the mould growth level, was used to predict the risk of mould growth. The laboratory experiment showed that the waterproofing membrane is suitable for protection against moisture in a still-water setup. Field experiment results suggested that the primary moisture source was below the basement floor when the floor was finished inadequately. The moisture content of CLT walls was significantly increased by floor flooding and decreased by heating the basement interior. The acceptable mould index of three was surpassed during periods of abundant water below the basement floor due to flood events, showing that the CLT panels were at risk of mould growth development. • CLT use inbasements is in research stage. This paper contains insights for developing future research on this subject. • CLT in basement construction requires robust envelope with waterproofing membranes that perform well below grade. • Elevated moisture levels could pose structural and biological risks to the CLT basement and its occupants. • CLT basement walls take time to dry, and during this period, the walls may be exposed to risky levels of mould growth. [ABSTRACT FROM AUTHOR]

Porous asphalt concrete (PAC) generates significant less noise during the loading of vehicles compared to conventional pavements. However, it might be clogged during lifespan, which results in a reduced noise reduction function. To evaluate the noise reduction function of PAC during service, the change in sound absorption coefficients of PAC under different clogging conditions was investigated by the means of laboratory tests. The standing wave tube method was used in this paper, with considering the changes in void ratios, clogging materials, and cleaning methods. The attenuation parameters of PAC sound absorption coefficients under continuous clogging and cyclic clogging-cleaning conditions were investigated. Based on this, the prediction model of the sound absorption coefficient under two clogging states was proposed. The results showed that aeolian sand had the most negative impact on the noise reduction function, with a 56 % decrease in the sound absorption coefficient after clogging. The sound absorption coefficient of the PAC remained between 0.3 and 0.4 after completely clogged. The sound absorption coefficient of the PAC can be partially even fully restored after cyclic clogging cleaning. High-pressure water washing is the most effective approach, recovering up to 80 % of the original value before clogging. Therefore, regular cleaning and maintenance of the PAC during its survice life is necessary. Predictive modeling of the sound absorption coefficient was highly correlated with measured values, allowing accurate prediction of changes after clogging and cleaning. • PAC sound absorption coefficient changes during continuous and cyclic clogging cleaning. • Clogging times has the most significant on the PAC sound absorption coefficient. • A prediction model of PAC sound absorption coefficient based on mix parameters and plugging parameters was developed. [ABSTRACT FROM AUTHOR]

In recent years, with the improvement of construction safety requirements in deep well mining, the backfill mining method has been widely used. However, the strength of paste filling acquired in quarry often surpasses the design strength determined in laboratory settings. In view of the problems that indoor conditions cannot restore deep mining environment, and the mechanism of coupling effect under multiple fields is unclear. This paper has carried out relevant research work through theoretical analysis and indoor experiments. First of all, after completing the preparatory experiments, this paper analyzed the strength difference of backfill under different curing stress and drainage conditions, and studies the influence of different curing conditions on the strength. Secondly, MPS-6 and 5TE sensors were used to monitor the electrical conductivity, pore water pressure, porosity and other parameters of backfill during the stress-drainage curing process, and changes of parameters during curing process were analyzed. Finally, the relationship among relevant parameters and strength properties of paste backfill was analyzed, as to clarify the influence mechanism of stress-drainage curing conditions on the strength formation for paste backfill. Research shows that both stress-undrained and stress-drained conditions can effectively increase the strength of backfill. Under stress-drainage conditions, the internal porosity of backfill will decrease, and the pore water pressure of backfill will first increase slightly and then continue to decrease. Under this condition, the electrical conductivity of backfill will first increase and then continue to decrease. The entire research has important positive significance for reducing mining costs, optimizing mining processes, and developing mining technology. • The instrument is a self-developed equipment, which can monitor changes of backfill in real time. • The test blocks were cured under different stress and drainage conditions. • Binarize the scanned image of samples, and then use ImageJ to analyze the processed image. • Combined with two sensors, the relationship between microscopic parameters and strength can be explored. [ABSTRACT FROM AUTHOR]

Spalling is the main problem concerning safety in concrete structures under rapid heating. Despite being studied for nearly a century, its prediction remains a challenge. In addition, the main recommendations for its prevention are merely the addition of a fixed amount of polypropylene fibres, without accounting for mix design. This paper presents an experimental study focusing on the thermo-hygral mechanism contribution to spalling. The use of mercury intrusion porosimetry and X-ray microtomography for the determination of pore connectivity is considered a key parameter. The results of the experiment are used for the development and calibration of an analytical equation capable of predicting spalling in concrete samples. The equation is then validated using over 100 examples extracted from literature, achieving an accuracy of 91.2%. Based on the validation, the proposed equation is a step forward in the prediction of concrete spalling based on the mix design parameters. • Development of analytical equation to predict concrete spalling. • Validation with more than 100 examples from literature reached 91% accuracy. • Experimental campaign emphasizing thermo-hygral contribution to spalling. • Definition and use of pore connectivity to predict spalling behaviour. [ABSTRACT FROM AUTHOR]

In this study, a standard pH test procedure, based on the high alkalinity of electric arc furnace oxidizing slag, was developed for rapid content evaluation of potentially hazardous slag in the fine aggregate and recommended standards are further proposed. The advantages of the developed procedure include easy equipment acquisition, simple test method, short time, and high accuracy. This study found that sample size, water source, and filtrate process were the factors affecting the pH test accuracy. In the test, the pH increased with a decrease in the aggregate size when the proportion of electric arc furnace oxidizing slag in aggregate was fixed, especially when the aggregate size was less than 0.225 mm. Upon comparison of the results of autoclaved mortar bar expansion tests, a good logarithmic relationship was observed between pH and electric arc furnace oxidizing slag content. It is suggested that pH 9.0 could be used as the standard to determine excessive electric arc furnace oxidizing slag in fine aggregate. • Proposed a standardized process for rapidly assessing pH in fine aggregates, addressing hazards from electric arc furnace oxidizing slag (EAFOS). • Optimized pH testing factors: D100 particles, RO water, 10 % solid content, filtration through 5A + 5B paper before measurement. • Sample pH values consistently showed a logarithmic relationship with EAFOS content proportion. • pH values over 9.0 indicate excessive EAFOS content in fine aggregates, making them unsuitable for further application. [ABSTRACT FROM AUTHOR]

The traditional method of crumb rubber modified asphalt (CRMA) preparation can improve the stability but is not conducive to cleaner production. From the perspective of process optimization, ultrasound is introduced into the crumb rubber modified asphalt preparation process, and the high temperature, high pressure and high energy accompanied by the cavitation effect are used to generate free radical triggering chemical effects at the two-phase interface between crumb rubber and asphalt. In this paper, the influence of ultrasound on the compatibility and stability of crumb rubber modified asphalt system was evaluated by combining experiment and molecular dynamics simulation. An experimental platform for ultrasound-assisted preparation of crumb rubber modified asphalt was established. The effects of ultrasonic on the physical properties of asphalt and crumb rubber modified asphalt were studied through Brookfield viscosity test, thin film oven aging test and Fourier infrared spectroscopy. The base, aged, and ultrasonically treated asphalt samples were simulated using molecular dynamics, and various parameters such as Cohesive Energy Density (CED), Mean Square Displacement (MSD), and Free Volume Fraction (FFV) of asphalt and its components were calculated and analyzed. The results showed that under the ultrasonic-assisted preparation, the agglomeration phenomenon of rubber particles is weakened, the particle size is reduced, the penetration degree is reduced, and the compatibility between rubber and asphalt is improved. Under the action of ultrasonic, the MSD and diffusion coefficient of crumb rubber modified asphalt are much higher than other kinds of asphalt, the dipole moment is increased, and the molecular motion range is wider. This indicates that the diffusion ability of crumb rubber modified asphalt is significantly enhanced under the external force of ultrasonic simulation. The molecular bonds of crumb rubber modified asphalt changes greatly, the energy decreases obviously, and the system stability increases. In conclusion, ultrasonic action on crumb rubber modified asphalt preparation is a green and effective way to improve system stability and compatibility. • The crumb rubber modified asphalt was prepared by ultrasonic method, which improved the compatibility and stability. • Perl script is used to simulate the sinusoidal force of ultrasonic field, and the molecular diffusion ability is enhanced. • Ultrasonic technology has a positive effect on preventing crumb rubber particle agglomeration during short-term aging. • An efficient production method of modified asphalt prepared by ultrasonic was proposed in the process innovation. [ABSTRACT FROM AUTHOR]

Accurately predicting the rutting development law of asphalt pavement is of great significance for preventing and controlling pavement diseases. The aggregate skeleton of the asphalt mixture is the main load-bearing part and plays an important role in its anti-rutting performance. However, quantitative and mesoscopic evaluation indicators and standards for aggregate skeletons have not been established. This study aims to reveal the relationship between the mesostructured characteristics of asphalt mixtures and rutting damage. This paper uses two-dimensional image technology to analyze the dynamic change process of internal skeleton information of two graded asphalt mixtures under cyclic wheel load. According to the fractal theory, the fractal dimension and multifractal spectrum of the full-depth aggregate were calculated. The results indicate that the linear regression model between the mesoscopic skeleton information of asphalt mixture and the average rutting depth during the rutting test can be used to quantify the rutting performance. There is an obvious correlation between the fractal dimension of the section aggregate and the loading times, and there is a certain linear relationship between the multifractal spectrum indexes and the loading times. It indicates that the fractal theory index of aggregate can reflect the change of the macro performance of loading times. • The fractal and multifractal analysis of the section aggregate of the rutting test was carried out. • T The relationship between meso skeleton information and rutting depth is established. • The multifractal index of aggregate can reflect the change of macro performance after loading times. [ABSTRACT FROM AUTHOR]

To study the differences in material performance between HRB400E steel and conventional strength steel, this paper performed monotonic and cyclic loading tests on HRB400E and Q355B steels under a series of loading protocols. Additionally, the self-designed fixtures were used to achieve large strain rate loading. The ductility, monotonic behavior and hysteretic characteristics of HRB400E and Q355B steels were assessed, along with the energy dissipation capacity evaluated through the energy dissipation coefficients. The cyclic skeleton curves of both steels were fitted using the Ramberg-Osgood model, with further investigation into the influence of kinematic hardening parameters on hysteretic curves. The combined hardening parameters of the Voce-Chaboche model were calibrated based on the experimental results, and the hysteretic curves were simulated under different loading protocols via ANSYS. The analysis results reveal that the energy dissipation coefficients of HRB400E steel are larger than that of Q355B steel, yet smaller than those of Q460D, LYP100, LY100, LY160, and LY225 steels. Both HRB400E and Q355B steels demonstrate significantly improved material strength under cyclic loading. Excellent agreement between simulated and experimental curves is achieved when using four pairs of kinematic hardening parameters. Additionally, the hysteretic performance of HRB400E and Q355B steels under different cyclic loading protocols can be precisely simulated by employing calibrated combined hardening parameters. Through this paper, the cyclic behavior and constitutive relations of HRB400E steel are comprehensively understood, which provides a reliable theoretical basis for engineering design and structural analysis. Furthermore, this research provides a scientific basis for material applications of HRB400E steel. • HRB400E steel and conventional strength steel are compared in material performance. • Monotonic and cyclic loading tests are conducted. • Ductility, monotonic property, and hysteretic performance of HRB400E and Q355B steels are assessed. • Self-designed fixtures are utilized to achieve large strain rate loading. • The hysteretic property of the HRB400E steel can be accurately simulated. [ABSTRACT FROM AUTHOR]

This paper introduced a novel Artificial Neural Networks (ANN)-based bond–slip model for the Near-surface mounted (NSM) FRP system using cement-based adhesives, as an alternative to epoxy adhesives due to their high-temperature resistance and moisture-durability problems, employing experimental data. Therefore, closed-form formulas were presented for key components of the bond-slip law, including maximum bond stress, corresponding slip, fracture energy, and post-peak branch, while taking important factors into account. Compared to available bond-slip laws, this innovative model demonstrates promising potential in predicting the bond behaviour, thereby enabling more efficient and reliable designs for the NSM FRP strengthening applications using cement-based adhesives. • A novel ANN-based bond–slip model for NSM FRP systems with cement-based adhesives. • Closed-formed formulas for key bond-slip components. • An efficient solution to address inadequacies in current bond-slip laws. • Reliable predictions for the NSM FRP bond behaviour with cement-based adhesives. [ABSTRACT FROM AUTHOR]

The bond performance of a carbon fiber-reinforced polymer (CFRP) tendon in ultra-high performance concrete (UHPC) deteriorates significantly under impact loads. However, the post-impact bond performance, which is crucial for the design and safety assessment of CFRP-UHPC structures after experiencing impact loads, remains unclear. This paper delved into the post-impact bond performance of a CFRP tendon in UHPC through 21 groups of pullout tests, and the influences of the embedded length of the tendon in UHPC, impact height, and initial pretension on the residual bond properties after impact were analyzed. The results show that after exposure to the impact with a higher drop height, the CFRP tendon tended to slide out of UHPC with slighter damages on the tendon surface, and correspondingly, the residual bond strength between the CFRP tendon and UHPC after impact was higher. With the increase in the embedded length of the CFRP tendon in UHPC, the pullout capacity increased and the constraining effect of the external steel barrel to the inside CFRP tendon and UHPC improved, which resulted in a higher residual bond strength. A higher initial pretension induced more pronounced shear damage and abrasion on the CFRP ribs, therefore, weakening the remaining resistance to pullout tension after impact. Finally, prediction formulas for the residual bond strength of a CFRP tendon with different embedded lengths and pretension in UHPC, following impacts at various strain rates, were developed. • The post-impact bond performance of a CFRP tendon in UHPC was investigated. • The residual bond strength between the CFRP tendon and UHPC was enhanced with the increase in the embedded length and the height of the impact, but it diminished with a reduction in the initial pretension. • Prediction formulas for the residual bond strength of a CFRP tendon in UHPC after impact were developed. [ABSTRACT FROM AUTHOR]

Shrinkage cracks pose significant challenges to the long-term durability of concrete structures, and it can be effectively address by incorporating various types of fibres. Synthetic textile fibres show a significant 10–50 % shrinkage reduction, while natural cellulosic fibres achieve a comparable 5–30 % reduction. This improvement is attributed to the bridging and anchorage effects between fibres and the cement matrix, enhancing overall concrete performance. However, the factors such as fibre length, diameter, volume fraction and characteristics have significant effect on shrinkage performance. This paper aims to present a comprehensive analysis of these critical mechanisms and factors that impact the shrinkage behaviour in both synthetic textile and natural cellulosic fibre-reinforced concrete. The inclusion of fibres creates a three-dimensional fibre matrix within the concrete that provide an internal effect to restrain the absorb water and it reduce the shrinkage of the concrete. Moreover, the presence of fibres introduces a secondary reinforcing mechanism to release tension during the drying process, thereby preventing crack propagation. The highly porous nature of the cellulose structure enhances the porosity of the concrete, creating cross-linked pathways for water evaporation. However, pre wetted cellulose fibre mitigates drying shrinkage by providing internal curing of the concrete. Furthermore, various physical, chemical, and combined surface modification methods have been used to improve the properties of natural fibres. • Shrinkage, cracks in synthetic and natural cellulosic fibre concrete were discussed. • Synthetic fibres show 10–50 % shrinkage reduction while cellulose give 5–30 %. • Bridging and anchorage effect between fibres and matrix cause shrinkage reduction. • Fibre volume fraction is a key factor for shrinkage and crack behaviour in concrete. • Fibre dimensions, strength, modulus, water interaction impact shrinkage and cracks. [ABSTRACT FROM AUTHOR]

Under-slab voids are critical to traffic safety, The acoustic vibration method can be used to accurately determine whether the road surface is de-voided or not. This paper utilizes ABAQUS to construct models of concrete pavement panels with various parametric study. The fundamental vibration frequencies of these models are computed, and their characteristics are summarized. Additionally, a model of impacting cement concrete pavement with a falling ball is established to investigate the vibration properties at different points. it can be concluded that the most significant factors affecting the vibration fundamental frequency are the foundation reaction coefficient and the void area. Delamination at the corners of the panels experiences higher maximum vibration accelerations under falling ball impact when support conditions are poorer. Longer delaminated edges correspond to greater vibration accelerations. The frequencies at various points within the delaminated area are identical, while the amplitudes mirror the same acceleration. Indicating that the position of deflation has a small effect on the vibration frequency and a relatively large effect on the vibration acceleration. This study can provide an effective and non-destructive basis for future intelligent traffic pavement inspections. • We found the most important factors affecting vibration fundamental frequency. • We established the ranking parameters based on sensitivity to develop priority. • We established a model of impacting cement concrete pavement with a falling ball. • We established the link between vibrational sound and road de-vacuuming. [ABSTRACT FROM AUTHOR]

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]

Rock formations naturally contain intricate internal fractures due to various environmental factors. Such fractures result in significant weakening of the mechanical properties of the rock mass. As factures have different geometric features and fill material characteristics, it is difficult to replicate their complex behavior in the laboratory. This poses a serious limitation on the experimental investigation of the mechanical properties of fractured rocks. Sand powder 3D printing (3DP) can overcome the limitations of casting methods in preparing samples with complex fractures and thus is widely applied in soft rock mechanics experiments. This paper utilizes Computer Tomography (CT) scanning to obtain the probability distribution patterns of fractures in fractured rock samples. Additionally, it combines sand powder 3DP technology to generate soft rock-like samples with internal networks of filled fractures. Uniaxial compression experiments employing digital image correlation (DIC) and acoustic emission (AE) techniques are used to investigate the mechanical properties, deformation characteristics, and fracture evolution patterns of samples with different fracture densities. By increasing the fracture density, the peak strength of the soft rock-like samples exponentially decreases, and the deformation characteristics linearly decrease. Crack propagation paths mostly follow the prefabricated fracture trajectories and loading direction. An RA-AF analysis suggests that the failure mode of the soft rock-like samples transitions from diagonal shear failure to block-shaped shear failure with increasing fracture density. These research findings represent a novel sand powder 3DP approach for studying the complex mechanics of complex fractured rocks. • A novel method to generate rock analogs with filled internal fractures is proposed. • Internal fracture density has great effect on the mechanical properties of samples. • Effect of fracture density on failure patterns are investigated with DIC and AE. [ABSTRACT FROM AUTHOR]

Cementitious materials in durability can be improved by membrane protection and osmotic hydrophobicity with Polystyrene acrylate (PSA) and polysiloxane (PSE), respectively. However, due to the significant differences in molecular structure, the fabrication of PSA- PSE composite coatings with multiple protective effects have been a thorny issue. In order to enhance the interfacial binding effect between PSA and PSE, and to solve the problem of poor stability caused by poor compatibility, this paper innovatively utilizes the topological network structure growth regulation mechanism of secondary surface functional nanoparticles to prepare PSA-PSE copolymer emulsions with highly crosslinked star and dendrimer structures, respectively, with branch grafting ratios of over 94% and semi-crystallinity of over 5.39%. As a consequence of surface treatment, numerous dense calcium-silicate crystals with low Ca/Si ratios are deposited inside the cementitious materials, decreasing the volume proportion of harmful micropores and connected capillary pores to below 10.4%. The modified copolymer coatings decrease the capillary water absorption and static permeability of concrete by over 55%, and lead to nearly 80% reduction in carbonation depth of cement hydrates, and have an adhesion strength of up to 3.3 MPa. Particularly, the proportion of ordered hydrogen bond within the composite coating reached 45.1%, demonstrating excellent reversible elastic deformation recovery performance. [Display omitted] • Multicomponent PSA-polysiloxane composite emulsions with gradient topology were designed and synthesized. • The copolymer coatings decrease the proportion of harmful connective pores to below 10.4%. • The modified copolymer coatings exhibit superior water repellency, ionic resistance and carbonation resistance. • The modified copolymer coatings have superior tensile performances and adhesion strengths of 3.3 MPa. • The modified copolymer coatings exhibit superior reversible elastic deformation recovery performances. [ABSTRACT FROM AUTHOR]

This paper presents an innovative application of a one-part geopolymer for microwave absorption. The influences of frequency, ageing time and mixing formulations on the mechanical, dielectric, and microwave-absorbing performance of the one-part binary geopolymer using fly ash and ladle furnace slag were investigated. The mixing formulations included alkali activators-to-aluminosilicate sources, sodium metasilicate-to-sodium hydroxide, and water-to-binder ratios. The results demonstrated that the dielectric constant decreased while the dielectric loss and loss tangent increased and remained constant with increasing frequency. The geopolymers have the highest dielectric values at an early age and diminish with ageing time. These resulted in the geopolymers having excellent microwave absorption (50 – 80%) at high-frequency levels and later ages. A higher water content resulted in higher porosity, reducing mechanical strength but enhancing microwave absorption. An optimal water content must be attained to achieve dual mechanical strength and microwave absorption performance. • One-part binary geopolymer based on FA and LFS was synthesized. • Geopolymers show excellent microwave absorbing performance at higher frequency. • Microwave absorption of the geopolymers improved at later age. • Porosity creates path to attenuate the microwave energy. [ABSTRACT FROM AUTHOR]

3D printing technology revolutionizes construction by creating custom building components with increased efficiency and reduced waste. This paper reviews advancements in the 3D printing of cementitious materials, focusing on integrating mineral additives (MAs) like metakaolin, micro-silica, slag, and fly ash to address environmental and economic challenges linked with high-Portland cement content in 3D concrete printing (3DCP). MAs enhance the pumpability, printability, and buildability of 3DCP while reducing its environmental impact. The review emphasizes optimizing cement mixtures, including alkali-activated materials, to enhance sustainability and performance. It discusses the mixture design's importance, balancing mechanical properties and environmental impacts, and examines MAs' influence on rheological properties, mechanical performance, and 3DCP durability, including layer bond strength. The paper also discusses global 3D printing technology adoption in construction and challenges in additive manufacturing implementation. By analyzing printing parameters, mixture proportions, and materials' effects on long-term performance, this review highlights 3D printing's potential for economically viable and eco-friendly structural elements. It aims to guide future advancements in 3D printable cementitious materials, meeting modern construction demands while addressing traditional concrete production's environmental challenges. • Using recycled mineral additives reduces 3D-concrete printing's environmental impact. • Optimizing printing parameters strengthens layer bonds in 3D-concrete printing. • Recycled materials promote sustainability and innovation in 3D-concrete printing. [ABSTRACT FROM AUTHOR]

This paper aims to examine the effect of coal gangue aggregate (CGA), fly ash (FA), and ground-granulated blast slag (GGBS) on the rheological, mechanical and microstructure properties of concrete. The rheological properties, compressive strength, splitting tensile strength, flexural strength, and uniaxial tensile behaviour of coal gangue concrete (CGC) were determined, and the microstructure of the concrete mixtures were investigated by use of XRD and SEM analyses. The results revealed the action mechanism of CGA and mineral admixtures on the microstructure and macroscopic properties of CGC. FA first increased and then decreased the yield stress and plastic viscosity, while GGBS considerably increased the yield stress and plastic viscosity. Furthermore, a constitutive model was established for CGC containing FA and GGBS under compression. The proposed stress–strain model for CGC is accurate and can be used for nonlinear analysis of structures made of this type of concrete. Moreover, the addition of FA and GGBS consumes calcium hydroxide, but increases products such as hydrated calcium silicate aluminate. These findings elucidate the understanding and optimisation of CGA use in concrete production, while contributing to lowering carbon emissions. • Concrete strength degrades with increasing coal gangue aggregate substitution rate. • Fly ash degrades coal gangue concrete mechanical properties, and slag enhances them. • Fly ash and slag combination provides a complementary superposition effect. • A precise coal gangue concrete uniaxial compression analysis model is proposed. [ABSTRACT FROM AUTHOR]

Grouting is one of the most commonly used methods to control water inrush disasters in fractured rock mass. At present, most of the research on the diffusion process of fracture grouting is carried out on the hypothesize that the groundwater was completely displaced by the slurry, which is lack of sufficient theoretical basis. Therefore, a one-dimensional visual fracture grouting experimental system was developed and a new characterization method of slurry concentration based on the image gray level was proposed in this paper in order to characterize the variation law of slurry-water mixing region during the grouting process. Results show that there exists slurry-water mixing region at the frontal surface of the diffusion slurry in the grouting process in fractured rock mass. The slurry-water mixing region can be characterized by the gray level of the images captured by cameras. The relationship of water to cement ratio of slurry (w/c) and image gray level of slurry (G) conforms to linear function, which can be expressed by G = 19.17 w/c when w/c is between 0.8 and 10. In addition, slurry concentration decreased linearly along the diffusion flow path in the slurry-water mixing region. The size of slurry-water mixing region is positively related to grouting flow rate, the mass ratio of water to cement (w/c) and fracture aperture when the grouting flow rate is between 0.6 L/min to 2.4 L/min, w/c is between 0.8 and 1.6 and fracture aperture is between 1 mm to 5 mm. Furthermore, the ratio of slurry-water mixing region size to hypothetical diffusion radius (RSR) was proposed to characterize development degree of slurry-water mixing region. The stable value of RSR was between 0.04 and 0.24 under the experimental conditions in this paper. The index of RSR can be used to provide theoretical basis for the simplification of the interface between slurry and water. The distribution rules of the slurry-water mixing region can be applied to predict the diffusion range more accurately and perfect the grouting theory. • Image gray level method was introduced to characterize the variation of slurry-water mixing region during grouting process. • Experimental system for simulation of one-dimensional visual fracture grouting was presented. • The ratio of slurry-water mixing region size to hypothetical diffusion radius was developed. [ABSTRACT FROM AUTHOR]

Automatic crack defect detection plays an important role in early road maintenance. However, the crack defect detection accuracy is seriously affected by some challenging factors, such as complex background, class imbalance issue, poor texture, etc. In this paper, a deep crack defect segmentation network with dual-path encoding and hierarchical fusion schemes, named DEHF-Net, is presented to accurately and effectively segment the crack defects generated in crack images. In order to capture rich feature information of crack defects, a dual-path encoder unit is built to extract the spatial information and context information from crack images simultaneously. On the basis, to strengthen the features extracted from two encoding paths, an attention fusion (AF) block and feature enhancement (FE) block are proposed for effective feature learning to achieve information complementarity of dual-branch encoding paths. Meanwhile, to alleviate the problem of semantic gaps arising from large information differences between the encoding path and decoding path, a residual refinement unit (RRU) is also introduced to enable effective refinement of edges and details. Finally, to make the segmentation results more significant on multi-scale cracks, a weighted hierarchical fusion (WHF) block is introduced in the decoding stage to fuse the shallow texture information with the deep semantic information more effectively. Experimental results show the proposed model has obtained an excellent performance comparison with advanced methods. • A dual-path encoding network with hierarchical fusion is proposed for pixelwise crack detection. • A residual refinement unit is proposed to enable effective refinement of edges and details. • A weighted hierarchical fusion block is introduced for effective feature fusion. [ABSTRACT FROM AUTHOR]

Environmental characteristics such as low pressure, high-frequency freeze–thaw cycles, and salt erosion in a plateau region have a significant impact on the mechanical properties and durability of concrete. To reveal the damage mechanism of high-performance ecological geopolymer concrete (HPEGPC) incorporating tunnel spoils, slag, and fly ash (FA) in extreme environments, this study used HPEGPC with 12 % alkali-activated binders (AABS) and a binding material to machine-made sand ratio of 0.36 and ordinary Portland cement concrete (OPCC) with 12.4 % cement and a water-cement ratio of 0.5 to simulate the deterioration process of mechanical properties and durability under the action of low-pressure–salt–erosion–freeze–thaw cycles. The mass, compressive strength, relative dynamic elastic modulus loss rate, microstructure, and pore evolution patterns of HPEGPC and OPCC were analysed using experimental and microscopic tests. The results showed that the HPEGPC was significantly more resistant to freezing and salt erosion than the OPCC in both standard and hypobaric environments. The interfaces of HPEGPC before and after the low-pressure–salt-erosion–freeze–thaw cycles underwent a developmental process from a dense structure with microcracks to microcracks expanding into fracture surfaces and the dispersion of hydration products. The cementitious materials of HPEGPC have a high percentage of non-hazardous and less hazardous pores, and their dense structure results in a high resistance to freezing and salt erosion. In addition, by establishing a damage decay model and damage accumulation model for the compressive strength and relative dynamic elastic modulus, this paper provides theoretical guidance for the application of HPEGPC under low pressure, salt erosion, and freeze–thaw cycle environments of the plateau. ● HPEGPC has significantly better resistance to sulfate attack and freezing at both standard and low pressures than OPCC. ● The damage decay models and damage accumulation models were developed to predict the loss rate of compressive strength and dynamic elastic modulus of HPEGPC. ● The microstructure and pore evolution of HPEGPC and OPCC were analysed using SEM and NMR. ● The internal structural degradation mechanism of HPEGPC before and after different pressure–salt–erosion–freeze–thaw cycles was revealed. [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]

In this paper, the method of dehydration condensation reaction was used to establish a superhydrophobic cement mortar surface with the contact angle of 159.3° and the slide angle of 6.1° by using organosilane and inorganic nanomaterials. The nanoparticles built roughness and the silane provided low surface energy, which in combination achieved self-cleaning, waterproof and durability improvement. The superhydrophobic coating with good penetration depth is able to show superhydrophobicity after simply brushing and curing at room temperature for 24 hours and maintain hydrophobicity after surface abrasion. A variety of liquid droplets can roll freely from the surface of superhydrophobic cement mortar and carry contaminants rolling down to show self-cleaning performance. In terms of durability, the coating appears good adhesion to the surface of cement mortar, which retained its hydrophobic property after tape-peeling tests and outdoor simulation tests. In addition, compared with ordinary cement mortar, the superhydrophobic cement mortar demonstrates excellent waterproof ability and freeze-thaw resistance through low water absorption and slow quality reduction after multiple freeze-thaw cycles. These key characteristics provide advantages for concrete protection applications in harsh environments. • A simple method for preparing superhydrophobic surface by brushing chemically-modified liquid is proposed. • The penetration depth of the superhydrophobic coating is 5 mm. • The coating optimizes pore structures and water absorption is reduced by 70.66%. • The coated mortar exhibits pretty icephobic performance and freeze-thaw resistance. [ABSTRACT FROM AUTHOR]

Damage induced in mass transfer process is a ubiquitous phenomenon in nature and living systems. A coupled physical–chemical modeling framework is proposed to clarify the mass transfer in damaged media. Such a theoretical framework shows that the mass transfer problem is no longer linear but non-linear, due to the mass transfer behavior is influenced not only by transport driving mechanisms but also by physical consumption mechanisms, chemical consumption mechanisms, and damage evolution. Based on the theoretical framework presented in this paper, one can choose specific mechanisms in each category, different mass transfer theories can be constructed to meet specific practical applications requirements. To verify the correctness and validity of this theoretical framework, we choose the theoretical model of sulfate ion transport in cement-based materials. This is because sulfate ions are the main cause to induce the corrosion cracks in concrete in the marine environment. The following mechanisms are considered: concentration gradient driven transfer, chemical reaction, continued hydration, filling effect, and expansion damage. 3D nonlinear partial differential equations with variable coefficients are derived for the system. The numerical results show that the chemical reaction has the dual characteristics of self-stagnation and acceleration of sulfate ion transport. The chemical reaction products consume the free ions and fill the pore structure, which reflects the self-stagnation of mass transfer, while the expansion force generated by the chemical products leads to the initiation of corrosion crack, which reflects the acceleration of mass transfer. The competitive outcome of the two mechanisms is acceleration feature as the dominant one. Finally, the proposed model efficacy is validated by comparing the numerical results with previously reported experimental data. [Display omitted] • Based on damage evolution, a coupled physical–chemical model for mass transfer is established. • Corrosion cracks is induced by the expansive stress of ettringite. • Corrosion cracks significantly accelerate corrosive ions transport. • Sulfate ions can be transported in the pores of the C-S-H gel. • 1D and 3D spatial–temporal distributions of damage and sulfate ions are evaluated. [ABSTRACT FROM AUTHOR]

This paper investigates the problem of bond in post-tensioning strands in the presence of grout injection defects. In particular, the paper describes a campaign of experimental pull-out tests with a single 7-wire steel strand in the centre of a galvanised sheet metal duct with no grouting defects and with 25% and 50% defects, i.e. voids in the cross-section area of the grout. The grouted length is short in order to obtain a local bond–slip relationship. This relationship has an initial branch followed by a jump descent and a subsequent growing branch in the form of a sawtooth. The experimental data are used to define a specific bond–slip relationship that takes into account the presence of defects. The results show that the obtained bond–slip law is very different from those proposed in the literature for the case of ribbed steel bars. Furthermore, the defects cause a decrease in bond stresses and a flattening of the shape of bond–slip curves. • Bond of post-tensioning strands is studied. • Experimental pull-out tests are performed. • Effect of grout injection defects is investigated experimentally. • A bond-slip relationship for post-tensioning strands with defects is proposed. [ABSTRACT FROM AUTHOR]

The maintenance design for existing asphalt pavements, characterized by their typical structure and material composition, falls short of meeting the diverse requirements of pavements. There is an urgent need for a more rational design approach that can achieve accurate pavement design while also reducing construction costs. This paper focuses on selected conventional road surface structures and conducts an analysis of how pavement structure and materials impact fatigue life and construction expenses. It employs Python to perform three-dimensional finite element road modeling, analysis, and data extraction at specific locations, using normalized fatigue equation to calculate pavement fatigue life. The optimization variables selected are the modulus E and thickness h, with pavement maintenance cost serving as the optimization target function. The particle swarm optimization algorithm is employed for optimizing these variables. A comparative analysis is carried out for five improved optimization algorithms, optimizing combinations of inertia weight, learning factors, particle speed, number of particles, and iteration times. The results reveal that the enhanced optimization algorithms significantly improve iteration trends, featuring velocity limitations and natural selection mechanisms. Between 0 and 20 iterations, all algorithms search for the optimal solution over a wider interval with greater fluctuations. Between 20 and 30 iterations, each algorithm gradually converges towards its solution, stabilizing in the later stages. Based on optimization speed and actual engineering cost benchmarks, the NDPSO algorithm is selected, resulting in a 52.8% reduction in actual engineering costs. Adjustments to the particle count and iteration number of the NDPSO algorithm are made based on computational cost and optimization accuracy, thus choosing 20 particles and 50 iterations as the recommended parameter combination. By combining automated finite element modeling, analysis, and particle swarm optimization, this paper offers a novel and effective automated design reference for extending the lifespan of asphalt pavement structures. • An improved particle swarm optimization model for fatigue life with consideration of the modulus E and thickness h. • The automation of finite element modeling, calculation and data extraction is completed by using further development. • Normalized fatigue equation is used to calculate pavement fatigue life. • A novel and effective automated design reference for extending the lifespan of asphalt pavement structures is proposed. [ABSTRACT FROM AUTHOR]

To prepare SBS modified asphalt (SMA) waterproofing membrane with excellent self-healing performance, in this paper, four self-healing agents (ASHA-A, ASHA-B, ASHA-C, ASHA-D) with acylhydrazone bonds and carbon-carbon double bonds (C C) were synthesized, and were used to prepare self-healing SMA waterproofing membranes (SSMA-A, SSMA-B, SSMA-C, SSMA-D). The effects of ASHAs with different structures on the structure, high and low temperature properties, joint peel strength and self-healing performance of SSMAs were investigated. The Fourier transform infrared spectroscopy and fluorescence microscope results showed that acylhydrazone bonds of ASHAs were introduced into the chains of SBS molecules, and the SBS in SSMAs occurred crosslinking through the C C of ASHAs and SBS, the crosslinked network structures of SBS in SSMA-C and SSMA-D were denser and more complete because ASHA-C and ASHA-D contained more C C involved in the crosslinking reaction. The softening point and low temperature flexibility of SSMAs were enhanced by the formation of the SBS crosslinked network structure, and the optimum dosage of ASHAs was 0.6%. The joint peel strength of SSMA-A, SSMA-B, SSMA-C and SSMA-D increased by 26.68%, 31.25%, 49.52% and 56.97% compared to SMA. The introduction of acylhydrazone bonds with reversible fracture and rearrangement significantly improved the crack self-healing performance of SMA, the impermeability times of SMA, SSMA-A, SSMA-B, SSMA-C and SSMA-D were 13.28 min, 37.29 min, 42.53 min, 53.34 min and 59.67 min after self-healing at 40℃ for 8 h, which indicated that ASHA-D with benzene ring and multiple C C had the best improvement in self-healing performance of SMA. [Display omitted] • Acylhydrazone self-healing agents with different structures were synthesized. • The introduction of acylhydrazone bonds improved the crack self-healing performance of SBS modified asphalt waterproofing membrane. • The effect of acylhydrazone self-healing agents on the properties of SBS modified asphalt waterproofing membrane was investigated. [ABSTRACT FROM AUTHOR]

This paper presents a thorough investigation into utilizing hybrid fibers, comprising both steel and polymeric fibers, to enhance the compressive and tensile behaviors of ultra-high-performance concrete (UHPC). Flowability tests revealed potential usability challenges with polymeric fibers, emphasizing the necessity for careful consideration. Compressive strength results demonstrated that hybridizing straight steel fibers with short hooked steel fibers results in performance similar to that of reduced steel fiber content. Elastic modulus trends correspond with those of the compressive strength, and unexpectedly positive effects on the ultimate strain capacity under compression are observed with long polyvinyl alcohol fibers. Tensile behavior analysis highlights the superiority of both short and long hooked steel fibers, with the latter contributing the highest tensile strength. However, the use of polymeric fibers significantly decreases the tensile strength owing to insufficient dispersion and low tensile strength. Scanning electron microscopy images of UHPC with polymeric fibers reveal debonding and surface damage, with potential advantages observed for polypropylene fibers through methods such as surface moisture coating. In conclusion, this paper provides insights into optimizing fiber content and types for UHPC, emphasizing a balance between reduced fiber content and maintained performance. The proposed hybrid reinforcement approach, particularly with short hooked fibers, is promising for practical usability and cost-effectiveness in construction applications. • Addition of hybrid fibers, particularly polymeric fibers, results in a decrease in flowability. • Hybridizing with hooked fibers decreases the fiber content by 0.5 % given similar strength levels. • Long PVA fiber is effective in increasing elastic modulus of UHPC due to limited deformation. • Hybrid use of straight and hooked steel fibers exhibits improved tensile performance of UHPC. • Introduction of PVA and PP fibers causes a decrease in the tensile strength of UHPC. [ABSTRACT FROM AUTHOR]

Construction and demolition wastes (CDW) are promising sources for geopolymer production; however, the great variability of CDWs arising from their origin causes an abstention from implementation. As one of the key challenges in the CDW management and recycling practices, origin-depended variations in the waste materials and their reflection on the final product performance can be overcomed through in-depth waste characterization and design optimization. To this end, this paper aims to characterize CDWs collected from five different demolition zones with regard to their physical-, chemical-properties and the mechanical performance of geopolymer pastes produced with them. The compressive strength of geopolymer pastes was found to be significantly influenced by the chemical composition, crystalline nature, and fineness of CDWs. Optimization of precursor characteristics resulted in consistent mechanical performance ranging from 54.5 to 68.0 MPa after curing at 115 °C for 48 hours, regardless of the CDW origin. The aluminosilicate and calcium content of the precursor heavily influenced the ultimate gel structure in a positive manner, which determined material strength. The optimized use of CDWs from the same source increased the compressive strength of geopolymer pastes by up to 64%. • CDWs from different demolition zones were characterized. • Physical, chemical and crystalline properties of CDWs were examined. • CDWs from 21 different origin were used to produce geopolymers. • Aluminosilicate content and fineness were dominant in mechanical performance. • Precursor-based optimization resulted in 54.5–68 MPa compressive strength. [ABSTRACT FROM AUTHOR]

In this paper, a new approach of bidirectional electro-migration rehabilitation (BIEM) using pulse currents was proposed. The effect of the duty cycle and frequency of the square wave pulse current on the BIEM was investigated. The results showed that the desalination efficiency was improved by 10 % with the decrease of duty ratio and frequency. Furthermore, With the increase of duty ratio and frequency, the hydrogen permeation of steel bars decreased by 28.5 %. More uniform desalination efficiency was obtained by using pulse current. The half-cell potential of the rebars was also measured and it was higher for the samples using pulse currents than for those using direct currents, indicating a lower risk of corrosion after pulse current treatment. The pH value of the concrete also increased during the BIEM process. • The amount of hydrogen permeation in the rebars of concrete repaired by pulse current is reduced. • Increasing frequency and decreasing duty cycle of pulse current make the desalination efficiency distributed more evenly. • Decreasing frequency and duty cycle of pulse current will increase the efficiency of chloride ions removal. [ABSTRACT FROM AUTHOR]

Elevated temperatures may influence greatly the mechanical properties of adhesives, and it is difficult for adhesives with a single curing agent to meet the requirements of adequate heat resistance and toughness simultaneously. First, this paper proposes a nano-SiO 2 -modified epoxy adhesive (GY34) using mixed curing agents to improve the bond performance of CFRP-steel joints at a high temperature. Then, studies are taken to examine the impact of elevated temperatures on the mechanical performance of GY34 with mixed curing agents and the interfacial properties of CFRP-steel double-lap joints bonded by GY34. After that, models are developed to predict the bearing capacity and bond-slip of CFRP-steel double-lap joints at different temperatures using the test data. The results indicate the toughness is optimal at 70 °C when the curing agents C105 and D230 are mixed with a mass ratio of 1:2. The bearing capacity of the CFRP-steel lap joint bonded with GY34 is much higher than the cases only bonded with a single C105 or D230, respectively. Moreover, the load-displacement curve has a significant ductile development stage as the temperature rises below the glass transition temperature (T g, S), beyond which, the bearing capacity declines. In addition, the length of shear stress transmission and the effective bonding length increase significantly at high temperatures. The bond-slip curve bonded with GY34 has a trilinear trapezoid shape at different temperatures, and the peak shear stress and stiffness decline at various elevated temperatures. Finally, the relative slip and interfacial fracture energies increase first and then decrease with the rise of temperature. • A nano-SiO 2 -modified epoxy adhesive using mixed curing agents to improve the bond performance of CFRP–steel joints at a high temperature. • The impact of ambient temperature on the interfacial bond of CFRP–steel double-lap joints bonded by nanosilica-modified adhesive is analyzed. • The bond-slip model of the interface considering the effect of temperature is expressed analytically. [ABSTRACT FROM AUTHOR]

In this paper, the interfacial bonding properties between alkali-treated bamboo fibers and the matrix in fiber-reinforced high-performance seawater sea-sand concrete (HPSSC) materials were investigated. The natural bamboo fibers were modified with NaOH solution, and the cellulose crystallinity, chemical composition, and microstructure of the bamboo fibers before and after modification were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The impact of alkali treatment on the water absorption and mechanical properties of bamboo fibers were evaluated by water absorption test and single fiber tensile test. In addition, the influences of NaOH concentration, treatment time, and embedded length on the interfacial bonding properties were analyzed by pull-out test. Subsequently, the bonding mechanism between the fibers and the matrix was revealed based on the SEM scans of the extracted fiber surfaces. The experimental results indicate that appropriate alkali treatment could significantly eliminate the non-structural substances on the surface of bamboo fibers, reduce the water absorption, and increase the cellulose crystallinity. This process made the bamboo fibers exhibit better stability and bonding performance while ensuring the initial mechanical properties. Moreover, various fiber embedded lengths have a significant impact on the pull-out behavior of bamboo fibers. The maximum pull-out force of bamboo fibers increased with the increase of embedded length, while the fiber-matrix interfacial shear strength decreased. Based on the experimental results, a theoretical model for the pull-out behavior of bamboo fibers was proposed, and the predicted results showed a strong correlation with the experimental results. • The crystallinity, chemical composition, and microstructure of alkali-treated bamboo fibers were analyzed. • The interfacial bonding properties of bamboo fibers were analyzed by pull-out test. • A theoretical model with good agreement for the pull-out behavior of bamboo fibers was proposed. [ABSTRACT FROM AUTHOR]

For the buildings with pile foundations adjacent to or even right above the metro tunnels, mitigation measures in isolating the metro-induced vibration propagation along the pile become necessary to reduce annoyance to residents. To achieve this goal, a novel vibration isolation measure concept of the rubber-coated bored pile (RCBP) is proposed in this paper. An analytical solution is deduced to investigate the dynamic impedance of the pile. A field application of the RCBP is presented, along with two in-situ tests conducted for metro-induced vibration and pile head dynamic stiffness. The results confirm the dominant frequencies of the metro-induced dynamic response at the pile head is highly related to its dynamic stiffness. The influence of the rubber-coated layer is further examined by a parametric study in which the analytical and the numerical solutions are both of consideration. It is demonstrated that the effect of the variation of the rubber-coated layer thickness is negligible in engineering practices, while the variation of the rubber-coated layer depth has a significant impact on both the dynamic stiffness and the dynamic response at the pile head. Results from the in-situ test, analytical and numerical solutions confirm the potential of the rubber-coated bored pile in isolating metro-induced vibrations. • The rubber-coated bored pile (RCBP) is proposed for isolating metro-induced vibrations. • An analytical solution of pile head dynamic characteristics is deduced. • A field installation of the RCBP is presented and its vibration isolation performance is examined. • A numerical parametric study is conducted to investigate the influence of rubber-coated layer thickness and depth. [ABSTRACT FROM AUTHOR]

In order to realize the resource utilization of coal gasification fine ash (CGFA) in cement fields, a key is to solve the problem of low activity of CGFA. This paper studied the performance of CGFA as supplementary cementitious materials in cement. Furthermore, to enhance the activity of CGFA, targeted chemical activators were employed, with triethanolamine (TEA) and simulated high salinity wastewater (SHSW) chosen as representatives of organic and inorganic agents, respectively. It was found that CGFA had a synergistic effect with cement at a low dosage, while the inhibition effect on cement hydration was dominant at a high dosage. TEA promotes the strength development of the CGFA-cement system by promoting early hydration of cement and dissolution of active minerals in CGFA. However, the promoting effect of TEA on cement hydration will change to an inhibiting effect with the development of time, which will have an adverse effect on the development of strength. In general, the optimal dosage of TEA is 0.03 %, which can increase the 28-day activity index of CGFA from 69.1 % to 75.6 %. SHSW accelerates the strength development of the CGFA-cement system by promoting the hydration of cement and facilitating the dissolution and hydration of active minerals in CGFA. In addition, X-ray diffraction results show that a new hydration product, Friedel's salt, is formed under the excitation of SHSW. But this new hydration product will gradually dissolve as the pH decreases. The 28-day activity index of CGFA can be increased to a maximum of 83.3 % under the excitation of 2 % SHSW. [Display omitted] • The direct use of CGFA has adverse effects on the properties of cement. • Activity index of CGFA can be increased to a maximum of 83.3 % by chemical activators. • Activators promote the dissolution and hydration of active minerals in CGFA. [ABSTRACT FROM AUTHOR]

This paper focuses on the experimental and analytical behavior assessment of novel sandwich panels fabricated with recycled glass-fiber/polyester resin (GFRP) core and PVC face sheets. The originality of the present work is based on sustainable development and waste recovery to design lightweight and eco-friendly structures. In this respect, the panels cores were fabricated using fully recycling of fiber-glass waste issued form the boats building. Accordingly, a set of sandwich panels with various core configuration and fibers orientation were manufactured and tested up to failure under three-point bending to characterize flexural and shear properties. In addition, validated analytical equations were advocated to assess the bearing capacity of the studied panels. The obtained results in terms of mechanical, thermal and physical features are emphasized, discussed and confronted with a good agreement to literature ones. A principal component analysis was conducted to optimize the effect of the geometrical parameters on the panel failure mechanisms. As main outcomes, the work can provide environmental and economic solutions for the design of sandwich structures. • Lightweight and eco-friendly sandwich structures-based GFRP waste core were designed • Validated analytical equations were advocated to assess the bearing capacity of the studied panels under bending • A principal component analysis was conducted to optimize the geometric parameters of the panels • The paper results provide environmental and economic solutions for the design of sandwich structures [ABSTRACT FROM AUTHOR]

Alkali-activated binders (AAB) are low-carbon alternatives to cement used in traditional concrete manufacture. This paper presents a state-of-the-art survey of the historical background, synthesis development, reaction mechanism, and recent advances of the AAB. The parameters influencing the engineering performance of the AABs, including the physicochemical characteristics of the precursor materials, formulation and dosage of alkaline activators, and type and period of curing, were critically reviewed. In this regard, three different precursor material sources are identified: industrial by-products, natural aluminosilicates, and agricultural waste materials, which have various availability, reactivity, cost, and value worldwide. In addition, recent advances in the life cycle assessment of AAB mixtures are compiled. The challenges that AABs face towards commercial applications are also discussed. The selection of appropriate precursors, the production of low-cost alkaline activators, mix design parameters, fundamental mechanisms, engineering properties, construction processing and application, performance standards, and sustainability aspects constitute the challenges. Alkali-activated concrete can be a potential low-carbon substitute for conventional concrete if it ensures true sustainability and not just greenwashing. • Collation of recent technical updates on alkali-activated cementitious composites. • Informs readers of the nuances and challenges of alkali-activated materials. • Recent progress in understanding the reaction kinetics and engineering properties of alkali-activated binders summarized. • An overview of LCA studies conducted on alkali-activated binders. [ABSTRACT FROM AUTHOR]

This study investigates the impact of incorporating lime mud (LM) as a filler material to develop sustainable, cementless ultra-high performance concrete (UHPC) by replacing silica powder (SP) and silica sand (SS) at varying percentages. Flowability analysis reveals that LM, with its distinctive particle size, influences flow characteristics differently at different replacement levels. Compressive strength was improved by 5.4% with 30% SP replacement, showcasing the role of LM in nucleation, as well as its particle size advantage. The heat of hydration analysis indicates that LM likely influences the early curing stages, enhancing reactivity and nucleation. TGA analysis also confirms that LM plays a role in hydration reaction, influencing weight loss and hydration peaks. The mercury intrusion porosimeter results show the impact of LM on pore distribution, with 30% for SP and 50% for SS replacements, favoring denser matrices. Life cycle assessment (LCA) demonstrates reduced CO 2 emissions and favorable environmental performance, highlighting the sustainability potential of LM replacements. Overall, the incorporation of LM in UHPC shows promise in terms of enhancing its mechanical properties and environmental sustainability. [Display omitted] • Lime mud (LM) in UHPC boosts material strength, leading to denser, more effective concrete. • LM enhances hydration, flowability, and refines pore structure. • High LM ratios in UHPC increase sustainability and reduce CO 2 emissions. • LM's use in UHPC significantly advances its mechanical properties and eco-friendliness. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the variation rule of coarse aggregate and pore structure of shotcrete by adding MWCNTs. In the paper, X-ray computed tomography scans are used to study the coarse aggregate distribution and pore structure of the preparation of shotcrete, high-temperature curing shotcrete and shotcrete with MWCNTs. The distribution pattern of coarse aggregate and pore of shotcrete is obtained. The results show that: the coarse aggregate loss of shotcrete is serious within 30 mm from the wall and the coarse aggregate increases significantly in 30–70 mm. The addition of 0.03% MWCNTs increased the coarse aggregate of shotcrete by 36.63% and the volume of coarse aggregate by 25.64%. The largest increase is in coarse aggregates of 5–7 mm. This show that MWCNTs can improve mortar adhesion and reduce aggregate rebound. The number of shotcrete pores decreases with the increase of pore diameter. The proportion of small pores is up to 85%, the proportion of large pores is only 2%, but the volume of large pores reaches 87%. The addition of 0.03% MWCNTs can reduce the number of small pores in the shotcrete and reduce the mean pore diameter, resulting in a decrease in the porosity of the shotcrete. When the curing temperature is 80℃, the porosity of shotcrete increases, and the pores decrease due to interconnection. The pores around the coarse aggregate account for over 70% of the total porosity, with pores larger than 1 mm accounting for 75%. This paper has a good reference value for the development of shotcrete and the selection of coarse aggregate in the actual working conditions. • The coarse aggregate distribution and pore structure characteristics of shotcrete were revealed. • The influence of MWCNTs on the rebound of shotcrete coarse aggregate was analyzed. • The relationship between pore distribution of shotcrete and coarse aggregate distribution is discussed. [ABSTRACT FROM AUTHOR]

The compressive behavior of ultra-high performance concrete (UHPC) is experimentally investigated in this paper for three different micro steel fiber volume fractions (V f = 1.0%, 1.5% and 2.0%) under uniaxial monotonic and cyclic compression. The cube specimens are loaded and fully unloaded twice per displacement increment to track the evolution of damage. Cycles are included till the peak load and after attaining the peak load, all the way till the load carrying capacity becomes marginal. A one dimensional (1D) elastoplastic damage constitutive model is proposed to simulate the damage of UHPC under uniaxial cyclic compression, incorporating the damage parameters within a damage function deduced from the tests. Damage is incorporated as a nonlinear function and thus the hysteresis behavior (distinguishable unloading and reloading paths) is adequately captured in the model. The experimental results from this study and the accompanying model demonstrate that the strength and stiffness degradation in UHPC due to low cycle fatigue stabilize at higher fiber dosage levels. • Strength degradation due to cyclic loading stabilizes at higher fiber dosage even at large strain cycles. • Strength and stiffness degradation due to cyclic loading is marginal till attainment of peak load. • Nonlinear damage variable proposed can accurately trace the unloading and reloading branches during cyclic loading. [ABSTRACT FROM AUTHOR]

Calcareous sand is a favored unbound granular fill-in island project where complicated stresses are often applied. Traffic and ocean loadings are frequent in praxis, but poorly understood about the normalization of the pore pressure for both. This paper deals with an experimental simulation study on the pore pressure of calcareous sand subjected to ocean waves, traffic, and cyclic loading. Particular attention is devoted to the effect of the initial shear stress and the dynamic stress ratio (CSR). Results showed that, owing to the features of traffic loading and initial shear stress, the soil skeleton can still withstand partial external loading when reaching the failure criterion, hence the pore pressure at failure(r uf) is much smaller than liquefaction. In terms of the influence mechanism, unlike the initial shear stress, the increase in CSR accelerates the destruction of the soil skeleton, reducing the r uf , but having less effect on the critical pore pressure. Expressions for the number of cycles at failure(N f) and r uf were obtained and the exponential model was simplified by changing N / N f to ε 1/0.05 to reflect the characteristics of traffic loading. To normalize the pore pressure under different loadings, each stress component on N f and r uf has been analyzed and the noteworthy finding is that torque has a very minor impact on the soil skeleton. Based on this finding, a new normalization method was proposed in which N f needs to combine all loads including torque, while r uf only needs to consider axial forces. Hence, a pore pressure equation under three different loadings was established, taking into account the role of CSR and the initial shear stress. • Failure under traffic loading is governed by strain, allowing the soil skeleton to partially sustain external loads without complete destruction. • The influence mechanisms of the initial shear stress and CSR on pore pressure have been found to be distinct. • A model of pore pressure considering the initial shear stress to dynamic stress ratio under different loading types is derived. [ABSTRACT FROM AUTHOR]

Engineered Cementitious Composites (ECC) utilize the bridging effect of high toughness fibers to improve the brittle failure of concrete materials, achieve the effective control of cracks in cementitious materials, and significantly improve the deformation capacity. In view of the multi-stage crack-blocking effect of different fibers incorporated in ECC materials, 91 ECC specimens of steel-polypropylene hybrid fiber by mixing steel fiber (SF) and polypropylene fiber (PPF) into cement-base are made in this paper. The specimens are tested in compression, tensile, bending and damping properties, respectively, which is of great significance to study the response of ECC structures under the earthquake action. The effects of the volume content of SF and PPF on the mechanical properties of ECC are studied in this paper. The results show that the cube specimen has better ductility than the prismatic specimen under monotonic compression, and there is no obvious brittle failure. With the increase of the volume content of SF to PPF, the compressive strength and elastic modulus of hybrid fiber ECC gradually increase, while the corresponding strain and axial compressive toughness gradually decrease; the tensile strength and tensile modulus increase, while the bending strength and damping ratio decrease. According to the test results, constitutive models of monotonic and repeated loading of hybrid fiber ECC suitable for finite element (FE) analysis are proposed. This investigation provides a theoretical basis and an experimental reference for further study of steel-polypropylene hybrid fiber ECC. • Steel fiber and polypropylene fiber are mixed as hybrid fiber of ECC. • The mechanical properties of ECC are investigate. • Volume content of steel-polypropylene hybrid fiber has influence on concrete material. • The hybrid fiber ECC cube has better ductility than that of prismatic. • Constitutive models of hybrid fiber ECC are suitable for finite element analysis. [ABSTRACT FROM AUTHOR]

Polymer emulsion impregnation is a common method for strengthening recycled fine aggregate (RFA). By mixing Nano carbon black (NCB) into the polymer emulsion, highly conductive modified RFA (MRFA) can be simultaneously obtained. In this paper, highly conductive and self-sensing concrete was prepared by using the MRFA impregnated with the NCB and polydimethylsiloxane (PDMS) solution. The microstructure of MRFA and MRFA concrete physico-mechanical properties were studied. The effects of replacement ratio of MRFA, temperature, water content, and loading rate on the conductivity and self-sensing of prepared MRFA concrete was explored. The results show that the PDMS fills the pores of the RFA surface. The water absorption decreases by 2.53%, the apparent density and fineness modulus increased by 1.5% and 8.3%, respectively. With the increase of MRFA replacement ratio, the resistivity of concrete gradually decreases, and a sharp decline appears from 60% to 70%. The percolation threshold of concrete is calculated to be 3.37 vol% of NCB. Meanwhile, the MRFA concrete has good temperature sensitivity and humidity adaptability. Under the stress cycle loading, the stress sensitivity of the MRFA concrete with 70% replacement ratio MRFA is as high as 4.45%/MPa. Besides, the stress sensitivity of MRFA concrete decreases as the loading rate increases. • Recycled fine aggregate was treated with carbon black and polydimethylsiloxane. • Self-sensing concrete resistivity was measured by four-electrode method. • Self-sensing concrete piezoresistivity was studied. [ABSTRACT FROM AUTHOR]

The high ductility of high ductility cementitious composites (HDCC) relies on both fiber dispersion uniformity and defect size distribution. While fiber dispersion is often prioritized in HDCC design, the impact of defect distribution, particularly pore structure, is overlooked. Correspondingly, there is scant information available on the connection between pore structure and mechanical properties of high ductility cementitous composites under rheological adjusting. This paper aims to explore the correlation between rheological properties, pore structure, and mechanical characteristics of HDCC. By adjusting fly ash (FA) dosage, water-binder ratio (W/B), and additive dosage, rheological properties are modified to optimize fiber dispersion and pore structure. Results show that increased harmful porosity (>20 nm) correlates with heightened HDCC tensile ductility, while greater harmless porosity is associated with elevated initial crack strength and fracture toughness, albeit at the expense of reduced tensile ductility. Higher plastic viscosity (0.21 Pa·s∼2.38 Pa·s) and lower yield stress (1.24 Pa∼15.35 Pa) increase harmful pore formation, reducing matrix fracture toughness but enhancing HDCC tensile ductility. Considering both fiber dispersion and pore structure alterations is crucial in HDCC design. Under specified conditions, adjusted rheological parameters yield HDCC with over 40% harmful pores, over 90% fiber dispersion, compressive strength up to 30 MPa, and 5% ductility, with crack widths below 100 μm and an average spacing of 2.37 mm, indicating multislit cracking close to saturation. These findings provide valuable insights for HDCC ratio design. • A method to optimize HDCC's mechanical properties by analyzing preferred rheological parameters and harmful pores. • The significant determinants that influence the tensile ductility of HDCC encompass the fiber dispersion and harmful pore proportions. • High plastic viscosity and low yield stress foster harmful pore formation, reduce fracture toughness, and enhance tensile ductility. [ABSTRACT FROM AUTHOR]

Unmodified thermal-activated recycled cement (RC) paste has unfavorable properties like fast setting. This paper intends to modify RC by adding phosphogypsum (PG) and ground-granulated-blast-furnace-slag (GGBS). A comprehensive experimental program combining isothermal calorimetry, mechanical tests, TG, XRD, MIP, 29Si NMR and SEM of modified RC (PG-GGBS-modified-recycled-cement) pastes was conducted. The results show that GGBS and PG not only effectively modified the setting time but also contributed to a more compact skeleton. The final setting time was extended from 12 mins to 84 mins. The 28d and 90d compressive strength reached 29.8 and 36.9 MPa, increaseing by 21.1 % and 39.9 %, respectively. It is shown that PG acted as a sulfate excitation to the active Al 2 O 3 in the GGBS and RC to generate AFt. Rehydrated C-S-H gel could both wrap and protect the CaSO 4 ·2 H 2 O crystals and crystalline contact points, and effectively filled the pores of the hardened paste, thus promoting the generation of C(-A)-S-H and Ca 5 (SiO 4) 2 (OH) 2. The rehydration of modified RC was associated with a remarkable amount of AFt and AFm intergrowing with the reformed C-S-H gel and generating a compact network skeleton. • Modification of recycled cement with phosphogypsum and GGBS was investigated. • GGBS and PG not only effectively modified the setting time but also contributed to a more compact skeleton. • Rehydrated C-S-H gel could effectively fill the pores, thus promoting the generation of C(-A)-S-H and Ca 5 (SiO 4) 2 (OH) 2. • The final setting time of recycled cement was extended from 12 mins to 84 mins. • The 28d and 90d compressive strength reached 29.8 and 36.9 MPa, increased by 21.1 % and 39.9 %. [ABSTRACT FROM AUTHOR]