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Surface (microscale) roughness of coarse aggregates influence the cement suspension' viscosity and the interfacial bonding strength of concrete, but its characterization method is not consolidated and still a research challenge. 3D scanner determines accurately the shape, volume, but it is incapable of describing the roughness at microscale. Roughness at microscale (surface index – cm2/cm2) can be measured accurately using interferometry, but it cannot describe shape and volume of the particles. Once the volume of aggregate particles may vary 200% and it seems crucial to establish the (micro)roughness per volume (cm2/cm3) to better understand the effects in the properties of cementitious materials. This paper presents a method of obtaining volumetric surface area of coarse aggregates at micrometric scale by joining (cm2/cm3) both techniques. Three types of aggregates were assessed: gneiss, low-grade meta-carbonate (dolomite) and quartzite (gravel), with one hundred particles in the size range of 4.75 mm to 37.5 mm. For coarse aggregates, the larger the particles, the more of their surface area will be influenced by (mesoscale) shape and less by surface (microscale) roughness. However, the smaller the particles, SI index will differ considerably. The surface area determined by the method proposed in this paper provides a good correlation with the methylene blue method. • New method to determine volumetric surface area (VSA) of aggregates. • Light white interferometry and 3D scanning methods combined. • Shape and roughness (multiscale) morphological descriptors discussed. [ABSTRACT FROM AUTHOR]

In this paper, a thermo-mechanical sequential coupling mesoscopic simulation method was established and verified, which considered the interaction between steel tube and meso-components of concrete due to the difference in thermal parameters, as well as the low-temperature effect on mechanical parameters. On the basis of heat conduction analysis, the damage evolution and failure mechanism of CFST column under axial compression were subsequently revealed, and the effects of low temperature (20, −30, −60 and −80 °C), cross-section size (160, 320, 480 and 640 mm), width-thickness ratio (27, 36, 53 and 107) and cross-section shape (square and circular) on axial compression performance and the corresponding size effect of CFST columns were quantitatively analysed. Research results show that the low-temperature action can enhance the nominal peak strength and residual strength of CFST column, but weaken the ductility. As the cross-section size increases from 160 to 640 mm, all the nominal peak strength, nominal residual strength and peak strain of circular CFST column decrease with the maximum reductions of 16.2, 28.7 and 16.9%, respectively. Besides, the low-temperature action can enhance the size effect on nominal peak strength of CFST column with the maximum increase of 68.8%. Whether at ambient or low temperature, the size effect on nominal peak strength of square column is stronger than that of circular one. The size effect behaviour on axial compressive peak strength at various temperatures can be also well described by the previous proposed prediction formula. The research results of this paper can provide reference for the engineering application of large-sized CFST columns in the extreme low-temperature environment. • The thermo-mechanical sequential coupling method at low temperature was developed. • The effect of low temperature, width-thickness ratio, cross-section size and cross-section shape were considered. • The mechanical properties and corresponding size effect of CFST columns at low temperature were quantitatively analyzed. [ABSTRACT FROM AUTHOR]

In this paper an overview is presented on the use of diatomaceous earth (DE) as a partial substitute for binder and fine aggregate in mortars. For this purpose, this paper was divided into two sections. In the first one, concepts related to physical, chemical and microstructural properties of DE, as well as results of previous studies about its reactivity used in different construction materials (cement, concrete, mortar, bricks, phase change materials etc.) were summarized and discussed. In the next section, the effects of using DE on the fresh, hardening and durability properties of cement and lime-based mortars were discussed. In general, the results suggest that increasing DE content may reduce mortar performance due to the high porosity of its particles. However, this deficiency was observed for DE contents higher than 20%, which, however, can be compensated for by using superplasticizer additives or by volumetric dosage instead of by weight one. This critical value of up to 20% of DE was calculated using T2 statistical on the scores of principal components analysis obtained from the results collected from publish manuscripts. Nevertheless, the results of this review research may contribute to provide information on an under-explored alternative source of supplementary cementitious materials (SCMs) and therefore help mitigate the negative effects generated by the cement industry and assist in the production of mortars with a lower carbon footprint that can play an important role in the thermal behavior of buildings. • State of the art systematic review of diatomaceous earth (DE) for mortar production. • Statistical analysis of the mechanical properties of mortar with DE. • Understanding the effects of DE on properties of mortars. • When up to 20% DE is used, the mechanical behavior of mortars can be improved. • Paths for the development of new studies on mortars incorporating DE are shown. [ABSTRACT FROM AUTHOR]

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

Freeze-thaw modification is a novel method that improves recycled aggregates by utilizing the expansion of pore water during phase transitions. However, there is still a lack of theoretical analysis regarding each component in recycled aggregates during freeze-thaw. In this paper, we introduce the parameter of pore radius to transform the traditional 2D phase diagram into a 3D phase diagram of pore water. This transformation makes the phase transition conditions of pore water more clear to understand. It is then combined with the pore size distribution of each component in recycled aggregate to calculate the ice content and freezing pressure. To achieve a more intuitive evaluation of frost susceptibility, this paper establishes a frost vulnerability index (FVI). Based on the FVI curves of different rocks, their frost resistance is categorized into three levels. Finally, according to the FVI of recycled aggregates with diverse material properties, some recommendations are provided for the engineering application of freeze-thaw modification. • By introducing the pore radius, the 2D phase diagram of water is transformed into a 3D diagram. • FVI has been established to assess the susceptibility of different materials to freeze-thaw damage. • The commen natural rocks are classified into three levels based on their frost resistance. • The necessity of thermo-drying is verified through analysis. • Theoretical analysis is conducted on the saturation level required and during the vacuum saturation. [ABSTRACT FROM AUTHOR]

Cement-based grout is widely used for backfill grouting in shield tunnels. However, traditional cement-based grout is prone to segregation, layering, and low retention rates, which leads to a not ideal filling effect of the shield tail gap. This paper innovatively uses three industrial solid wastes as supplementary cementitious materials (SCMs), to replace cement in the composition of backfill grouting materials: silica fume (SF); ground granulated blast-furnace slag (GGBS); and fly ash (FA). Taking the content of SF, GGBS and FA as variables, and fluidity, bleeding rate, concretion rate, setting time and compressive strength as response targets, a regression model was established by the Response Surface Method to explore the effects of the different factors and their interactions on the responses. Results show that the SF content has a significant effect on the characteristics of the grout; the GGBS content is positively correlated with the setting time and compressive strength; the content of FA has a significant effect on the hardening characteristics of the grout, being positively correlated with the setting time and negatively correlated with the compressive strength. Additionally, combined with the desirability function, multi-objective optimization was performed and an optimized mix ratio of SF=5.3 wt%, GGBS=9.0 wt%, FA=60.0 wt%, PC=25.7 wt%, was obtained. The response values of the grout for this composition were verified by experiments and the errors are less than 10%. Compared with the traditional cement-based grout, the grout with the optimized composition uses SCMs to reduce the PC content and significantly improve the grout stability and later strength, indicating that the SCMs used in this paper are effective and the RSM has high accuracy and good reliability. Consequently, RSM can be used to analyze, predict and optimize the mixing ratio of backfill grout in shield tunnelling. • Three types of solid waste were innovatively used to create optimized backfilling grouting materials for shield tunneling. • The interactions among various influencing factors have been elucidated through the implementation of Response Surface Method. • The developed backfill grouting materials have a good performance, environmental friendliness and cost-effectiveness. [ABSTRACT FROM AUTHOR]

Polymer grouting materials are widely used in the trenchless rehabilitation of underground pipe networks and infrastructures. Numerous publications focused on the mechanical properties of the composite's interface, which is critical for the stability and strength of composite structures. However, there is a scarcity of reports on the microscopic characterization and interactive mechanisms of polymer-bentonite system. In this paper, a microscopic combination interface model of polymer-bentonite was constructed based on the molecular dynamics simulation method, and the interfacial shear mechanical properties were investigated under different working conditions. The results show that the shear strength of the polymer-bentonite interface increases with the increase of shear rate and normal stress, which is consistent with the experimental results. The application of normal stress leads to a decrease in the van der Waals gap at the interface and an increase in the density of the dense interface, thus increasing the shear strength of the interface. In addition, the shear strength of the interface in the presence of defects on the surface of the clay crystals is determined by the nonbonding interaction potential energy together with the roughness. As the shear rate increases, shear thinning occurs at the polymer-bentonite interface, and the effect of roughness on the interfacial shear properties gradually decreases. This paper reveals the mechanical properties of the polymer-bentonite interface under the influence of different factors from a microscopic point of view. • Micromechanical characterization of bentonite-polymer interfaces using molecular dynamics simulations. • Pull-out simulations of the interface were performed considering the effects of pull-out rate, normal stress, clay crystal defects, and different interface types. • Mechanism of synergistic enhancement of interfacial properties by roughness and non-bonded interaction potentials revealed. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive review of calcium sulfate whiskers (CSW), focusing on their synthesis methods, morphological characteristics, and diverse applications across industries. Whiskers, known for their specific length-to-diameter ratio and ordered atomic structure, offer exceptional physical and mechanical properties, making them valuable reinforcements for various materials. Through a bibliometric analysis, a comprehensive overview of the existing research landscape within this field is provided, offering valuable insights into potential future research directions, and identifying promising avenues for further investigation The paper highlights the significance of controlling reaction parameters to achieve high-quality whiskers with desirable morphologies. Furthermore, the crystal symmetry and composition of calcium sulfate whiskers play crucial roles in determining the thermal behavior and performance of CSW. The multifaceted applications of CSW are extensively discussed, ranging from enhancing the mechanical properties of plastics, ceramics, and rubber to improving friction materials, paper production, and environmental filter materials. This review underscores the growing importance of CSW as versatile reinforcements and highlights the need for further research to optimize synthesis techniques and explore novel applications in emerging fields. [Display omitted] • Innovative applications of Calcium sulphate whiskers. • Enhancement in Mechanical properties. • Slender needle like structures. • Acts as pore filler. • Atmospheric and hydrothermal acidification synthesis of CSW. [ABSTRACT FROM AUTHOR]

The development of ultra-high performance concrete (UHPC) with lower carbon emission has conducted by many researchers. However, there is a lack of quantitative comparison of carbon reduction efficiency, such as carbon emission and energy consumption values, of UHPC materials with various components. This paper reviews the trends toward lower-carbon UHPC based on Life Cycle Assessment related to the used materials, especially different binders, aggregates, and steel fibers. The environmental indicators, including embodied carbon emissions (EC), embodied energy consumption (EE), and embodied CO 2 index (CI) value, of UHPC mixtures in published paper are discussed. Since compressive strength is an important indicator, the minimum value of compressive strength of UHPC should be greater than 120 MPa in the assessment process. Moreover, the effectiveness of using various low-carbon alternatives is discussed and then ranked according to the reduction degrees of EC and EE. Results found that ultra-high performance geopolymer concrete (UHPGC) shows the lowest EC and EE and the highest CI. This indicates that UHPGC has decreased carbon emissions without compromising compressive strength. The use of supplementary cementitious materials and recycled powder obtained from waste aggregates to substitute cement is another effective way to reduce EE and EC. However, using waste aggregates or waste fibers to replace conventional aggregates or steel fibers is less efficient than cement replacement with supplementary cementitious materials (SCMs). Especially, the use of waste aggregate leads to negligible reductions in EC and EE. The study seeks to find out the most promising route for low-carbon UHPC in the circular economy through identifying low-carbon alternatives, which has great significance in designing low-carbon UHPC. • Multiple strategies to develop lower-carbon UHPC are reviewed. • The environmental impacts of different UHPC are systematically calculated based on LCA at a material level. • These strategies are discussed and ranked based on performances and environmental impacts. • The most effective strategy for developing lower-carbon UHPC is indicated. • Perspective for how to develop lower-carbon UHPC is given. [ABSTRACT FROM AUTHOR]

Recycling of UV-aged asphalt has been a hot research issue. In this paper, waste cooking oil, plasticizer, toughener, and petroleum resin were used as raw materials for asphalt rejuvenator. This paper explores the effect of regeneration conditions on the regeneration effect of UV-aged asphalt binders through high-temperature rheology and chemical compositions. The paper also attempts to reveal the regeneration mechanism of asphalt binder regeneration using waste cooking oil. Dynamic shear rheology (DSR) and fourier transform infrared (FTIR) spectroscopy assess high-temperature rheological properties and chemical compositions. The Pearson correlation coefficient relates the rheological parameters to the chemical microstructure. And the functional relationship between carbonyl-corrected peak area and aging factor Ai of recycled asphalt and high temperature rheological parameters were established. Molecular simulation investigates WCO-recycled asphalt binder micro-morphology and adsorption mechanisms. The results showed that significant changes in the carbonyl and sulfoxide peak areas affected the high-temperature rheological properties. Regeneration conditions significantly affect asphalt regeneration effectiveness. WCO reduces C O and S O groups, crucial in asphalt viscoelastic behavior. Molecular interaction analysis reveals WCO's regenerative mechanism. This work emphasizes integrating molecular structure, chemical composition, and macroscopic properties in asphalt binder research, providing insights for sustainable pavement practices. • The content of C=O and S=O are the main factors determining the recycling effect of WCO recycled asphalt. • WCO rejuvenator changes the molecular structure of aged asphalt. • The -OH group of WCO increases the interaction between WCO molecules and aged asphalt molecules. [ABSTRACT FROM AUTHOR]

In this paper, the hydration process of cement paste with hydrophilic nano-TiO 2 particles was studied by microcalorimeter and electrochemical impedance spectroscopy, and the hydration mechanism was explored based on Krstulovic-Dabic kinetic model. Meanwhile, the photocatalytic activity and antibacterial properties of TiO 2 -modified cement pastes were investigated by ultraviolet spectrophotometer and enzyme activity analyzer respectively. The results show that TiO 2 nanoparticles can promote the hydration rate of cement in the acceleration stage, increase the cumulative heat release of early hydration, but delay the hydration process in the later stage. The Krstulovic-Dabic model can effectively simulate the hydration process of cement pastes with TiO 2. Nano-TiO 2 helps to increase the hydration rate of the crystal nucleation and growth process (NG) and shorten the duration of phase boundary reaction process (I), but has a negative impact on ion diffusion process (D). The functional relationship between the resistivity ρ of TiO 2 cement-based composites and the hydration kinetic parameters was established: ρ (t) = − 1 k 1 ln [ β 1 + t 50 t − t 0 ].The degree of hydration of cement can be assessed by electrochemical in-situ non-destructive monitoring of the sample. In addition, the photocatalytic oxidation rate of TiO 2 -modified cement-based composites was up to 69.4%. Compared with the control sample without nano TiO 2 , the antibacterial ability was increased by 72.35%. In this paper, nano-TiO 2 was applied to cement system, which provided a new idea for the preparation and application of photocatalytic antibacterial cement-based composites. • The hydration mechanism of cement pastes with nano-TiO 2 has been explored by EIS and kinetic model. • The equation between cumulative heat release and resistivity is: Q (t) = k 1 e k 2 ρ (t) . • The cement pastes with TiO 2 have excellent photocatalytic activity and antimicrobial properties. [ABSTRACT FROM AUTHOR]

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

Geopolymer concrete is a sustainable replacement to the Ordinary Portland Cement (OPC) concrete as it mitigates some of the associated problems of OPC manufacturing such as greenhouse gas emission and natural resource depletion. There has been significant recent research in the design of fly ash-based geopolymer concrete using advanced machine learning techniques which can address some of the problems with classical mix design approaches. However, practical application of geopolymer concrete is limited due to lack of standard mix design procedure. This comprehensive review summarizes the current literature on machine learning methodologies to predict the compressive strength of fly ash-based geopolymer concrete. Firstly, the input parameters used for the machine learning model development are categorized based on feature selection or feature extraction. Secondly, available machine learning approaches are categorized based on analysis methods namely, nonlinear regression, ensemble learning, and evolutionary programming. The effect of hyperparameters on the individual model performance, and model comparison based on the prediction performance are also discussed to identify potentially more suitable model type and hyper parameter ranges. Further, the paper discusses the input variable's sensitivity towards the model performance which provides guidance towards future model developments. Overall, this paper will provide an understanding of the current state of machine learning approaches to predict the compressive strength of geopolymer concrete and the gaps in research for the development of models and achieving the required performance. Hence, the summarized knowledge will be highly beneficial to design prospective research towards sustainable cement-free concrete using fly ash. • Artificial neural networks (ANN) predict geopolymer concrete strength well, offering reliable forecasts for new data. • Support vector machines and random forests offer ANN- like performance, serving as alternatives in machine learning (ML). • The success of ML model relies on proper selection of inputs and tuning hyperparameters for optimal performance. • The chemical, physical, and mineralogical characteristics of fly ash emerge as pivotal input variables in ML models. • Validating models through laboratory experiments is imperative, ensuring generalization for real-world applications. [ABSTRACT FROM AUTHOR]

In this paper, data from the PURWheel-G2 , a rubber tire wheel tracker, was utilized alongside several techniques to better understand isolation of the effects of moisture on asphalt rutting. Techniques commonly used to interpret wheel tracking data, particularly to evaluate moisture damage, were summarized and used to evaluate over 150 PURWheel-G2 tests where wet and dry pairs of tests were conducted to directly isolate the effect of moisture on rutting. Among all the available wheel tracking analysis techniques and models for moisture evaluation, there lacks a consensus approach, and available approaches vary widely highlighting the need for a standard test method. The rubber tire wheel tracker presented in this paper aims to take a step towards developing test protocols to isolate moisture damage. The ability to measure the effects of moisture on rutting is a feature that other existing wheel tracking methods cannot do on their own. • Rubber-tire wheel tracker tests were evaluated to isolate the effects of moisture. • Over 150 PURWheel-G2 tests in wet and dry conditions were conducted. • There is no consensus on how to analyze wheel tracking data for moisture evaluation.. [ABSTRACT FROM AUTHOR]

The increasing volume of waste rubber generated from end-of-life tyres has raised significant concerns regarding the safe and sustainable recycling and reuse of this material. A viable solution is to incorporate waste rubber into asphalt mixtures, which contributes to recycling waste tyres and promotes the sustainability and resilience of pavement infrastructure. In recent years, Crumb Rubber-Stone Mastic Asphalt (CR-SMA) mixtures have received considerable attention due to their remarkable performance. However, the feasibility of implementing CR-SMA in the field on a large scale requires further investigation. This paper aims to evaluate this matter by reviewing the mix design practices of CR-SMA, assessing the performance characteristics of CR-SMA, and identifying gaps and potential areas for improvement. The gaps related to various factors like aggregate gradation, compaction technique, processing temperature, CR grains size and their concentration, and binder content have been identified and discussed in the paper. In addition, the key performance characteristics of CR-SMA mixtures, including binder drain-down, moisture susceptibility, permanent deformation, and fatigue cracking, are evaluated. • Review history of waste tyre rubber in bituminous mixtures, tracing its evolution. • Explore the mix design practices of Crumb Rubber-Stone Mastic Asphalt (CR-SMA). • Investigate the mechanical properties and performance of CR-SMA. • Discuss the influence of CR characteristics on SMA performance. • Critically highlight CR-SMA research gaps, providing direction for future studies. [ABSTRACT FROM AUTHOR]

Fully utilizing regional resources such as marine sand, coral, and desert sand, along with a diverse range of solid wastes from industries, agriculture, and urban areas, not only effectively reduces the costs and carbon footprint of construction activities but also contributes to achieving sustainable development in the building sector. Despite earlier studies focusing on the feasibility of solid waste as lightweight aggregates, the comprehensive evaluation of the performance of alternative aggregates in such innovative materials as geopolymers and ultra-high-performance concrete remains significantly limited amid their rapid development. Therefore, this paper concentrates on a thorough exploration of regional sand and gravel resources, as well as efficient and value-added approaches to incorporating solid wastes from industries, agriculture, and urban areas as alternative aggregates in construction. It provides a comprehensive review of the physical properties of alternative aggregates and their impacts on the workability, mechanical properties, and durability of concrete. Additionally, the paper offers a detailed assessment of the production processes and performance of sintered and cold-bonded artificial aggregates. This research provides valuable insights for researchers and practitioners in the fields of construction, sustainable waste management, resource conservation, and recycling. • Regional resources, industrial and agricultural and urban solid wastes are used as clean aggregates. • Potential legal challenges to the use of clean aggregates are revealed. • Reviewed the modification methods of granular solid waste. • Reviewed artificial agglomeration techniques and potential challenges for powdered solid waste. [ABSTRACT FROM AUTHOR]

In this paper, the central pull-out tests were carried out on shape memory alloy fiber-reinforced concrete (SMA-FRC) under monotonic load. The failure modes and failure mechanisms of the specimens were observed and analyzed, and the bond strength and slip distance were measured. The effects of different influencing factors on the mechanical behavior of bond-slip were investigated, and the bond-slip constitutive model of shape memory alloy (SMA) bar and SMA-FRC was proposed. The test results indicated that the ultimate bond strength between SMA bars and SMA-FRC gradually increased with the addition of SMA fiber, the reduction of SMA bar diameter, the decrease of anchorage length, and the lowering of temperature within a certain range. In this paper, based on the theoretical analysis of the test data, a reasonable bond-slip constitutive model was established, which can better predict the test results. • The effect of various factors on the bonding properties is analyzed and the best combination of factors is obtained. • The influencing factors were analyzed by response surface method, and the optimal solution of bond strength was obtained. • A new bond-slip constitutive model is proposed, which has wide applicability and accuracy. [ABSTRACT FROM AUTHOR]

The effects of ageing on pavement performance are significant, particularly in terms of fatigue cracking. South Africa has the 10th longest road network in the world, requiring innovative approaches to road construction due to severe budget constraints. Innovative solutions such as thin asphalt concrete layers for surfacing, result in unique ageing rates of the layers, which, in general, have a higher incidence of fatigue cracking than, for example, thicker asphalt concrete layers used in other parts of the world. The objective of this paper is to evaluate how ageing mechanisms affect various asphalt binder properties, and whether they affect them to the same extent or not. Furthermore, the objective of the paper is also to determine the accuracy of the Rolling Thin Film Oven Test (RTFOT) in simulating short-term ageing in the field. The RTFOT provides a relatively good indication of short-term ageing, according to this multi-decade ageing study, and the effect on the asphalt binder properties used as ageing indices depends on the specific property chosen for comparison before and after ageing. • From 2001 to 2012, the prevalent surfacing in South Africa was a dense-graded asphalt mix with 50/70-grade asphalt binder. • Asphalt binders were consistent over 2001 to 2012, originating from four South African refineries. • A short-term ageing method in the laboratory cannot emulate the reaction kinetics during manufacturing and placement. • Binder properties such as penetration and softening are affected to different extents in an oxidation / ageing environment. • The rolling thin film oven provides a good indication of ageing under typical conditions of manufacturing and laying. [ABSTRACT FROM AUTHOR]

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

Eucalyptus is one of the most important plantation species in South China. Alternate applications of plantation grown hardwood such as eucalyptus need to be developed due to decreased demands of fibers for pulp and paper industry. The feasibility of manufacturing three-layer cross-laminated timber (CLT) using fast-grown small diameter eucalyptus wood ( Eucalyptus urophylla × Eucalyptus grandis ) was evaluated in this study. L 9 (3 3 ) orthogonal tests with three factors and three levels were adopted to study the effects of adhesive spread rate, pressure, and pressing time duration on the block shear strength (BSS), wood failure percentage (WFP), and rate of delamination (RD) of CLT via block shear tests and cyclic delamination tests. The results indicated that the optimal pressing parameters were adhesive spread rate of 160 g/m 2 , pressing pressure of 0.8 MPa, and pressing time duration of 200 min with one-component polyurethane adhesive used. The values of modulus of elasticity (MOE) and modulus of rupture (MOR) in the major and minor strength directions of CLT were 11,466 MPa, 24.5 MPa, 681 MPa, and 8.6 MPa, respectively. The values of transverse shear moduli and interlaminar shear strength in the major and minor strength directions of CLT were 91.8 MPa, 1.3 MPa, 241.6 MPa, and 0.5 MPa, respectively. The mechanical properties of eucalyptus CLT were equivalent to those of commercially available softwood CLT. These results indicate CLT panels manufactured from fast-grown small diameter eucalyptus lumber is promising for structural applications. [ABSTRACT FROM AUTHOR]

The paper evaluates the sensitivity of sonic tomography imaging of historic masonry structures to variations in stress level and damage. Six stone masonry walls with different geometries representative of historical typologies were constructed by a professional mason. A laboratory campaign was carried out, subjecting the walls to cyclic uniaxial compression tests. During the test, an automated sonic tomography system was used to inspect the wall under loading cycles of increasing amplitude, which led to obtain tomographic images during loading and compare them under different stress level and damage condition. The use of robotic systems was proved essential to carry out the sonic inspections simultaneously to the compression tests. Results show that sonic wave propagation is not only sensitive to damage level, but also to the stress state. Thus, sonic tomography has the potential to be used to measure damage and stress level of masonry components over time, for example during renovation works on an existing construction. • A novel automated sonic tomography system has been used to inspect masonry walls during laboratory tests. • Sonic tomography of stone masonry structures is sensitive to variations in the stress level and damage propagation. • Automated sonic tomographic systems may be used to monitor historic buildings during construction works. • The paper explores the correlation between the sonic wave velocity through stone masonry and material properties. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of CO 2 concentration and water on bonding strength evolution of the steel-concrete interface, this paper studied the carbonation process at the steel-concrete interface of composite samples in dry gas, pure water and 70% relative humidity (RH) environments with 100 kPa, 500 kPa and 1000 kPa CO 2 partial pressures. The results showed that the formation of aragonite and Fe(OH) 3 at the interface had a negative effect on the bonding strength, while the formation of calcite at the interface had a positive effect on the bonding strength. Also, the reaction environment had a noticeable effect on Fe-bearing corrosion products formed at the interface. In summary, if the concentration and the pressure of CO 2 reach a certain level (i.e., 100% concentration and 1000 kPa partial pressure or higher) and abundant water is present, the CO 2 -induced carbonation of concrete and corrosion of steel can eventually lead to damage at the steel-concrete interface. • This paper studied the mechanical degradation of the steel-concrete interface caused by high concentration CO 2. • A pure water environment induced formation of aragonite and Fe(OH) 3 , which caused a decrease in the bonding strength at the interface. • A dry gas environment induced formation of calcite, which caused an increase in the bonding strength at the interface. [ABSTRACT FROM AUTHOR]

To address the challenge posed by traditional methods of modifying recycled concrete aggregates (RCA), which struggle to achieve properties comparable to natural coarse aggregates (NCA) while ensuring a high utilization rate, this paper proposes a combination of freeze-thaw modification and sodium silicate modification. The process subjects the RCA to freeze-thaw cycles (FTC) to detach the attached mortar, which results in the extraction of recycled aggregates (Near-NCA) with properties similar to NCA, along with the spalling mortar (SM). These materials are used in the recycled concrete and mortar, respectively. Considering the inferior properties of SM, sodium silicate solutions are employed to modify it, serving as a replacement for river sand in the recycled mortar. The outcomes reveal that concrete cast using Near-NCA demonstrates mechanical properties comparable to ordinary concrete. Furthermore, the sodium silicate proves to be effective in modifying SM, reducing its crushed index and water absorption by approximately 30%. Through the SEM and XRD, it is determined that these improvements can be attributed to the formation of C-S-H gel. Finally, a multi-objective model is developed to consider modification effects, carbon emissions, energy consumption, economic and time costs, with the utilization of TOPSIS for determining the optimal modification plan. • This paper proposes a method that combines freeze-thaw modification with mineralization strengthening. • Modifying spalling mortar with sodium silicate solution can improve its various properties. • The modification mechanism of sodium silicate is investigated through microscopic tests. • The TOPSIS method is utilized to obtain the optimal modification scheme considering multiple objectives. [ABSTRACT FROM AUTHOR]

Using geopolymer concrete (GC) is a technically feasible decarbonization strategy in the cement and concrete industry shown by numerous papers. A key factor determining its commercial application is whether its cost is competitive. However, related study is scarce. In this paper, we present the analysis of GC's CO 2 avoidance cost, the cost incurred to reduce one metric ton of CO 2 emissions. The results show that among the 486 GC mixtures analyzed, only seven yield negative CO 2 avoidance costs, while 379 are even more expensive than capturing CO 2 from cement plants, which is another technically feasible decarbonization strategy and has been evaluated to have a CO 2 avoidance cost of 55 USD/tCO 2 in Chinese demonstration project. Only a few GC mixtures with lower CO 2 avoidance costs will be considered by the industry, and they are associated with low activator dosage and high compressive strength. To quantify this relationship, we introduce the activator index (Ai), which refers to the activator dosage (kg·m−3) required to achieve 1 MPa of compressive strength. The result shows that Ai values below certain thresholds correspond to lower CO 2 avoidance costs and significant emission reductions of GC. This Ai -based criterion helps identify the optimal GC mixture that effectively reduces CO 2 emissions at the lowest possible cost, thereby promoting its commercial application. [Display omitted] • Only 7 of 486 geopolymer concrete (GC) mixtures have negative CO 2 avoidance costs. • CO 2 avoidance costs of most GC in literature exceed CO 2 capture. • The lower activator dosage per MPa strength, the lower CO 2 avoidance cost of GC. [ABSTRACT FROM AUTHOR]

Nowadays 3D-printing technology is part of many construction processes in different engineering fields, thanks to the possibility of precisely reproducing the shape of complex elements and the availability of different printing materials. In this context, the paper presents the results of tensile experimental tests on samples 3D-printed in PLA (PolyLactic acid), and analyse the effect of the printing process and aging test. Referring to the interest in producing smart components, some samples were printed with an embedded single-mode fiber optic with acrylate coating, commonly used for FOSs (fiber optic sensor). In particular, some samples were produced with pristine optical fiber to test the procedure, while others were produced with the FBG (Fiber Bragg Grating) sensor. The results are discussed in terms of strength and stiffness in both pre-peak stage and post-peak one (ductility and softening), and the functionality of the embedded FBG sensors in operating as strain sensors is reported. • The paper deals with tensile test on dog-sample sample 3D printed in PLA. • The effect of the printing direction on the tensile behavior of PLA samples is investigated. • The effect of aging test on the tensile behavior of PLA samples is investigated. • A multi-phase printing process is adopted to include optical fiber for monitoring is presented. • The FBG sensor has been introduced in the 3D printed samples. [ABSTRACT FROM AUTHOR]

Many challenges persist with traditional self-sensing cementitious composites, such as selecting conductive fillers, determining optimal aspect ratios, controlling dosage, achieving filler dispersion, designing practical electrodes, and overcoming fabrication difficulties. Therefore, this paper proposes a novel self-sensing technique for cementitious composites by incorporating a 2-dimensional (2-D) carbon-fibre textile network to address these challenges. Additionally, instead of using the entire composite volume as the sensor, an alternative approach is explored, which involves utilising the interlaminar interface by incorporating the 2-D carbon-fibre textile network. This approach provides an integrated self-sensing system, including electrical leads and conductive pathways, which can be tailored based on the design requirements. The paper introduces fundamental concepts and measurement circuit design, followed by a comprehensive study covering measurement techniques, electromechanical properties, and microstructural analysis. Furthermore, it discusses the impact of ambient conditions, such as temperature and relative humidity, on the measurements. Experimental results demonstrate a remarkable maximum fractional change in contact resistivity, reaching up to 70%. The reversibility during cyclic compression is excellent, with a maximum negative gauge factor of − 2500. These findings represent a significant step toward achieving a practical and simplified method for manufacturing self-sensing cementitious composites and open avenues for self-sensing, sustainable textile-reinforced concrete structures (TRC). [Display omitted] • A novel self-sensing system for cementitious composites has been introduced. • The system can be considered as an integrated solution, encompassing the essential components required for self-sensing. • A simplified equivalent circuit model and an equation to calculate the overall contact resistivity have been proposed. • A remarkable maximum fractional change in the overall contact resistivity, reaching up to 70%, has been achieved. • The reversibility during cyclic compression has been excellent, with a maximum negative gauge factor of − 2500. [ABSTRACT FROM AUTHOR]

Using recycled tyre polymer fibres (RTPF) to replace part of polyvinyl alcohol fibres (PVAF) is a strategy to produce green and economical engineered cementitious composites (ECC). This paper systematically investigated the influence of RTPF dosage (0.25–1.0 vol%) on split tensile performance of ECC under different strain rates. Results indicated that replacing PVAF with RTPF up to 0.5 vol% could still show a pronounced strain-hardening behaviour for ECC, although accompanied by a decrease in static split tensile strength. The dynamic split tensile performance of all ECC mixes was strongly sensitive to strain rate and all hybrid fibre reinforced ECC presented a greater strain rate effect than the mono-PVAF reinforced ECC. Under dynamic split tension, the specimens with various RTPF dosages could maintain their structural integrity. This paper suggested that RTPF can be adopted to replace part of PVAF to produce a greener and more economical ECC with satisfactory static and dynamic mechanical performance but the highest substitution amount should be set to 0.5 vol%. • The split tensile resistance of ECC was evaluated under strain rates up to 101 s−1. • The influence of RTPF replacement content on dynamic performance was investigated. • Acceptable dynamic split properties can be achieved through replacement of RTPF. • The DIF fitting model of green ECC was developed using the improved bilinear model. [ABSTRACT FROM AUTHOR]

The hydrophobicity nature of the waste carbon fiber felt (WCF) surface results in the formation of a weak interface with the paste during the curing process of WCF concrete, which seriously affects the performance of WCF concrete and the reuse of WCF. To address this problem, this paper utilized polydopamine (PDA) for the functionalization of WCF to enhance bonding between WCF and paste. The wettability, Ca2+ complexation, and functional groups of PDA coating on WCF were analyzed by contact angle, ICP-OES, and XPS, respectively. Additionally, the effects of incorporating PDA-functionalized WCF on the flowability, compressive strength, hydration kinetics, pore structure, water absorption capillary, and SEM of mortars were tested. Experimental results showed that the PDA coating improved the wettability of WCF and enhanced the flowability of WCF mortar. What's more, the PDA coating could chelate Ca2+ and promote the formation and deposition of hydration products on the WCF surface, resulting in a denser interfacial transition zone (ITZ). Compared with ordinary WCF mortar, the compressive strength of the PDA-modified WCF mortar was increased by 18% at 28d. Furthermore, the capillary water absorption of the modified group mortar was also decreased by up to 13%, significantly enhancing the durability of mortars. This paper presents a green and simple bio-inspired method to strengthen the ITZ between WCF and paste, which is fundamentally different from the traditional modification methods, and also offers a theoretical basis and technical foundation for the sustainable utilization of WCF. • Introducing hydroxyl and amino groups on WCF using PDA. • The contact angle of WCF was maximum decreased to 40.49°. • The interface gap of WCF/paste was enhanced owing to the chelation of PDA with Ca2+. • The compressive strength of WCF mortars modified by PDA was improved from 39.43 MPa to 46.52 MPa at 28d. [ABSTRACT FROM AUTHOR]

Capillarity has an important effect on the durability of buildings, and the capillary absorption coefficient is a key parameter to describe the strength of material capillarity. Most of the methods currently used to measure the capillary absorption coefficient of materials can damage the sample or are not accurate enough and need to be improved. This paper proposes a method to measure the capillary absorption coefficient of brick, sandstone, mortar and concrete by using a single-sided nuclear magnetic resonance (NMR) technique, which has the advantages of accuracy, nondestructiveness, continuity and rapidity. The relative error of the capillary absorption coefficient obtained from three repetitions of the experiment ranges from 0 to 5.11%, which is in the range of 0.64%∼1.30% compared with that obtained by the partial impregnation method. This method has great potential for application in in situ testing. This paper also analyzed the water transport behaviors in porous building materials based on the variation in NMR signal intensity in the measured materials and established a water transport model. The model is divided into two stages: the first stage is mainly the one-dimensional rise in moisture in the vertical direction. The second stage is mainly the diffusion of moisture in the horizontal direction, which continuously fills each pore space to saturation. Difficulty in removing air leads to a reduced rate of water absorption in the second stage. • A method is presented for measuring capillary absorption coefficients of porous building materials using single-sided NMR. • The water absorption behavior of porous building materials was analyzed. • A water absorption model is proposed for porous building materials. • The feasibility of conducting in situ measurements using single-sided NMR is discussed. [ABSTRACT FROM AUTHOR]

The thermal cracking of asphalt pavement has been the focus of research in cold regions of the world. The contraction and relaxation properties of asphalt mixtures were crucial for investigating the thermal stress of asphalt pavement based on the thermal cracking mechanism. This paper proposed a novel evaluation index for characterizing the low-temperature performance of asphalt mixtures by considering their contraction and relaxation properties. Firstly, the rank during the evaluation indexes for low-temperature performance was determined by comparative analysis of method. Secondly, the thermal contraction coefficient was used to characterize contraction properties and cumulative stress at per unit strain rate (CSSR) was used to characterize relaxation properties in this paper. According to the cumulation process of thermal stress, a novel index was constructed based on the contraction and relaxation properties. Finally, considering the correlation between the failure temperature and the novel indexes, the prediction model of low-temperature performance consistent with the order of failure temperature was established based on the multiple linear regression method. Through the standardized analysis of the prediction model, the influence of novel indexes for the low-temperature performance of asphalt mixtures under different temperature conditions was clarified. A novel evaluation index provided a theoretical basis for unifying the evaluation indexes of asphalt mixtures. • Analyze the relationship between different evaluation indexes for low temperature performance. • Propose a novel evaluation index for characterizing the low-temperature performance. • Establish a prediction model of the low-temperature performance. [ABSTRACT FROM AUTHOR]

Basalt fiber (BF) is an emerging environmentally-friendly fiber. Adding basalt fiber can improve the deficient recycled concrete's poor mechanical properties and durability. By reviewing nearly 120 related papers, the effects of variables such as BF content and length (0–1.5%, 9–18 mm), recycled aggregate substitution rate (0–100%), and cement mix ratio (w/b, 0.25–0.45) on the mechanical and durability properties of basalt fiber-reinforced recycled concrete (BFRAC) were discussed. Due to the presence of vulnerable interfacial transition zones, the mechanical properties of recycled concrete (RAC) continuously deteriorate over time. However, by adding an appropriate amount of basalt fiber, it is possible to improve these structural defects by forming a network structure that enhances cracking resistance within the matrix and improves interface bonding strength among other benefits. Consequently, this significantly improves the overall mechanical properties of RAC. Additionally, while incorporating recycled aggregate (RA) may reduce compressive strength initially, this deficiency can be mitigated through the proper inclusion of fibers in RAC mixtures. Optimal compressive strength for RAC is achieved with a replacement ratio between 25–50% and a fiber content ranging from 0.2–0.3%. Furthermore, properly incorporating fibers into RAC greatly enhances splitting tensile strength and flexural strength as well; specifically achieving optimal splitting tensile strength with a replacement ratio between 40%− 50%, a fiber content at 0.3%, and utilizing fibers with lengths measuring approximately 12 mm long. The primary cause for poor frost resistance in RAC lies within numerous micro-cracks and pores present in RA aggregates which lead to high water absorption rates ultimately reaching critical water saturation points resulting in freeze-thaw damage occurrences during exposure to freezing conditions. When exposed to sulfate attack, RAC undergoes a chemical reaction with sulfate ions present in the concrete, leading to the formation of numerous expansion products that negatively impact concrete performance. Progressive dehydration of hydration products under high-temperature conditions leads to a porous structure within the concrete matrix. Incorporating fibers can impede microcrack expansion during freeze-thaw, sulfate attack, and high-temperature environments, thus enhancing the erosion resistance of RAC. Compared to conventional concrete, interfacial bonding in RAC is less tight and more vulnerable to damage in complex environments. Current research on RAC suggests that the mechanism behind its damage under complex freeze-thaw load coupling environments remains unclear. It is recommended that future studies combine large-scale component tests with computational simulations to address this issue. • This paper discusses the mechanical properties and durability of BFRAC. • Numerous micro-cracks and pores in RA cause high water absorption. • When exposed to sulfate attack, CH reacts with SO2- 4 to form expansion products. • Hydration products' dehydration at high temperatures results in loose of concrete. • BF inhibits the growth of microcracks and enhances its erosion resistance. [ABSTRACT FROM AUTHOR]

This paper presents a study on the durability testing of a concrete facility located within the North Bay Port region, which has been in service for 200 months. Based on the results of 20 sets of concrete samples, an improved Kolmogorov-Smirnov (K-S) test method and gross error discrimination method are proposed to analyze the random distribution functions of the apparent chloride diffusion coefficient (D app) and the apparent surface chloride concentration (C s), and further explore the time-varying characteristics of chloride ion transmission in concrete. The research shows that the improved K-S method presented in this paper can effectively reduce the probability of type II errors by selecting a rational sample size, which can also improve detection efficiency. When the sample size does not exceed 10, the 2 σ criterion proposed in this paper can effectively identify and eliminate gross errors. In general, D app and C s follow the log-normal distribution, while the time factor (m) follows a normal distribution parameter. The value of C s basically stabilized after exposure to 80 months, whereas D app tended to stabilize after exposure to 100 months. The value of m obtained through fitting short-term experimental data is typically overestimated, and its value decreases as the exposure time prolongs. Therefore, m should also be considered a time-varying parameter that decreases with time. The tested RC structure will begin to experience rebar corrosion after 48.5–60 years of exposure to the marine environment based on the probabilistic assessment. • The 2 σ criterion was introduced to identify and rectify significant errors. • The improved K-S method was developed to minimize the likelihood of type II errors. • Chloride profiles were extracted from 200 months aged harbor concrete structures. • Both D app and C s demonstrated a good fit with the log-normal distribution. [ABSTRACT FROM AUTHOR]

The ultimate capacity of pultruded glass fibre reinforced polymer (pGFRP) profiles depends significantly on geometrical imperfections (GIs), given their sensitivity to buckling phenomena arising from both thin walls and low elastic moduli. However, GIs are not yet comprehensively addressed in design guidance. This paper proposes a new approach to characterize the initial GIs of pGFRP profiles based on a modal approach. Given the lack of comprehensive knowledge in this area, this study presents a highly accurate and robust methodology to measure GIs and dimensional deviations (DDs) in pGFRP profiles using a 3D contact coordinate measurement machine (CMM). The modal approach encompasses the measurement of dimensional parameters and a point cloud transformation that enables the assessment of GIs associated with pure buckling modes of pGFRP profiles. This procedure allows the quantification of three types of global GIs associated to (i) minor-axis (weak axis), (ii) major-axis (strong axis) bending, and (iii) twist. Additionally, the procedure also includes the assessment of local GIs, considering the wall (plate-like) imperfections. The separation of GIs into these four types (shape and amplitude) is of major relevance as its paves the way to the development of analytical design formulas for the strength prediction of pGFRP members. The approach described in this paper also serves two important purposes: (i) the statistical analysis of DDs and GIs of pGFRP members, and (ii) the identification of distinct shapes and amplitudes of GIs that form the basis for reliable design considerations of pGFRP members. [Display omitted] • Measurement of geometric imperfections (GIs) in prismatic pGFRP profiles with automated 3D coordinate measuring machine. • Shapes and amplitudes of GIs identified with a modal approach. • Integration of GIs in FE model with damage initiation and propagation. • Towards a comprehensive dataset of GIs and reliable strength predictions. [ABSTRACT FROM AUTHOR]

The use of corrosion inhibitors for steel rebar in concrete is one of the best-demonstrated methods to mitigate the corrosion process and extend the service life of reinforced concrete structures exposed to chloride laden environment. However, the research progress on corrosion inhibitors for reinforcing steel is slow and classical, as the traditional experimental methods revealed. Recently, the application of computational methods, such as density functional theory (DFT) and molecular dynamics (MD) simulation, to corrosion research has become an essential area for gaining more insights into the detailed mechanisms of corrosion as well as identifying ways and means of technological innovation. This paper presents a systematic review of the research progress and advances in the molecular simulation of corrosion inhibitors for steel in concrete. The DFT calculations conducted on different inhibitor molecules were reviewed, and the related theoretical chemical reactivity parameters along with the donor-acceptor process were discussed. In addition, the MD simulations of various molecule/surface adsorption systems were studied, considering different steel substrates. The valuable insights gained from the computational models were introduced and consolidated into the experimental inhibition efficiency. Finally, the challenges and future perspectives of the research topic are highlighted. This paper is believed to promote the utilization of theoretical methods in corrosion research of reinforcing steel for a deep understanding of the corrosion process at the atomic level and innovative design of corrosion-resistance materials. [Display omitted] • Atomistic modeling and simulation of corrosion inhibitors for reinforcing steel are reviewed. • Research progress and advances are highlighted. • Theoretical reactivity parameters and adsorption behavior are correlated to experimental inhibition efficiency. • Molecular modeling provides a fundamental understanding of the corrosion mechanism. • Computational methods can derive the innovation process for corrosion-resistance materials. [ABSTRACT FROM AUTHOR]

The global production of concrete, being one of the most commonly utilised materials in the world, is associated with significant CO 2 -emissions and a substantial depletion of mineral resources. In order to improve sustainability, concretes thus are increasingly produced using recipes containing a large variety of different raw materials, including e.g. CO 2 reduced cements or recycled materials and industrial wastes. However, these actions result in heightened susceptibility of the concrete to variations in raw material characteristics, consequently diminishing the concrete's resilience and decreasing the concrete's robustness. Against this background, the quality control of fresh concrete before casting becomes of significant importance. However, current quality control is mainly conducted based on analogous, empirical, and often subjective test approaches. In this paper, a novel method is introduced for automatically and comprehensively evaluating the quality of fresh concrete at construction sites. In particular, the paper presents an end-to-end trainable framework for the image-based characterisation of fresh concrete properties. More specifically, a camera-based setup is proposed, in which image sequences of the discharge process of a mixing truck are acquired, on the basis of which the fresh concrete properties such as the consistency and rheology are determined. In this context, this paper introduces the concept of Spatio-Temporal Flow Fields , which provide a compact representation of the concrete's flow behaviour and serve as input to a multi-task convolutional neural network (CNN) predicting the target parameters describing the fresh concrete's properties. A thorough examination of the performance of the suggested method is carried out using highly challenging real-world data, showcasing extremely compelling outcomes with average prediction errors for the concrete properties of only about 6%. [Display omitted] • Novel strategy for camera-based characterisation of fresh concrete from flow observations. • Proposal of Spatio-Temporal Flow Fields as compact representation of the open-channel concrete flow. • A multi-task CNN predicting both, the fresh concrete's consistency and rheology • Highly promising results on a challenging real-world data set. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of temperature on autogenous deformation and early-age stress (EAS) evolution in ordinary Portland cement paste using a recently developed Mini Temperature Stress Testing Machine (Mini-TSTM) and Mini Autogenous Deformation Testing Machine (Mini-ADTM). In the Mini-TSTM/ ADTM, CEM I 42.5 N paste with a water-cement ratio of 0.30 was tested under a curing temperature of 10, 15, 20, 25, 30, and 40 °C. X-Ray diffraction (XRD) tests were conducted to measure the amount of ettringite and calcium hydroxide, which reveals the micro-scale mechanisms of autogenous expansion. The applicability of the Maturity Concept (MC) for the prediction of autogenous deformation and relaxation modulus under different temperatures was also examined by the experimental data and the viscoelastic model. This paper leads to the following findings: 1) The autogenous deformation of ordinary Portland cement paste is a four-stage process comprising the initial shrinkage, autogenous expansion, plateau, and autogenous shrinkage; 2) Higher temperature leads to higher early-age cracking (EAC) risk because it accelerates the transitions through the first three stages and causes the autogenous shrinkage stage to start earlier. Moreover, higher temperatures also result in increased rates of autogenous shrinkage and EAS in the autogenous shrinkage stage; 3) Autogenous expansion and plateau are attributed to the crystallization pressure induced by CH. Temperature-dependent CH formation rates determine the duration of the plateau stage; 4) Low-temperature curing can delay but not completely prevent the EAC induced by autogenous deformation; 5) The MC cannot predict the autogenous deformation at different temperatures but can be used to calculate the relaxation modulus, which in turn aids in EAS prediction based on autogenous deformation data. • The effects of temperature on early-age cracking risk induced by autogenous deformation is systematically analysed. • The autogenous deformation and the stress evolution were tested by a mini–Temperature Stress Testing Machine. • The effects of calcium hydroxide on autogenous expansion were found. • A viscoelastic model combined with maturity concept was developed to predict the stress evolution. [ABSTRACT FROM AUTHOR]

Metaconcrete, as a new type of composite material with vibration attenuation characteristics, is formed by replacing traditional coarse aggregates with a heavy metal core wrapped with an elastic soft coating and mixing with cement mortar. However, due to the high bandgap frequency and narrow bandgap width, it is greatly limited in the engineering application of low frequency vibration control. In order to broaden the range and number of elastic wave bandgap of metaconcrete materials and solve the problem of low frequency vibration, a novel three-component cement-based phononic-like crystal model is proposed based on local resonance theory, and phononic-like crystal metaconcrete vibration reduction material is developed accordingly. Secondly, the band structure, bandgap mechanism, and frequency response function of the phononic-like crystal metaconcrete are calculated and analyzed, and indoor tests of the phononic-like crystal metaconcrete are conducted. Finally, a phononic-like crystal metaconcrete subway track bed is prepared using the developed phononic-like crystal metaconcrete material, and applied to the practical subway engineerings to solve the low frequency vibration problem generated during subway operation. The results show that the phononic-like crystal metaconcrete opens 6 low frequency bandgaps in the frequency range of 200 Hz, and the attenuation values are mostly above 10 dB in the frequency range of the bandgap, and the attenuation effect is good. Meanwhile, the on-site monitoring results show that the phononic-like crystal metaconcrete subway track bed has good low frequency vibration reduction effect in the 200 Hz frequency range. The maximum value of the one-third octave insertion loss of the tunnel wall is 13.22 dB, the maximum vertical Z-vibration level difference of the tunnel wall is 5.052 dB, and the maximum vertical frequency division vibration level difference of the tunnel wall is 5.926 dB. The maximum value of the vertical frequency division vibration level difference in the frequency range of 4–200 Hz is 13.87 dB, and the average value is 5.74 dB. The relevant research results of this paper provide a new technical approach to solve the problem of low frequency vibration in subway engineering and other engineering construction, breaking through the traditional vibration reduction control technology of civil engineering structures, and providing new idea and method for long-term vibration reduction and application of engineering structures. • This paper develops phononic-like crystal metaconcrete vibration reduction material. • The material can open multiple low frequency vibration reduction bandgaps. • The material is used to prepare a new type of subway vibration reduction track bed. • The subway track bed has remarkable low frequency vibration reduction performance. [ABSTRACT FROM AUTHOR]

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

This paper is focused on the effect of initial pretension on the dynamic bond performance of the anchorage under impact loads. Drop-weight impact tests were conducted on 15 groups of specimens with four embedded lengths and various pretension ratios; the effects of pretension and embedded length on the bond strength and slip of the anchorage are discussed in the paper. The test results show that a higher pretension ratio led to severer surface damage on the CFRP tendons. With the increase of the pretension ratio, the mechanical interlocking between CFRP ribs and UHPC was improved, leading to an increased average bond strength. By contrast, the relatively large shear deformation and severe damage of CFRP ribs induced by pretension formed "initial defects", which resulted in a lower residual bond performance during impact loading. Based on the test results, a pretension ratio-dependent strength retention function was proposed to quantify the shear damage effect of CFRP ribs caused by pretension; by incorporating this function, accurate formulas were developed for determining the dynamic bond strength of a pretensioned anchorage. • Drop-weight impact tests were conducted on UHPC-filled bond-type anchorages for CFRP tendons under different initial pretensions. • The initial pretension enhanced the mechanical interlocking between CFRP ribs and UHPC, which led to an improved dynamic bond strength of the anchorage. • Accurate formulas were developed for determining the dynamic bond strength of a pretensioned anchorage. [ABSTRACT FROM AUTHOR]

The disposal of steel slag in landfills not only squanders precious landfill resources but also results in significant environmental contamination. Steel slag can be used to replace cement and natural aggregates in concrete. Nonetheless, utilizing untreated steel slag directly presents a substantial hazard to the structural characteristics and durability of concrete. To avoid this problem, study on accelerated carbonation of steel slag as construction materials has been extensively conducted. This review paper begins by introducing the classification and physicochemical properties of steel slag; it then describes the typical approaches of steel slag carbonation, including direct carbonation (dry carbonation, wet carbonation) and indirect carbonation (pH-swing, microbial carbonation), along with their processes and carbonation mechanisms. Furthermore, based on the reviewed literature, the influences of various reaction parameters such as reaction time, liquid-to-solid ratio, temperature, additives, CO 2 concentration, pressure, pH on carbonation effectiveness are analyzed. Also, the impact of carbonated steel slag on the micro-pore structure, stability, workability, and mechanical properties of concrete is discussed. Finally, the challenges and future work of using carbonated steel slag as construction materials are provided. • The current papers on steel slag classification, physicochemical properties, and methods for accelerated carbonation are reviewed. • The traditional carbonation methods, as well as recently proposed microbial carbonation methods are analyzed. • The factors influencing the efficiency of steel slag carbonation are summarized. • The impact of carbonated steel slag on concrete properties are concluded. • Insights into accelerated carbonation methods for steel slag and future work are provided. [ABSTRACT FROM AUTHOR]

Flexible and rigid pavements are commonly built for airport pavements to support the moving loads of aircraft during the pavement design life. At the planning stage, the pavement structure, materials, aircraft loads, environmental conditions, and pavement damage models should be evaluated. Comparing with road pavement design, airport pavement structural design is unique in terms of the traffic loads supported by pavements with high load magnitude, significant tire pressure, and dynamic traffic conditions. With the transition from conventional empirical design to mechanistic-empirical approaches, the mechanistic-empirical approaches are adopted in the various computer programs as the main methods for pavement structural design. The methods developed by the Federal Aviation Administration (FAA) and other approaches of airport pavement structural design are discussed in this paper to compare their analysis methodology and identify the advancement of each design method. A highlight of this paper is to examine the recent specifications for airport pavement structural design (FAA AC 150/5320–6 G) and the structural evaluation (FAA AC 150/5335–5D) released by the FAA. In addition, in order to support the maintenance and rehabilitation (M&R) strategy, the pavement structural condition and material properties can be assessed by a Falling Weight Deflectometer (FWD) or a Heavy Weight Deflectometer (HWD) test. Future structural design of airport pavements should consider potential pavement failure patterns caused by complex gear loading types, and continuous pavement M&R using FWD or HWD tests. • Airport pavement structural design is unique in terms of the traffic loads. • The difference between traditional empirical and mechanistic methods is reviewed. • The latest specifications for airport pavement structural design are reviewed. • The application of nondestructive tests in the pavement design is reviewed. • The maintenance and rehabilitation (M&R) strategies of pavements are reviewed. [ABSTRACT FROM AUTHOR]

According to a recent estimate, over 1.5 billion wasted tyres which containing over 40% of vulcanised rubber and 15% of steel fibre are discarded yearly, which posing a serious threat to circular economy implementation and transition to net zero. To minimise the greenhouse gas(GHG) emission and the environmental side effect caused by burning and burying these waste tyres, recycling and reusing these materials for sustainable structural designs has become the centre of attention. This paper focuses on applying recycled bead steel fibre to improve the shear capacity of fibre-reinforced concrete beams. Moreover, the existing national standard known as Eurocode 2 and TR63 can hardly illustrate the relationship between fibre and high-strength concrete. This study is the first to investigate shear behaviours of high-strength industrial and recycled steel fibre reinforced concrete beams with consideration of different shear span ratios. Therefore, twenty real-scale beams are constructed to examine the shear capacity of high-strength industrial and recycled steel-fibre reinforced concrete beams, which aims to compare the improvement of shear strength through experiments and identify different shear strength improvements of the two categories of steel fibre. Besides, comprehensive data of 164 beams from previous studies have been collected to benchmark with the experimental results for the formula design. This study proves the feasibility of replacing industrial steel with recycled steel fibre to improve the shear capacity of fibre-reintroduced concrete beams. Moreover, there are six novel equations designed developed using Eurocode 2 and TR63 as a basis in this study. Based on the findings of the paper, the proposed formulas demonstrate remarkable accuracy, with an average value of 0.982 and standard deviation of 0.213, respectively. Following an exhaustive comparison of RSF and ISF reinforced concrete beams, with a focus on economic expenditure and GHG emissions, it can be concluded that RSF offers superior economic and environmental benefits, which reduce the emissions up to 25.39% and price up to 28.04% when replacing ISF 0.8% RSF, respectively. • This study stems from full scale experiments using recycled steel fibres. • It is the first to establish sustainable design framework for fibre reinforced concrete beams. • Sustainability design and assessments of recycled steel fibre reinforced concrete is established. • The outcomes highlight new pragmatic technical solutions to reduce wastes and implement circular economy. • The insight will enable an innovative alternative to achieve net-zero infrastructures. [ABSTRACT FROM AUTHOR]

Direct injection modifiers revealed vast development potential because of their convenience utilization and no need for professional equipment. However, different characteristics of each direct injection modifier fluctuate significantly on the mixing process and road performance of their modified asphalt mixtures. The purpose of this paper is to evaluate the effectiveness of two novel asphalt rubber pellets (ARP) and asphalt desulfurized rubber pellets (ADRP) in improving the performance of asphalt mixtures. Firstly, this paper used orthogonal experimental design method to determine the priority order of the influencing factors on direct injection modifiers (ARP and ADRP), and further optimized the mixing technology of asphalt mixtures containing direct injection modifiers. Then, using base asphalt, commercial asphalt rubber (AR) and SBS (styrene-butadiene-styrene block copolymer) modified asphalt as control groups, the road performance of five asphalt mixtures was evaluated. Finally, the volatile organic compounds (VOCs) release characteristics of the asphalt mixtures were quantitatively analyzed. The results indicated that the priority order of factors affecting the ARP and ADRP is digestion time > dry mixing time > mixing temperature, and the optimal mixing process parameters are dry mixing for 90 s, mixing temperature of 180 °C, and digestion time of 90 min. Additionally, road performance of ADRP modified asphalt mixtures (ADRP-AM) is superior to that of ARP modified asphalt mixture (ARP-AM), which reaches or even exceeds the road performance of asphalt rubber mixtures (AR-AM) and SBS modified asphalt mixtures (SBS-AM) prepared by wet process. The five asphalt mixtures demonstrate the similar VOCs composition, and the total concentration of VOCs emissions is ARP-AM > AR-AM > ADRP-AM > B-AM > SBS-AM. P-/m-xylene, acetone, benzene, ethylbenzene and substances containing chlorine emerge high concentration for the VOCs composition of the five asphalt mixtures. This research can provide technical support for promoting the widespread application of direct injection asphalt rubber pellets. • Mixing technology of asphalt mixtures containing direct injection asphalt rubber pellets were optimized. • Road performance of asphalt mixtures containing direct injection asphalt rubber pellets were investigated. • VOCs of asphalt mixtures containing direct injection asphalt rubber pellets were evaluated. [ABSTRACT FROM AUTHOR]

Modified bitumen is a critical material to ensure the durability of asphalt pavements. Traditional polymer-modified bitumen (PMB) has been widely researched and applied in the past two to three decades. Recently, a high-content SBS (Styrene-Butadiene-Styrene) polymer-modified bitumen (HSBSMB) with a higher SBS content of up to 7–9% by weight has started attracting interest from researchers. There are, however, still few specifications or technical guidelines for HSBSMB. To gain a better understanding of HSBSMB, the composition and structure of typical polymer SBS and base bitumen, the micromorphology and micromechanics of HSBSMB, its rheological and aging characteristics, as well as its asphalt mixture and field pavement performance were reviewed comprehensively in this paper. The content covered in this paper is primarily derived from 210 pertinent papers published between 1990 and 2023 in two databases, Web of Science and Google Scholar. It appears from our review that HSBSMB has a stronger internal polymer network than conventional SBSMB and thus exhibits better resistance to rutting, fatigue, and cracking as well as better aging resistance. Furthermore, findings from both laboratory scale and field pavement scale indicate that HSBSMB not only offers higher performance and durability but also leads to reduced pavement structural layer thicknesses in ensuring performance. However, many issues and challenges still remain before HSBSMB will become a viable option for large-scale application in road infrastructure, aspects such as the mechanism of its internal structural changes, the optimization of methods for evaluating its rheological properties, the life cycle assessment of its long-term benefits, as well as the storage stability and workability of HSBSMB. It is hoped that this review will contribute to a better understanding of HSBSMB and promote its application. • The chemical properties of SBS polymer and base bitumen as well as their interactions were comprehensively summarized. • The mechanisms of SBS in bitumen and polymer phase inversion were discussed under different microscopy techniques. • The current standard rheological evaluation methods may need to be improved for high-content SBS polymer-modified bitumen. • High-content SBS polymer-modified bitumen exhibits better resistance to rutting, fatigue, cracking, and aging. [ABSTRACT FROM AUTHOR]

Mesoscale modelling is a promising tool to analyse the phenomenological causes of mechanical failure of recycled aggregate concrete (RAC). Most mesoscale models of RAC are two-dimensional (2D) and 3D models are lacking. This prevents the full understanding of the behaviour of each mesoscopic phase. This paper presents a 3D model of RAC and analyses its mechanical behaviour based on mesoscale phenomena. The analyses concern three types of tests carried out in concrete specimens: uniaxial compressive, uniaxial tensile and splitting tensile strength tests. The mechanical response and fracture behaviour of each mesoscopic phase is analysed in relation to the response of RAC specimen. The comparisons between uniaxial behaviour of 3D and 2D modelling as well as between uniaxial and splitting tensile behaviour of RAC are presented. The main findings of the paper are: (1) the full curve of uniaxial stress-strain response from 3D modelling is comparable to that from 2D modelling for RAC (therefore, 2D models are validated for RAC modelling); (2) the overall behaviour of the concrete elements remains elastic regardless of the fracture development in the ITZ and attached mortar of recycled aggregates until damage propagates to the new mortar matrix; (3) a relationship between modelled uniaxial and splitting strength of RAC is established and validated. [Display omitted] • Realistic mesostructural model of RAC - particle size, attached mortar content and ITZ with real thickness. • Replicate the strength test of uniaxial compression, uniaxial tension, and splitting tension. • Validate the use of 2D model through comparison of the outcomes from 2D and 3D models. • The influence of each mesoscopic phase on the overall mechanical behaviour of RAC. • Establish the relationships between the modelled uniaxial and splitting tensile strength. [ABSTRACT FROM AUTHOR]

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

In recent years, the utilization of recycled aggregate concrete (RAC) as an environmental-friendly material in the construction industry has been actively promoted. A sufficient bond between rebar and RAC is crucial for the load carrying capacity and long-term durability of RAC structure. However, many connection sections between rebar and RAC may be destructed, especially in cold regions where freeze-thaw cycles can worsen the deterioration of structures, under uniaxial compression. To investigate the coupling effect of freeze-thaw cycles and uniaxial lateral pressure on bonding properties of rebar and RAC, variables, such as number of freeze-thaw cycles (F), uniaxial lateral pressure stress ratio (ξ), and recycled aggregate replacement ratio (R), are considered in this study. 117 specimens were fabricated and divided into 39 groups for pull-out test. Different bond-slip curves were obtained, and corresponding characteristics were analyzed. Moreover, this paper proposed a novel bond strength theory by combining a superposed stress field distribution function with a splitting surface stress analysis. The distribution function consisted of the stress distribution of uniaxial lateral pressure loading state without pullout and pullout process without lateral pressure, while the stress analysis amended the softened sleeve theory with a spatial intensity model. The results show that both bond strength and peak slip are positively correlated with uniaxial lateral compression but negatively correlated with the accumulation of freeze-thaw damage. The recycled aggregate (RA) replacement ratio has a minor effect on bond strength and peak slip. The factor of uniaxial lateral pressure is dominant and mitigates the adverse effects of freeze-thaw damage and RA substitution on bonding properties. Notably, the methods of decomposition and stress synthesis break through the limitations of traditional bond strength theory, resulting in a wider scope of application. The bond strength theory applies not only to elastic sleeve bonding part but also to softened sleeve bonding part in reinforced concrete building structure. This theory can more accurately predict the failure morphology and ultimate bond strength in freeze-thaw conditions under uniaxial lateral pressure load. • The coupling effects of F and ξ on bonding properties of rebar in RAC were studied. • The bond-slip characteristics and the instability of test data were analyzed. • A novel bond strength theory is established in this paper. [ABSTRACT FROM AUTHOR]

Protein retarders can not only prolong the setting time of gypsum in application, but also lower the reduction in strength. The chemical activity of proteins is determined by the basic unit of amino acids (AAs). To enhance the understanding of protein retarding action mechanism, this paper focuses on the AAs-adsorbed gypsum structure, and investigated the retarding effects, crystal morphologies, and nanoscale interactions. Results indicate that the AAs had varying retarding effects on gypsum, and the effects from greatest to smallest were L-arginine, L-glutamic, and L-leucine acid. The rate of initial hydration heat release was reduced, and the peak of hydration release was delayed. Retardation of AAs on gypsum involves chemical adsorption on the surface of dihydrate gypsum crystals, which mainly occurs on the (1 2 0) face and affect gypsum morphology. The mechanism of AAs adsorption involves electrostatic interactions between charged functional groups of AAs and gypsum particles, as well as hydrogen bonding at additional carboxyl and amino groups. The adsorption strength depends on longer chained structure and number of functional groups of the AAs. And intrinsic strength of AAs-adsorbed gypsum nanocrystals contributes to the strength reduction on the macroscale. This paper provides basic data for designing and tailoring enhanced protein retarders for gypsum. • The amino acids adsorbed gypsum mechanism was revealed to evaluate protein retarding effects. • Retardation of AAs on dihydrate gypsum crystals mainly occurs on the (1 2 0) face. • Intrinsic strength of AAs-adsorbed gypsum nanocrystals contributes to the strength reduction on the macroscale. • Electrostatic interactions and hydrogen bonding determine the AAs adsorption effects. [ABSTRACT FROM AUTHOR]

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

Blast furnace slag (BFS) is commonly used as a substitute for cement clinker due to its hydration properties. However, the demand for BFS is outpacing the supply, and its price is rising steadily. Moreover, the significant accumulation of industrial waste with potential hydration properties poses a severe environmental threat. To address these challenges, this paper aimed to prepare high-performance composite blast furnace slag powder (CBFS) by incorporating red mud (RM), fly ash (FA), desulfurization gypsum (DG) and BFS, guided by the synergistic effects and the theory of medium-calcium systems. This paper reveals that the primary activation methods of the amorphous silicon-aluminum mineral phases in CBFS are alkali activation and sulfate activation. The optimal results demonstrate that the compressive strength of CBFS-cementitious material (50% CBFS + 50% cement) can reach 52.8 MPa, meeting the standards of Portland Cement PO 42.5. Additionally, RM, FA and DG account for 66% of CBFS and the hydration activity of CBFS is better than that of S95-grade BFS. Furthermore, the CBFS-cementitious material effectively immobilizes hazardous elements of the raw materials, and the leachate meets drinking water standards. The application of CBFS facilitates the recycling of industrial solid wastes, improves the quality of construction materials and reduces the construction industry's dependence on BFS. [Display omitted] • CBFS was prepared using RM, FA, DG, and BFS, aiming to achieve integrated clean production in multiple industries. • The total content of RM, FA and DG in CBFS reaches 66%, and its properties meet the requirements of S95-grade BFS. • RM, FA, DG and BFS showed a positive synergistic effect in CBFS, which enhanced the strength of the matrix (52.8 MPa). • CBFS can reduce carbon emissions in the cement industry and solidify the hazardous elements in the raw materials. [ABSTRACT FROM AUTHOR]