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This review compiles the main scientific and technical findings on the viability of using paper sludge waste as a supplementary cementitious material in the manufacture of future eco-efficient cements. It contains a detailed analysis of the scientific (characterisation, activation conditions, pozzolanic activity, system reaction kinetics) and technical (rheology, physical and mechanical properties, and resistance to chlorides, sulphates, sea spray and CO 2 ) properties of this type of waste when used as a supplementary cementitious material. On the grounds of the literature reviewed, paper sludge waste can be confirmed to be an environmentally sound source of recycled metakaolinite, a conclusion with significant social and economic benefits. [ABSTRACT FROM AUTHOR]

Abstract: The use of paper-mill residuals in concrete formulations was investigated as an alternative to landfill disposal. The mechanical and durability properties of concrete containing paper-mill residuals collected from a wastewater treatment-plant were evaluated. Class F fly ash was used as a replacement for Portland cement (PC) when incorporated into concrete mixtures containing paper-mill residuals and the resulting products were compared to normal concrete. Compressive, splitting tensile, flexural strength and drying shrinkage tests were carried out to evaluate the mechanical properties for up to 90days. Rapid chloride-permeability tests and initial surface-absorption tests were carried out at 28days to determine the durability properties. Concrete containing paper-mill residuals showed improvement in the durability test results when PC was replaced with class F fly ash. [ABSTRACT FROM AUTHOR]

• An original multielectrode embedded capacitive sensor is developed. • Multielectrode embedded capacitive sensor allows to assess permittivity in concrete. • Optimum dimensions chosen for capacitive electrodes are rectangular 30 × 10 mm2. • Measurements in liquids and concrete show a very repeatable and reproducible system. • Permittivities obtained with the developed embedded sensor are validated. This paper discusses the development of a capacitive sensor embedded within concrete blocks in order to continuously monitor water content, which is a crucial parameter in the assessment of concrete degradation. The embedded capacitive sensor undergoes continuous interrogation by an automatic monitoring system, in order to track permittivity changes over time through a frequency measurement system. The methodology involves a two-step calibration process: first, obtaining permittivity from frequency, then converting permittivity profiles into water content profiles. This paper focuses on the sensor design and first calibration in the aim of assessing permittivity profiles. Numerical methods enable optimizing both electrode geometry and design of the embedded capacitive sensor. Experimental validation of the sensor in liquid and concrete environments, along with a metrological validation, reveals the sensor's ability to monitor permittivity profiles as well as its uncertainty at 8 different depths inside the concrete structure. Permittivity measurements were also conducted using reference methods. The results demonstrate very good agreement with less than 10% difference between the embedded sensor and the reference results. This step provides insights into its applicability and potential perspectives for future research. [ABSTRACT FROM AUTHOR]

This paper focuses on the investigation of fresh, mechanical, and durability properties of concrete with the influence of fly ash and polypropylene fiber. In this study, cement was partially replaced by 15 % and 30 % fly ash content in weight, whereas polypropylene fiber was incorporated in concrete mixes at 0.06 %, 0.12 %, and 0.18 % by volume. Twelve concrete mix proportions were developed, and slump, density, ball penetration, and compacting factor tests were conducted to examine the fresh concrete properties. Besides, mechanical characteristics, including the uniaxial compressive and splitting tensile strength of concrete, were evaluated at 7, 28, and 90 days. Further tests of concrete durability, including rapid chloride permeability test, sorptivity, and water penetration, were performed at 90 days. The results exhibited that the incorporation of fly ash developed fresh concrete properties, while polypropylene fiber decreased the fresh characteristics of concrete. Furthermore, the combination of fly ash and polypropylene fiber in concrete was substantially attained to improve the mechanical and durability characteristics compared to the control mix. Mix proportion of 15 % fly ash and 0.12 % polypropylene fiber exhibited a pronounced influence on compressive strength, chloride permeability, sorptivity, and water penetration compared to other concrete mixtures. [ABSTRACT FROM AUTHOR]

Experiments and field observations have shown that supplementary cementitious materials (SCMs) mitigate the risk of alkali-silica reaction (ASR) in Portland cement blends, but this is difficult to describe thermodynamically due to the lack of appropriate thermodynamic database information, and challenges in defining the kinetic factors. This paper examines how four well-known SCMs (namely ground granulated blast furnace slag, silica fume, metakaolin, and fly ash) mitigate ASR, by using a multi-stage simulation and a newly extended thermodynamic database. Calcium hydroxide consumption by SCM hydration, dilution of available alkalis, and alkali binding in calcium-alkali-aluminosilicate hydrate solid solutions, play pivotal roles in understanding the influence of SCMs in ASRs. Blending aluminium-rich SCMs in ASR-prone systems appears to act by preventing the dissolution of reactive silica in aggregates rather than by suppressing the formation of ASR products. This paper provides new thermodynamic insights into the mechanisms by which SCMs enhance concrete durability against ASR. [ABSTRACT FROM AUTHOR]

Glass Fiber-Reinforced Polymer (GFRP) bars can enhance the flexural bearing capacity and durability of concrete beam members under sustained loading and alkaline environment over an extended period. However, addressing the challenges related to durability and deformation resistance remains crucial for long-term service. In this paper, the flexural performance of GFRP-reinforced concrete beams with different glass fiber contents under the coupling action of the alkaline environment and continuous load is studied, and the mechanism of improving the flexural performance of GFRP-reinforced concrete beams by dispersed fibers is analyzed from a microscopic point of view by scanning electron microscope (SEM) test. In addition, the finite element analysis software was used to simulate and verify the improvement effect of singly dispersed fiber on the bending of GFRP-reinforced concrete beams. The results demonstrate that GFRP-RC beams containing 0.5%, 1.0%, or 1.5% glass fiber exhibit a reduction in deflection ranging from 11% to 23% compared GFRP-RC beams without glass fiber, thereby improving their deformation resistance. The optimal glass fiber content is 1.5%. Simulation analysis demonstrates that the model exhibits enhanced resistance to deformation when the glass fibers are randomly dispersed. Specifically, increasing the random scattering of fibers at the bottom of the beam by two to three times results in a reduction of 7%-12% in mid-span displacement of the model. Additionally, within the cracked area, the fibers bear greater tensile stress compared to those in other uncracked regions, effectively preventing further cracking of GFRP-RC beams. This study offers valuable design guidance for enhancing performance of GFRP-RC members during long-term service. • This paper studied glass fiber GFRP-RC beams. • The working condition is the coupling of sustained loading and alkaline environment. • The influence of fiber on the flexural property of beam was investigated by finite element method. • The corrosion age of alkaline environment is 450 d. [ABSTRACT FROM AUTHOR]

• Paper presents economic and environmental benefits of concrete made with IBWA. • Fine aggregate replaced with 0%, 5%, 10%, 15% and 20% Incinerated Biomedical Waste Ash. • Strength, permeability, water absorption and sorptivity properties investigated. • Use of 5% IBWA improves strength and reduces permeability. • Cement stabilization reduces the leaching of metals from IBWA concrete. Biomedical waste is combination of medical waste from various sources like hospitals, research centers, clinics etc. and that presently or in the future poses a significant risk to human, plant or animal life. As it is produced in abundance and therefore cannot be treated or disposed of without special precautions. Generally biomedical waste is burned in incineration plant and produce Incinerated Biomedical Waste Ash (IBWA). It is considered dangerous or lethal because it may contain toxic substances such as heavy metals (hazardous waste). Typically, IBWA is dumped in a landfill to limit its spreading in the environment. But as none of the landfills is 100% leak-proof. This paper presents the influence of incinerated biomedical waste ash as fine aggregate replacement on the strength and permeation properties of concrete. For this purpose, a control concrete mix was made and four concrete mixes were made with four different percentages (5, 10, 15, and 20%) of IBWA. Results from the experimental study show that the incorporation of 5% IBWA as a partial sand replacement advances the strength and durability performance of the concrete. Compressive and split tensile strength test were performed upto age of 56 days and rapid chloride penetrability test (R.C.P.T.), water absorption, sorptivity and leachate analysis were performed upto age of 28 days. Toxicity characteristic leaching procedure (TCLP) test was performed and results indicates that it is non-hazardous. [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 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 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]

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]

• Analysis of the impact of recycled wastewater on the physical, chemical, and mechanical aspects of concrete. • Comprehensive assessment of recycled wastewater influence on concrete durability, microstructure, and strength properties. • Examination and elucidation of interrelationships among diverse properties of environmentally friendly concrete. • Future research insights and recommendations to drive innovation in sustainable concrete practices. The present paper endeavors to examine the viability of utilizing recycled wastewater as a foundational component in the creation of eco-friendly concrete. This paper entails an in-depth analysis of the chemical and physical attributes inherent in recycled wastewater, with a particular focus on its potential as a substitute for conventional freshwater in the concrete mixing process. To address limitations observed in prior research and to achieve a more profound comprehension of recycled wastewater's performance within green concrete, this study conducts an exhaustive review of existing literature. Through a systematic evaluation, the study meticulously assesses the influence of recycled wastewater on diverse properties inherent to green concrete, encompassing pivotal factors like flexural and compressive strength, alongside durability properties. The outcomes drawn from this investigation accentuate the viability and efficacy of recycled wastewater as a feasible alternative to freshwater in the production of green concrete. Notably, this approach holds promise for ameliorating detrimental environmental impacts while concurrently reducing the cost burden associated with sustainable concrete fabrication. Nevertheless, a central message emerges concerning the necessity for vigilant monitoring and meticulous regulation of recycled wastewater's quality and composition. This requisite vigilance is aimed at ensuring its compatibility and appropriateness for integration into concrete formulations. By virtue of delivering a comprehensive and thorough analysis of recycled wastewater's effects on the production of green concrete, this study plays a pivotal role in bridging gaps in knowledge and advancing the boundaries of this field. The practical implications of these findings extend to the development of sustainable and ecologically mindful concrete structures, while also serving as a guiding light for future research endeavors in this pivotal domain. [ABSTRACT FROM AUTHOR]

• The feasibility of waste concrete powder-based geopolymer reclaimed concrete was verified. • Carbonation depth, uniaxial compressive strength and dynamic elastic modulus of under different carbonation time were studied. • The changes of mineralogical phases and micromorphology characteristics of reclaimed concrete were analyzed. • The deterioration mechanism of carbonization and freeze–thaw-carbonization of reclaimed concrete was revealed. • It makes it possible to achieve the complete recycling of waste concrete. In order to realize the complete recycling of waste concrete, this paper used waste concrete powder (WCP), fly ash (FA) and granulated ground blast furnace slag (GGBS) as raw materials to prepared geopolymer, mixed with recycled waste concrete aggregates to prepare waste concrete powder-based geopolymer reclaimed concrete (WCPGRC). The WCPGRCs cured for 28 days were carried out carbonization test (group C-28d) and freeze–thaw cycle carbonization test (group DC-28d), and the WCPGRCs cured for 84 days were carried out carbonization test (group C-84d) to study their durability. The carbonation depth, uniaxial compressive strength (UCS) and dynamic elastic modulus (DEM) of three groups of WCPGRC under different carbonation times and different freeze-thawed-carbonation times were tested respectively. The mineralogical phases and micromorphology characteristics of WCPGRC before and after carbonization and freeze-thawed-carbonization were characterized through XRD and SEM. The results show that: (1) The carbonation depth of WCPGRC in groups C-28d, DC-28d and C-84d all increased with the carbonation time and freeze-thawed-carbonation time, and the maximum carbonation depth was 4.4 mm, 4.9 mm and 4.1 mm, respectively. (2) The UCS of C-28d increased by 9.7% from 39.11 MP to 42.56 MPa with carbonization time; The C-84d increased by 4.6% from 40.51 MPa to 43.31 MPa; The DC-28d first increased and then decreased with the increase of freeze–thaw-carbonization time, and the maximum UCS was 40.51 MPa on the 28th day. (3) The DEM of C-28d increased by 16.5% from 17.22GPa to 20.06GPa with carbonization time; The C-84d increased by 7.6% from 20.05GPa to 21.57GPa; The DC-28d first increased and then slightly decreased with the increase of freeze–thaw-carbonization time, the maximum DEM was 18.41 GPa on the 14th day. (4) Prolonging curing time increased the UCS and DEM, while freeze–thaw decreased the UCS and DEM of WCPGRC. (5) After the carbonization of WCPGRC, new carbonate crystals and geopolymer gels were generated, continued to fill the voids and cracks, making the overall structure denser. However, after the freeze–thaw-carbonization, the freeze–thaw cycle inhibited the geopolymerization, and the freeze–thaw damage intensified the carbonization, which reduced the structural integrity of WCPGRC. [ABSTRACT FROM AUTHOR]

Sulphoaluminate cement (SAC) was widely used for rapid repair and strengthening of building structures due to its excellent quick hardening and high early strength behavior. This study developed a SAC-based engineering cement composites (ECC) with ultra-high molecular weight polyethylene (UHMWPE) and investigated its mechanical properties. Chloride ion permeability coefficient were evaluated by new alternating-current sectioning and rapid chloride migration (RCM). The mechanism of the SAC-ECC against chloride erosion were quantified using nitrogen isothermal adsorption. The results show that the fracture energy, tensile strength and strain of SAC-ECC samples are higher than that of normal ECC. The polyethylene (PE) fiber could significantly improve the flexural strength and toughness with PE fiber content of 0.75 % by volume. The hydration products generated could react with chloride ion to make it chemically stabilized, leading to reduce the chloride ion diffusion coefficient significantly. Based on microscopic analysis (SEM), the pore structure in SAC-ECC composite improved remarkedly while the volume of harmful pore decreased evidently as well. SAC-ECC developed in this paper could be poetically applied to strengthening and repair of marine concrete structures. • Develop a SAC-based ECC with ultra-high molecular weight polyethylene (UHMWPE). • Investigate mechanical properties SAC-based ECC. • Evaluate chloride ion permeability coefficient using new alternating-current sectioning and RCM. • Mechanism of the SAC-ECC against chloride erosion were quantified using nitrogen isothermal adsorption. [ABSTRACT FROM AUTHOR]

3D concrete printing represents a modern trend in construction automation, characterized by the layer-by-layer deposition of concrete using 3D printers to construct structures without traditional formwork. This process alters the rheological behavior, microstructure, mechanical properties, and durability of 3D-printed concrete compared to conventional cast concrete. This review outlines the porosity and durability tests conducted in previous research papers. It presents the details and procedures of these tests, along with any referenced standards or guidelines. By comparing printed specimens to cast specimens, both similar and controversial results from the tests are also comprehensively discussed. It becomes evident that the durability properties of printed specimens differ from those of cast specimens due to their distinct pore systems. Ultimately, this review aims to bridge research gaps in 3DPC durability performance and assist in the selection of methodologies for porosity and durability tests. • Tabulation of conducted porosity and durability tests for 3D printed concrete. • Comparison of pore structure between 3D printed and cast specimens. • Comparative analysis of durability aspects between 3D printed and cast concrete. • Recommended test methods for porosity/permeability and durability tests. • Durability of 3D printed concrete is highly related to its pore system. [ABSTRACT FROM AUTHOR]

This review paper provides a detailed evaluation of the existing landscape and future trends in applying machine learning and deep learning approaches for predicting concrete strength in construction engineering. The study contextualizes the investigation of machine learning and deep learning in concrete strength prediction, emphasizing the need for precise strength forecasting in construction. This hybrid review uses quantitative analysis of an extensive collection of 1005 research publications from the Scopus database (2010−2023) to identify clusters, hotspots, and gaps in this area, giving a systematic way to analyze the field's dynamics. This review reveals major research clusters such as concrete characteristics, sustainability, error analysis, and optimization. It identifies research hotspots like compressive strength prediction, reinforced concrete, and neural networks. The review illuminates future research paths, ethical concerns, and environmental implications. It emphasizes the relevance of fairness, bias reduction, and sustainability in developing and deploying machine and deep learning models in the construction sector and the necessity for specialized models in forecasting concrete durability, sustainable concrete strength, and shear strength. • Thorough review of on the use of ML and DL in concrete strength prediction is offered. • Critical insights and patterns in the prediction using ML and DL are identified. • Research directions in ML for concrete strength prediction are elaborated on. • Future role of deep learning in advancing concrete strength prediction is revealed. • Notable research paths, ethical concerns, and environmental implications are given. [ABSTRACT FROM AUTHOR]

Corrosion of steel reinforcing bars (rebars) in reinforced concrete structures can be addressed by using corrosion-resistant materials like Fiber-Reinforced Polymers (FRP). However, in France, FRP rebars are primarily restricted to temporary applications due to lack of comprehensive durability data. While numerous studies have explored FRP durability in alkaline environments, understanding the combined effect of alkali ions and sustained loading remains limited. Furthermore, the impact of incomplete matrix curing on the long-term performance of FRP rebars is limited. Accordingly, this paper investigates the durability of Glass FRP (GFRP) rebars exposed to alkali environments at varying temperatures. A batch of partially cured rebars was selected for this study, with part of them undergoing post-curing to investigate the effect of curing state on the ageing behaviour. Additionally, some partially cured specimens were subjected to combined sustained tensile loading at 20 % and 40 % of ultimate strength. Mechanical, physico-chemical and microstructural characterizations were conducted after various exposure durations. Results revealed that incomplete curing minimally impacted long-term tensile properties but significantly affected the interlaminar shear strength of aged rebars. Moreover, applying a combined load had little influence on residual properties at 20°C but led to rapid reduction in GFRP residual tensile strength at higher ageing temperatures (40 and 60°C). • Incomplete curing of GFRPs did not affect residual tensile properties after 90 days of direct alkaline aging. • For partially cured GFRP rebars, both post-curing and degradation occur during aging. • Sustained load significantly impacts the durability of GFRPs in alkaline environments. • This load effect exhibits high dependence on temperature. • Partial curing of the GFRPs may amplify the effect of load on long term performance. [ABSTRACT FROM AUTHOR]

Micro polypropylene (PP) fibers are commonly utilized to increase concrete's durability and fire resistance in building projects. High-Performance-Fiber-Concrete (HPFC) has become increasingly popular in the sustainable buildings industry in the past two decades. Some important structures were constructed using HPFC with micro polypropylene fibers to limit corrosion and increase fire resistance. This paper presents an experimental and analytical investigation to study the effect of micro PP fibers on the shear strength of HPFC beams with and without stirrups. The experimental results were used to obtain a new and simple approach that can calculate the shear strength of HPFC beams without needing for experimental findings. Also, the effect of PP fibers was compared with that of using steel (ST) fibers only or the hybridization of both PP and ST fibers. Twelve simply supported beams were fabricated and loaded with a concentrated load up to failure and all the required data were obtained and examined. The results indicated that adding PP fibers was effective in increasing both the shear capacity and the toughness of HPFC beams, either with or without stirrups, especially for beams with 1 % PP fibers. For beams without stirrups either with or without PP fibers, the mode of failure was diagonal tension shear failure. The presence of stirrups and / or ST fibers changed the failure mode from diagonal tension shear failure to compression shear failure. Analytically, a new approach of ten equations, was proposed based on the angle of compression struts and the splitting tensile concrete strength, to calculate the shear strength of HPFC beams. The equations of the proposed approach were compared with the results of forty five experimental specimens from four different research studies to examine their validity. The results were in a very good agreement and accuracy with the experimental results. • The effect of micro polypropylene fiber content on the shear strength of HPFC beams. • The effect of materials of fiber on the shear strength of HPFC beams without stirrups. • The effect of materials of fiber on the shear strength of HPFC beams with stirrups. [ABSTRACT FROM AUTHOR]

The study of the durability of steel-reinforced concrete (SRC) columns under the influence of coastal moisture–heat coupling has grown in prominence. In this study, electrochemical corrosion and axial pressure loading tests were performed on 10 SRC columns. These tests studied the effects of varying corrosion rates and CL − concentration on the axial pressure performance of the SRC columns when conducted in an energized medium, and the results revealed the modes of failure and the degradation laws. The ultimate bearing capacity and stiffness of SRC columns increasingly deteriorate with increasing corrosion rate; the ductility index also deteriorates to certain extent. When the corrosion rate exceeds 20 %, each index parameter of the test column deteriorates. During the axial compression test, the concentration of CL − in the energized medium primarily increases the growth rate of strain in the elastic-plastic phase during the middle and late loading stages. This leads to further deterioration of the SRC columns in multiple ways, such as cracking of the protective layer of concrete, weakening of the material properties, and damage to the cross-section. Based on this experimental study, the modeling of SRC columns under chloride salt erosion was performed using a new finite-element method. In addition, the Mander constrained concrete model and the Biondini concrete cracking model were used to theoretically derive the ultimate bearing capacity of the corroded SRC column. • Paper reports on the durability degradation patterns of marine structural columns. • Studies include electrochemical corrosion and axial pressure tests. • Different design corrosion rates and different CL- concentrations. • A finite element modelling method for corroded columns is proposed. • Establishment of corroded column bearing capacity prediction formula. [ABSTRACT FROM AUTHOR]

Chemical organic admixtures play a significant role in engineering structures. This paper reviews the effects of organic admixtures with different molecular scales and functional groups on the cement hydration process and discusses their roles in the microstructure and properties of cement-based materials. According to the current research, the molecular structure of admixtures determines their adsorption performance on cement, which in turn affects their mechanism of action and durability in cement-based materials. Incorporating organic admixtures can regulate the properties of cement-based materials. Most admixtures can adsorb onto the surface of cement particles and complex with Ca2+ in the liquid phase, thus exhibiting a retarding effect. The hydration products of cement develop more completely, potentially positively impacting the durability of concrete, particularly its impermeability. [Display omitted] • The impact of functional group types on the properties of chemical organic admixtures was reviewed. • Chemical organic admixtures can alter the hydration products and hydration process of cement. • Workability, mechanical properties and durability of chemical organic admixtures on cement were discussed. • Chemical organic admixtures can be an ideal selection for optimizing cement performance. [ABSTRACT FROM AUTHOR]

• Design of an embedded sensor to monitor concrete resistivity profiles. • The designed solution is a multi-electrode printed circuit board (PCB) sensor. • Numerical validation of the sensor was performed. • Validation of the sensor in solutions of known conductivity. • Validation of the sensor in concrete to monitor concrete drying. Electrical resistivity is sensitive to various properties of concrete, such as water content. Usually used on the surface of old structures, devices for measuring such properties could also be adapted in order to be embedded inside the constitutive concrete of the linings of new tunnels or in new bridges, to contribute to structural health monitoring. This paper introduces a novel multi-electrode embedded sensor for monitoring the resistivity profile over depth in order to quantify concrete durability. The paper focuses on the design of the sensor as a printed circuit board (PCB), which brings several advantages, including geometric accuracy and mitigation of wiring issues, thus reducing invasiveness. The study also presents the numerical modeling of the sensor electrical response and its ability to assess an imposed resistivity profile, together with experimental validations using (i) saline solutions of known conductivity and (ii) concrete specimens subjected to drying. The results demonstrate the capability of the sensor to evaluate resistivity profiles in concrete with centimeter resolution. [ABSTRACT FROM AUTHOR]

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

• Up to 5% WTS can be applied without significant effect on concrete performance. • 10% of alum-WTS reduces the mechanical strength of bricks by 24.6–45.5%. • 10% of iron-WTS increases mechanical strength of bricks by 7–97%. • Application of WTS in construction materials increases permeability. • WTS-fly ash geopolymer being 12 times stronger than clay–cement during wetting/drying cycles. Water treatment sludge (WTS) management is a growing global problem for water treatment plants (WTPs) and governments. Considering the scarcity of raw materials in many parts of the planet and unique properties of WTS, extensive research has been conducted on the application of WTS in the production of construction materials such as roof tiles, bricks, lightweight aggregates, cement, concrete and geopolymers. This paper critically reviews the progress in the application of WTS in construction materials, by synthesizing results from recent studies. Research findings have revealed that incorporation of ≤10% alum-based sludge in ceramic bricks is satisfactory with a small reduction of mechanical performance. Using the iron-based sludge, the bricks presented better mechanical strength than the reference clay-bricks. Concerning WTS application in concrete, 5% replacement of cement or sand by WTS was considered as the ideal value for the application in a variety of structural and non-structural concrete without adverse effect on concrete mechanical performance. Furthermore, this paper discusses sludge-amended concrete in terms of durability, potential leaching of toxic elements and cost, and suggests topics for future research on the sustainable management of WTS. [ABSTRACT FROM AUTHOR]

• CPF liners help to improve near surface concrete characteristics. • Improvement in surface characteristics by commercially manufactured CPF is highest. • Cheap and easily available gunny bag produced noteworthy improvement in NSC. • With the increase in water content the efficiency of CPF increases. The durability of concrete cast near the conventional formwork (steel or wood) is reduced because of higher water-cement (w/c) ratio as compared with the concrete present in the core of the member. Various controlled permeability formwork (CPF) liners absorb or drain out excess water near formwork, can reduce the increase in w/c ratio of concrete near the formwork. This paper presents a quantitative study showing improvement in the properties of near surface concrete (NSC) by the use of a commercially available CPF liner, and comparing the performance of more easily available and cheaper alternatives to CPF liner used. Two types of concrete mixes with identical w/c ratio but different water contents were used. Three specimens were made for each of the two types of concrete mix and one surface for each of the specimen was cast using one of the CPF liners among a commercially manufactured CPF, particle board, and gunny bag. Four tests: Rapid chloride permeability test, AgNO 3 colorimetry test, initial surface absorption test and pull off test were performed to study durability properties of NSC. Study of physical appearance in terms of blowholes and grey area on the concrete surface using image processing is also presented in the paper. Though commercially manufactured CPF produces better surface than the particle board and gunny bag, the improvement in NSC properties by use of gunny bag is also noteworthy. [ABSTRACT FROM AUTHOR]

The repair of concrete structures damaged by water or water borne chemicals is estimated to cost billions of dollars annually worldwide. However, the solutions that can make concrete structures more sustainable and durable, are limited. The use of crystalline admixtures (CA) has a potential of improving the durability and reducing permeability of concrete structures especially those exposed to corrosive environments. This paper presents various investigations on the influence of crystalline admixtures on the strength, self-healing, and durability characteristics of concretes with two different cement types (Ordinary Portland Cement [OPC] and Portland Limestone Cement [PLC]). Test methods include the rapid chloride permeability (RCP), surface/bulk electrical resistivity and water permeability tests, self-healing test, compressive strength test and salt ponding test. The results indicate that the water permeability coefficient decreased by 3 times whereas the self-healing ratio increased by a higher rate by adding crystalline admixtures into the concrete mix. This paper presents empirical equations to correlate resistivity, total charge passed, or water permeability with each other. Further, the correlation between the surface and bulk resistivity is strong and the evidence from self-healing test suggests faster sealing of crack widths up to 250 μm for CA treated specimens. • Chloride and water permeability tests are compared/correlated for concretes containing crystalline admixtures (CA). • Influences of CA on the crack self-healing of concrete are studied based on permeability reduction of cracked specimens. • Portland Limestone Cement (PLC) is more effective than ordinary cement in improving concrete's durability and strength. • Influencing parameters on electrical resistivity of concrete treated with CA are investigated. [ABSTRACT FROM AUTHOR]

Highlights • The paper presents a literature review of healing agents for cementitious materials. • Strategies to deliver the healing agent into the concrete are discussed. • Mechanical and long-term performance of healing agents are analysed. • Evaluation of healing efficiency methodologies is presented. • Life cycle cost analysis of conventional vs. healed concrete is discussed. Abstract Concrete is a widely used material in the construction industry due to its affordability and availability; however, it is also sensitive to crack formation typically under tension stresses. Due to cracking, the durability of concrete is compromised via contaminant ingress such as rapid chloride penetration and atmospheric water that infiltrate through these cracks and potentially lead to corrosion of steel in reinforced concrete. Self-healing materials embedded in cementitious materials is emerging as an innovative method to improve concrete durability. This paper reviews available self-healing approaches considering various healing materials with respect to performance and application. Attention to the efficiency of healing materials including biotechnological, polymeric and chemical components for crack healing and improvement in strength is a major focus. Consideration is also placed on methods of testing, evaluation methods for calculating efficiency and comparison of self-healing materials and their efficiency. Finally, a conceptual life-cycle cost for conventional and self-healing concrete structures is provided. [ABSTRACT FROM AUTHOR]

Highlights • Waste marble slurry used as an important resource in concrete and reducing the carbon footprint of cement. • Long-term strength and durability performance of concrete on partially replacing cement by weight by dried waste marble powder slurry assessed. • Both Mechanical and durability parameters of hardened concrete tested for a period of 1 year after exposing samples to adverse environmental conditions. • Marble slurry replacement percentages kept as 10%, 15%, 20%, 25% and water binder ratios as 0.35, 0.40 and 0.45. • Surface mesh for variation in all the properties with different replacement levels, curing conditions and water binder ratios plotted. • Relationship between mechanical and durability properties with compressive strength derived for marble slurry incorporated concrete. Abstract Present study assesses and evaluates the long-term strength and durability performance of concrete on partially replacing cement by weight by dried waste marble powder slurry. Four different replacement percentages (0, 10, 15, and 20 and 25%) and three water-binder ratios (0.35, 0.40 and 0.45) have been tested in the paper. The main reason for the study is to check whether use of dried marble slurry affects the properties of concrete in long term as the amount of binder is reduced, when cement is partially replaced. Long-term impact is analyzed by testing the concrete samples for 28, 56, 90, 180 and 360 days after curing the specimens in water for 28 days and exposing the samples to adverse environmental conditions in the state of Rajasthan, India where the temperature ranges from 0 °C in winters to as high as 47 °C in summers. The concrete mixes were tested for strength parameters mainly compressive, tensile and flexural strength, also durability parameters water permeability, abrasion resistance and water sorptivity. Surface mesh for variation in all the properties with different replacement levels, curing conditions and water binder ratios are plotted in the paper. Based on the analysis of concrete with various replacement levels of marble slurry, it can be concluded that for up to 15% replacement, an enhanced physical strength and durability of concrete blocks was observed across testing periods of 28 days to 360 days. It was observed that marble dust generated an effective dense mix for higher replacement ratios, thus improving the properties in long-term duration. Finally, relationship between strength and durability properties with compressive strength are derived for marble slurry incorporated concrete. [ABSTRACT FROM AUTHOR]

Abstract Reliable predictions of the time to onset of corrosion in reinforced concrete are essential for service life modelling, to ensure sufficient durability, and for holistic sustainability assessments of new materials. All existing models are based on the same concept, that is, predicting the development over time of the chloride content at the level of the steel and comparing this numerical result with the critical chloride content for corrosion initiation, C crit. This paper presents example calculations utilizing input data derived from both laboratory specimens and from structures, illustrating the poor predictive power of state-of-the-art models. While it is generally assumed that improving chloride ingress models will improve the prediction of the time-to-corrosion, this paper shows that the bottle neck to more reliable predictions are rather i) the lack of fundamental understanding of corrosion initiation, ii) the use of non-representative laboratory results, and iii) ignoring the size-effect in localized corrosion. [ABSTRACT FROM AUTHOR]

Abstract Disposal of waste tyre rubber has become a major environmental issue in all parts of the world representing a very serious threat to the ecology. One of the possible solutions for the use of scrap tyre rubber is to incorporate it into concrete, to replace some of the natural aggregate. An estimated 1000 million tyres reach the end of their useful lives every year and 5000 millions more are expected to be discarded in a regular basis by the year 2030. Up to now a small part is recycled and millions of tyres are just stockpiled, landfilled or buried. The volume of polymeric wastes like tyre rubber and polyethylene terephthalate bottles (PET) is increasing at a fast rate. This paper reviews the tests performed to determine the compressive strength, flexural tensile strength, water absorption and water penetration of using rubber tyre waste concrete samples. Scanning Electron Microscopy (SEM) images were also presented in this paper. It was observed that the compressive strength, flexural tensile strength and depth of water penetration of the rubberized concrete were less than that of the control mix, while the abrasion resistance and water absorption (up to 10% substitution) exhibited better results than that of the control mix concrete. This paper also reviews the performance of concrete mixtures incorporating 5%, 7.5% and 10% of discarded tyre rubber as aggregate and cement replacements. Numerous projects have been conducted on replacement of aggregates by crumb rubbers but scarce data are found on cementitious filler addition. Hence to examine characteristics of tyre crumb-containing concrete, two sets of concrete specimens were made. In the first set, different percentages by weight of chipped rubber were replaced for coarse aggregates and in the second set scrap-tyre powder was replaced for cement. Selected standard durability and mechanical test were performed and the results were analysed. [ABSTRACT FROM AUTHOR]

Cupola slag, a non-toxic and harmless industrial waste, has recently piqued the interest of researchers as a green building material. This paper reviews the potential use of cupola slag as a supplementary cementitious material, fine aggregate, and coarse aggregate in cement-based concrete composites. Moreover, this paper provides a holistic approach to the review of appropriate literature from the last two decades, critically examines the characteristics of cupola slag and the impacts of partial substitution on performance, and conducts a gap analysis to specify the direction of further research on cupola slag-based concrete. From the environmental perspective, the earth's ecological and environmental balance can be achieved by employing cupola slag in concrete manufacturing rather than natural resources. In terms of replacement rate and replacement method, the fresh performance, mechanical property, and durability of cupola slag-based concrete are reviewed. In conclusion, cupola slag can effectively increase the strength, water permeation resistance, resistance to aggressive environments, chloride ion penetration resistance, and other durability attributes of concrete when used as a partial replacement for cement or aggregate. The process to enhance pozzolanic behaviour, long-term mechanical and durability qualities, and microstructural analysis of cupola slag-based concrete need to be further explored, according to the gap analysis of the data from the literature. • Studies revealed near similar properties of tradional concrete can be achieved with cupola slag. • Cupola slags were found to be slow when reacted with cements. • Cupola slags as a binder were found to used at a range of 5-30%. • As an aggregate, cupola slags can be used upto 60%. • A good resistance to chloride and chemical ingress is achievable through the use of cupola slag. [ABSTRACT FROM AUTHOR]

• Need for hydrophobic modification. • Different methods and materials. • Mechanical and durability properties of hydrophobic geopolymer. • Microstructure study of hydrophobic geopolymer. • Pilot study yielding WCA as 106.038˚. The long-term durability of geopolymer concrete is one of the main problems that needs to be overcome before it can be universally acknowledged as a viable alternative to conventional concrete. The main cause of the durability issue is the migration and transport of water in the hydrophilic porous structure of geopolymer materials. To increase the long-term durability of geopolymer concrete, hydrophobic modification of geopolymers has recently garnered the interest of the researchers, and there is a lack of comprehensive summarization of the literature on hydrophobic geopolymer concrete composites, their preparation strategies, characterization methods, and properties, which has been the inspiration behind this literature review. This paper discusses the recent developments in the field of hydrophobic modification of geopolymer concrete, the different modification approaches, surface classification based on wettability, materials used, and the properties affected due to hydrophobic alternation. Properties studied include Water Contact Angle (WCA), surface energy, physical, mechanical, durability, and microstructural properties of the modified composites. Based on the literature reviewed, a pilot study was also carried out using an organosilane-based material to induce hydrophobicity in geopolymer concrete. Integral hydrophobic modification yielded a WCA of 66.083˚ whereas surface modification yielded a WCA as high as 106.038˚, which indicates successful modification of a hydrophilic surface to a hydrophobic one. Although the work on hydrophobic geopolymer concrete is limited, this paper is anticipated to serve as a roadmap for future investigations into the creation, processing, and characterization of hydrophobic geopolymer concrete. [ABSTRACT FROM AUTHOR]

3D printed concrete (3DPC) creates opportunities, including a reduction in construction waste and time and increased design freedom. However, because of the differences in the construction technique compared to traditional concrete casting, the structures also perform differently; namely, the micro- and meso-structure and durability are shown to be different. For the 3DP technology to find its way to the market, one needs to be aware of these differences and needs to know how to quantify the above-mentioned properties, as differences in the testing methodologies impose themselves when characterizing printed instead of cast concrete. In this paper, we elaborate on the test methods to investigate the micro- and meso-structure and the durability of 3DPC. We start with a discussion on the micro- and meso-structure of the 3D printed concrete and how it is different from conventional mold-cast concrete. An in-depth discussion of the test methods to assess the durability of 3D printed concrete is outlined. Reported findings related to the two aforementioned properties are discussed. In addition, we report on the technologies proposed to improve the durability performance of 3DPC, and we highlight the remaining challenges and opportunities related to 3DPC. [ABSTRACT FROM AUTHOR]

Highlights • Coral concretes are highly demanded in the construction of offshore structures. • Porous coral aggregates affect workability, mechanical properties and durability. • Many proper ways can improve the suitability of using coral aggregates. Abstract The utilization of locally available raw materials is extremely necessary for the offshore island construction in ocean. Coral can be used as aggregate but is usually light and porous, having rough surface, weak adherence to the attachments and high concentration of sea salts. These characteristics affect the workability, mechanical properties, volume stability and durability of resulting concretes. This review paper discussed the instability of Portland cement hydration products under the ocean environment, the low strength and stiffness of coral aggregates, their large connected porosity and the weak interface microstructure between the cement matrix and coral aggregates. To overcome these problems, such as low grade of strengths, inadequate corrosion resistance and high brittleness, this paper proposed some perspective techniques: modification of coral aggregate, development of new cementitious materials, fiber reinforcement and mix proportion design. [ABSTRACT FROM AUTHOR]

Durability is one of the primary concern in new buildings and also for the old existing infrastructures. This paper deals with the durability properties of concrete containing sandstone slurry as a filler material. A significant quantity of sandstone slurry gets deposited, and their disposal problem becomes acuter. In order to utilize these wastes and to practice a sustainable construction, the ultimate solution is to use these types of sandstone slurry in concrete. Since durability plays an enormous role in maintaining the infrastructure for years, various tests such as compressive strength, flexural strength, water absorption, sulfate attack, acid attack, carbonation, DIN-Permeability, sorptivity are done to get the durability of the sandstone slurry mix in concrete. This paper presents the result of experimental research to examine the suitability of sandstone slurry as a partial replacement of total aggregates in cement concrete. It was observed that up to a certain level of substitution, compressive and flexural strength show a comparable result to that of control concrete. Also, it shows a good result with a controlled replacement towards acid-attack as well as sulfate attack and are equivalent to that of Portland cement concrete. Similar effect were also observed towards carbonation and permeability. From the results, it can be said that there is a promising future for the use of sandstone slurry as a partial replacement of total aggregate, which can lead to more significant environmental and sustainable benefits. [ABSTRACT FROM AUTHOR]

In order to improve the durability of airport pavement concrete, four kinds of synthetic fiber reinforced concrete were researched in this paper. Modified polyester synthetic fiber concrete (MPFC), Monofilament polypropylene synthetic fiber reinforced concrete (MPSFC), Reticular polypropylene synthetic fiber reinforced concrete (RPFC), and Polyacrylonitrile synthetic fiber reinforced concrete (PSFC) were prepared in this paper. Strength, impermeability and frost resistance of them were investigated. The impermeability test was carried out by hydrostatic pressure and chloride ion penetration method, while the frost resistance test was conducted by quick freezing method. The results show that the synthetic fiber improves concrete flexural strength, but it has little effect on compressive strength. Under the same volume fraction (0.1%), the flexural strength of MPFC and PSFC increased by about 6% compared with that of ordinary concrete (PC), but the flexural strength of PSFC increased slightly, with only 1–2%. Single fiber can improve concrete impermeability and frost resistance. Among them PSFC impermeability is the best, which is 2.4 times of that of PC, up to P24; the frost resistance of MPFC is the best, which is 2 times of that of PC, reaching F350. Polycarboxylic synthetic water-reducer (SDJ) can improve concrete impermeability and frost resistance greatly. It has best impermeability when mixing with polyacrylonitrile fiber, and its frost resistance grades were all up to above F600 when mixing with the four kinds of fibers separately. It is suggested that the optimum volume fraction is 0.10–0.14%, as the fiber content also has certain influence on the performance of the synthetic fiber concrete. At last, the Cost-benefit analysis of the fiber reinforced concrete was put forward, which showed that the application of fiber concrete in the airport pavement engineering has great economic benefits and broad prospects for development. [ABSTRACT FROM AUTHOR]

Long-term durability of concrete has been of interest for researchers in past decades, and throughout their numerous research endeavors, they have tried to improve durability with the application of different methods. One technique is the integration of a new material into the concrete. One material that has attracted great attention of researchers is nano-SiO 2 (NS). Its considerable performance in the enhancement of durability properties of concrete and mortar provides reasonable specifications satisfaction for scholars. In this paper, important durability characteristics of concrete, including the chloride ion penetration, electrical resistivity, water penetration, water absorption, the pore size distribution, the carbonation, the sulfate resistance, frost resistance, shrinkage, and thermal properties were explored. Additionally, the effects on the microstructure of concrete and mortar in the previous studies were discussed. Mechanical properties, such as compressive strength, flexural strength, tensile strength, and abrasion resistivity were also investigated in the past and most recent papers. [ABSTRACT FROM AUTHOR]

The quick accumulation of recycled organic components with the modern society development has caused serious environment issues, and the utilization of these recycled organic components in concrete production can effectively mitigate recycling pressure. Portland cement concrete mixes containing recycled organic components behave differently in both fresh and hardened stages compared to conventional concrete, which need to be thoroughly studied before a large-scale field application. This paper aims to critically review the currently-reported performance of concrete with recycled organic components and to identify the knowledge gap for future sudies. This paper first conducted the characteristic investigation of recycled organic components, which provided the needed information for the classification of recycled organic components. Then the property performance, including workability, mechanical properties, and durability of concrete containing recycled organic component was evaluated. It has been concluded that both the workability and concrete strength will decrease with the added recycled organic components. However the durability performance, including freeze-thaw, impact resistance, and the resistance to alkali-silica reaction can be enhanced with the added recycled organic components. Aiming at the decreased strength, surface treatment methods have been reviewed. The current finding demonstrated the NaOH surface treatment for rubber particles and oxidation method for reclaimed asphalt mixture aggregates can enhance the concrete performance, respectively. Finally, the practice of applying recycled organic components in high strength and self-consolidating concrete was summarized, which demonstrated the potential of high performance concrete production with recycled organic component. Current knowledge gaps were identified to point out the challenges for the further study, including the difficulties to produce high strength and self-consolidating concrete with replacement ratio of recycled organic components higher than 50%. This study will provide the firm base for the application and future study on concrete containing recycled organic components, including reclaimed asphalt pavement (RAP), recycled asphalt shingles (RAS) and recycled crumb rubber (RCR). [ABSTRACT FROM AUTHOR]

This paper reviews the potential use of electric furnace ferronickel slag (FNS) as a fine aggregate and binder in Portland cement and geopolymer concretes. It has been reported that the use of FNS as a fine aggregate can improve the strength and durability properties of concrete. Use of some FNS aggregates containing reactive silica may potentially cause alkali-silica reaction (ASR) in Portland cement concrete. However, the inclusion of supplementary cementitious materials (SCM) such as fly ash and blast furnace slag as partial cement replacement can effectively mitigate the ASR expansion. When finely ground FNS is used with cement, it shows pozzolanic reaction, which is similar to that of other common SCMs such as fly ash. Furthermore, 20% FNS powder blended geopolymer showed greater strength and durability properties as compared to 100% fly ash based geopolymers. The utilization of raw FNS in pavement construction is reported as a useful alternative to natural aggregate. Therefore, the use of by-product FNS in the construction industry will be a valuable step to help conservation of natural resources and add sustainability to infrastructures development. This paper presents a comprehensive review of the available results on the effects of FNS in concrete as aggregate and binder, and provides some recommendations for future research in this field. [ABSTRACT FROM AUTHOR]

The service life and durability of concrete structures strongly depend on the transport properties of the concrete. Water permeability is one of the important indicators for durability of concrete. The water acts as a carrier of aggressive agents, such as chloride ions, sulphate ions and acid that can activate many chemical reactions, speeding up the degradation process of concrete structures. Pore structure is the most important characteristics controlling the transport properties of the hydrated cement paste. Hence, knowledge of the relationship between water permeability and pore structure of cement paste is needed for engineers. Owing to the pozzolanic reaction, fly ash can refine the pore structure of cement paste, eventually affect the water permeability. In this paper the effect of fly ash on the water permeability of cement paste is investigated at ages of the cement paste up to 2 years. The basic pore parameters of cement paste blended with fly ash were already discussed in previous study. This paper only investigates the pore parameters, such as capillary porosity, connectivity of the capillary pores, related to transport properties of cement paste. The results show that at later ages, such as 180 days, cement paste blended with fly ash is less permeable than pure Portland cement paste. This mainly results from the refinement of the pore structure caused by the pozzolanic reaction of fly ash. Based on the comprehensive comparison of the pore structure and the water permeability between ordinary Portland cement paste and cement paste with fly ash, the crucial pore parameter governing the water permeability of cement paste blended with fly ash is the Connectivity of the capillary pores. Capillary porosity is not the significant factor affecting the permeability of cement paste. The comparison obtained in this study enables a good understanding of fly ash incorporated in cement-based materials, and provides information for the use of fly ash in practice. [ABSTRACT FROM AUTHOR]

• Elucidating the various factors that impact the longevity of concrete structures. • Revealing that the construction of a hydrophobic barrier to safeguard concrete materials against environmental factors is crucial for ensuring their protection and durability. • Suggesting that silane-based protective materials have emerged as a promising solution that reduces the surface energy of substrates, limits the penetration of harmful substances, and provides multidimensional protection for concrete substrates. Concrete is the most commonly used construction material in infrastructure worldwide. However, due to its porous nature, it is highly susceptible to the surrounding environment which can lead to corrosion and deterioration, thereby reducing its service life and increasing maintenance costs. Inspired by the "lotus leaf effect" effective waterproofing measures can improve the durability of concrete structures. Silane-based protective materials have emerged as a promising solution that reduces the surface energy of substrates, limits the penetration of harmful substances, and provides multidimensional protection for concrete substrates. The versatility of silanes makes them valuable materials for improving the durability of concrete structures under harsh environmental conditions. This paper initiates with an exploration into the formidable challenges confronting concrete infrastructure. Subsequently, it provides an exhaustive analysis of the utilization of silane-based protective materials in augmenting the longevity of concrete structures, accompanied by a thorough assessment of their applicability in diverse aspects of concrete infrastructure. Furthermore, this study introduces pioneering strategies designed to elevate the protective efficacy of these materials, particularly within forthcoming corrosive environments. As we look ahead, safeguarding infrastructure through the implementation of silane-based materials presents a novel perspective on resource efficiency, assuming escalating significance within the realm of concrete construction. [ABSTRACT FROM AUTHOR]

This paper presents the mechanical characteristics and durability of concrete reinforced with basalt and bamboo fibres. The study involved testing specimens that were cured for varying durations ranging from 7 to 90 days, and subjecting the specimens to compressive, splitting, and tensile strength analyses. Four types of specimens were used, including control, bamboo fibre-reinforced concrete, basalt fibre-reinforced concrete, and a combination of both basalt and bamboo fibre-reinforced concrete. The durability of the concrete was evaluated through tests such as water absorption, acid attack, and water permeability. The results show that the optimum curing age is 60 days, and the hybrid fibre-reinforced concrete (HFRC) exhibited a higher compressive and flexural strength by 6.5% and 21.5% respectively, as compared to the control specimen. Moreover, HFRC had a 28.6% lower water permeability than the control specimen, implying higher durability. HFRC is also more resistant to acid attack, with a 3.9% reduction in weight loss compared to the control specimen. The post-acid attack test revealed that the HFRC has a compressive strength that is 21.8% higher than the control specimen. This study demonstrates that a hybrid of bamboo and basalt fibre can be used to produce a low-cost and eco-friendly concrete building material. • The mechanical properties of HFRC are greater than those of the control specimen. • The synergistic performance of hybrid fibre enhanced the concrete's durability. • HFRC has a higher water absorption capacity than the control specimen. • HFRC is promising as a sustainable building material. [ABSTRACT FROM AUTHOR]

The construction industry seeks innovative solutions like smart concrete. Traditional concrete faces durability issues, environmental impact, and high rehabilitation costs. To address this, smart concrete combines eco-friendly materials with advanced nano-technology, featuring self-sensing and self-healing properties to detect damage early and autonomously repair cracks. Researchers explore methods to reduce concrete's carbon impact through clinker replacement and alternative binders. The industry moves toward sustainable and technologically advanced practices, where "smart concrete" marks a transformative shift in construction, promising eco-conscious, technology-driven building methods. This review explores smart technology in concrete construction, focusing on structural health monitoring and autonomous crack repair advancements. It consolidates diverse self-sensing and self-healing mechanisms, emphasizing their role in viable construction goals. The paper delves into the impact of nanomaterial on the mechanical and durability of self-sensing, self-healing, and self-adjusting concrete, showcasing smart concrete's potential for transformative construction practices. Biomimetic Structural Health Monitoring (SHM) systems using self-sensing concrete and nanomaterials detect strain changes independently, which is vital for effective monitoring. Real-time Structural Health Monitoring using embedded sensors aids in timely decision-making for asset management and ensures continued structural safety. Self-activated bacteria in concrete provide an eco-friendly solution for crack healing by producing calcium carbonate and reinforcing structural integrity. Bacteria-based agents show promise in enhancing concrete's crack repair potential, aligning with better construction practices. In conclusion, smart concrete presents a significant opportunity to transform the construction sector, emphasizing eco-friendliness, resource optimization, and robust infrastructure. • Smart concrete features self-sensing and self-healing properties to detect damage early. • Researchers are exploring methods to improve the properties of smart concrete through alternative binders. • Structural Health Monitoring (SHM) systems using self-sensing concrete aid in effective monitoring. • Self-activated bacteria in concrete provide a solution for crack healing, enhancing construction practices. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • At a same depth in concrete prism, the moisture content and sulfate concentration are higher at the diagonal of the prism. • There is no clear demarcation between ion convection and diffusion zones in concrete prism under dry-wet cycles. • The longer the wetting time in one dry-wet cycle, the deeper the spalling of concrete prism caused by sulfate attack. External sulfate attack (ESA) coupled with wetting–drying alternation poses a significant threat to the concrete durability, while there are few models to simulate the above ESA behavior. In this paper, a simplified transport-mechanical model is proposed to numerically analyze the deterioration of concrete prism under ESA and dry-wet cycles. Firstly, a transport model of sulfate ion in concrete prism is established by considering the behaviors of ion diffusion, convection and chemical reaction, and numerically solved by the finite difference method. Secondly, the crystallization pressure of sulfate products in porous system is analyzed to calculate the equivalent expansion force. Then, the expansion strain and its-induced damage are calculated, and the criterion of boundary movement is further proposed. On the basis of model validation, a numerical simulation is performed to analyze the transport-mechanical response in concrete prism under ESA and dry-wet cycles. The results show that, there is no clear demarcation between the convection and diffusion zones in the prism. The spatial–temporal evolution of ESA-induced damage is similar to that of ion concentration. The longer the wetting time in one dry-wet cycles, the deeper the spalling of concrete prism caused by ESA. [ABSTRACT FROM AUTHOR]

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

Palm oil fuel ash (POFA) is a waste material generated in power plants as a result of the combustion of palm oil industry waste for the generation of electricity. They are generally disposed to open fields causing traffic hazards besides potential of health hazards and environmental pollution problems. Due to its abundance and high pozzolanic characteristics, many researchers have evaluated its potential as a construction material. This paper presents an overview of some of the published results on the successful utilization of palm oil fuel ash as a supplementary cementitious material and the properties of such concrete at fresh and hardened stages. Studies indicate that there is a promising future for the use of POFA in normal, high strength and self compacting concrete as it shows high strength, low shrinkage and permeability, high resistance to carbonation, chloride, sulfate and acidic environments. At elevated temperature, the POFA concrete perform better than the ordinary Portland cement (OPC) concrete. The summery and discussions provided in this paper should provide new information and knowledge on the applications of greener and sustainable palm oil fuel ash concrete. [ABSTRACT FROM AUTHOR]

[Display omitted] • The silica fume addition enhances the mechanical and permeability properties of concrete. • The refinement of pores due to silica fume was effective in improving the permeability of concrete. • The excess amount of silica fume above the optimum limit shows an adverse effect on concrete. • The thermal performance of concrete using silica fume improves the peak cooling and heating load. • The silica fume has the feasibility to be used with other supplementary cementitious materials. The present paper discussed the silica fume (SF) as the SCM to replace cement partially in concrete. The paper aims to summarize till date literature findings and suggest necessary gaps in utilizing SF as SCM. The study's necessity and framework are highlighted through bibliographic analysis using VOS viewer software and Scopus search engine data and found a lack of research in the field of SCM in the last 5 years. The production process of SF and its physical and chemical properties are studied location-wise. The range of these properties is analysed, and it found that SF mean particle size is 10 times finer than cement which enhances the mechanical and durability of concrete. The mechanical properties studied reported that the optimum percentage of silica fume generally ranges between 7.5 and 12%. However, it is not constant and found to be dependent on w/c. An adverse effect on the characteristics of concrete was observed on excess addition of SF over the optimum limit. The feasibility of SF with other SCM and fibers was found effective in improving the concrete properties. The different properties based on the action of water transport through the concrete are studied, such as permeation, diffusion, migration, convection, void formation, sorption, wick action, absorption, and adsorption. The permeability properties were optimum between 7.5 and 10% SF. Further, the thermal performance of the building with and without SF-added concrete was performed using Revit software (BIM). It was reported that SF concrete is effective by 2.25 % and 4.30 % for cooling and heating load, respectively. Very few papers were found on the utilization of silica fume for the development of different construction products. The review concludes with recommendations for future research, aiming to stimulate more studies in this field. [ABSTRACT FROM AUTHOR]

Corrosion of reinforcement and concrete deterioration induced by aggressive media could severely reduce the bearing capacity of structures. The durability of alkali-activated materials (AAMs) in aggressive environments, such as carbonation, chloride penetration and sulfate attack, have been a research focus worldwide. Reaction products and microstructures of AAMs are different from ordinary Portland cement (OPC), therefore the corrosion mechanisms and assessments are different. This paper reviews factors influencing water absorption and permeability of AAMs, effect of gel composition and exposure environments on carbonation, chloride penetration and chloride migration test methods, and sulfate resistance in high-calcium and low-calcium alkali-activated systems. There remains a large space in these aspects to completely understand the deterioration of AAMs, as pointed out in the end. The perspectives suggested in this paper will be useful for future study on long-term durability of AAMs. [ABSTRACT FROM AUTHOR]

Application of nano-SiO 2 (NS) particles to reinforce high performance concrete (HPC) has received widespread attention from both construction industry and researchers due to their interface improving effect, small size effect, filling effect and surface effect. This paper critically reviews previous research carried out on the effect of NS on properties of HPC. Detailed review on the fresh properties, mechanical properties and durability of high performance concrete containing NS particles are presented. Through 76 recent and past literatures, the influence of SiO 2 nano-particles on workability and setting time of fresh mixture, compressive strength, flexural properties, fracture properties, water anti-permeability, chloride permeability, abrasion resistance, frost resistance, water absorption capacity, resistance to high temperatures and microstructure of HPC is discussed in this paper. The properties of NS modified concrete are compared with control concrete. Furthermore, this paper presents on the benefits and advantages to improve the HPC by using NS. It is shown that, in general, the incorporation of SiO 2 nano-particles significantly improves the mechanical properties and durability of HPC though the flowability of the fresh concrete is decreased by the usage of NS. This literature review also aims to provide a comprehensive insight into possible application of NS modified concrete in the construction industry today. [ABSTRACT FROM AUTHOR]

The use of hybrid short fibers in a suitable combination as reinforcement for cement based materials has attracted widespread attention because of their benefits compared to mono fiber reinforcement in recent years. This paper provides a review of recent developments on the area of the cement-based composites reinforced by hybrid short fibers. The aim of paper is to represent the effects of hybridization by elaborating upon the chemical, physical and mechanical properties of fibers on the performance of fiber reinforced concretes (FRC). This provides a summary of the existing knowledge about the successful use of different hybrid forms such as combination of steel, polymer and natural fibers in cementitious composites. Different types of hybrid system depending on fiber type are classified and reviewed. Furthermore, the physical and mechanical properties of resultant composites are also presented. Generally, inclusion of fibers in concrete as hybrid forms, improves many of its engineering properties such as toughness, ductility, energy absorption capacity and durability performance in comparison with mono fiber reinforcement. [ABSTRACT FROM AUTHOR]