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Alkali-activated binders (AABs) have been and continue to be extensively explored as an alternative to ordinary Portland cement (OPC), addressing environmental and sustainability issues. A large number of studies that were conducted earlier focused mainly on the mechanical properties and some durability aspects of industrial waste-based AABs. However, chloride migration and diffusion causing reinforcement corrosion in AAB-based concrete (AAC) have not been thoroughly investigated. The present study focuses on the durability of AAC produced using multiple precursors that included industrial waste materials and natural minerals such as limestone powder (LSP), red mud (RM), silicomanganese fume (SMF), and natural pozzolan (NP) activated by alkali. Firstly, the dosages of all four precursors were optimized through trials and then NP was partially replaced by 10, 20 and 30% OPC to enhance the performance of the AABs. The AAC mixtures were prepared and cured under different conditions and tested for compressive strength and durability characteristics related to chloride permeability, chloride migration, chloride diffusion, and chloride-induced reinforcement corrosion to evaluate the performances of the mixtures. The results show that the composition of the AABs and curing regimes significantly influenced the performance of the AAC. The inclusion of the OPC resulted in a very significant enhancement of the strength and durability characteristics of the AAC. In addition, there is a sharp increase in the performance of the AAC mixtures when the OPC content of the precursor was increased from 10 to 20%, irrespective of the curing method. Therefore, an optimum dosage of the OPC in the precursor can be considered as 20%, allowing utilization of 80% waste materials and natural minerals as the precursor with much higher strength and durability characteristics than traditional OPC concrete, thus saving energy and reducing environmental pollution leading to a cleaner production of concrete. Lastly, electrochemically measured corrosion potential (Ecorr) and corrosion current density (Icorr) values for the reinforcing bars (rebars) embedded in AAC mixtures were found to be misleading, as confirmed by visual inspection of the extracted rebars in addition to gravimetric test results. Hence, there is a need for further research to develop corrective measures before the utilization of the electrochemical-reinforced corrosion monitoring methods in the case of AACs. [ABSTRACT FROM AUTHOR]

Emerging demands to achieve zero carbon emissions and develop renewable energy resources necessitate the development of appropriate energy storage systems. To achieve this, several alternatives to conventional energy storage devices, such as Li‐ion batteries or capacitors to more sustainable and scalable energy storage systems, are being explored. Supercapacitors, possess unique characteristics that include high power, long life, and environmental‐friendly design. They may be used to bridge the energy‐power gap between typical capacitors and fuel cells/batteries. Recently, structural supercapacitors being capable of storing electrochemical energy besides bearing mechanical load have caught the attention of researchers. As such, efforts have been made worldwide to study both the fundamental and applied aspects of structural supercapacitors. Further, the possibility of using construction materials for interdisciplinary applications is being studied because they are relatively cheap and easily available. Thus, construction materials can be considered as potential candidates for the development of structural supercapacitors. Herein an overview on the use of construction materials, such as Portland cement concrete, geopolymer concrete, and bricks, as a component of structural supercapacitors has been presented. [ABSTRACT FROM AUTHOR]

The release of carbon dioxide (CO 2) into the earth's atmosphere is a substantial global environmental concern that arises from the processes of industrialization and urbanization. The increase in atmospheric CO 2 concentrations has resulted in the phenomenon of global warming and subsequent alterations in climate patterns. Accelerated CO 2 sequestration in cementitious materials is currently the subject of extensive research as a highly efficacious approach to mitigating the carbon footprint of the concrete industry. The sequestration procedure entails the transformation of gaseous CO 2 into carbonate minerals. The review presented in this paper outlines the most recent carbonation (i.e., CO 2 sequestration) techniques, such as mineral carbonation, accelerated CO 2 curing (ACC), pre-carbonation, and carbonation mixing, that have been recently explored. The potential of mineral carbonation of industrial wastes and the advantages of their incorporation in the concrete matrix is investigated. Carbonation technologies and their effect on the performance of cementitious composites are reported. Information on life cycle assessment are also included to evaluate the environmental impact associated with the production of carbonated materials. Various commercialized CO 2 utilization technologies in construction sector, such as CarbonCure, Solidia, Carbstone, Calera, and Carbon8 are reviewed. Moreover, this review offers a thorough insight into the carbonation technologies, evaluating their advantages, limitations, and the existing gaps in research. • Various carbonation techniques for CO 2 incorporation in concrete comprehensively reviewed. • Limitations and research gaps of carbonation technologies are discussed. • Potentials uses of CO 2 -mineralized industrial wastes in the concrete discussed. • Commercial CO 2 utilization technologies in the construction sector identified. • LCA of carbonated materials to ensure sustainable production practices presented. [ABSTRACT FROM AUTHOR]

Highlights • Use of natural pozzolan as partial replacement of cement and microsilica in UHPC mixtures. • No negative impact on the key properties of UHPC due to addition of natural pozzolan. • Significant saving of microsilica and cement due to use of natural pozzolan. Abstract Ultra-high performance concrete (UHPC), comprising of high amounts of cement and microsilica as binder and micro filler, is a new generation of concrete possessing highly dense microstructure with excellent mechanical properties, durability characteristics and ductility (fracture toughness). However, the use of high amounts of cement and microsilica makes UHPC costly and environment-unfriendly. In the present study, an effort is made to study the effects on properties of UHPC mixtures due to incorporation of natural pozzolan (NP) as a partial replacement of cement and microsilica. Targeting a significant reduction in consumption of cement and microsilica without compromising the required workability, six UHPC mixtures were considered. The first mixture was taken as control mixture without replacement of cement and microsilica by NP. In the second and third mixtures, 25 and 50% microsilica was replaced by NP, respectively. In fourth, fifth and sixth mixtures, 10, 20 and 30% of cement was replaced by NP, respectively. Specimens were moist-cured for 14 days before exposing them to air in the laboratory conditions. All the six UHPC mixtures were tested to determine the mechanical properties (compressive and tensile strengths, modulus of elasticity, and fracture toughness), drying shrinkage, and chloride permeability. Test results indicate that the replacement of cement (up to 30%) and microsilica (up to 50%) by NP did not significantly affect the fresh and hardened properties of UHPC mixtures confirming the potential of using NP for producing cost-effective and environment-friendly UHPC mixtures. [ABSTRACT FROM AUTHOR]

Self-consolidating concrete (SCC) is a concrete material possessing an ability to take formwork shapes and pass through congested reinforcement bars without being vibrated, making it a 'smart concrete' material. However, the high cost of SCC resulting from the use of mineral fillers and high cement content has been a main factor impeding the widespread use of this smart material. Consequently, there is a need to investigate the use of low cost materials in the production of SCC to ensure adoptability of SCC in concrete construction. This paper presents the results of a study conducted to develop and evaluate the performance of four SCC mixtures using different combinations of filler materials, such as silica fume, natural pozzolana and metakaolin, in conjunction with limestone powder. The developed SCC mixtures exhibited high strength (compressive, tensile, bond and elastic modulus), excellent shrinkage behavior and good durability characteristics (high corrosion resistance and related indices). The findings of this study indicated the possibility of producing cost-effective and high-performance SCC mixtures using the mineral fillers considered in this study. [ABSTRACT FROM AUTHOR]

Permeability of concrete is often used as a key material property for assessing its durability. For a porous material in general, permeability depends upon the pore characteristics (i.e. porosity and tortuosity of pore channels). In this study, an attempt has been made to observe the relationship between pore characteristics and permeability of concrete. Data pertaining to porosity, tortuosity and permeability of concrete were typically obtained by testing different concrete mixtures prepared with varying water/cement ratios, cement contents and coarse/fine aggregate ratios. The experimental data were used to explore the correlation between pore characteristics and permeability of concrete. The results show that a correlation exists between the porosity/tortuosity ratio and the permeability of concrete, the coefficient of permeability increasing with increasing porosity/tortuosity ratio. The experimentally observed correlation bears resemblance to Kozeney's theoretical formation of intrinsic permeability in which permeability is expressed as a function of the porosity/tortuosity ratio. [ABSTRACT FROM AUTHOR]

The advent of ultra-high-performance concrete (UHPC), a new generation of cementitious material having excellent material properties, has generated a great deal of interest in the field. In this study, the fracture properties of UHPC mixtures reinforced with steel fiber (fiber content varying from 0 to 6.2 % by weight) and subjected to thermal cycles were investigated to examine the effect of heat--cool cycles. The standard prism of 100 x 100 x 400 mm³ with a central notch was used in a three-point bend test to determine fracture properties that include critical stress-intensity factor (Kic), critical crack tip opening displacement (CTODc), energy release rate, and total fracture energy. All specimens were water-cured for 28 days. Two exposure conditions were used: a 6-month thermal cycling and a 6-month laboratory exposure for further self-curing. The thermal cycling comprised heating in an oven at 60°C for 2 days and then cooling them at room temperature for the next 2 days over a period of 6 months. Test results show that UHPC reinforced with 6.2 % steel fiber exhibited excellent fracture properties with significant ductility. Both thermal cycling and prolonged self-curing of water-cured UHPC specimens enhance fracture properties because of more complete hydration of cement in UHPC. This improvement in properties signals an additional advantage of water-cured UHPC for its application in hot climatic conditions. [ABSTRACT FROM AUTHOR]

Corrosion of steel in concrete is a slow process. Due to the protective nature of concrete, it takes a reasonably long time for initiation and progress of reinforcement corrosion even in the case of severe corrosive exposure conditions. It is difficult to achieve a significant degree of reinforcement corrosion in a limited duration available for performing research studies evaluating (i) the loss of bond and loss of load-bearing capacity of corroding reinforced concrete members, (ii) the effect of mineral admixtures in reducing reinforcement corrosion, (iii) the performance of coated or alloyed reinforcing bars against reinforcement corrosion, and (iv) the effectiveness of electrochemical techniques applied for the prevention of reinforcement corrosion. For this reason, various techniques for inducing accelerated corrosion of steel in concrete are used by the researchers. In this paper, an attempt has been made to firstly describe the impressed current technique commonly used for accelerating reinforcement corrosion in small- as well as large-sized concrete specimens in the light of state-of-the-art information available in the literature. Then the procedure for calculating degree of induced corrosion in percentage by mass and in terms of average corrosion current density using the intensity and duration of the applied current is presented. The effectiveness of the applied current in inducing reinforcement corrosion, guidelines for effectively using the impressed current technique, and some of the alternative techniques for inducing accelerated corrosion of steel in concrete are also described in the paper. [ABSTRACT FROM AUTHOR]

An experimental study was conducted to evaluate correlations between the depth of water penetration, chloride permeability, and coefficient of chloride diffusion in plain, silica fume, and fly ash cement concretes. A total of 27 concrete mixtures were prepared by varying the water to cementitious materials ratio and cementitious materials content and using Type I, fly ash (20 %), and silica fume (7.5 %) cements. The test results were statistically analyzed to develop correlations between the depth of water penetration, chloride permeability, and coefficient of chloride diffusion. A good correlation was noted between the depth of water penetration and chloride diffusion, and chloride permeability and coefficient of chloride diffusion (R²>0.80). [ABSTRACT FROM AUTHOR]

• The use of CDP reduced water demand and increased the setting time of paste blends. • CDP improved the early strength of concrete, contributing positively to industrial waste recycling. • Mortar mixtures incorporating up to 50% CDP exhibited comparable 28-day compressive strength to the control mixture. • CDP type and curing procedure have no significant effect on the 28-day strength of concrete. This study evaluated the strength development in hyperalkalized concrete mixtures incorporating cement waste-derived Portlandite (CDP), synthesized from two variants of cement kiln dust (CKD). The source CKDs (coded CKD1 and CKD2) and synthesized CDPs (coded CDP1 and CDP2) were characterized physically and mineralogically, after which the CDPs were used as cement replacement, from 0 to 60 %, in the mortar phase of a base concrete mixture at w/b of 0.5 and 0.425. After in-mold curing, the mortar mixtures were subjected to 12 h of accelerated carbonation curing (ACC), and then moist–cured until 28 days. The strength development and alkalinity of mortar mixtures were investigated using the strength activity factor (SAF) and pH analysis, respectively. The incorporation of more alkaline and fine-grained CKD1 (D50 = 14.74 µm) was found to increase the water demand and setting time of CKD-cement paste blends, compared with the coarse-grained CKD2 (D50 = 27.51 µm). Additionally, the use of CDP reduced water demand but increased the setting time of paste blends. Further, the incorporation of CDP increased the early-age compressive strength of mortar, but its effect diminished as the mixtures matured, with SAF reduction of over 50 % in most cases. Finally, CDP1 mixtures exhibited about 30 % higher early–age compressive strength than CDP2 counterparts but the difference evened out at a later age, with the studied mixtures exhibiting 28-day compressive strengths varying between 23 and 54 MPa. [ABSTRACT FROM AUTHOR]

Abstract: In this study, plain, silica fume and fly ash cement concrete specimens prepared with varying water to cementitious materials ratio and cementitious materials content were tested for compressive strength, water permeability, chloride permeability, and coefficient of chloride diffusion after 28days of water curing. The data so developed were statistically analyzed to develop correlations between the compressive strength and the selected durability indices of concrete. Very good correlations were noted between the compressive strength and the selected durability indices, particularly chloride permeability and coefficient of chloride diffusion, irrespective of the mix design parameters. However, these correlations were observed to be dependent on the type of cement. [Copyright &y& Elsevier]

The increasing trend in the use of silica fume blended cement in Eastern Saudi Arabia for the improvement of corrosion resistance of reinforced concrete has brought into focus a need for a better understanding of the transport mechanism of chloride ions in silica fume concrete in the prevailing environmental conditions. In the present work, chloride penetration into plain and silica fume cement concrete specimens was investigated under different exposure conditions to determine the apparent diffusion coefficients. For this purpose, data pertaining to chloride profiles were generated through an experimental program in which cylindrical and slab concrete specimens, cast with different water/cement ratios and quantity of silica fume, were exposed to 15% sodium chloride solution under four exposure conditions that included indoor and outdoor environments and heat-cool and wet-dry cycles. Using the experimental data, apparent chloride diffusion coefficients were calculated using Fick's second law of diffusion. Test data show that the apparent chloride diffusion coefficient for a given concrete depends on the type of cement in concrete and the exposure conditions. While the chloride diffusion coefficients in the silica fume cement concrete were less than that in the plain cement concrete, these values in the concrete specimens exposed to heat-cool cycles were found to be higher than those in the specimens exposed to other conditions investigated in this study. [ABSTRACT FROM AUTHOR]