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This experimental research addresses the physical properties of eco-friendly Ultra High Performance Concrete (UHPC) incorporating industrial by-products including coal bottom ash, fly ash and two types of slag powder. Slump flow, compressive strength development, porosity, setting time, autogenous shrinkage and thermogravimetric analysis of UHPC are characterized. The experimental results indicate that coal bottom ash and fly ash are promising industrial by-products by effectively replacing silica powder in UHPC without significant losses in workability and strength development. It is revealed that normal-sized and finer-sized ground granulated blast furnace slag can be effectively used without additional activator to partially substitute cement and silica fume, respectively, which results in enhanced workability and comparable compressive strength, albeit relatively slow strength development. Furthermore, it is found that the adoption of various forms of industrial by-products in UHPC does not play a significant role in affecting autogenous shrinkage, porosity and capillary water absorption of UHPC. [ABSTRACT FROM AUTHOR]

The effect of fiber addition on the properties of fresh and hardened concretes casted by centrifugation was investigated. Workability of fresh concrete mixtures, sludge bleeding after centrifuging, and mechanical properties of hardened concrete including compressive and splitting tensile strengths and modulus of elasticity were examined. Post-crack behavior of spun cast concrete was investigated by splitting tensile testing. Considering sanitary sewer environments, concrete resistances against sulfuric acid erosion and sulfate expansion were evaluated. Although the addition of low fiber fractions (below 0.15 vol.%) did not significantly affect workability and strength of the spun cast concretes, it enhanced their toughness and resistance against sulfate expansion. [ABSTRACT FROM AUTHOR]

A novel non-destructive method of monitoring chloride penetration in reinforced concrete structures prior to corrosion is proposed. By measuring the change in the electrical characteristics induced by chloride in cement composites containing carbon nanotubes (CNTs), chloride penetration in the structures could be monitored in real time. To evaluate the feasibility of this method, cement composites containing various amounts of CNTs and sodium chloride were fabricated and their electrical characteristics were measured. Although the conductivity of the composite without CNTs fluctuated as a result of both reinforcement and moisture content, that of the composites with CNTs was seldom influenced by these factors, and the conductivity generally increased with increasing chloride content. The chloride content in the composites was estimated via regression analysis based on the electrical characteristics, implying that the CNT/cement composite could be used as a sensor for chloride penetration monitoring. [ABSTRACT FROM AUTHOR]

A novel method to accurately measure the water absorption of a fine aggregate with a macroporous surface, such as by-product aggregates, was investigated. Due to their unique particle shape and macropores on the surface, the saturated surface-dry (SSD) condition of the aggregate was hard to be defined by means of conventional test methods. In the present study, the SSD condition of the aggregate was newly defined via centrifugal compaction of the cement mortar considering the penetration of cement paste into the macropores. The water absorption values for aggregates, i.e., the moisture contents for it at SSD condition, were measured using the present method and compared to those measured using conventional methods. From the standpoint of concrete mix design, the water absorption values of porous aggregates measured using the proposed method were more reasonable than those measured using the conventional methods. [ABSTRACT FROM AUTHOR]

In the present study, sieved and ground coal bottom ash powders were utilized in high-strength mortar as a coarse binder to help improve workability. The chemical and physical characteristics of the powders were evaluated. The hydration heat of blended binders was measured. The workability, hydration kinetics, compressive strength, and autogenous shrinkage of the mortar were investigated. The workability of the high-strength paste and mortar mixtures with bottom ash powders was significantly higher than that of mixtures including only cement and fly ash. Owing to their higher pozzolanic reactivity, the mortar containing bottom ash powders exhibited a higher degree of hydration and similar compressive strengths at 3 and 28 days compared to the mortar with fly ash. [ABSTRACT FROM AUTHOR]

• Mechanical properties of FRCM composites with different types of textile grids. • Application of aluminum powder on textile grids surface. • Effect of textile characteristics on the strength and toughness of FRCM composites. • Investigation on the flexural behavior of RC beams with FRCM composites. This experimental work aims to evaluate the flexural strengthening effectiveness of, as well as to mechanical characterize, the different types of textile grid and AL (Aluminum) powder surface coating. The experiment variables were weaving method (Pillar stitch, Leno weave) type of impregnation (SBR, EPOXY), and AL powder surface coating. The mechanical properties of FRCM systems were evaluated by direct tensile and bending tests of FRCM and flexural tests of RC beams. Direct tensile tests of FRCM were performed with clevis grips (AC434.13). Bending tests of FRCM were performed with ASTM C 1609 M. Flexural behavior and performance were analyzed in flexural tests using reinforced concrete beams strengthened with FRCM systems. For flexural tests, nine reinforced concrete beams 2,500 mm long, 150 mm wide, and 250 mm deep were fabricated. The RC beams were classified into two groups according to the rebar ratio (1.5ρ min , 0.75ρ max), and consisted of two reference specimens and seven specimens externally strengthened with the FRCM system. Test results showed that the mechanical property of FRCM systems and the flexural capacity of RC beams highly depend on the weaving methods and the impregnation types of textile grids. [ABSTRACT FROM AUTHOR]

• The effect of web opening located in the plastic hinge region on the cyclic flexural performance of RC beams. • The maximum opening diameter applicable to the plastic hinge region was estimated using the effective depth and the net tensile strain in the extreme tension reinforcement. • The minimum spacing between web openings in RC beams was estimated using the inclination of the critical shear crack. This paper describes the effect of a small circular web opening located in the plastic hinge region on the cyclic flexural performance of RC beams. The variable in the design of specimens is the diameter of the circular web openings installed in the plastic hinge region. Two rectangular beams scaled down to 67% of a practical RC beam were fabricated to have circular openings in the plastic hinge region with diameters 0.2 and 0.3 times the height of the beam. In another beam, in addition to the opening in the plastic hinge region, a web opening with a diameter of 0.3 times the height of the beam was installed at a location 180 mm from the center of the span. A total of four beams including a control beam were subjected to cyclic anti-symmetric moment. The cyclic flexural performance of the beams was evaluated in terms of hysteretic response, including strength, stiffness, ductility, and energy dissipation capacity. The neutral axis depth of the plastic hinge during the cyclic loading test was calculated using the linear distribution of strains of longitudinal reinforcing bars placed at the top and bottom of the openings. In addition, using the effective depth of the RC beams and the net tensile strain in the extreme tension reinforcement for tension-controlled sections, which are recommended by ACI 318–19, the maximum diameter of the circular web opening in the plastic hinge region was approximated and compared with the test results. Furthermore, with reference to the results of certain exiting studies, the ratio of the spacing between openings to the maximum diameter of the circular web opening was suggested by assuming the case of designing web openings to leap over major shear cracks expected to occur in a flexural RC beam undergoing shear-flexural failure. [ABSTRACT FROM AUTHOR]

• Efficient and accurate continuum mechanics-integrate ML technique was proposed. • Higher replacement rate of CCB aggregates led lower elastic characteristics of concrete. • Derived multi-phase constitutive equation was implemented into a FE analysis. • The optimal nonlinear parameters of model were estimated by ML algorithm. In this paper, we present micromechanics-integrated machine learning studies of concrete containing crushed clay brick as a coarse aggregate. Initially, the stress-strain responses of normal and crushed clay brick aggregates were quantitatively measured. Concrete specimens with various water/cement ratios and replacement rates of the aggregate were then fabricated and their stress-strain responses were evaluated. Concrete mixed with crushed clay brick aggregate showed lower compressive strength compared to concrete containing normal aggregate, and it was difficult to predict the material performance based on existing specifications and models. Based on results from an experimental assessment, micromechanics-integrated machine learning approaches that can effectively predict the properties of concrete mixed with crushed clay brick aggregates was developed. Several parametric studies and comparisons are carried out to verify the potential capacity of the proposed model framework. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the design, analysis, and fabrication of a steel-reinforced hybrid GFRP (glass-fiber-reinforced polymer) deck panel that can be used to furnish the roadway surface of temporary bridges. Two hybrid cross-sectional profiles were proposed to increase the flexural stiffness of the GFRP deck panel, and the structural performance of the hybrid deck profiles was compared on the basis of finite element analysis. The results indicate that the flexural stiffness of the GFRP deck panel can be effectively increased by the proposed method of hybridization presented in this paper. The results and findings are summarized. [Copyright &y& Elsevier]

• Long-term irradiation damage on reinforced concrete (RC) member is numerically investigated. • Deformation due to radiation induced volume expansion is consistently evaluated. • The irradiation on RC members leads to changes in structural characteristics. • Irradiation effects must be carefully considered for RC structural design and analysis. • The present study can provide a basis for the standardization of the assessment of irradiated RC structures. In the long-term operation of nuclear power plants (NPPs), irradiation can adversely affect the behavior of reinforced concrete (RC) members because of the degradation of the constituent materials. Degradation of concrete may be associated with the volume expansion of concrete due to irradiation, which is known as radiation-induced volume expansion (RIVE). As the compressive strength of concrete decreases under irradiation environments, the yield stress increases, and the ductility of steel decreases. Furthermore, the material properties of concrete and reinforcing steel vary within the cross-section of RC members because of the flux attenuation. In this study, such complicated changes in the material characteristics are systematically considered by using a simple fiber modeling approach to analyze the RC member behaviors. The effects of RIVE on the flexural members are computed by employing compatibility and equilibrium conditions. Based on the proposed framework, the behaviors of RC members are investigated under static and seismic loading conditions. The computational results demonstrate that the irradiation on RC members leads to changes in the structural characteristics such as the maximum load capacity, ductility, toughness, and the maximum spectral acceleration and corresponding period. Therefore, the irradiation effects must be carefully considered in RC structural analyses. [ABSTRACT FROM AUTHOR]

• Pure torsional behavior of RC beams in relation to the amount of torsional reinforcement and cross-sectional properties. • The experimental results were compared to the analytical results obtained from ACI 318-19 building code to examine the validity of ACI 318-19 building code. • The angle of the concrete compression strut θ can be calculated using the sum of forces occurring in the shear flow. According to the current ACI318-19 building code, torsional strength is calculated by reflecting the effective area of concrete and the properties of torsional reinforcement, regardless of the cross-sectional properties of the reinforced concrete members. Past research has revealed that the torsional failure mode of RC members subjected to torsional strength is influenced by the contribution of the concrete and the amount of torsional reinforcement. In this study, 11 experiments were conducted to examine the pure torsional behavior of RC members in relation to their cross-sectional properties, and the amount of torsional reinforcement. The experimental variables were (1) the properties of the solid and hollow cross-sections, (2) the amount of arranged torsional reinforcement compared to that of the ACI 318-19 building code, (3) the yield strength of the torsional reinforcement, and (4) the spacing of the torsional reinforcement. The results showed that solid cross-sections and hollow cross-sections had similar levels of torsional strength. In addition, the specimens with a smaller amount of arranged torsional reinforcement were engaged in ductile behavior when compared with the ACI 318-19 building code, regardless of their cross-sectional properties. [ABSTRACT FROM AUTHOR]

• Method of using EAF (electric arc furnace) oxidizing slag aggregates to efficiently reduce environmental loads. • Bond strength of RC beams using EAF oxidizing slag aggregates. • Excellent bond performance of concrete with EAF oxidizing slag aggregates. • Performance evaluation of RC members with EAF oxidizing slag aggregates, reflecting mechanical properties. The present study was conducted to evaluate the bonding performance of reinforced concrete beams with electric arc furnace oxidizing slag aggregates. The specimens were tested by varying the aggregates, and the top and bottom longitudinal reinforcement position, depending on concrete placement. The specimens containing electric arc furnace oxidizing slag aggregates showed bond performance that was on average of about 8% to 20% higher than that of the specimens using natural aggregates. The bond strength was higher at the corner longitudinal reinforcement than at the inner longitudinal reinforcement and higher at the bottom reinforcement than at the top reinforcement, regardless of the aggregate type. The experimental results were consistent with results from previous studies with concrete containing natural aggregates. Comparison with previous studies confirmed the excellent bond performance of the concrete with electric arc furnace oxidizing slag aggregates, and demonstrated the use of concrete containing electric arc furnace oxidizing slag aggregates for structural members. [ABSTRACT FROM AUTHOR]

This study investigates the role of slag in the hydration and carbonation of carbonation-cured slag cements. Slag-blended cement paste samples with slag contents of 0, 10 %, 30 % and 50 % were carbonation-cured for up to 28 days. The result revealed an increase in the carbonation depth to 20 mm with prolonged curing time and higher slag content facilitated greater carbonation penetration. The CaO content did not adversely affect the final CO 2 uptake capacity; rather, an optimal slag content of 10 % slag replacement enhanced CO 2 uptake, forming 57.4 g of CaCO 3 on the surface after 28 days of carbonation curing, while PS30, PS50 and P100 formed 52.2 g, 45.2 g and 43.4 g, respectively, though higher slag levels accelerated the carbonation rate. Moreover, slag hydration led to Ca2+ ion consumption and subsequent reduction in portlandite content. The extent of belite reaction was significantly improved in the slag-blended cements, providing a source for enhanced CO 2 binding capacity in the blended cements. These findings contribute to improved understanding of behavior of blended cements prepared by carbonation-curing, enabling the development of more sustainable and durable concrete structures. • The role of slag in hydration of carbonation-cured slag cements was studied. • Increased slag content in blended PC enhances carbonation depth, especially with prolonged curing. • Optimizing slag content increases CO 2 uptake capacity, making it essential for sustainable construction. • Slag content enhances belite dissolution rate, resulting in higher CO 2 binding capacity in slag-blended PC. [ABSTRACT FROM AUTHOR]

• Slag-based composites show different self-healing phenomena according to activator types. • CaCO 3 is the major healing material of the calcium hydroxide-based AAS composite. • C-(N)-A-S-H and other carbonates are the dominant healing products of sodium-based AAS composites. This paper presents an experimental investigation of the self-healing ability of fiber-reinforced slag-based composites activated by a single type of alkali activator at an early age. In order to investigate the effects of the type of alkali activator on the self-healing ability of fiber-reinforced slag-based composites, three mixtures reinforced by polyethylene fibers and with different alkali activators, in this case calcium hydroxide, sodium hydroxide, and sodium silicate, were designed and prepared. Compressive strength and uniaxial tension tests were conducted to measure the mechanical properties of each mixture. The self-healing ability in each case was evaluated by observing the crack width and by measuring the resonance frequency. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were also utilized to analyze the morphology and chemical compositions of the healing materials. The results of these tests showed that autogenous healing of alkali-activated slag-based composites is accomplishable through structural restoration, specifically by reducing the crack opening and through mechanical recovery. The dominant healing materials of the calcium activator-based alkali-activated slag composite was CaCO 3 , in contract to the C-(N)-A-S-H, CaCO 3 , and some amount of Na 2 CO 3 which formed in the sodium activator-based alkali-activated slag composites. [ABSTRACT FROM AUTHOR]

This experimental study was conducted to evaluate the abrasion resistance of ultra high performance concrete (UHPC) that incorporated pre-selected coarser aggregates. The aggregates were selected based on their properties and local availability. In addition, coal bottom ash powder was also used with coarser aggregates as a replacement for silica powder. The examination was made according to the ASTM C 944 test method and the results were determined and presented as mass loss and depth of abrasion. All the results from the tests reveal the excellent abrasion resistance of UHPC; however, when compared to each other, the UHPC with coarser aggregates shows a lower abrasion resistance than the UHPC with no coarser aggregates. [ABSTRACT FROM AUTHOR]

This study aims to investigate the feasibility of recycled aggregates (RA) as an internal curing agent for an alkali activated slag (AAS) system. The physical and chemical characteristics of the aggregates were studied through various analytical techniques including X-ray diffraction, thermogravimetry, mercury intrusion porosimetry, and indirect alkalinity measurements. The compressive strength, degree of hydration, and autogenous and dry shrinkages of AAS generated with RA were measured and compared with those of AAS made using artificial lightweight aggregates. The use of RA can reduce the autogenous shrinkage of an AAS system without a decrease in compressive strength. The degree of hydration for AAS mortar was not increased by the addition of RA owing to the dilution effect of the alkali activator, which was caused by the additional water supplied from internal curing materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Activation of WCP phases at comparatively lower temperature of 650 °C. • Thermo-mechanical activation of waste concrete powder (WCP) improved the reactivity. • Up to 40% activated WCP can be effectively utilized without degradation of strength. • The presence of cementitious phases in activated WCP were characterized. • WCP based binder resulted in 37.6% less CO2 emission in comparison to OPC. The objective of present study is to utilize and study the reactivity and hydration behaviour of thermo-mechanically activated waste concrete powder (WCP). For activation, the WCP was burned for 2 h at 650 °C, followed by mechanical grinding through ball milling. The reactivity of the activated WCP was improved significantly, as corroborated through the Chapelle test, hydration analysis and compressive strength analysis. Different blends were prepared with 10 to 40 % OPC replacement. Activated WCP was found to be effective in enhancing the reactivity of cement mixtures for all replacement proportions and developed comparable compressive strength in comparison to OPC. At 56 days, the application of activated WCP resulted in the developed of 75.5 % better compressive strength than the application of as received WCP. Mineralogical analysis exhibited the development of more secondary C-S-H gel with the formation of calcite at the later age. Using lifecycle analysis software, the replacement of 40 wt% of OPC with activated WCP was calculated with 37.6 %, 39.8 % and 19.7 % less CO 2 emissions, less mineral resources consumption and less energy consumption, respectively. [ABSTRACT FROM AUTHOR]

Coal ash generated from the combustion process of thermal power plants and excavated soil from construction sites in Jeolla Province (South Korea) have significant environmental and economic impacts. The aim of this study is to evaluate the feasibility of controlled low strength material (CLSM) production using wastes (e.g., ponded ash, fly ash, and excavated soil) and cementless binder as full replacement of Portland cement in CLSM mixtures by assessing its engineering properties. First, control mixtures were produced with Portland cement or cementless binder, Class F fly ash, ponded ash, and water. Then, for other mixtures, excavated soil substituted for ponded ash in amounts of 10, 20, 30, and 40% by weight. The bleeding, flowability, and initial setting time of fresh CLSM mixtures were measured; afterward, they were hardened and tested for compressive strength, water absorption, and corrosivity. It was found that the engineering properties of CLSM with excavated soil, possibly up to 30%, satisfied the specifications of ACI 229R. In particular, it was found that an increase in excavated soil content as replacement could lead to an improvement in the stability (bleeding rate) of the proposed CLSM mixtures. Finally, it is worth noting that cementless binder could be feasibly used to completely replace Portland cement in CLSM production. [ABSTRACT FROM AUTHOR]

• Hollow glass microspheres (HGMS) were used a lightweight material in UHPC matrix. • HGMS were found to be pozzolanic in nature. • Lightweight UHPC having oven dry density of 1862 kg/m3 was developed. • Performance of lightweight UHPC containing HGMS was studied. The present study proposes the development of ultra-high performance lightweight concrete (UHPLC). Hollow glass microspheres (HGMS) were used as a lightweight material, and their pozzolanic activity was verified through different tests under multiple curing conditions. High volume of HGMS was incorporated into ultra high performance concrete (UHPC) matrix, and UHPLC with a compressive strength of 160 MPa and oven dry density of 1862 kg/m3 was developed. The UHPLC was exposed to temperatures up to 1000 °C and a coupled cycle of chloride penetration and carbonation. The developed UHPLC performed well in high temperature exposure tests, with the oven-cured samples showing around 10 % mass loss after 30 h exposure. Despite such reduction of density, the UHPLC did not show any significant degradation to chloride ions and carbonation. The experimental results show that the developed UHPLC is durable in terms of high temperature exposure and coupled loading of chloride penetration and carbonation. [ABSTRACT FROM AUTHOR]

The present study investigated the effect of the lightweight aggregate content on the carbonation response of concrete according to its compressive strength and water-to-cement ratio. Twenty-five concrete mixes containing structural lightweight aggregates produced using artificially expanded bottom ash and dredged soil granules were tested in a controlled chamber with a temperature of 20 ± 2 °C, a relative humidity of 60 ± 5 %, and a CO 2 concentration of 5 ± 0.2 %. Nonlinear regression analyses were conducted to examine the effect of the 28-day compressive strength and density of the concrete on the propagation of carbonation and CO 2 diffusion coefficients at different exposure times. The experimental and regression results clearly revealed that the propagation of carbonation was somewhat affected by the density as well as the compressive strength of the concrete. The increase in the lightweight aggregate content slightly delayed the diffusion of CO 2 within the concrete. Consequently, lightweight aggregate concrete (LWAC) exhibited a slightly lower carbonation depth compared to normal-weight concrete with a similar mixture proportion to achieve the designed compressive strength. The proposed empirical equations also show promise for the assessment of carbonation depth and CO 2 diffusion coefficients for LWAC exposed to a controlled carbonation environment. • This study presents compelling experimental data on carbonation response of LWAC. • We formulated CO2 diffusion coefficients exposed at different times for LWAC. • We found that lightweight aggregate content slightly delays the diffusion of CO2. • We demonstrated that the carbonation depth was lower for LWAC than for NWC. [ABSTRACT FROM AUTHOR]

In this study, the overall carbonation depth of existing bridges was investigated to establish practical guidelines for diagnosing structural carbonation. Carbonation depth was measured by obtaining cross-sections and core samples of girder-slabs from six existing concrete bridges scheduled for dismantling. The variation in carbonation depth based on the structures' location was analyzed. Moreover, various protocols were proposed for deriving the characteristic values of in-situ carbonation depth for concrete structures and each protocol was verified through probabilistic simulations. Carbonation depth exhibited inconsistency across the cross-section, varying significantly depending on the location, but a deeper carbonation was especially noticeable in locations subjected to bending or tensile stress by design. The method to select the largest value from the core data obtained are considered suitable to prevent both underestimation and overestimation. • Carbonation depth varies widely (0–100 mm) across bridge sections. • Normal distribution of carbonation depth observed in experiments. • Upper girder sections showed relatively consistent carbonation. • Lower flange portions exhibited deeper carbonation due to stress. • Method selecting the largest core value suitable to prevent bias. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ocean-borne plastic flakes applied to cement composite materials. • Equivalent-strength-based mix proportion was applied. • Material cost and CO2 footprint of the mixtures using this model was discussed. • Use of ocean plastic as fine aggregates for concrete required about 0.50 USD and 1.1 kg CO2 per 1 kg plastic. The economic and environmental effects resulting from the use of ocean-borne plastic flakes applied to cement composite materials were quantitatively evaluated in terms of the equivalent-strength-based mix proportion. Waste plastic flakes were collected from ocean debris, and chemical properties were characterized to confirm the types of plastics. The plastic flakes were incorporated as fine aggregate to cement mortar mixtures at various mix proportions, and their effects on the workability and mechanical properties of the mortar were evaluated. A regression model of the compressive strength and mix proportion was established, and the effect of the use of flakes on the material cost and CO 2 footprint of the mixtures using this model was discussed. According to the concept of equivalent-strength mix proportion, the calculated social cost to utilize 1 kg of waste plastic from the ocean as fine aggregates for concrete was approximately 0.50 USD (0.30 USD for treatment and 0.17 USD for mix proportioning), which was approximately 80% higher than that of simple disposal. Moreover, an additional 1.1 kg of CO 2 emission related to strength compensation was yielded, which was also much higher than the CO 2 -equivalent value for simple disposal, i.e., 0.255 kg. [ABSTRACT FROM AUTHOR]

• Whole process on utilize coal bottom ash as a fine aggregate for concrete was evaluated. • Pretreatment of bottom ash including particle size control is essential. • Strength and durability of concrete was constant by use of pretreated bottom ash. • Cost of concrete was strongly influenced by treatment process of ash and incentives. • CO 2 emissions were determined by the binder, rather than the use of bottom ash. The production cost of concrete using coal bottom ash as a fine aggregate, along with the associated CO 2 emissions, was critically assessed through a case study. Two types of reinforced concrete buildings, one with a beam-column rigid frame system and the other with a slab beam-wall frame system, were selected. Structural designs and concrete mix proportions were determined in accordance with domestic standards. The study estimated the total cost and CO 2 emissions associated with the production and transportation of concrete for these buildings considering treatment of bottom ash. The advantages of using bottom ash as a fine aggregate, in terms of cost and CO 2 emissions, were found to be significantly influenced by various factors, including the handling and treatment processes of ash, as well as the availability of relevant subsidies or incentive. [ABSTRACT FROM AUTHOR]

• Parameters that influence autogenous shrinkage of AASA are explored by modeling. • High capillary pressure and creep-like behavior of AASA were the main drivers of its large shrinkage. • The shrinkage of AASA correlated well with its pore formation. In this study, a simple modeling scheme was employed to observe the autogenous shrinkage of sodium silicate-activated slag (SSAS)- one of the most widely used alkali-activated materials. The model parameters, including internal relative humidity, saturation degree of pores, capillary pressure, bulk modulus, and hydration degree were experimentally obtained. The mechanism of SSAS shrinkage was explored using the obtained modeling parameters, which may have some physical quantities, and was discussed comparatively with the shrinkage characteristics of OPC. The results indicated that the most important factors influencing the large shrinkage of SSAS were the high capillary pressure and creep-like behavior, which correlated with pore formation, rather than the stiffness of the matrix and the hydrate type. [ABSTRACT FROM AUTHOR]

• A hydration kinetics model for sodium silicate-activated slag cement is proposed. • Despite a less amount of water is consumed, sodium silicate-activated slag experiences larger chemical shrinkage. • The larger chemical shrinkage of sodium silicate-activated slag is associated with the internal relative humidity. • The hydration kinetics is influenced by the pore distribution, and is higher when pores were distributed in a wider range. A hydration kinetics model for sodium silicate-based alkali activated slag (AAS) is proposed. The hydration kinetics model for AAS is derived either using mass conservation during internal phase transformation, or by considering chemical affinity of hygro- (thermo-) chemical kinetics by adopting parameters obtained from various calculations and experiments. The obtained modelling result indicates that although the amount of water consumed by slag is lower than that by OPC at an identical mass ratio, the slag binder experiences larger chemical shrinkage, which leads to a dramatic reduction in the relative humidity during hydration. In addition, the modelling result suggests that the hydration rate after 1 day is higher when the pores are distributed in a wider range of diameters (i.e., capillary pores and gel pores are both present as in OPC), in comparison with the case when the pore distribution is in a narrower range (i.e., gel pores are dominant as in AAS). [ABSTRACT FROM AUTHOR]

• Calcined oyster shell (COS) waste was utilized as an additive for high volume slag cement binder. • Addition of COS had a positive effect on strength development of high volume slag cement binder. • COS increased the percentage of Ca2+ leading to higher cumulative heat evolution. • Incorporation of COS refined the pore structure of high volume slag cement binder. • Increased degree of hydration and mean chain length was observed for binder mixes containing COS powder. The present study investigates the effect of calcined waste oyster shell powder as additive on the fresh, hardened and microstructural properties of high volume slag cement. The results provide that addition of calcined oyster shell powder enhanced the early age compressive strength. The hydration of calcined oyster shell powder resulted in additional portlandite formation during the initial reaction stage. The observations drawn from porosity measurements indicated that calcined oyster shell powder decreased the porosity of binder matrix at early and elongated duration of curing. Furthermore, by 29Si NMR it was observed that the hydration of high volume slag cement was also benefited by calcined oyster shell powder as indicated by increased degree of hydration and chain length. However, excess addition of calcined oyster shell powder caused decreased compressive strength development. Considering the results, calcined oyster shell powder can be used as additive in high volume slag cement. [ABSTRACT FROM AUTHOR]

• Steel fibers on surfaces of UHPC immersed in chloride solution were corroded after a year. • Flexural strength of thin UHPC panel (10 mm) was decreased by fiber corrosion. • Fiber corrosion on surface led no substantial strength decrease of thick UHPC panel. The results of experimental investigation of ultra-high performance concrete (UHPC) by evaluating the flexural response are presented in order to qualitatively evaluate the effects of chloride-induced corrosion. The third-point bending test is carried out using the hydraulic servo-controlled testing machine. The experimental variables are thickness of specimen (10, 25 and 50 mm), immersion duration, and mixture design of UHPC. The specimens are immersed in 10 wt% NaCl solution up to a year to induce corrosion. The effect of chloride-induced corrosion of steel fiber of UHPC is evaluated in terms of compressive strength, flexural strength and flexural toughness. The experimental results indicate that there is no significant loss in flexural strength and toughness for the specimens which were thicker than 25 mm over a period up to 365 days of immersion in chloride solution; whereas, the specimen with thickness of 10 mm showed about 10% decrease in maximum stress and corresponding toughness after 180 days of the immersion. Furthermore, it is revealed by comparing the compressive strength with and without fibers that the presence of steel fibers in UHPC under corrosive environments do not lead to substantial strength decrease. [ABSTRACT FROM AUTHOR]

High production cost and scarcity of raw materials may hinder the application and accessibility of ultra-high performance concrete (UHPC). In the present study, mine tailings, mineral waste products from mining sites, were applied to mitigate these problems. Two types of quartz-based mine tailings produced in South Korea were used to substitute silica powder and silica sand by half and fully in UHPC. The characteristics of UHPC with the tailings, including the compressive strength, workability, water absorption, and leachability of toxic elements, were experimentally evaluated. The effects of the tailings on the characteristics of UHPC varied according to the shape and size of particles of the tailings. The leaching of toxic trace elements from the tailings was highly controlled due to the chemical and physical capsulation of UHPC. [ABSTRACT FROM AUTHOR]

The internal curing effect of raw and carbonated recycled aggregates on the properties of high-strength slag-cement mortar was investigated. First, the aggregates were characterized using different methods and their effects on the shrinkage, drying mass loss, non-evaporable water content, and compressive strength of the mortar were evaluated. Their incorporation reduced the shrinkage and improves non-evaporable water content, i.e., degree of hydration, with a slight reduction in compressive strength. Because of the carbonation of the aggregates, the mixtures incorporating carbonated aggregates show lesser improvements in non-evaporable water content and compressive strength than the ones with non-carbonated aggregates. However, the shrinkage property was better improved by the incorporation of the carbonated ones. [ABSTRACT FROM AUTHOR]

The present study investigates the fresh and hardened properties of controlled low-strength materials (CLSM) utilizing circulating fluidized bed combustion (CFBC) ashes, activated with cement or sodium carbonate. Engineering properties such as flowability, settlement, setting behavior, compressive strength, and hydration characteristics were evaluated. The results provided new insights, demonstrating that CFBC ashes can be effectively utilized in producing CLSM with suitable material design as the CLSM could achieve the required performances specified in the ACI 299R-13. The CLSM mixtures showed a self-destruction characteristic due to the formation of ettringite, while it showed stable strength development in a dry condition. [ABSTRACT FROM AUTHOR]

Concrete cast at low temperatures can have an adverse effect on the concrete quality owing to both a delay in the hydration reaction of the concrete and the occurrence of early frost damage. Therefore, a heating sheet was developed, which exploited the exothermic reaction between quicklime and water. A form with the heating sheet attached experienced a temperature rise and had a high compressive strength. TG-DTA analysis confirmed that a larger amount of the Ca(OH) 2 hydration product was generated in the form with the heating sheet attached, while SEM analysis visually confirmed the size and shape of the hydration product. [ABSTRACT FROM AUTHOR]

This paper proposes a new analytical model for the relationship between the axial and transverse strains of confined concrete in uniaxial compression. The proposed model was developed based on empirical data for a circular section confined by spirals. A column with a circular section and subjected to uniaxial compression was considered. The proposed model predicts the stress in the transverse confinement reinforcement to estimate the relationship between the axial strain of the column and tensile strain of the transverse confinement reinforcement. The model can also produce the axial stress–strain relationship of the confined concrete of the column. The predicted axial and transverse strains of the confined concrete section corresponded to the observed axial peak stress of a column evaluated in previous research with good accuracy. This model will be an effective tool for investigating the effect of circular spirals on the structural behavior of confined concrete and enhancing the accuracy of structural behavior analysis for a column under uniaxial compression. [ABSTRACT FROM AUTHOR]

• Reliability of electrical properties of CNT/cement composites after further hydration was evaluated. • Chemical change of CNTs under high pH was tested. • Electrical resistivity of the composites with well-dispersed CNT networks was constant even after accelerated hydration. A series of simple, short-term experiments were conducted, utilizing an accelerated testing method, to investigate the long-term reliability of the electrical properties of carbon nanotube (CNT)/cement composites after further cement hydration and the corresponding alkali attack on CNTs. The CNTs were exposed to an alkali solution at high temperatures, their chemical structures were evaluated using X-ray photoelectron spectroscopy, and their electrical properties were evaluated via cyclic voltammetry. The hardened CNT/cement composite specimens were cured in high-temperature water and their electrical resistivities were measured. The non-evaporable composite water content was measured to evaluate the increase in hydration degree via high-temperature water curing. The resistance of the CNT networks scarcely changed, even under the strong alkali conditions of the pore solution; the electrical resistivity of the cement composites with well-dispersed CNT networks remained unchanged. The findings indicate that the CNT/cement composites exhibit acceptable electrical stability for practical sensors. [ABSTRACT FROM AUTHOR]

• Presence or absence of atmospheric carbonation highly affected self-healing. • Ideal crack width can be derived from Darcy's law and Poiseuille flow parameters. • Self-healing is dependent ideal crack width more than measured crack width. • CFBC ash activated slag in cracks when atmospheric carbonation was prevented. • Slag and CFBC replacement resulted in dense ettringite networks in healing material. The potential of circulating fluidized bed combustion (CFBC) bottom ash, which has high contents of sulfate, free lime, and portlandite, for improving the self-healing capacity of Portland cement (PC) and slag cement binder systems was evaluated. Ordinary and slag cement binders were replaced with 10% and 20% CFBC bottom ash in this investigation. The decrease in permeability observed across successive permeability measurements was used as a measure of crack healing. It was found that using flow parameters from Darcy's law and Poiseuille flow to classify cracks, instead of measuring the crack width, better related with the self-healing inside various crack sizes. The healing materials were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The results showed that addition of CFBC bottom ash can activate slag and form healing products provided that atmospheric carbonation is prevented. Dense ettringite network was found on the crack surfaces for specimens with the ashes. [ABSTRACT FROM AUTHOR]

• Flowability and electrical properties of CNT/cement composites was compared. • Mechanical dispersion of CNTs was influenced by type of CNTs and flowability of mixture. • 100–101 Ω·m for cement composites was obtained with 0.3 wt.%/cement of CNT. • Intuitive model of CNT dispersion on the resistance of cement composites was conducted. The present study aims to understand the relationship between flowability and electrical properties of cement composites with mechanical dispersion of carbon nanotube (CNT) and to establish a guideline of mix proportioning for the CNT/cement composites with suitable workability and high electrical conductivity. In this study, mixtures composed of different mix proportions and CNT types were designed, and their flow diameter, electrical resistivity, basic mechanical properties in terms of strength and elastic modulus, and microscopic morphology were measured and evaluated. Intuitive and simple modeling was performed to quantitatively assess the effect of CNT dispersibility on conductivity. The results indicated that the flowability and resistivity of cement composites were significantly affected by the dispersibility of CNTs. [ABSTRACT FROM AUTHOR]

• Mechanical properties of composites incorporating crumb rubber were investigated. • Tensile strain capacity up to 10.7% was achieved by incorporating crumb rubber. • Crumb rubber increased number of cracks and decreased crack spacing. • Silica fume increased the tensile strength and toughness of rubberized composite. • Sustainability was evaluated according to material sustainability indicators. This study investigated the effect of the addition of crumb rubber (CR) particles in a range of 5% to 10% of binding materials on the compressive strength and tensile behavior of alkali-activated slag (AAS) composites reinforced by polyethylene (PE) fiber. The effect of silica fume (SF), as a partial binder replacement, on the properties of the composite was also investigated. Four mixtures were designed including two with different amounts of CR, one with a combination of CR and SF, and one control. Test results showed that the tensile strain capacity of the AAS composites can be increased by incorporating CR; however, the compressive strength and tensile strength decreased with an increase in the amount of CR. The mixture using CR to replace 5% of the binder amount achieved ultra-high-ductile behavior with a tensile strain capacity of 10.7% and saturated cracking patterns (average crack spacing: 0.70 mm). In addition, the robust greenness of the rubberized composites was completely demonstrated, making this a sustainable model. [ABSTRACT FROM AUTHOR]

• Cement concrete with atomized basic oxygen furnace slag was cracked itself. • Corrosion of metallic Fe was considered as the main reason for the cracking. • Hydration of free MgO in the slag helps in crack growth and propagation. A series of experiments was conducted to investigate the crack-expansion of a cement matrix containing atomized basic oxygen furnace slag with a metallic iron. The BOF slag particles were dispersed in supersaturated Ca(OH) 2 solution mimicking the pore solution in a cement matrix and the changes in these particles were visually observed. X-ray diffraction, thermogravimetry, and X-ray photoelectron spectroscopy were conducted on different slag powders and cement paste in the slag. Our major observations indicated that 1) cracks in the BOF slag-containing cement matrix were initiated from the slag particles, 2) the BOF slag contained metallic Fe and free MgO, and 3) Fe oxides, portlandite, and brucite were formed at slag crack points. Therefore, corrosion of metallic Fe is proposed as the main reason for the cracking of a cement matrix with atomized BOF slag; further, hydration of free MgO helps in crack growth and propagation. [ABSTRACT FROM AUTHOR]

• CFBC bottom ash was used as an expansion agent in OPC and slag cement. • Cracking potential was evaluated by direct tensile and shrinkage tests. • Ash delayed cracking times due to its shrinkage compensation. • This cracking times varied with the drying condition rather than ash content. The effect of bottom ash produced from circulating fluidized bed combustion (CFBC) on the shrinkage-induced cracking potential of ordinary Portland cement (OPC) and slag cement mixtures were investigated by evaluating the time to crack initiation, predicted by comparing tensile strength obtained from direct tensile tests with shrinkage-induced stress obtained from shrinkage strain and elastic modulus results. Although replacing OPC and slag cement amounts with CFBC bottom ash delayed cracking times due to its shrinkage compensation, the effect varied with the drying condition. Therefore, for effective application of CFBC ash in cement mixtures, boundary conditions affecting drying rates need careful consideration. [ABSTRACT FROM AUTHOR]

• Synergetic effects of CFBC ash and blast furnace slag on the strength and shrinkage was found. • The ash could reduce the shrinkage of high-volume slag cement at an early age. • Unwanted expansion owing to ash in OPC could be controlled in slag cement. • Strength of the HVSC mixture seldom influenced by CFBC ash. Circulating fluidized bed combustion (CFBC) bottom ash was used in high-volume slag cement (HVSC) as a secondary activator. To understand the effects of the bottom ash on the HVSC mixture, a series of experiments relating to hydration heat release, hydration products, and the microstructure and engineering properties were performed. For comparison, the ash was also mixed with ordinary Portland cement (OPC). Although the ash could activate the hydration of slag, this did not increase the initial strength of the HVSC mixture. However, the HVSC mixture did not exhibit undesirable swelling caused by ash and the consequent strength reduction that was observed in the OPC mixtures. Furthermore, the ash could reduce the autogenous shrinkage at an early age. When 20 wt% of ash was replaced with slag in the HVSC, the compressive strength of the mixture exhibited a coefficient of variation within 15% depending on the bottom ash content, which is negligible considering the standard deviation. [ABSTRACT FROM AUTHOR]