Cement and Concrete Composites(2024 - 2025)
Carbon capture and storage CO2 foam concrete towards higher performance: Design, preparation and characteristics
Fan D.; Lu J.-X.; Lv X.-S.; Noguchi T.; Yu R.; Poon C.S.
Cement and Concrete Composites, Elsevier Ltd., Vol.157, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2025.105925)
Abstract
This study introduces a novel strategy for carbon capture and utilization by incorporating CO2 into foams to develop CO2 foam concrete (CFC) with high performance. A conceptual design approach for CFC was first proposed by incorporating tailor-made CO2 foam into an optimized cement-based paste. The engineered CO2 foam exhibited fine size and good stability, but increasing CO2 concentration decreased stability. Then, the CO2 foam was used to fabricate CFC with high strength (about twice that of normal foam concrete at a similar density), excellent durability (comparable to normal concrete), and low thermal conductivity. Moreover, it was demonstrated that CO2 foam induced positive internal carbonation effects to further enhance the CFC performance. These effects included promoting cement hydration efficiency and generating CaCO3 on the foam wall for strength enhancement. Also, the rational use of CO2 foams optimized the CFC pore structures, including reducing porosity, refining pore size, and improving pore uniformity. The CFC exhibited exceptional carbon capture, sequestering 87 kg of CO2 per m3 of concrete by internal and external carbonations (active carbon reduction), and could reduce electricity consumption and the corresponding carbon emissions (indirect carbon reduction). This innovative material offers a promising pathway towards sustainable construction and carbon neutrality. c 2025 Elsevier Ltd
Anisotropy mechanism of alkali-silica reaction at the material scale: From expansion behavior to mechanical property degradation
Fujishima M.; Miura T.; Multon S.; Kawabata Y.
Cement and Concrete Composites, Elsevier Ltd., Vol.159, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2025.106008)
Abstract
This study aimed to elucidate the anisotropic relationships among expansion, cracking, and mechanical properties in compression caused by the alkali-silica reaction (ASR) under applied stress using mesoscale modeling based on a 3D-rigid body spring model. A concrete model consisting of a composite phase of aggregate and mortar was used, and the ASR expansion was reproduced by considering two mechanisms of generation of swelling pressure. Consequently, both the difference in the expansion models and the creep of the aggregate affected the anisotropy of expansion and cracking. It was thus suggested that the creep of the aggregate should be considered when discussing ASR expansion because the accumulation of swelling pressure caused a significantly high compressive stress in the aggregate. Furthermore, the expansion cracks under restraint exhibited an orientation parallel to the restraint direction, which resulted in the anisotropy of the compressive properties. The cracks perpendicular to the loading axis caused a significant reduction in the compressive properties compared with the parallel cracks. Consequently, the indices related to expansion alone are insufficient to estimate the change in compressive properties owing to ASR under restraint conditions. c 2025 The Authors
Rapid visualization and quantification of water penetration into cement paste using near-infrared hyperspectral imaging
Li S.; Sakai Y.
Cement and Concrete Composites, Elsevier Ltd., Vol.161, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2025.106103)
Abstract
Water penetration is the leading cause of durability deterioration of cementitious materials, and the rapid in-situ visualization and quantification of water penetration process is important for evaluating water absorption behavior and durability of material. This study proposed a novel method to rapidly visualize and quantify the water penetration into cementitious materials using near-infrared hyperspectral imaging. Specifically, three different areas were distinguished as the dry area, the transition area (including wetting front) and completely wet area during the water absorption process based on the reflectance gradient of cement paste. A strong linear relationship between reflectance and water content was established through slice weighing calibration, enabling accurate quantification of water absorption. The real-time tracking of the water content distribution and penetration depth evolution was realized. Furthermore, the study revealed that water absorption behavior is significantly governed by local pore structure, and momentum balance of capillary water absorption behavior in porous media was used to explain the dynamic water transport mechanisms. Compared to traditional visualization techniques, the proposed method has achieved a millisecond-level breakthrough in time. This study provides an efficient and practical reference for on-site in-situ quantitative evaluation of cementitious engineering structures. c 2025 The Authors
Fully coupled physicochemical-mechanical modeling of sulfate attack-induced expansion in cement-based materials
Ohno M.; Maekawa K.
Cement and Concrete Composites, Elsevier Ltd., Vol.161, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2025.106076)
Abstract
Sulfate attack-induced expansion in cementitious materials is a complex physicochemical-mechanical phenomenon influenced by numerous factors. To deepen our understanding of this deterioration process, multiphysics modeling and simulations that can consider various material, structural, environmental conditions are invaluable. This study presents a fully coupled physicochemical-mechanical model to simulate sulfate attack-induced expansion in cement-based materials. The proposed model integrates multiscale models of cement hydration, pore structure formation, moisture and ion transport within the cement matrix, and the geochemical code PHREEQC to compute chemical equilibrium in pore solutions. The model assumes that secondary formation of both ettringite and gypsum contributes to expansion. The mechanical response is simulated using elasto-plastic and damaging constitutive models for compression, tension, and shear in cement-based materials. In cases of cracking, the reactive transport model adjusts the mass-transfer properties of the material accordingly. Model validation against experimental data demonstrated that the proposed model reasonably predicts expansion trends under various conditions. Furthermore, the simulations suggested that sulfate attack-induced expansion is primarily driven by secondary ettringite formation, but also quantitatively showed the significant contribution of secondary gypsum under high sulfate ion concentrations. Sensitivity analysis also revealed the significant impact of mineral compositions of cement, particularly tricalcium aluminate (C3A) and tricalcium silicate (C3S) contents and the initial amount of gypsum in cement. This study provides a baseline for further investigations aimed to link sulfate attack-induced material deterioration with structural degradation, facilitating the assessment of structural integrity and remaining service life of deteriorated concrete structures. c 2025 The Authors
Estimating RC corrosion distribution from surface cracks using mesoscale analysis integrated with machine learning
Shao T.; Luo J.; Nagai K.
Cement and Concrete Composites, Elsevier Ltd., Vol.157, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2025.105950)
Abstract
Understanding the degree of reinforcing bar corrosion in reinforced concrete (RC) structures is crucial for evaluating their residual performance. This study proposes a simulation system for estimating the distribution of corrosion along the rebar of a RC beam member based on surface crack widths. The system integrates the rigid body spring model (RBSM) with machine learning methods. The inputs are surface crack widths and the desired output is the distribution of corrosion-induced expansion. A large dataset of training samples for machine learning is generated by running RBSM simulations using different expansion distributions. After training with this dataset, the neural network is able to correlate inputs and outputs, allowing it to estimate an expansion distribution from given cracking data. The estimated expansion distribution is then used to simulate the surface cracks using RBSM, and the error between the given (input) cracking data and simulated cracks is returned as an input to the trained network in order to optimize the results and enhance performance of the system. The applicability of this RBSM-neural network system is validated using both synthetic and experimental test data. The estimation results correlate well with the target data, demonstrating the effectiveness of the system in estimating internal expansive strain along the rebar and reproducing the cracking distribution using surface crack data. Internal distributions of cracking and stress are extracted from the simulations, providing additional information for analyzing structural performance. c 2025 Elsevier Ltd
Understanding the influence of slag fineness and water-to-binder ratio on the alkali-silica reaction in alkali-activated slag mortars
Wang W.; Zhang S.; Zhang Y.; Noguchi T.; Maruyama I.
Cement and Concrete Composites, Elsevier Ltd., Vol.157, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2024.105907)
Abstract
The use of alkaline activator in alkali-activated materials (AAMs) may pose risk of alkali-silica reaction (ASR), and the variations in the mixture design could have great influence on the performance of AAMs system. In this case, this paper investigated the effects of slag fineness (3000?8000 cm2/g) and water-to-binder (w/b) ratio (0.5?0.8) on ASR behavior of alkali-activated slag (AAS) mortars under accelerated mortar testing conditions as specified in ASTM C1260. The length change, mass gain, microstructure and formation of ASR products were examined to evaluate the degradation caused by ASR. It was found for the first time that slag fineness induces a gpessimum effecth in the ASR expansion of AAS mortars. On the other hand, there is a gpessimum effecth in the influence of w/b ratio on ASR expansion in the early-stage (?14d), and the induced expansion increased with an increase in w/b ratio in the late-stage (>14d). The mechanism governing the effect of slag fineness and w/b ratio is complicated and cannot be explained solely by the properties of ASR products. This work contributes to the understanding of ASR in AAMs system and could provide a basis for the mixture optimization of AAMs. c 2024 Elsevier Ltd
Stabilization of metastable calcium carbonate polymorphs on the surface of recycled cement paste particles: A two-step carbonation approach without chemical additives
Zhou Q.; Meawad A.; Wang W.; Noguchi T.
Cement and Concrete Composites, Elsevier Ltd., Vol.155, 2025, .
(https://doi.org/10.1016/j.cemconcomp.2024.105829)
Abstract
In this study, a two-step carbonation method is developed to control the formation of calcium carbonate (Cc) polymorphs on the surface of recycled hardened cement paste (RHCP) without the use of chemical additives. In the first step, RHCP undergoes semi-dry carbonation under controlled humidity conditions, followed by wet carbonation at various temperatures in the second step. The results show that vaterite and aragonite are stabilized during the wet carbonation process, forming primarily on the surface of RHCP particles. The stabilization of the metastable Cc phases is driven by the synergistic effect of existing Cc seeds in the RHCP and the reaction temperature. A temperature range of 9?48 C promotes the formation of vaterite, while higher temperatures (60?90 C) lead to its dissolution. The calcite seeds present in RHCP do not enhance the formation of vaterite and aragonite during wet carbonation. This method offers a potential practical approach for valorizing concrete waste while capturing CO? from the atmosphere. c 2024 Elsevier Ltd
Mechanisms on the inhibition of alkali-silica reaction in supersulfated cement
Ban J.; Fan D.; Li K.; Yao J.; Lu J.-X.; Wang Z.; Poon C.-S.
Cement and Concrete Composites, Elsevier Ltd., Vol.145, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2023.105320)
Abstract
The supersulfated cementitious system gains increasing popularity for lowering carbon emissions of the construction industry. However, the alkali-silica reaction (ASR) behavior of this sulfate-rich cement is still unclear. This study first reports the characteristics and suppressing mechanisms of ASR in supersulfated cement (SSC). The results show that nearly no ASR-induced expansion is found in the SSC even if 100% glass aggregates are used, while the expansion ratio of the traditional OPC is twenty times higher than the SSC. In the SSC, the further hydration of unreacted slag during the ASR test refines the pore size and enhances the compressive strength of the matrix. Meanwhile, the consumption of the alkali ions in the pore solution during the formation of N-A-S-H gel reduces the concentration of the alkali ions and the contact possibility with the aggregates. The high bulk electrical resistance of the SSC can mitigate the diffusion of alkali ions from the external solution to the mortar. Moreover, the higher Al/Si ratio of C-A-S-H in the SSC than C?S?H in the OPC system results in a higher adsorption capacity of Na+ due to the more negatively charged surface, reducing the concentration of alkali ions in the pore solution. Furthermore, the high concentration of SO42? in the pore solution of SSC can inhibit the diffusion of OH?. As a result, the low-carbon SSC system would be a promising cementitious material to mitigate the ASR risk. c 2023 Elsevier Ltd
Interlayer bonding performance of 3D printed engineered cementitious composites (ECC): Rheological regulation and fiber hybridization
Ding Y.; Ou X.; Qi H.; Xiong G.; Nishiwaki T.; Liu Y.; Liu J.
Cement and Concrete Composites, Elsevier Ltd., Vol.154, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105805)
Abstract
The weak interlayer adhesion caused by the layer-by-layer 3D printing (3DP) process and the incorporation of organic fiber in Engineered Cementitious Composites (ECC), detrimentally impacts the integrity of 3DP-ECC structures, particularly for large-scale structures requiring extended open time. To optimize the printing quality and extent the operation time, cellulose filaments (CF) were employed as nano-reinforcement, viscosity modifier and water retainer, and were hybridized with polyethylene fiber (PE) and steel fiber (ST). The highest bonding strength was raised up to 3.51 MPa. The time-dependent escalation of rheological parameters was mitigated, reducing interlayer porosity to 0.56 % and limiting the reduction in bonding strength to 12.01 % within 60 min open time. The compressive anisotropy was almost eliminated, verifying the potential of CF in modifying interlayer adhesion. A linear correlation between rheological behavior and interlayer bonding performance was established, and a 0.508 Pa s/min plastic viscosity growth rate was suggested to avoid cold joint and ensure printing quality. c 2024 Elsevier Ltd
Anisotropic expansion behavior and crack orientation of reinforced concrete due to the alkali?silica reaction
Farooq S.; Aoki G.; Miura T.; Kawabata Y.; Nakamura H.
Cement and Concrete Composites, Elsevier Ltd., Vol.151, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105568)
Abstract
In this study, the expansion behavior, surface and internal crack developments due to the alkali?silica reaction in two types of reinforced concrete prisms with and without stirrups are investigated. Longitudinal and transverse expansions are continuously monitored at various positions on the prism surfaces. Image analysis is employed to determine the densities of surface and internal cracks. Crack orientations for several groups of crack angles are measured to characterize the dominant crack pattern. The findings indicate that longitudinal expansion was transferred to the transverse direction at the middle region in both prisms, regardless of the presence of stirrups. However, average longitudinal, transverse, and volumetric expansions are reduced in prisms with stirrups. The anisotropy coefficient of expansion exhibits a strong proportional relationship with the surface and internal crack densities of each crack angle group. Therefore, the trend of internal crack orientations and expansion anisotropy can be estimated based on surface crack information. c 2024 Elsevier Ltd
Mechanical property evaluation of 3D multi-phase cement paste microstructures reconstructed using generative adversarial networks
Hong S.-W.; Kim S.-Y.; Park K.; Terada K.; Lee H.; Han T.-S.
Cement and Concrete Composites, Elsevier Ltd., Vol.152, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105646)
Abstract
This study proposes an artificial intelligence based framework for reconstructing the 3D multi-phase cement paste microstructure to evaluate its mechanical properties using simulation. The reconstruction of cement paste microstructures is performed using modified generative adversarial networks (GANs) based on microstructural images from micro-CT. For computational efficiency, 2D microstructures are first reconstructed and then extended to 3D microstructures. The reconstructed microstructures exhibit the same microstructural features as the original microstructures when characterized by probability functions. Mechanical properties such as stiffness and tensile strength are evaluated for the original and reconstructed specimens using a phase-field fracture model, and similar behaviors are observed. The results confirm that the reconstructed virtual microstructures can be used to supplement the real microstructures in evaluating the mechanical properties of 3D multi-phase cement paste. This approach thus provides a critical element of a data-driven approach to correlating its microstructure and properties. c 2024 The Author(s)
Redox reaction models for carbonation of hardened cement under elevated temperature up to 1000 C
Iwama K.; Maekawa K.
Cement and Concrete Composites, Elsevier Ltd., Vol.153, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105738)
Abstract
Concrete structures are exposed to various temperature environments and often come into contact with CO2 under these conditions. With the recent surge in interest in carbonation, there is a growing demand for a numerical model that can more comprehensively and flexibly account for the reactions of hydration, carbonation, decomposition, and recovery of cement hydrates. A comprehensive framework for concrete carbonation is proposed from a wide perspective of temperature with thermo-chemical modeling including de-carbonation and re-carbonation. By overlaying rates of bidirectional redox reactions, the dominant reaction at any temperature can be determined. The model framework, encompassing cement hydration, carbonation, de-hydration, de-carbonation, re-hydration, and re-carbonation, was experimentally validated by previous measurements of changes in weight and porosity under different CO2 concentrations and repeated exposure to high temperatures followed by post-fire-curing. These validations demonstrate a strong connection between the micro- and macroscopic properties of concrete in the proposed model. With this scheme, fire resistance of concrete composite under unexpected cases was explored computationally. Significant weight loss and strength reduction of cement paste are predicted after the first heating cycle, followed by gradual decline in subsequent repetitions of temperature. In the cases with water post-fire-curing, it is observed that the strength tends to restore even with repeated heating. In the cases with RH-60 % vapor post-fire-curing, the strength recovery is significantly increased by re-carbonation, but is still smaller than that of the cases with water post-fire-cuing. c 2024 The Authors
Microstructural analysis of cement paste blended with blast furnace slag using 1H NMR relaxometry
Joseph S.; Mutti M.; Ohkubo T.; Maruyama I.; Cizer O.
Cement and Concrete Composites, Elsevier Ltd., Vol.146, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2023.105377)
Abstract
1H NMR is a powerful technique for characterizing the microstructure of cement pastes; however the analysis of the data poses significant challenges. This work presents a comparative analysis of the microstructure evolution in cement pastes using 1H NMR relaxometry, MIP and thermoporometry. We developed and implemented a cumulative T2 distribution to improve the reproducibility and robustness of the results obtained from the CPMG raw data. Although NMR and thermoporometry measured similar pore sizes, MIP measured considerable deviations at pores>10 nm for matured white cement pastes, but blends with slag were more comparable. Nevertheless, deviations were observed in the blends when the degree of slag hydration was low. These discrepancies are attributed to the C/(A + S) ratio of C?S?H which decreases with slag hydration. The findings suggest that the pore refinements typically measured with MIP for blended cement compared to reference Portland cement may be an artefact of sample preconditioning. c 2023 The Author(s)
Evaluation of the thermal stability of metakaolin-based geopolymers according to Si/Al ratio and sodium activator
Kim G.; Cho S.; Im S.; Yoon J.; Suh H.; Kanematsu M.; Machida A.; Shobu T.; Bae S.
Cement and Concrete Composites, Elsevier Ltd., Vol.150, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105562)
Abstract
The thermal stability of geopolymer pastes with different Si/Al ratios (1.5?3.0) and sodium activators (Na2SiO3 and/or NaOH) were evaluated in this study. The inclusion of Na2SiO3 induced an active geopolymer reaction, enhancing pre-heating compressive strength, but gradually reduced from 300 C due to vapor pressure and microstructural deterioration caused by entrapped physically bound water. Conversely, the strength of geopolymers containing only NaOH remained stable or increased up to 600 C, owing to additional geopolymerization from unreacted raw materials and compact matrix induced by thermal shrinkage. The aluminosilicate networks of all geopolymers remained relatively stable until crystalline nepheline formed above 800 C; larger crystalline particles were formed in geopolymers with Na2SiO3 owing to its denser geopolymer matrix, whereas smaller crystalline particles were formed in geopolymers with smaller Si/Al and only with NaOH, resulting in fewer voids and stable mechanical strength. Swelling of silica was notable in Na2SiO3-activated geopolymer, resulting in greater strength loss upon heating, indicating that Na2SiO3 hinders the thermal stability of geopolymers at extreme temperatures. c 2024
Development and verification of an integrated hydration, geochemical and transport model for the hydrated cement paste exposed to an aggressive chemical environment
Krishnya S.; Kopitha K.; Yoda Y.; Kitagaki R.; Elakneswaran Y.
Cement and Concrete Composites, Elsevier Ltd., Vol.146, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2023.105374)
Abstract
This study established a new transport model by using the COMSOL-IPHREEQC interface to simulate the changes in the morphology of hydrated cement paste due to the diffusion of carbon dioxide and chloride ion. A series of constitutive models such as the cement hydration model (to compute the dissolution rate of each clinker mineral), thermodynamic model (to perform the hydration reaction, reaction due to transport of ions, chemical and physical adsorption of chloride ion during the chloride ion ingression and dissolution rate of calcium-silica-hydrate (C?S?H) simultaneously with portlandite for the carbonation), porosity determination, and COMSOL Multiphysics (for the calculation of transport problems) were integrated using MATLAB language to determine the pore solution chemistry, hydrates assemblage, and porosity of the cement paste exposed to aggressive environments. During the diffusion of carbon dioxide gas, the decalcification of C?S?H was realistically considered by assuming that the Ca/Si ratio of C?S?H decreased from 1.67 (Jennite type C?S?H) to 0.67 (Tobermorite C?S?H), and then from 0.67 to 0 (silica gel). The proposed integrated platform was well verified with different sets of reported and raw experimental results and existing models, indicating a realistic predictability for chloride ion ingression and carbonation. The developed model discloses the effect of coupling the progression of hydration with reaction due to the transport of ions by using the free chloride ion profile and phase assemblages during the chloride ion ingression. c 2023 The Authors
High-modulus engineered cementitious composites: Design mechanism and performance characterization
Liang L.; Lu X.; Ding Y.; Yu J.; Li V.C.; Yu K.
Cement and Concrete Composites, Elsevier Ltd., Vol.154, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105782)
Abstract
Engineered cementitious composites features with high tensile performance while relatively weak compressive stiffness. This study endeavors to address the inherent trade-off between tensile properties and elastic modulus in conventional Engineered Cementitious Composites (ECC). Utilizing the distinctive characteristics of iron ore aggregates, known for their relatively stiff nature, smooth surface and rounded shape, an Iron Sand-based ECC (IS-ECC) emphasizing both high elastic modulus and ductility is formulated. Guided by micromechanical design theory and multiscale homogenization model, this study systematically explores the impacts of aggregate types, water-to-binder (w/b) ratios, sand-to-binder (s/b) ratios, and sand particle sizes on ECC properties. Compared with Quartz Sand-based ECC (QS-ECC), IS-ECC exhibits notably enhanced matrix fluidity and elastic modulus, reduced matrix toughness, and more robust strain-hardening behavior. The proposed three-level multiscale homogenization model accurately predicts the elastic modulus of ECC and provides insights into the underlying mechanism contributing to the enhanced elastic modulus of IS-ECC. With a resulting high elastic modulus of 33.3?48.6 GPa and superior tensile properties, IS-ECC holds promise for widespread applications in structural engineering. c 2024 Elsevier Ltd
Exploring the reinforcing mechanism of graphene oxide in cementitious materials through microstructural analysis of synthesised calcium silicate hydrate
Nithurshan M.; Elakneswaran Y.; Yoda Y.; Yano K.; Kitagaki R.; Hiroyoshi N.
Cement and Concrete Composites, Elsevier Ltd., Vol.153, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105717)
Abstract
Graphene oxide (GO) has been shown to enhance the mechanical properties and durability of cementitious materials, although the exact reinforcement mechanism is not fully understood. Given the critical role of calcium silicate hydrate (CSH) in determining these materials' properties, this study investigates the microstructural changes in CSH with the incorporation of GO. Using a co-precipitation method, CSH samples with and without GO were synthesised and characterised through thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and nuclear magnetic resonance (29Si NMR and 1H NMR). The results demonstrated that GO incorporation enhances the polymerisation and crystallinity of CSH, as evidenced by TGA and XRD. FTIR and SEM analyses indicated that the CSH structures became more ordered and denser with GO addition. NMR analysis further confirmed improved structural order and reduced interlayer spacing. Overall, incorporating GO into CSH significantly increases crystallite size and promotes a more ordered CSH structure. These effects collectively result in enhanced load transfer, improved crystal interlocking, and a synergistic improvement in the mechanical properties and durability of cementitious materials. c 2024 Elsevier Ltd
Natural carbonation boost for hardened cement fines by dripping technique
Oh D.; Kitagaki R.; Masuo T.; Li Z.; Kurihara R.; Noguchi T.; Maruyama I.
Cement and Concrete Composites, Elsevier Ltd., Vol.153, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105731)
Abstract
This study proposes a dripping technique to improve the carbonation efficiency of hardened cement fine (HCF), which mimicked the binder part of waste concrete, sized between 0.6 mm and 1.18 mm under atmospheric CO2 concentration. After a 7-day carbonation using the dripping technique, the carbonation degree doubled compared with that at 85 % relative humidity (RH). This improved carbonation efficiency can be attributed to two factors: 1) The pores created during drying accelerate the infiltration of the solution, releasing more calcium ions; 2) The difference in calcium ion concentration between the surface aqueous film and pore solution causes calcium ions to migrate to the surface, accelerating the dissolution of calcium-bearing hydrates in the pore solution and releasing more calcium ions. Adjusting the dripping interval and drying conditions according to the particle size and amount of carbonatable calcium improves the carbonation efficiency. This strategic approach offers a practical means to contribute to the sustainable recycling of waste concrete. c 2024
Assessment and mitigation of early-age cracking for on-site concrete structures by a combined scheme using Temperature Stress Testing Machine (TSTM) and long-span restraining frame
Ou G.; Lin Z.; Kishi T.; Liu L.
Cement and Concrete Composites, Elsevier Ltd., Vol.145, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2023.105321)
Abstract
From the field survey, thermal cracking frequently occurs in substructural concrete walls, although a high dosage of Calcium Sulfoaluminate (CSA) expansive additive is widely utilized. Conventional assessment methods fail to characterize the failure of CSA expansion under coupled realistic conditions. Therefore, an assessment scheme is proposed in this study: Firstly, mix proportions, temperature, restraint and curing conditions are used as input for a developed Temperature Stress Testing Machine (TSTM). By testing, limited expansions of CSA additive under low water-to-binder ratio, high temperature or drying condition, is unfolded. Corresponding countermeasures are also proposed. Secondly, long-span restraining frames are constructed to validate, and upscale findings from TSTM. Eventually, normal and optimized mixtures are applied and compared in real substructural walls. This combined scheme newly reveals that the lack of free water is the mechanism for CSA's stagnant expansion and a combination of CSA and lightweight aggregates shows promising potential as a countermeasure. c 2023 Elsevier Ltd
Meso-scale simulation of moisture transport in concrete during wet-dry cycles using 3D RBSM conduit model with variable diffusion model
Ren D.; Jiradilok P.; Waghmare D.; Nagai K.
Cement and Concrete Composites, Elsevier Ltd., Vol.149, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105497)
Abstract
This paper introduces the 3D RBSM Conduit model, an improved simulation program based on the Rigid Body Spring Model (RBSM), designed to accurately depict the intricate phenomenon of moisture transfer within concrete. This is achieved by incorporating an expanded diffusion model into the simulation framework. The diffusion coefficient is dynamically adjusted at each location and at each time step to accurately represent the precise moisture transfer processes occurring in the concrete. This dynamic adjustment allows the program to efficiently simulate the rate of moisture transport in concrete based on the moisture degree and the dry or wet state of the material. By adapting the diffusion coefficient to the changing conditions in this way, the program achieves simulated moisture transfer rates that align closely with the real-world behavior of moisture in concrete. It offers a dynamic model of the changes in concrete transmission during the switch from drying and wetting conditions. Further, the program exhibits inherent advantages in addressing water transfer problems involving nonlinear boundary conditions and transfer equations. In this study, the program is used to simulate various processes including drying, wetting, local wetting, and combined wet-dry cycles. The results reveal the lag in wet-dry transitions between the interior and exposed surface during the wet-dry conversion process due to retained interior moisture. The simulation captures the moisture variation in the transitional zone. c 2024 Elsevier Ltd
Natural carbonation process in cement paste particles in different relative humidities
Saeki N.; Cheng L.; Kurihara R.; Ohkubo T.; Teramoto A.; Suda Y.; Kitagaki R.; Maruyama I.
Cement and Concrete Composites, Elsevier Ltd., Vol.146, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2023.105400)
Abstract
Finely ground hardened cement pastes (hcp) under 75 Jm were carbonated at varying relative humidities (23?95 % RH) to determine the carbonation rate that minimized CO2 diffusion in the bulk paste. The amounts of portlandite (CH) and calcium carbonate (CC) polymorphs were quantified, and the decalcification and decomposition of C-A-S-H were analyzed using TGA, XRD, mass balance calculation, FTIR, and 29Si MAS NMR spectroscopy. A higher RH accelerated the reaction rate, and CH dissolution stopped midway at 58 % RH or below because of the loss of connectivity with the pore solution in the CC shell around CH. The precipitated CC phase included calcite at high RH, whereas all three polymorphs formed at 58 % or lower RH; amorphous CC were detected at low RH. The decalcification and decomposition of C-A-S-H were observed at 45 % or higher RH; it was rarely carbonated at 33 % or lower RH. c 2023 Elsevier Ltd
Investigation into the changes in the splitting tensile strength of concrete subjected to long-term drying using a three-phase mesoscale RBSM
Sasano H.; Maruyama I.
Cement and Concrete Composites, Elsevier Ltd., Vol.148, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105462)
Abstract
The fracture process of dried concrete under splitting tensile loading was investigated using a three-phase mesoscale rigid-body spring model (RBSM). Although many studies have reported changes in the splitting tensile strength (ft) owing to drying, the mechanism remains unclear. The ft values under different drying conditions were predicted using a mesoscale concrete model that accounted for the drying-induced mechanical property change (DMPC) of mortar and microcracking. This result supports the assumption that DMPC and microcracking predominantly affect the strength under long-term drying. An investigation of the fracture behavior showed that drying-induced microcracking degraded ft by uniformly reducing the load-bearing capacity of the mortar. However, the cracks also had a slightly positive effect on ft by spreading the fracture area near the peak load, but this benefit was outweighed by the negative effect of cracking at 80 % RH or more intense drying conditions. c 2024 Elsevier Ltd
Effect of accelerated carbonation of fully recycled aggregates on fracture behaviour of concrete
Tang Y.; Xiao J.; Zhang H.; Wang D.; Zhang M.; Zhang J.
Cement and Concrete Composites, Elsevier Ltd., Vol.148, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105442)
Abstract
Accelerated carbonation of recycled aggregates (RAs) enables fast carbon sequestration while improving engineering properties of prepared concrete. This paper presents a systematic experimental study on the fracture behaviour of concrete with carbonated recycled coarse and fine aggregates (RCA and RFA), in terms of fracture parameters and fracture process zone (FPZ). The relevant influencing mechanism was investigated by relating the macroscopic fracture responses to microstructural features. Results indicate that carbonated RFA mainly enhanced the initial fracture toughness of concrete, while carbonated RCA primarily increased its unstable fracture toughness. The enhancement of fracture energy was closely associated with carbonated RCA and RFA. The utilization of RFA resulted in the looseness and higher porosity of mortar matrix, which reduced the crack initiation resistance of concrete, mainly affecting its initial cracking stage. The incorporation of RCA reduced crack bifurcation and deflection of concrete, leading to a smaller width of FPZ, which made the initial descending segment of the tension softening curve (TSC) steeper and its tail segment shorter. The carbonation treatment of RAs improved the densification of the adhered old mortar and reduced the porosity of prepared concrete, rising the cracking resistance and inducing a wider FPZ. As a result, the initial descending segment of TSC became flatter and its tail segment tended to be longer. c 2024 Elsevier Ltd
An efficient method for determining the pozzolanic reaction degrees of low-calcium supplementary cementitious materials in blended cement pastes
Wang T.; Medepalli S.; Zheng Y.; Krishnan S.; Li N.; Ishida T.; Zhang Z.; Bishnoi S.; Zhang K.
Cement and Concrete Composites, Elsevier Ltd., Vol.151, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105595)
Abstract
The pozzolanic reaction degree of supplementary cementitious materials (SCMs) is a crucial parameter influencing the performance of SCM-blended concrete. Although several methods, such as partial-or-no-known-crystal-structure (PONKCS) analysis with X-ray diffraction (XRD) testing and image analysis, have been developed to estimate the pozzolanic reaction degree of SCMs, they have their own challenges in achieving reliable estimation. Ethylenediaminetetraacetic acid (EDTA) with NaOH is an efficient and reliable agent for selectively dissolving calcium-rich phases (e.g., cement clinkers and hydration products) without dissolving low-calcium SCMs. In this study, the ionic selective dissolution method (ISDM) that combines the use of an EDTA?NaOH dissolving agent and inductively coupled plasma?optical emission spectroscopy is developed to efficiently and reliably determine the pozzolanic reaction degree of low-calcium SCMs. Furthermore, the chemical compositions of aluminium-incorporated calcium?silicate?hydrate gel are determined via the ISDM coupled with the Rietveld analysis of XRD data, according to mass conservation principles. c 2024 Elsevier Ltd
Impact of exposure conditions on alkali-silica reaction in alkali-activated material systems
Wang W.; Maruyama I.; Noguchi T.
Cement and Concrete Composites, Elsevier Ltd., Vol.153, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105695)
Abstract
The influence of different testing methods on alkali-silica reaction (ASR) behavior is a result of the difference in the effect of exposure conditions on it. This study investigated the impact of temperature and the addition of alkali on ASR behavior in an alkali-activated material (AAM) system and compared it with an ordinary Portland cement (OPC) system. The results showed that the ASR in the AAM system was more independent of the exposure conditions than that in the OPC system because of its inherently high alkalinity and dense microstructure. More ASR products with higher Na:Si ratios were evident in the alkali-activated slag (AAS) mortars than in the OPC mortars. The accelerated test conditions developed for OPC systems could be applied to AAM systems. However, owing to the difference in the acceleration effect, comparing the ASR-induced expansion in OPC and AAM systems using the accelerated test method was misleading to some extent. This study contributes to the understanding of the ASR in AAM systems and is of considerable importance for the industrial application of AAMs. c 2024 Elsevier Ltd
Influence of volcanic glass powder on alkali-silica reaction expansion in alkali-activated slag mortars
Wang W.; Noguchi T.; Tomoyose A.; Zhang Y.; Maruyama I.
Cement and Concrete Composites, Elsevier Ltd., Vol.152, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105665)
Abstract
High-calcium alkali-activated materials (AAMs) can somewhat replace ordinary Portland cement (OPC) to reduce its environment impact, but these materials suffer from deleterious expansion due to the alkali-silica reaction (ASR). Here, the role of volcanic glass powder (VGP) addition in mitigating the ASR in alkali-activated slag (AAS) mortars was investigated for the first time and compared the performance with that of fly ash (FA). Optimal additions of VGP can effectively mitigate the expansion of AAS mortars, which is a combination of ASR- and zeolite-induced expansion. With increasing replacement level of VGP or FA, the ASR-induced expansion decreased and the zeolite crystallization-induced expansion increased. AAS mortars containing VGP exhibited higher overall expansion than those containing FA. The slightly lower ASR mitigation performance of VGP than FA in AAS mortars is due to the different roles of alumina and silica in suppressing the ASR in AAM systems. c 2024 Elsevier Ltd
Investigation of corrosion-induced cracks using corrosion products quantified by an X-ray technique and FE analysis of single- and multiple-rebar beams
Xu Z.; Akiyama M.; Lim S.; Srivaranun S.; Frangopol D.M.; Miyazato S.; Li A.
Cement and Concrete Composites, Elsevier Ltd., Vol.151, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105565)
Abstract
The effects of corrosion methods, galvanostatic (GS) vs. artificial climate environment (ACE), on the relationships between corrosion products and corrosion cracks of corroded reinforced concrete beams are investigated. The experimental results show that the GS method induces smaller corrosion crack width. A novel quantitative detection method of corrosion product thickness using X-ray and digital image processing techniques is proposed for investigating the continuous development of corrosion products. As the corrosion level increases, a smaller steel-to-rust volume expansion ratio caused by continuous leakage and a lower oxidation degree of corrosion products for the GS specimens are the major reasons for the smaller corrosion cracks. Regarding the effect of rebar arrangement on the development of corrosion-induced cracks, the expansion stress from corner-located rebars restrained the growth of corrosion products and further limited the propagation of corrosion-induced cracks of the center rebar. Estimated corrosion crack width via FE analysis using measured corrosion products as input show good agreement with experimental results. c 2024 The Authors
On the hydration of limestone calcined kaolinitic clay cement and energy-efficient production
Yu Y.; Gunasekara C.; Elakneswaran Y.; Robert D.; Law D.W.; Setunge S.
Cement and Concrete Composites, Elsevier Ltd., Vol.153, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105698)
Abstract
Understanding hydration kinetics of cement composite incorporating calcined clay is crucial in further progressing low-carbon binder designs. However, due to diversity of clays and complex synergy with further limestone addition, it is challenging to predict the hydration process. In this study, a coupled kinetic-thermodynamic model is developed based on unified functional form to generate comprehensive hydration studies on cement binders including calcined kaolinitic clay and limestone. Dedicated model parameterisation analyses are performed, following available rapid, relevant, and reliable (R3) tests, to determine the kinetic models. Moreover, a numerical framework is proposed to describe the synergy in hydration of limestone calcined clay cement (LC3) utilising clays of diverse kaolinite contents. The model is demonstrated to be capable of generating robust hydration assessments on both binary and ternary systems. In enhancing the overall sustainability, the proposed hydration model is leveraged to gauge the energy-efficient production of LC3 binders utilising local resources. c 2024 The Authors
In-situ wet carbonation of steel slag powder paste made with carbonated water: Interaction mechanism between carbonation and hydration
Zhang Z.; Xiong Y.; Jia Z.; Cao R.; Gao Y.; Maruyama I.; Zhang Y.; Wang W.
Cement and Concrete Composites, Elsevier Ltd., Vol.152, 2024, .
(https://doi.org/10.1016/j.cemconcomp.2024.105677)
Abstract
The utilization of steel slag powder is severely limited by its low activity. This study reveals that in-situ wet carbonation with carbonated water can significantly enhance its hydration activity. The influencing mechanism of carbonation on the hydration process and its kinetics during hydration are explored, and on this basis, the interaction between carbonation and hydration is discussed. It is found that both hydration and carbonation exhibit distinct characteristics before and after the acceleration stage. Before the acceleration stage, the hydration rate is affected by mineral dissolution rate, which is dependent on carbonation reaction, with carbonation rate determined by the CO2 concentration. After entering the acceleration stage, the hydration rate is promoted by the increased nucleation effect (e.g., nano-CaCO3 precipitation). The hydration in this period dominates carbonation by controlling mineral dissolution rate, with carbonation rate dependent on the mineral dissolution rate. As a result, mineral dissolution is shown to act as a bridge between hydration and carbonation interactions. Based on these results, the lack of further increase in hydration activity of steel slag powder with higher concentrations of carbonated water is also explained. This study provides a deep understanding for wet carbonation in steel slag powder paste. c 2024 Elsevier Ltd