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Recent California regulatory efforts, United States goals, and industry roadmaps all target net-zero greenhouse gas (GHG) emissions from the cement and concrete industries within a few decades. While changes in production of cement and concrete, including varying constituents, can greatly reduce GHG emissions, carbon dioxide removal (CDR) will be needed to meet this net-zero goal. Hydrated cement in concrete can carbonate (i.e., form carbon-based minerals with atmospheric CO2) and thus act as a CDR mechanism. This process occurs faster with a large surface area, such as crushed concrete at its end-of-life (EoL), which can be uniquely leveraged by transportation infrastructure projects. In this work, a literature review of key parameters that can facilitate desired CO2 uptake for transportation projects at their end of life is conducted and an initial meta-analyses of data from the literature to inform CO2 uptake for individual projects is performed. Initial considerations for what concomitant impacts may arise from this process are presented. Finally, experiments to fill a key gap in understanding how thin crushed concrete must be spread to maximize uptake reactions are conducted. Cumulatively, findings will inform whether carbonation can be implementedin a way that would support policies that include carbonation as a route for reducing emissions from cement-based materials in transportation applicationsView the NCST Project Webpage

Concrete's dynamic performance and energy dissipation are critical areas of interest that are significantly influenced by strain rate and aggregate content. This study investigated concrete's dynamic deformation, strength development and energy dissipation characteristics from specimens containing 0, 32%, 37% and 42% aggregate. These specimens were subjected to impact compression tests using a split Hopkinson compression apparatus, which allowed the effects of strain rate and aggregate content on the deformation, strength and energy dissipation of the concrete to be analysed. The results show that the concrete exhibits deformation hysteresis under impact loading, with splitting tensile failure as the predominant damage mechanism. Dynamic strength was more sensitive to strain rate than aggregate content. The dynamic increase factor (DIF) varied with aggregate content at different strain rates. The extent of specimen damage significantly influenced the energy distribution ratio, with absorbed energy showing a more pronounced strain rate effect than transmitted and reflected energy. Conversely, the amount of transmitted energy had a more pronounced impact on aggregate content than the amount of absorbed and reflected energy. [ABSTRACT FROM AUTHOR]

Proper concrete vibration is vital to the final quality and durability of concrete structures. There is a lack of objective methods to assess conformance to the requirements of vibration behavior of concrete systems used in various engineering structures. So, in the current work for the first time, nonlinear vibrations of a composite thick panel made of concrete materials are presented. In the current work, the GPLs are used to reinforce the thick concrete panel in the length direction. In the current work, according to the higher-order shear deformation shell theory the effects of the von Kármán strain-displacement kinematic nonlinearity are presented in the constitutive laws of the shell. The nonlinear governing equations for various nonlinear boundary edges are solved via discretization of equations on the space domain, derivation of Duffing-type equations, and Hadamard and Kronecker Products. The results are validated by comparing the current results with deep neural networks (DNN) and open-source results in the literature. For DNN, it is introduced a supervised neural network based on physical information to predict the vibrational behavior of the current system. In this context, data-driven solutions and data-driven discovery are presented to solve the problem of determining nonlinear frequency. Consequently, new results are investigated to show the effects of the Pasternak modulus, Winkler modulus, and the GPLs' weight fraction on the nonlinear vibrations of concrete panels. [ABSTRACT FROM AUTHOR]

The characteristics of shotcrete can lead to significant shrinkage deformation, presenting potential threats to tunnel structure safety. To research this concern, in this study the effects of three accelerators on the volume stability of cement paste, cement mortar and concrete were investigated. The correlation equations of the shrinkage deformation of cement paste, cement mortar and concrete were established, and the drying shrinkage prediction model of cement mortar with accelerator was constructed by combining the ACI 209 model and the GL2000 model. Findings from this study show that the liquid alkali accelerator AR had the greatest autogenous shrinkage and drying shrinkage, with the highest mass loss under drying conditions. The study demonstrated that there exists a good linear relationship between the shrinkage deformation of cement paste, cement mortar and concrete with accelerator. Finally, the proposed prediction model for drying shrinkage of cement mortar exhibits strong predictive capabilities. [ABSTRACT FROM AUTHOR]

With the extensive use of manufactured sand and admixtures, it has been observed that as the shear rate increases, the shear rate–shear stress curve of some fresh wet shotcrete materials increasingly deviates from a linear correlation. It is necessary to study the rheological properties of wet shotcrete using a nonlinear model due to the large error when utilizing the Bingham model to describe the concrete. The torque-velocity curve of wet shotcrete was determined using an ICAR rheometer in this study. The experimental data was fitted using the Bingham model, Herschel-Bulkley (H-B) model, and modified Bingham (M-B) model, resulting in the determination of the associated rheological parameters. The M-B model exhibits the most optimal fitting effect, followed by the H-B model and the Bingham model. As the shear rate reaches a specific value, the M-B model consistently represents a higher degree of divergence from linearity compared to the H-B model. Furthermore, considering the limitations of the H-B model which includes varying dimension parameters, this study enhanced the calculation approach for determining the equivalent plastic viscosity based on Larrard et al.'s (Mat Struct 31:494–498, 1998) research. Ultimately, the impact of the mix parameters on the yield stress and plastic viscosity of the three rheological models was analyzed through the range approach. This study is beneficial for enhancing the comprehension of the rheological characteristics of wet shotcrete. [ABSTRACT FROM AUTHOR]

Neutron activated concrete reference material for measurement of residual radioactivity by gamma-ray spectrometry has been prepared. The main radionuclides were 60Co, 152Eu, 54Mn, 154Eu and 134Cs. One-way ANOVA homogeneity test has shown that the samples are homogeneous. The activity concentrations of 54Mn, 59Fe, 154Eu and 134Cs were relatively low; only 60Co activity concentration was found to be higher therefor it was considered as the main target isotope. The prepared sample can be used as a tool to prove compliance to radiation protection and environmental regulations during decommissioning of cyclotron buildings or other irradiation facilities that produce residual radioactivity. [ABSTRACT FROM AUTHOR]

The present study investigated the synergistic influence of bottom ash as a Portland cement (PC) and natural fine aggregate (NFA) replacement in concrete. Coal bottom ash (CBA) is a heavy ash that settles at the bottom of the combustion chamber of a thermal power plant. It was ground (GCBA) for two hours prior to replacing 10–30% PC, while CBA was used in raw form to replace 25% and 50% NFA. The mechanical properties along with durability properties (accelerated carbonation and chloride penetration) were studied after 28 days and 90 days of curing. Non-destructive tests were also performed to check the quality of CBA-based concrete. Microstructural characterisation was conducted using various techniques, namely X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The concrete with 20% GCBA and 25% CBA (G20C25) reported the best performance in terms of parameters studied owing to the pozzolanic reactivity of GCBA and the filler effect of fine CBA. The microstructural investigations also validated the findings and trends observed in the experimental results. Well-fitted mathematical models were derived and optimisation was carried out using the desirability function approach. Multi-objective optimisation recommended 21.80% GCBA and 24.17% CBA as the optimum amount, resulting in a significant reduction of 19.19% and 18.19% in carbon footprint and eco-cost, respectively, compared to the control mix. [ABSTRACT FROM AUTHOR]

Engineering materials in constructed systems in service exhibit complex patterns, including structural damage, environmental artifacts, and artificial anomalies. In recent years, machine vision methods have been extensively studied, most of which train models using regular grey or color images in the visible bands and label at pixel levels with a large volume of data. The authors propose using hyperspectral imaging (HSI) for structural material condition assessment in this work. Compared with visible images, the research challenge is that HSI pixels with high-dimensional spectral profiles are beyond human perceptive capabilities with hidden discriminative power. Learning from labeled and unlabeled data is one direct approach to unlocking this power. A deep neural network-enabled spatial-spectral feature extraction and a semisupervised learning architecture were developed in this work. A human-in-the-loop (HITL) framework was comparatively studied with three incremental training-data configuration schemes. The paper concludes with the following empirical findings: (1) fully supervised learning determines the baseline of the detection performance; (2) an extensive range of ratio values exists between the unlabeled and the labeled data for incremental semisupervised learning, and a 1∶1 ratio can be taken as a conservative and operational ratio; and (3) with parametric semisupervised learning with equal labeled and unlabeled data participation, the proposed HITL operational workflow can be implemented as a practical approach for HSI-based structural material and damage detection. [ABSTRACT FROM AUTHOR]

The acoustoelastic technique shows considerable potential for in situ stress measurement in concrete. However, the current technology is not fully developed, and challenges primarily arise from the intricate nature of concrete, along with various factors affecting its acoustoelastic properties, such as material strength, aggregate size, porosity, temperature, and humidity. A comprehensive understanding of how these factors influence the acoustoelastic characteristics of concrete is essential for advancing acoustoelastic technology in engineering applications. This study specifically focuses on the material strength, a pivotal factor influencing the quality of concrete, and explores its correlation with the acoustoelastic coefficient (AEC). An initial theoretical investigation was conducted to establish a theoretical model between the two factors, involving two steps: (1) integrating the empirical formula correlating material strength and Young's modulus into the acoustoelastic equations for bulk waves to derive the formula connecting AECs and concrete strengths; (2) applying qualitative analysis and statistical methods to assess the monotonic properties of the formula within its defined domain. To validate the accuracy of the theoretical model, acoustoelastic tests were conducted on prismatic concrete specimens with five different strength levels under axial compressive stress. The findings revealed a consistent pattern, demonstrating that the AECs of concrete decrease with an increase in material strength under axial compressive stress. The outcomes of this study make a substantial contribution to establishing a theoretical foundation for the development of concrete stress monitoring technology based on the ultrasonic method. Practical Applications: The safety of concrete structures is paramount. Currently, structural performance assessment relies primarily on on-site inspections and evaluations by professionals to detect visible cracks and deformations. Typically, cracks become apparent only once the damage has reached a critical level. Failure to identify deterioration processes before reaching this critical stage necessitates significant repairs to prevent premature failure of concrete structural components. If the in situ stress information of structures can be nondestructively obtained would be highly beneficial for warning the early deterioration, tracking the evolution of crack or damage, and forecasting the remaining service life of structures. Acoustoelastic techniques have demonstrated significant potential in achieving this objective. Nonetheless, concrete acoustoelastic effects are influenced by various factors, such as material strength, aggregate size, porosity, and environmental conditions, which impede further advancement of this technology. Therefore, this study investigated the dependence of concrete acoustoelastic effects on material strength. Correlation equations between concrete strength and acoustoelastic coefficients have been formulated. The application of these equations in practice can mitigate the impact of material strength on acoustoelastic measurements. This research contributes to advancing the engineering applications of acoustoelastic techniques in concrete stress assessment. [ABSTRACT FROM AUTHOR]

Concrete structures, such as armories, military bunkers, and petrochemical facilities, are susceptible to explosive loads during service. The superior mechanical properties of ultrahigh-performance concrete enable structures built with it to endure explosive loads. This study aims to characterize the behavior of ultrahigh-performance concrete at different ages, namely, 1, 3, 7, 14, and 28 days, at different strain rates. The compressive stress–strain response of ultrahigh-performance concrete is studied at static and high-strain-rate loading. The high-strain-rate response is characterized using a split-Hopkinson pressure bar of 100-mm diameter. The influence of age on strength, dynamic increase factor strain rate, elastic modulus, peak strain, and energy absorption are discussed. When tested at the same striker velocity, the dynamic increase factor and strain rate of ultrahigh-performance concrete of similar specimen size decrease with age. The elastic modulus and energy absorption increase from 1 to 14 days. There is no significant change in these quantities between 14 and 28 days. The strength, elastic modulus, and energy absorption increase with increasing strain rate for all ages. Experimental data are validated using the Tedesco model and current standards for stress, strain, and elastic modulus. The model from the standards overestimates strength, whereas the Tedesco model predicts strength conservatively. [ABSTRACT FROM AUTHOR]

This study is on fly ash (FA) concrete admixed with TiO2 nanoparticles (FAT), CaCO3 nanoparticles (FAC), and an equal ratio of TiO2 and CaCO3 nanoparticles (FATC) were exposed to seawater for 365 days in order to find the attachment of macrofoulants on their surface. The pH reduction studies were carried out in order to determine concrete deterioration in seawater, the results showed that FA specimens had more pH reduction than FAT, FAC and FATC. Total viable count, epifluorescence microscopy and denaturing gradient gel electrophoresis (DGGE) analysis confirmed the intensity of bacterial attachment and its diversity on FA, FAT, FAC, and FATC specimens. A systematic and comparative analysis predicted the overall relationship in terms of the dominant bacterial species on the different fly ash concrete specimens. To determine the biodeterioration of the fly ash concrete specimens in seawater, we used thermography experiments to evaluate the regions affected by bacteria on mortar specimens and confirmed that FA and FAC had more degradation and that FAT and FATC were the least degraded. Laser Raman Spectroscopy was interesting to find the white micron-sized particles of sulphur on FAC, FAT, and FATC specimens after 365 days immersed in seawater. We used a confocal laser scanning microscope to estimate the thickness of biofilm growth on FAT (13.91 0.38 mm), FATC (21.64 0.22 mm), FAC (33.56 0.26 mm), and FA (43.36 0.10 mm) specimens. The results showed that FAT and FATC specimens were the superior specimens, with enhanced biofouling and biodeterioration resistance in a seawater environment. Practical Applications: Fly ash is a waste material from thermal power plants and is used as a supplementary cementitious material in the construction industry. However, fly ash concrete has a slow hydration process and early strength problems. To overcome these problems, we used TiO2 and CaCO3 nanoparticles to enhance the properties of fly ash concrete. Nanoparticles have a high surface area and unique functional properties such as maintaining concrete pH, reducing porosity, enhancing pozzolanic activity, and so forth. In this study, we used TiO2 and CaCO3 nanoparticles to improve the strength of fly ash concrete and provide it with antibacterial properties. This study is significant in advancing our knowledge of fly ash concrete modified with nanoparticles and exposed to seawater with respect to its mechanical properties, durability, and antibacterial properties. Addition of nanoparticles upgraded the fly ash concrete towards its practical applications. [ABSTRACT FROM AUTHOR]

To solve the problem of the proportional design of cement concrete prepared by using manufactured sand instead of river sand, a new method of manufactured sand concrete mix design was proposed with the dense packing of coarse and fine aggregate. Compared with the original sieving method, the stone powder in the manufactured sand can be regarded as cementitious materials for slurry. With the proposed mix design method, there is no need to separate from the manufactured sand. This dense packing method considers the actual situation that both the manufactured sand and coarse aggregate are mechanically prepared, and all the aggregates can be unified in proportion. The composition ratio of aggregate with particle size greater than 0.075 mm is designed by the maximum density theory, and the rest of the part (below 0.075 mm) is treated as a cementitious material. As a parameter of the maximum density theory, the Fuller index of 0.45 was verified when the calculation values agreed well with the test results. With the proposed mix ratio design method, the different grades C30, C40, and C50 of manufactured sand concrete were designed. Furthermore, the properties such as workability and mechanical properties for the designed manufactured sand concrete were investigated to determine the applicability of the proposed mix design method. The test results show that the workability, uniformity, and strength of the manufactured sand concrete were better than the original mix ratio design method, which verifies the operability and reasonableness of the proposed mix ratio design method. [ABSTRACT FROM AUTHOR]

Calcium nitrate (CN: Ca(NO3)2) has been shown to mitigate alkali–silica reaction (ASR) in concrete. Such ASR mitigation has been suggested to be on account of precipitate (i.e., barrier or passivation layer) formation‐induced dissolution inhibition of reactive/dissolving aggregate surfaces. Herein, we examine the ability of CN to mitigate ASR across two cements (Type I/II and Portland Limestone Cement), for aggregates of varying reactivity, and across different types and dosages of SCMs (supplementary cementitious materials, i.e., amorphous steel slag and Class C and Class F fly ashes). Based on expansion measurements carried out as per ASTM C1260/C1567, it is observed that CN, as a function of dosage, substantively mitigates ASR in mortar formulations across aggregate types. Careful microstructural examinations, dissolution studies, and thermodynamic calculations indicate that CN induces the formation of C–S–H, portlandite (Ca(OH)2), and calcite (CaCO3) precipitate mixtures, which form on aggregate surfaces at the expense of typical ASR gels. Such precipitates create a dissolution barrier and inhibit ASR in both SCM‐free and SCM‐containing formulations. The outcomes indicate that CN is an efficient and cost‐effective ASR mitigation additive (∼$250–$600 per tonne), particularly in a time of dwindling fly ash supplies and unaffordable lithium prices (>∼$12 000 per tonne). [ABSTRACT FROM AUTHOR]

An experimental study is conducted on ten pre-tensioned concrete (PC) beams with different local corrosion degrees and positions to investigate the effect of corrosion on the transfer length and retraction slip of prestressing strand. A novel model, incorporating the combined effects of Hoyer effect and strand corrosion, is proposed to predict the corrosion-induced retraction slip of prestressing strand in PC beams. The accuracy of the proposed model is validated by experimental results. Results indicate that the transfer length and retraction slip of prestressing strand increase with the increase of corrosion loss, and this effect weakens when the local corrosion position changes from the end of the beam to the mid-span of the beam. The transfer length and retraction slip of prestressing strand increase by 30.6% and 5.18 times, respectively, once the corrosion loss reaches 33.5%. The retraction slip of corroded prestressing strand is positively correlated with the diameter of strand, but negatively correlated with the compressive strength of concrete. The diameter of strand, compared with the compressive strength of concrete, has a more significant effect on the corrosion-induced retraction slip. [ABSTRACT FROM AUTHOR]

Aggressive environments can lead to deficiencies or failure in reinforced concrete (RC) members because of the corrosion of reinforcing steel bars. Therefore, bars manufactured from fiber-reinforced polymer (FRP) composites have been employed as a possible substitute for steel bars in RC members. FRP bars have corrosion resistance greater than the conventional steel rebars and a higher ultimate tensile strength. The aim of current investigation was to examine the flexural and compression behavior of slender RC columns having Basalt FRP (BFRP) rebars. Six square slender columns of 240 mm size and 2.8 m long were fabricated in three sets with each set of 2 columns. The columns of the first set were reinforced with 6ϕ12 mm steel rebars (1.1%), whereas the columns of the second and third sets had internal BFRP rebars. The second and third sets differed in the diameter of BFRP rebars, and the percentage of reinforcement was nearly same. The second and third sets had longitudinal BFRP rebars of 6ϕ12 mm (1.1%) and 12ϕ8 mm (1.0%), respectively. Test specimens were subjected to concentric and eccentric (eccentricity = 50 mm) compression. The average compressive strain in BFRP rebars at maximum load was slightly greater than the crushing strain of concrete for both BFRP bar diameters (ϕ8 mm and ϕ12 mm) indicating that the compressive stress in BFRP bars can be calculated from strain compatibility. Analytical model was also carried out for developing the P–M interaction graphs for columns having BFRP rebars. The developed model included the compression resistance of BFRP rebars. The analytically predicted interaction diagrams were conservative and near the experimental ones. The test results of this study were compared with other similar studies from the literature, and the effects of eccentricity-to-depth and slenderness ratios on the second-to-first-order moment ratios were examined for eccentrically loaded FRP-reinforced concrete columns. [ABSTRACT FROM AUTHOR]

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The circular external difference family and its strong version are of great significance both in theory and in applications. In this paper, we apply the classical cyclotomic construction to the circular external differnece family and exhibit several concrete examples, in particular constructing an infinite family. Furthermore, we prove that all strong circular external differnece families are constructed by patching together several strong external difference families consisting of two subsets, thereby solving the open problem raised by Veitch and Stinson. We also present a new result on the non-existence of a certain type of strong external difference families. [ABSTRACT FROM AUTHOR]

Concrete-filled fiber tubes (CFFT) are gaining prominence as a feasible alternative to traditional materials for a variety of structural applications. However, research on structural performance of CFFT beams is still scarce. This paper presents a finite-element (FE) analysis of CFFT beams validated by experimental results from literature. Then, a parametric study investigating structural performance of post-tensioned (PT CFFT) beams was conducted using 34 FE models using ANSYS nonlinear FE software program. The parametric study results showed that both normal-strength concrete (NSC) and high-strength concrete (HSC) filled PT CFFT exhibit identical nonlinear responses. Increasing the prestressed and non-prestressed reinforcement ratio significantly improved the overall performance of PT CFFT beams. Placing the PT tendons at the bottom of PT CFFT beams enhanced the cracking, yielding, and ultimate load-carrying capacities by 7.98%, 12.32%, and 9.03% for NSC-filled PT CFFT beams, respectively. Doubling the axial stiffness of the tube laminate structure increased the ultimate load, energy absorption capacity (EAC), pre-yielding stiffness (Kpre), and post-yielding stiffness (Kpos) by 18.5%, 12.15%, 9.21%, and 8.2%, respectively for NSC-filled PT CFFT beams. Beams with straight PT tendons exhibited increased cracking, yielding, and ultimate load capacity by 10.85%, 14.60%, and 13.58% more than those with curved-profile tendons. The ductility of PT CFFT beams is more sensitive to the amount of prestressed reinforcement ratio and concrete strength has a minimal effect on the structural performance of PT CFFT beams. [ABSTRACT FROM AUTHOR]

To address the environmental impact of greenhouse gases in cement production, incorporating cement substitute materials is crucial. However, the slow degradation of discarded tires poses environmental challenges, making burial or incineration unsustainable. This study explores the integration of discarded tires as crumb rubber in concrete and the use of silica fume as a cement substitute. Experimental methods, coupled with neurofuzzy systems, were employed to predict the mechanical properties of the resulting modified concretes. In the experimental approach, silica fume replaced cement at weight percentages of 0%, 10%, 12%, and 15%, while crumb rubber substituted sand at volume percentages of 0%, 10%, and 25%. Compressive and flexural strengths were evaluated at seven, 28, and 90 days, with tensile strength assessed at 28 days. The neurofuzzy system utilized six inputs—cement, gravel, sand, silica fume, water–cement ratio, and sample age—to forecast tensile and compressive strength in silica fume-containing concrete. Similarly, six inputs—cement, gravel, sand, crumb rubber, water–cement ratio, and sample age—were used to predict flexural and compressive strength in rubber-containing concrete. The findings reveal that the inclusion of silica fume enhances the mechanical properties of concrete, while the introduction of crumb rubber diminishes these properties. Specifically, a quantitative analysis demonstrates the positive impact of silica fume on the strength and contrasting effect of crumb rubber. The neurofuzzy system exhibits remarkable accuracy in predicting tensile and compressive strength for silica fume-containing concrete and flexural and compressive strength for rubber-containing concrete. [ABSTRACT FROM AUTHOR]

This study investigates the influence of wollastonite fiber as a reinforcement in high‐performance concrete (HPC), focusing on its potential to mitigate autogenic shrinkage and enhance overall structural properties. HPC known for its superior strength and low permeability, often suffers from intensified autogenic shrinkage, leading to micro‐cracking and compromising durability. To address this challenge, wollastonite was incorporated at different substitutions (0%, 5%, 10%, and 15%) for both cement and aggregate. The experimental program involved a systematic evaluation of compressive strength, flexural strength, porosity, water absorption, and corrosion resistance with tests conducted at different curing periods. We found that the addition of 10% wollastonite significantly enhances compressive strength (up to 20% after 90 days) and flexural strength (maximum improvement of 21%). The water permeability was decreased by 29% and improved resistance to steel reinforcement corrosion, demonstrating enhanced durability compared to conventional HPC. However, diminishing returns were observed at higher wollastonite replacement levels (15%), indicating a threshold beyond which mechanical and durability benefits were reduced due to potential issues with fiber dispersion and workability. Our findings suggest that wollastonite is a promising, cost‐effective additive for improving HPC. The study contributes new understandings into optimizing HPC mixtures for greater durability and sustainability, while also reducing the environmental footprint through partial cement replacement. Future research is needed to explore the long‐term performance of wollastonite‐reinforced HPC under different environmental conditions and its combination with other supplementary cementitious materials for further enhancement. [ABSTRACT FROM AUTHOR]

This study investigates the potential use of waste ceramic powder as a filler in concrete. Different percentages of waste ceramic powder were added to the concrete, and the compressive strength and water absorption properties were assessed. Failure mechanisms were analyzed using scanning electron microscopy (SEM). The findings revealed that incorporating 5% ceramic powder into concrete increased its compressive strength by approximately 12.5%. However, adding more than 5% ceramic powder led to a proportional decrease in strength. Additionally, water absorption increased when the ceramic content exceeded 5%. SEM analysis showed that higher ceramic content weakened the adhesion of the ceramic particles, and noticeable aggregation was observed. [ABSTRACT FROM AUTHOR]

AbstractIn the present investigation, the gamma and neutron shielding parameters of nano Pb2O3 incorporated into cement in proportions ranging from 0 to 5 wt% were determined using EpiXS and NGCal software. It was observed that the mass attenuation coefficient decreased with increasing photon energy. The introduction of higher concentrations of nano Pb2O3 into the cement resulted in a marked increase in the Pb K-edge. Cement samples enhanced with Pb2O3 content exhibited a pronounced peak in the effective atomic number in the lower energy regions. The exposure buildup factor showed a decrease in its value with increasing Pb2O3 content. Among the compositions used, pure cement with no Pb2O3 addition demonstrated a superior mass attenuation factor for both thermal and fast neutrons. A blend of 95% cement with 5% Pb2O3 emerged as the most effective gamma-ray shielding material within the tested energy range. A comparative analysis of this mix with other concrete types was conducted to evaluate its effectiveness as a shielding material. The findings suggest that this composition could benefit medical imaging and radiation therapy facilities. [ABSTRACT FROM AUTHOR]

The efficiency of retrofitting systems with side near surface mounted (SNSM) CFRP ropes in boosting the flexural performance of intact/heat‐damaged reinforced concrete (RC) beams was investigated using a total of 14 RC beams (250 × 150 × 1450 mm) in two groups. In the first group, the beams were strengthened using SNSM CFRP ropes of a parabolic profile without and with end fan or hock anchorages, coupled with the implantation of lateral and/or vertical CFRP dowels in the high‐shear zone. The beams of the second group were repaired using similar configurations after being heated to 400°C in an electrical furnace for 2 h. A control beam in each group was designated as a reference. The mechanical performance and cracking sequence in all beams was evaluated under four‐point loading test setup. Heat‐damage resulted in reductions in load capacity and stiffness at 11% and 10%, yet an increase in toughness and displacement ductility by 18% and 20%, respectively. Implementing end hocks with end vertical and lateral dowels prevented concrete‐cover separation; imparting the best enhancement in structural performance for the repaired and post‐heated beams. All beams experienced flexural failure mode except for the heat‐damaged one, repaired with end‐hock anchorage without lateral doweling. [ABSTRACT FROM AUTHOR]

Research on the sustainable production of building materials has been increasing from time to time. The construction industry is one of the sectors that leads to the depletion of significant amounts of nonrenewable resources, such as minerals. The ecosystem is deteriorated, and carbon dioxide (CO2) emissions are enormous in the environment due to the use of fossil fuel-based materials. The purpose of this paper is to review the use of plant fibers (hereafter NF) for reinforcement in cementitious concrete. Concrete, plant fibers, their chemical nature, and characteristics are highlighted in an overview. The most important issues in NF-concrete compatibility were discussed, which could provide research opportunities. Modification of NFs and the cement matrix are examined as methods for improving compatibility and degradation. Moreover, the properties and longevity of cementitious materials that are reinforced with natural fibers are also examined. Finally, the review emphasizes the significant research gaps and future research prospects identified in the reviewed papers. [ABSTRACT FROM AUTHOR]

This study advances concrete workability prediction by integrating ensemble learning models like Random Forest (RF), Extreme Gradient Boosting (XGBoost), adaptive boosting (AdaBoost), and gradient boosted regression trees (GBRTs), and XGBoost showing superior accuracy. Using Shapley additive explanations (SHAPs), it identifies key factors such as the S/log(W) ratio and aggregate components affecting concrete performance. Theoretically, this enhances the predictive analytics framework in material science, while practically, it improves construction efficiency by optimizing material use and reducing physical testing. The development of a user‐friendly graphical user interface (GUI) makes these models accessible for industry application. Addressing gaps in model accuracy and interpretability, the research contributes to sustainable construction practices and underscores the need for future expansions in data diversity and computational optimization in the construction industry. [ABSTRACT FROM AUTHOR]

This investigation purposes to use the recycling waste materials in concrete to produce a sustainable environment for construction. The Costus lucanius bagasse fiber (CLBF) was utilized as supplementary cementitious material (SCM) to analyse the workability and mechanical properties of blended cement concrete. The concrete samples were made with the inclusion of 5–20% of CLBF at several w/c ratio by applying RSM modelling and optimization. Moreover, the cubical specimens were cast to study the compressive strength (CS), while beams were used to investigate the flexural strength (FS) on 28th days correspondingly. The outcomes show that the compressive and flexural strengths were decreased with rise in proportion replacement in concrete at various w/c ratio. The highest flexural and compressive strengths was attained at 5% of CLBF at 28 days respectively. Across the tested specimens, the values of compressive strength and flexural strength ranged from 30.20 to 53.92 N/mm2 and 2.15–8.81 N/mm2 for CLBF correspondingly. Besides, the workability and water absorption of concrete is getting decreased as the content of CLBF increases while it is recorded increasing as w/c ratio increases from 0.20 to 0.40. Furthermore, response model predictions were constructed and verified applying ANOVA at an acceptable level of significance of 95%. The coefficients of R2 for the mathematical models ranged from 98 to 99.99%. The research study also indicated that cement can be substituted by CLBF in the production of concrete for various construction purposes. [ABSTRACT FROM AUTHOR]

To counteract the contribution of CO2 emissions by cement production and utilization, biochar is being harnessed as a carbon-negative additive in concrete. Increasing the cement replacement and biochar dosage will increase the carbon offset, but there is large variability in methods being used and many researchers report strength decreases at cement replacements beyond 5%. This work presents a reliable method to replace 10% of the cement mass with a vast selection of biochars without decreasing ultimate compressive strength, and in many cases significantly improving it. By carefully quantifying the physical and chemical properties of each biochar used, machine learning algorithms were used to elucidate the three most influential biochar characteristics that control mortar strength: initial saturation percentage, oxygen-to-carbon ratio, and soluble silicon. These results provide additional research avenues for utilizing several potential biomass waste streams to increase the biochar dosage in cement mixes without decreasing mechanical properties. Highlights: A broad selection of biochars were used to replace 10 wt.% cement in mortars, resulting in similar or improved strength. Biochar moisture saturation percentage, O/C, and soluble silicon are the most important predictors of mortar strength. The data support the hypothesis that biochar improves strength via internal curing, found to be the most important mechanism. [ABSTRACT FROM AUTHOR]

Computed tomography (CT) is an excellent tool to solve certain engineering problems connected to material science (such as sulfate swelling, internal degradation due to freezing, and alkali silicate swelling) and to understand specific processes (frost peeling, acid action). Albeit borne and mostly used in the medical domain, CT is increasingly used in the examination of the internal structure of building materials, where degradation processes occur to the detriment of their mechanical performance and durability. This paper presents five engineering problems concerning concrete freezing and thawing, concrete at high temperatures, timber charring, spalling in asbestos‐cement pipes, and deterioration in prestressed concrete pipes due to the corrosion of metallic inserts. In each case, the degradation processes are monitored via CT, something that may be crucial in the renovation and preservation of historical structures. [ABSTRACT FROM AUTHOR]

The use of high-strength concrete in construction is expected to increase, and the manufacturing technology employed to produce such concrete needs to adapt to this rise. High-strength concrete has a workability that can vary significantly depending on the mixing conditions, even with the same mix design and in the same environment. This research focuses on the change in workability due to dry-mixing (i.e., mixing of fine aggregate with cement in the early stage) in the mixing process of a high-strength concrete mix using a revolving-double paddle mixer. As a result, it was confirmed that the slump flow value difference caused by dry-mixing was about 25 cm. Furthermore, Cryo-SEM (which can observe the specimens in the frozen state) image analysis revealed that dry-mixing causes flocculation of cement particles. The amount of admixtures adsorbed was then analyzed. This study concluded that flocculation affects the degree and timing of admixture adsorption in the later stages of the mixing process, leading to differences in concrete workability. [ABSTRACT FROM AUTHOR]

The use of membrane-forming curing compounds on fresh concrete has been widely adopted by many States' Departments of Transportation as it is feasible where there is a deficiency of water, on sloping surfaces where curing with water is challenging, and in cases where large areas like pavement have to be cured. However, the evaluation of the curing compound application effectiveness is difficult because most of the evaluation test methods are not performed during the early age of the concrete. Moreover, the ASTM C156 standards test of water retention for the qualification of curing compounds has met criticism as the moisture retention is performed only on the mortar specimens, with a fixed application rate and curing condition. Therefore, in this study, the embedded resistance technique was used as a test replacement for the moisture retention test to assess concrete curing. The findings from this study showed that a correlation can be found between the moisture retention test and the embedded resistance test. Based on the findings, the embedded resistance test could be a suitable replacement for the moisture loss test, because the test is much simpler and quicker to be performed both in the lab and in the field. [ABSTRACT FROM AUTHOR]

One of the ways to turn concrete into smart concrete involves the incorporation of conductive fillers. These fillers should be evenly distributed in the matrix to enable the charge propagation necessary for sensing. To homogenize the mixture, typical surface-active chemical compounds are routinely employed. Unfortunately, their presence often negatively impacts the characteristics of concrete. In this work, we show that conductive multi-walled carbon nanotubes (MWCNTs) can be included in the concrete matrix by using off-the-shelf lignosulfonate-based plasticizers. These plasticizers showed a much-improved capability to disperse MWCNTs compared to other routinely used surfactants. They also prevented a significant deterioration of the consistency of the mixture and inhibited the acceleration of the hydration process by MWCNTs. In concretes with MWCNTs and lignosulfonate-based plasticizers, the mechanical properties were largely preserved, while the nanocomposite became electrically conductive. Consequently, it enabled evaluation of the condition of the material by electrical impedance measurements. [ABSTRACT FROM AUTHOR]

Nanomaterials have garnered significant attention in recent years for their potential to enhance the mechanical properties of cementitious construction materials, particularly in high-strength concrete applications. This review aims to explore the effects of various types of nanomaterials on the mechanical properties of concrete materials. Current developments in the synthesis, characterization, and use of nanomaterials in the field of cementitious materials are thoroughly examined in this review. The incorporation of various nanomaterials such as nano-silica, nano-titania, carbon nanotubes, nano-clay, and nano-alumina can significantly enhance the mechanical properties of cementitious construction materials, particularly in high-strength concrete applications. These nanomaterials contribute to denser microstructures, improved hydration products, and enhanced interfacial bonding within the cement matrix, ultimately leading to superior mechanical performance. However, proper dispersion, dosage, and compatibility considerations are essential to realize the full potential of nanomaterials in cementitious materials. The optimum % of NS in cement was reported to be between 1 and 8%, whereas the optimum % of graphene oxide (GO) in cement was reported to be only between 0.05 and 0.5%, imparting high strength characteristics to concrete. The findings of the study promote the use of nanoparticles in cement concrete to enhance the strength of high-rise concrete buildings. The results of various studies are compared, and some significant recommendations are also made. Furthermore, this research underscores the practical applications of nanocomposite-based concrete materials while acknowledging their limitations and opportunities. [ABSTRACT FROM AUTHOR]

Creep recovery of concrete is essential for accurately assessing the performance of concrete structures over service time. Existing creep recovery models exhibit low accuracy, and the influencing factors of creep recovery remain inadequately elucidated. In this paper, interpretable machine learning (ML) techniques were employed to develop a prediction model for concrete creep recovery. Several ML techniques were selected including random forest (RF), support vector regression (SVR), extreme gradient boosting (XGBoost) and light gradient boosting machine (LGBM). In order to maximize the sample size of the dataset, 109 sets of creep recovery data were collected from existing literatures for model training. Feature selection is utilized to determine the input parameters for ML models, and 12 input variables were selected. The model is fine‐tuned using Bayesian optimization techniques. To ensure the reliability of ML models, 10‐fold cross‐validation and random data splitting were implemented. The results indicate that the ML models exhibited higher accuracy compared to the existing creep recovery model. Among these ML models, LGBM demonstrated superior accuracy, efficiency and stability (with R2 = 0.993, 0.978, and 0.973 for the training, testing, and validation sets, respectively). Shapley additive explanations (SHAP) were employed to interpret the significance of each input parameter on ML model prediction. Duration after unloading, stress magnitude, and ambient relative humidity were the main feature variables influencing concrete creep recovery. Upon comparing the influencing factors, it was discerned that there exists a distinct difference between creep and creep recovery of concrete. [ABSTRACT FROM AUTHOR]

Translation abstract Nonlinear analysis of the load‐bearing capacity of folded carbon reinforced concrete modulesGiven the increasing demand for low‐carbon construction, the shift from massive to thin‐walled, highly efficient elements are becoming increasingly necessary. The origami‐inspired folded carbon concrete shells are emerging as an alternative to traditional reinforced concrete structures for the development of economical and sustainable structures. However, the field currently lacks any well‐established design and analysis methods that can reliably predict how folded shells will behave structurally when optimal variants, load‐bearing capacity, stress redistribution, and failure mechanisms are considered. Based on this, two FEM modeling approaches to analyze folded waterbomb‐patterned shells were implemented. In these approaches, the carbon reinforcement is modeled in both smeared and resolved forms, whereas a damage plasticity model is applied to the concrete. The testing of the demonstrator elements validates the results of these approaches, which complement the foundation for the design and analysis of folded origami shells. [ABSTRACT FROM AUTHOR]

Translation abstract Survey of existing repairs to buildings made of exposed concrete – Interim results of the DFG research project “How to deal with historical concrete repairs?” DFG Priority Program 2255 Cultural Heritage ConstructionThe project aims to evaluate previous repairs to exposed concrete structures of the High Modern Age from both a heritage conservation and a structural engineering perspective, and to develop integrated strategies for their preservation. While the need for regular monitoring and condition assessment of these protected buildings is widely recognized, there is a lack of standards for monitoring strategies tailored to heritage conservation and structural engineering considerations. Accordingly, methodological approaches are presented, which were developed as interim results of the research project. The Sirius‐H recording method, developed at the Technical University of Munich allows the qualitative documentation of exposed concrete surfaces. The nature and extent of colour heterogeneity is analysed quantitatively using a spectrophotometer and paraphotographic diagrams. The CoMooD element current meter developed at the Munich University of Applied Sciences allows the measurement of carbonation‐induced reinforcement corrosion both in original concrete and in repaired areas, and thus to estimate the risk of damage. Non‐invasive investigation methods are particularly necessary for listed buildings, while the results must be documentable and reproducible in the long term in order to ensure continuous monitoring of the buildings. Based on exemplary observation results, it is shown that both methods usefully complement proven methods of condition assessment. [ABSTRACT FROM AUTHOR]

A proposal for the direct pure shear characterisation of steel-fibre-reinforced concrete specimens with two grooved shear planes is presented. In the first stage of work, crimped steel fibres (CSF) were used at volume fractions (Vf) of 0, 0.5, 1.0 and 1.5%, the concrete compressive strength was 35 MPa and the maximum coarse aggregate size (Dmax) was 9.5 mm. With these specifications, eight block specimens were subjected to the direct shear tests. A significant gain in shear strength was observed with an increase in fibre dosage – an increase of 90% when Vf = 1.5%. Based on this, three analytical expressions to compute the shear stress were formulated. The models were assessed by testing 15 blocks of smaller size and additional variables – hooked-end steel fibres (HSF), concrete compressive strength of 25 MPa and coarse aggregates with Dmax = 9.5, 19.0 and 25.0 mm. Better performance was obtained with the CSF rather than the HSF, with a strength gain of around 100% for Vf = 1.5% with the maximum coarse aggregate particle size of 25 mm and variability between the proposed analytical models of 2–7%. [ABSTRACT FROM AUTHOR]

Agricultural waste is one of the wastes with a significant value in producing environmentally friendly materials that can be used in the construction sector. This review paper focuses on the potential uses of walnut shell in some building materials. Walnut shell is a type of agricultural waste that can be converted from waste into usable materials by incorporating it into the manufacture of some building materials to achieve sustainability in the construction industry. Recently, walnut waste has drawn the attention of researchers to generate building-friendly materials to boost sustainability in the construction field. In this sense, the walnut shell's low specific gravity makes it a viable material, as a cheap agricultural waste product, for the development of building materials. According to a survey of the literature, walnut shells can be utilized in the production of structural elements and thermal insulating concrete, up to 30% and 50% as particles respectively. [ABSTRACT FROM AUTHOR]

An energy‐based isotropic elastoplastic damage model is developed for investigating the elastoplastic damage responses and stress–strain relationships of nano‐silica incorporated concrete. The formulation employs a multiscale micromechanical framework to determine the effective elastic properties of composites at different scales. The stress–strain constitutive relation is derived by splitting the strain tensor into "elastic‐damage" and "plastic‐damage" parts while introducing the homogenized free potential energy function and the undamaged potential energy function. The elastoplastic damage response of the material is further characterized by elastic–plastic‐damage coupling. To construct realistic 3D three‐phase concrete mesostructures in numerical simulations, this paper introduces an encapsulation placement method that avoids particle overlap checking when placing aggregates. This methodology allows adjustments for the aggregate compactness as needed and enhances computational efficiency in concrete mesostructure construction. The numerical results of the modeling show good agreement with the experimental values in the open literature. Further, the influence of nano‐silica addition contents and ITZ (interfacial transition zone) thicknesses on the elastoplastic damage response of nano‐silica incorporated concrete are quantitatively and qualitatively investigated for the optimization of nano‐silica incorporated cementitious composites. The proposed model facilitates simulating and optimizing the mechanical characteristics of nano‐silica incorporated concrete and enhances the computational efficiency of 3D concrete modeling with the introduced encapsulation placement method. [ABSTRACT FROM AUTHOR]

In this investigation, the bond performance between CFRP and concrete in Near Surface Mounted (NSM) strengthening system using cementitious-based adhesive (CBA) was evaluated at different exposure temperatures. Two types of CBA were used (CBA-A and CBA-B) with and without magnetic water (MCBA-A and MCBA-B). Magnetic device with magnetic strength of 9000 Gauss was used to magnetise the water for 15 mins with a flow rate of 0.1 m3/hr. The bond efficiency was evaluated by performing single-lap shear tests for CFRP laminate embedded in concrete prisms as a near surface-mounted strengthening system. The bond between CFRP and concrete was tested under ambient and high temperatures. The heating regime involves the exposure of NSM CFRP/concrete samples to constant temperature (200°C) for 2 hrs, then the load was applied until failure. In comparison with control samples, an improvement of 40% in the load failure was achieved for specimens strengthened with CFRP using magnetised water in CBA. Within the MCBA samples, higher failure load was conducted for MCBA-B samples when compared with samples of MCBA-A since the latter contain primer in its compositions in which its properties deteriorate by high temperature. All tested samples showed similar failure pattern, which is slippage of CFRP. [ABSTRACT FROM AUTHOR]

Translation abstract Durable and sustainable bridge caps made of non‐metallic reinforcement and recycled concreteDue to chloride‐induced corrosion, bridge caps made of steel‐reinforced concrete need to be replaced regularly or more often than planned. As part of a ZIM project funded by the Federal Ministry for Economic Affairs and Climate Action, bridge caps made of non‐metallic basalt fibre reinforcement and recycled concrete were developed to mitigate the weakness of corrosion and to better utilize the materials in terms of the material cycle. To achieve this, bend reinforcement elements made of chloride‐resistant basalt fibre reinforcement and concrete with high frost‐thaw resistance were developed, consisting of up to 100 % recycled aggregate. All sub‐developments were integrated into a holistic approach, and a prototype of a resource‐efficient and durable bridge cap was successfully produced and tested. [ABSTRACT FROM AUTHOR]

The escalating global plastic waste crisis has prompted a search for sustainable solutions, particularly in the construction industry. Recycling plastic waste to create sustainable construction materials, such as concrete, has emerged as a promising approach. This paper explores the potential of utilizing plastic waste in concrete to mitigate environmental impacts while enhancing construction practices. The study emphasizes the urgent need for sustainable practices in response to increasing plastic consumption and waste generation. By recycling plastic waste into concrete, the construction industry can reduce dependence on natural aggregates and minimize environmental pollution. The paper also highlights the economic feasibility and long-term performance of plastic-containing concrete, addressing key challenges and limitations. Through a comprehensive analysis of the environmental, economic, and technical aspects, this paper aims to provide valuable insights into the sustainable use of plastic waste in concrete construction. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSThe aggregate size and particle-size distribution (PSD) can change the packing density, slump, and strength of concrete. The micromechanical effects of aggregate size on the slump and strength remain unclear. The current numerical study examined concrete behavior using slump and uniaxial compressive strength (UCS) tests considering the aggregate size distribution using the discrete element method. The effect of the aggregate size on the packing density, UCS, and slump of the concrete was analyzed. To accomplish this, we evaluated how variations in the uniformity and curvature coefficients of the PSD, as well as the specific surface area of the samples, were affected by changes in aggregate size. Although the simulations were based on standard specimens from the laboratory, the results showed good agreement with the documented experimental results. Briefly, at a 40–60% fine aggregate content, the packing density and compressive strength of the concrete reached their peaks and caused a decrease in the height of the slump. The uniformity and curvature coefficients did not influence the slump height. The induced shear band could be tracked during the UCS tests and the crack angles could be measured. At the optimum fine content (40–60%), the shear bands were primarily localized and propagated through the samples having different fine contents.The use of the optimum level of the concrete fine aggregate content ensured its workability and strength.This optimum level of fine aggregate was 40–60%.The discrete element method can be used to evaluate the role of particle size on the performance of concrete.The particle size distribution changed the macro-parameters of the concrete.The maximum packing density was determined to be 40–60% of fine aggregates.The use of the optimum level of the concrete fine aggregate content ensured its workability and strength.This optimum level of fine aggregate was 40–60%.The discrete element method can be used to evaluate the role of particle size on the performance of concrete.The particle size distribution changed the macro-parameters of the concrete.The maximum packing density was determined to be 40–60% of fine aggregates. [ABSTRACT FROM AUTHOR]

The Mechanical properties of concrete significantly deteriorate when exposed to fire, with explosive spalling posing a major threat to structural integrity. This highlights the need for effective insulation systems to protect concrete structures in fire conditions. However, current insulation solutions are typically installed externally, requiring additional labour and materials. This review explores the potential of incorporating Phase Change Materials (PCMs) directly into concrete as an embedded insulation system. As a latent heat storage material, PCM offers promising fire-resistant properties, reducing the need for external insulation while improving the fire performance of concrete. This paper presents a bibliometric analysis and a systematic review of recent publications on the use of PCMs in concrete and their fire performance applications. One thousand two hundred and four publications retrieved from Scopus© and Web of Science databases were passed through the PRISMA flowchart to obtain a database of recent literature on the study area. The current trend of research shows a shift towards inorganic PCMs in concrete. There is a significant lack of studies on using inorganic and eutectic PCM in concrete for fire applications and existing studies show inorganic PCM can be a viable solution. Commercial availability and lack of synthesised encapsulated PCM were found to be barriers to research. [ABSTRACT FROM AUTHOR]

Translation abstract Load absorption of deflection forces – Investigations into the break‐out resistance of concrete reinforcing barsIn curved reinforced concrete structures, the steel tensile forces result in radially directed deflection stresses in the concrete, which can cause the concrete cover to spall and the reinforcing bars to pull out. To investigate the absorption of these deflection forces by the concrete, the influence of various parameters on the break‐out forces of reinforcing bars was determined at Münster University of Applied Sciences. The influence of different bar diameters (16, 20, 25, 28 and 32 mm) and the influence of the interaction between several reinforcing bars with different concrete mix designs were investigated. The result of these tests is that larger rebar diameters and a higher concrete quality generally generated higher breaking loads. [ABSTRACT FROM AUTHOR]

The decrease in dynamic elastic modulus is a primary indicator of quantitative damage in concrete. To quantitatively assess depth-by-depth damage within a concrete structure, cylindrical specimens obtained through coring can be cut into disk specimens to measure the dynamic elastic modulus of concrete at each depth. To minimize external damage during coring, it is essential to extract cylinders with the smallest possible diameter. In addition, for higher resolution in depth-based damage assessment, creating disk specimens with the smallest possible thickness is necessary. However, there is no information available in the literature on experimental limitation of smallest possible diameter and thickness for dynamic elastic modulus of disk-shaped specimens. This study evaluated whether the dynamic modulus measured from various sizes of concrete disk specimens provided sufficient reliability compared to reference values obtained from cylinders. Moreover, the study examined how the presence of coarse aggregate and variation in the water–cement ratio significantly influenced the dynamic modulus measurement. In addition, test results from impulse excitation technique (IET) and impact resonance (IR) were compared to find a more reliable test method for dynamic elastic modulus of disk specimen. The experimental findings revealed that as the thickness-to-radius ratio of the disk specimens decreased, measured data variation increased. Mortar specimens without coarse aggregates showed less variability compared to concrete specimens, and the variation in dynamic modulus measured by IR was lower than that measured by IET. [ABSTRACT FROM AUTHOR]

This study presents an exhaustive exploration into the development and rigorous evaluation of nano-TiO2-modified recycled aggregates (NT@RAs) as an environmentally sustainable substitute for natural aggregates in concrete applications. A methodical framework was devised for the synthesis and thorough characterization of NT@RAs, emphasizing the optimization of nano-TiO2 loading onto the RA surface and within its intricate porous structure. The investigation encompassed three distinct types of recycled aggregates: recycled glass sands (RGSs), recycled clay brick sands (RCBSs), and recycled concrete sands (RCSs). Of particular interest, NT@RGS, with its properties of an inherently smooth surface texture and low water absorption, was found to exert a favorable influence on the rheological behavior of concrete, manifested in reduced yield stress, thereby underscoring the potential for fine-tuning mix designs to enhance workability. As the substitution levels of NT@RGS and NT@RCBS escalated, an initial decrement in compressive strength was discernible, which subsequently reversed to strength restoration at optimized substitution ratios. This phenomenon is attributed to the synergistic interplay among NT@RA components. Remarkably, NT@RA-incorporated concrete demonstrated unparalleled self-cleaning abilities, surpassing the performance of concrete with direct nano-TiO2 powder incorporation. This comprehensive research contributes significantly to the advancement in sustainable, high-performance photocatalytic construction materials within the realm of concrete technology. It underscores the potential for enhancing not only the rheological and mechanical properties but also the environmental responsiveness of concrete through the innovative utilization of NT@RAs. [ABSTRACT FROM AUTHOR]

This study investigates the enhancement of recycled concrete aggregate (RCA) surfaces with nano-TiO2 for an improved degradation of low-concentration sulfur dioxide (SO2). Nano-TiO2 particles, known for their photocatalytic properties, were uniformly deposited on RCA surfaces. Upon exposure to SO2 under light irradiation, the functionalized RCA exhibited significantly improved degradation efficiency. This was attributed to the photo-induced oxidation of SO2 by nano-TiO2. Enhanced degradation was further observed under UV light due to increased photoactivation. The nano-TiO2 coating also showed good durability and stability, ensuring long-term effectiveness. The experimental outcomes reveal that TiO2-treated recycled aggregates exhibit an 85% retained photocatalytic activity post five cycles of reuse. Furthermore, the investigation employs a second-order polynomial-based mathematical fitting function to generate a three-dimensional trend surface, visually illustrating the inverse relationships between sulfur dioxide degradation and environmental variables, such as initial concentration and flow rates. Finally, this study demonstrates the potential of nano-TiO2-modified RCA for mitigating the environmental impact of low-concentration SO2, contributing to the development of more sustainable construction materials and broadening RCA's applications in environmental remediation. [ABSTRACT FROM AUTHOR]

Despite of intensive research on concrete fatigue, the transfer of fatigue characteristics determined at the material level to the structural level remains a challenging issue. In this paper, the propagation of fatigue‐induced damage through the concrete structure is analyzed using a microplane fatigue model for concrete recently developed by the authors. To this end, our recent experimental study in which the fatigue propagation was monitored at the structural level represented by prestressed concrete beams is used to derive a general interpretation of the stress redistribution process using of the developed model. The numerical studies show that the developed microplane fatigue model provides a powerful computational tool for in‐depth analysis of the correspondence between the fatigue behavior at the material and structural scales in a wide range of load configurations. In addition, the thermodynamically based constitutive model allows for the quantification of the energy dissipation during the process, revealing the possibility of deriving material‐specific energetic characteristics that can further help to make the predictions of fatigue life more accurate. Highlights: Structural experiments validate the constitutive fatigue hypothesis.Damage‐induced energy dissipation is an objective value for fatigue characterization.Insights into the fatigue life extension of concrete at the structural level are provided.Structural stress redistribution induces variable load amplitudes at local level. [ABSTRACT FROM AUTHOR]

Globally, the production of concrete is responsible for 5% to 8% of anthropogenic CO2 emissions. Cement, a primary ingredient in concrete, forms a glue that holds concrete together when combined with water. Cement embodies approximately 90% of the greenhouse gas emissions associated with concrete production, and decarbonization methods focus primarily on cement production. But mitigation strategies can accrue throughout the concrete life cycle. Decarbonization strategies in cement manufacture, use, and disposal can be rapidly implemented to address the global challenge of equitably meeting societal needs and climate goals. This review describes (a) the development of our reliance on cement and concrete and the consequent environmental impacts, (b) pathways to decarbonization throughout the concrete value chain, and (c) alternative resources that can be leveraged to further reduce emissions while meeting global demands. We close by highlighting a research agenda to mitigate the climate damages from our continued dependence on cement. [ABSTRACT FROM AUTHOR]