Search Results (22,726)

There are no unique and universally accepted procedures for the determination of the maximum and minimum void ratios, e_max and e_min. This issue is particularly pertinent in the characterisation of the alternative sustainable materials examined in this study: well-graded tyre-derived aggregate (TDA), recycled concrete aggregate (RCA) and their mixtures (RCA-TDA), with a rubber content by weight of Χ_M = 11, 23 and 55%. Uniformly graded TDA–sand mixtures with Χ_M = 0, 15, 27, 42, and 100% were also considered. The results from dry and moist samples were compared with void ratios obtained after Proctor compaction and static loading. It was found that, in contrast to vibration for sand and sand–TDA mixtures, the most efficient densification techniques involve impact compaction at the optimum water content for RCA and RCA-TDA and static loading for TDA. Inversion of dry RCA, TDA and RCA-TDA samples in a graduated cylinder was the most effective to consistently achieve e_max but induced visible segregation. Unlike sand–rubber mixtures, well-graded RCA-TDA did not exhibit a threshold rubber content at which e_max and e_min fell below those of RCA and TDA alone, suggesting reduced segregation. The findings offer practical guidance for improving specimen preparation reproducibility in the laboratory. Full article

Despite being fundamental to modern infrastructure, the cement and concrete industry is a major contributor to global carbon emissions, necessitating urgent decarbonisation strategies to mitigate climate change and achieve net-zero targets by 2050. This review explores technological pathways and innovations essential for lowering carbon emissions, including low-carbon materials, energy-efficient processes, carbon capture, utilization and storage (CCUS), and advanced production technologies. It also highlights the importance of supportive policy frameworks, financial incentives, and international collaboration in accelerating the transition to a low-carbon industry. While challenges such as high initial costs, resistance to change, and knowledge gaps persist, these can be addressed through innovation, education, and robust financial mechanisms. Furthermore, circular economy principles, sustainable procurement practices, and continued research and development are emphasized as critical enablers of the industry’s transformation. The paper concludes with recommendations for future actions, highlighting the role of cross-sector cooperation, research funding, and knowledge sharing in achieving a sustainable and decarbonised cement and concrete sector that can “go green” for eco-constructions. Full article

The recycling of waste clay bricks as raw materials for cement-based materials presents an effective solution to ecological pollution and resource shortages. Previous research has separately examined the effects of recycled brick fine aggregate and recycled brick powder on mortar or concrete, but few studies have investigated their combined use. This study aims to clarify the synergistic effect of recycled brick fine aggregate (RBA) and recycled brick powder (RBP) on mortar performance, quantify the influence of the RBP substitution rate on hydration characteristics and microstructural evolution, and determine the optimal mix proportion and curing system for fully recycled brick mortar. Mortar was prepared using 100% RBA and RBP at substitution rates of 0%, 10%, 20%, and 30%. The physical properties, mechanical performance, and durability of the mortar were evaluated, alongside an analysis of its microstructural morphology, mineral composition, and pore structure. The results indicate that adding an appropriate amount of RBP helped maintain the flowability of the mortar. As the RBP substitution rate increased, the mortar strength generally decreased in the early stages, but long-term curing (≥90 days) effectively mitigated this decline. The inclusion of RBP improved chloride ion permeability, with the 20% substitution rate achieving a favorable balance between compressive strength, fluidity, and durability without significantly affecting carbonation resistance. Microstructural analysis revealed that RBP regulated the morphology of hydration products and optimized the pore structure of the mortar, while the mineral composition of hydration products was similar to that of natural mortar. These findings provide a theoretical basis and technical support for the high-value utilization of construction and demolition waste in cement-based materials. Full article

This study presents an experimental investigation into the repair and seismic performance enhancement of earthquake-damaged reinforced concrete (RC) frame structures using high-strength cement mortar and viscous dampers. A 1/4-scale, four-story RC frame model—designed according to a seismic fortification intensity of 8 degrees (corresponding to 0.2 g PGA in China’s seismic code)—was subjected to shaking table tests under increasing levels of artificial seismic excitation. Following the first round of loading, the damaged structure was repaired using high-strength mortar infill, and 12 viscous dampers were installed for seismic upgrade. The second round of identical seismic loading was applied to evaluate the effectiveness of the repair strategy. Comparative analysis of structural responses before and after repair reveals that the combination of high-strength mortar and viscous dampers improved damping capacity. The initial natural frequencies of the repaired structure increased by 6% (X) and 24% (Y), and damping ratios rose—reaching 12.75% and 10.78% under rare ground motions (1.34 g). Peak acceleration and inter-story drift ratio (IDR) were effectively reduced under moderate seismic levels, although some increase in IDR was observed at higher intensities, all drift values remained within the seismic code limits. The viscous dampers significantly altered the inter-story deformation mechanism, reducing the deformation concentration factor (DCF) of the frame structure and resulting in a more uniform distribution of story drifts. In addition, the energy dissipation capacity of the dampers increased progressively with the intensity of seismic excitation. The results validate the feasibility and efficiency of integrating viscous dampers with high-strength mortar for seismic repair and retrofitting of RC frame structure. Full article

To address the issues of difficult heterogeneous image registration and low segmentation accuracy caused by the severe lack of illumination and significant modal differences in concrete cracks in extremely dark environments, this paper proposes a two-stage processing framework of registration–fusion first, and decoupling–segmentation later. In the registration and fusion stage, a registration algorithm based on morphological priors and multi-level quadtree spatial constraints is designed. This approach transforms the problem from pixel grayscale matching to spatial topological matching, achieving a feature fusion of high infrared saliency and high visible light sharpness. In the segmentation stage, a Latent Frequency-Decoupled Topological Network (LFDT-Net) is proposed. It utilizes Discrete Wavelet Transform (DWT) to achieve high-fidelity frequency decoupling of the low-frequency infrared backbone and the high-frequency visible light edges. Furthermore, a Cross-Frequency Guidance Module is utilized to eliminate double-edged artifacts, and a skeleton-aware topological loss function is introduced to constrain the topological integrity of the cracks. Experimental results on a self-built heterogeneous multi-modal crack dataset demonstrate that the proposed method significantly outperforms existing mainstream methods in registration accuracy, fusion quality, and segmentation accuracy. Achieving a mean Intersection over Union (mIoU) of 81.7%, the method effectively suppresses background noise in dark environments and precisely restores the microscopic edges and continuous topological structures of faint cracks. Full article

The paper deals with the concept of how to regulate structure formation in the interfacial transition zone (ITZ) between the Ordinary Portland Cement (OPC) matrix and basalt to ensure the durability of basalt fiber-reinforced concretes. It has been demonstrated that the alkali–silica reaction (ASR) can be transformed from a destructive (negative) process into a constructive one in OPC concrete through activation by sodium water glass combined with the incorporation of an Al₂O₃-containing additive, namely metakaolin. Alkaline activation increased the compressive strength of OPC basalt fiber-reinforced concrete by 1.6–1.9 times. The formation of stable zeolite-like hydration products within the Na₂O-CaO-Al₂O₃-SiO₂-H₂O system promoted self-healing of the ITZ. This resulted in a 5.6-fold increase in ITZ microhardness compared to the cement matrix, as well as transforming expansion into shrinkage of concrete with a final value of 0.01 mm/m after 360 days. The structure-forming processes in the ITZ ensured a 1.14-fold increase in the compressive strength of 180-day alkali-activated OPC basalt fiber-reinforced concrete compared to its 30-day strength, in contrast to a 0.92-fold decrease in the strength of the non-modified OPC analog under conditions accelerating the development of ASR. Full article

Concrete linings are used for water containment, in particular in reservoirs and canals. When the soil underlying a concrete lining has a high permeability, seepage into the ground of water from concrete-lined reservoirs and canals is essentially governed by leakage of water through the concrete linings. Therefore, it is essential to properly evaluate the hydraulic conductivity of concrete linings. It is known that cracks generally develop in concrete linings. This article provides material data and a method for the evaluation of the hydraulic conductivity of concrete linings, in particular cracked concrete linings, through two approaches. The first approach consists of a review of selected published values of the measured hydraulic conductivity of intact and cracked concrete. The second approach consists in developing an original analytical method to determine the hydraulic conductivity of cracked concrete using the results of an experimental evaluation of the influence, on water flow, of the tortuosity and rugosity of concrete cracks. The results obtained with the two approaches are compared and numerical examples are presented. Based on these results, practical guidance is provided to design engineers for a safe evaluation of the hydraulic conductivity of concrete linings, cracked or not cracked. Full article

Asphalt pavement on rigid base (cement concrete) differs significantly from traditional granular base pavement. To investigate its mechanical behavior, a viscoelastic–viscoplastic damage constitutive model for asphalt mixtures is proposed and verified. A user-material subroutine (UMAT) is developed to implement the model, and a three-dimensional finite element model is established to analyze pavement responses under various working conditions. Key numerical results include the following: the asphalt layer primarily experiences compressive–shear failure, with peak shear stress (τ₁₂) reaching 141.6 kPa under rigid base conditions; emergency braking increases τ₁₂ to approximately 270.3 kPa, a 91% increase; increasing vehicle speed from 15 m/s to 35 m/s raises τ₁₂ by 36.7%; based on stress analysis alone, the recommended asphalt layer thickness is between 0.10 m and 0.14 m, as thickness beyond 0.10 m yields diminishing stress reduction. The findings provide references for performance prediction, structural design, and material development of asphalt pavement on a rigid base. Full article

Accurate prediction of ultra-high-performance concrete (UHPC) compressive strength is essential for optimizing mixture design and reducing experimental iterations. Existing machine learning approaches suffer from limited algorithm diversity, insufficient statistical validation, and inadequate uncertainty quantification. This study presents a comprehensive framework through systematic evaluation of 20 algorithms across seven categories on 863 experimental observations. Six physically meaningful composite features (such as water-cement ratio, total binder content, and fiber aspect ratio) are engineered to capture intrinsic material relationships, with the Boruta algorithm employed for feature selection. Statistical robustness is ensured through 30 repeated experiments analyzed using both frequentist (p-value, effect size, 95% CI) and Bayesian approaches. CatBoost achieves optimal performance (R² = 0.8979 ± 0.0239, RMSE = 10.58 ± 1.45 MPa), with curing age, sand content, and steel fiber volume identified as dominant predictors through multi-perspective interpretability analysis integrating SHAP, ALE, permutation importance, and LIME. External validation on 810 independent samples yields R² = 0.5923 (RMSE = 25.68 MPa) under significant cross-dataset conditions, with performance reduction attributed to feature availability differences and distribution shift. Comprehensive uncertainty quantification yields prediction uncertainty of 3.48%, substantially below previously reported thresholds. The proposed framework offers practitioners a reliable tool for UHPC mixture screening while maintaining prediction confidence for structural engineering applications. Full article

Warm-mix asphalt (WMA) technology and basalt fiber modification have been increasingly applied in road engineering. However, conventional basalt fibers often disperse unevenly and tend to agglomerate. In this study, basalt fiber powder (BFP) was incorporated into a Sasobit-based WMA system and systematically compared with matrix asphalt, Sasobit-modified WMA, conventional basalt fiber-modified WMA, and styrene butadiene styrene (SBS)-modified asphalt. Multiscale characterization—including dynamic shear rheometry (DSR), bending beam rheometry (BBR), scanning electron microscopy (SEM), and nanoindentation—was conducted to elucidate rheological behavior and interfacial micromechanical responses. The corresponding Asphalt Concrete-13 (AC-13) mixtures were further evaluated through rutting tests, low-temperature bending tests, and moisture susceptibility tests. Results demonstrate that micronized BFP achieves more homogeneous dispersion within the asphalt matrix and may promote a more effective reinforcing morphology, significantly enhancing high-temperature deformation resistance while partially mitigating the low-temperature stiffness increase induced by Sasobit. Compared with conventional basalt fiber systems, BFP shows better stress relaxation capacity and interfacial mechanical response under the tested conditions. At the mixture level, the BFP–Sasobit system showed the best overall performance, with the dynamic stability increasing by 242.2% relative to the base asphalt mixture and the residual Marshall stability reaching 92.3%, while the low-temperature flexural strain increased by 33.3%. Overall, the findings suggest that morphology-controlled micronization provides a morphology-guided enhancement strategy for Sasobit-based warm-mix asphalt by promoting coordinated improvements across the rheological, micromechanical, and mixture scales. Full article

A novel procedure is proposed in this paper to investigate the capacity of parking structures to resist additional live loads that could come from many cars, potentially from heavier or driverless cars. In recent decades, the typical operating weight of passenger vehicles has risen significantly. The anticipated widespread adoption of electric vehicles (EVs), which contain heavy battery systems, may further increase live load demands. As a result, a new robust procedure is needed to assess the live load effects on parking structures. Hence, using the proposed innovative approach based on 3D influence surfaces, tributary areas (AT) and three-dimensional influence surfaces (AI) were calculated (for the first time) to examine the equivalent uniformly distributed load corresponding to selected column axial loads and beam midspan moments that are expected to be experienced during the lifetime of parking structures. As case studies, the responses of two existing multistory parking garages on the Ohio State University campus were investigated under different arrangements of two car types—standard cars and sports utility vehicles (SUVs)—and the calculated maximum live loads were compared with the current code requirements. The results show that the maximum live load for the midspan moment is conservative; however, the maximum axial column loading in the extreme scenarios presented in this paper can be larger than the specified (original) design limit of the selected parking garages. The novel methodology proposed in this paper is based on 3D influence line analysis and can be applied for any vehicle configuration and weight, and different parking arrangements or loading scenarios to investigate the performance of parking garages. Full article

In this study, the characteristics of concretes made from mixed recycled aggregate—the cheapest and most common secondary raw material in construction and demolition waste—were determined. For this study, besides experimental concretes using mixed recycled aggregate, reference compositions were developed using river gravel, recycled concrete aggregate, and recycled masonry aggregate. The workability of concrete mixtures was measured as class S1, which is acceptable for use with slipform concrete pavers, and was achieved by varying the water/cement ratio, considering the different water adsorptions of the concrete fillers. The following mechanical characteristics of the concretes were defined on the 3rd and 28th days: density, compressive strength, flexural strength, water absorption, and frost resistance. The test results showed sufficiently high indicators of strength and durability for the recycled aggregate concretes. Moreover, the strength of the concrete developed from mixed recycled aggregate was comparable with that of the reference concretes. Considering the low strength requirements for the construction of the lower layers of rigid pavements, it was established that such an application of recycled aggregate concrete, including that derived from mixed recycled aggregate, could be permitted. Full article

On 6 February 2023, Türkiye was struck by two devastating earthquakes with moment magnitudes of 7.8 and 7.6, causing severe damage to numerous tall reinforced concrete buildings and emphasizing the need for improved seismic design strategies. This study investigates the seismic response of a representative high-rise reinforced concrete building by systematically varying the shear wall area-to-floor area ratio, a key parameter directly influencing lateral stiffness and overall stability. Utilizing a solid modeling approach and incorporating three-directional seismic records, this research provides detailed insights into displacement behavior beyond conventional frame-based analyses. Focusing on Adana, a major urban center with a significant concentration of tall buildings and notable seismic risk, three design scenarios with shear wall ratios of 1.14%, 1.54%, and 2.1% were examined. The results demonstrate that increasing the shear wall cross-sectional area compared to the building plan area significantly reduces lateral and vertical displacements, with the most pronounced improvement observed when moving from 1.14% to 1.54%. Further increase to 2.1% provides additional enhancement in seismic performance. This study suggests that adopting a minimum shear wall area-to-floor area ratio of at least 2% along each principal direction (resulting in a total combined ratio of approximately 4% for the building) can substantially improve seismic resilience and mitigate collapse risk in tall structures. Importantly, the shear wall ratios were considered separately for each principal direction, with the total combined ratio doubling, highlighting the need for balanced wall distribution in both directions. Full article

The effect of steel fiber on the maximum crack width of steel fiber reinforced concrete (SFRC) members under normal service conditions was studied through tests on a series of 19 flexural beams, and the applicability of the crack spacing reduction coefficient of steel fiber in SFRC beams from Modified Rilem model that using for calculating maximum crack width was discussed, of which the reduction coefficient value was used to determine the influence of steel fibers on the crack width. Results show that the maximum crack width of the RC beam under bending conditions clearly decreased with the addition of fibers, and the reduction coefficient value of the crack width of the SFRC beam is greater when compared with that specified in the Modified Rilem model. The effect of steel fiber on reducing crack width was overrated, while the reduction coefficient proposed in the Modified Rilem model was used to calculate the maximum crack width. The probability of the reduction coefficient was analyzed based on experimental data collected from the relevant literature, and the reduction coefficients for different steel fiber types with various guarantee rates were obtained. Finally, the suggestion for the value of the reduction coefficient in the Modified Rilem model was proposed to be 1.19, which could be referred to for the code revision. Full article

This study presents an analytical framework for evaluating the admissibility of biaxial inclination of rectangular sinking wells. The inclination of the well is interpreted as an eccentric transfer of the vertical load to the concrete plug, which produces a two-dimensional linear stress field beneath the base. Closed-form expressions are derived for the stresses at the four corners of the rectangular base as functions of the eccentricity components associated with the two orthogonal tilt directions. Based on these expressions, the admissibility of inclination is represented by a tilt envelope in the space of the two tilt angles, defining the combinations of tilt components that satisfy the adopted serviceability criterion. The analytical formulation also allows for comparison between the stress-based admissibility limit, the geometric condition corresponding to loss of compressive contact beneath the base, and a simplified indicator of lateral wall-pressure asymmetry acting on the shaft. Parametric analyses show that biaxial inclination leads to stress concentration at the corners of the base and that even relatively small tilt components may combine to produce significant stress amplification. The geometry of the well strongly influences the shape of the admissible tilt envelope, with elongated rectangular wells exhibiting directional anisotropy of the allowable inclination. The proposed analytical approach provides a transparent tool for evaluating inclined wells using basic geometric parameters in engineering practice. Full article