The continuous demand for improved construction materials has encouraged the exploration of alternatives capable of enhancing the performance of conventional concrete. In the present study, an experimental investigation was carried out to compare the behavior of bitumen–hybrid concrete blocks with that of standard M30 grade concrete blocks. The study focuses on evaluating the influence of incorporating bitumen as a partial replacement for cement on key mechanical properties. Concrete specimens were prepared using standard materials, while the hybrid mix was developed by introducing a controlled proportion of bitumen to modify the binding characteristics. The performance of both types of blocks was assessed through a series of laboratory tests, including compressive strength, load-bearing capacity, and shear strength tests conducted under controlled conditions.

Abstract This study develops an innovative carbon nanotube yarn (CNY)‐based sensing method for real‐time interfacial behavior monitoring in carbon‐fiber reinforced polymers (CFRP) strengthened concrete systems. Single shear testing and piezoresistive monitoring were carried out on CFRP–concrete composite specimens to analyze the interfacial bond behavior and piezoresistive response of CNY mounted on CFRP. The results demonstrate the ability of CNY to monitor the interfacial loading behavior. Through bond slip relationship characterization, bilinear constitutive bond parameters are extracted and their quantitative influence on CNY monitoring signals is revealed. Either increasing local bond strength or reducing the corresponding slip leads to a more gradual rise in the piezoresistive response curve, while the ultimate slip shows minimal influence except for extending the curve to higher applied forces. The piezoresistive response accurately captures the effects of varying bond parameters, demonstrating piezoresistive monitoring is an effective method for interfacial performance characterization.

Traditional manual methods for measuring concrete crack depth are inefficient, time-consuming, and heavily reliant on operator experience, often resulting in inconsistent and subjective outcomes. Moreover, most existing studies on crack characterization primarily emphasize surface-level parameters such as crack length, width, and area. The crack depth, a key indicator of structural integrity and residual load-bearing capacity, remains insufficiently addressed. To bridge this gap, this study proposes an automated crack depth prediction framework that integrates infrared thermography (IRT) with an enhanced SE-ResNet-18 deep learning model. Concrete beam specimens with precisely calibrated crack depths were fabricated under controlled laboratory conditions, and corresponding thermal images were acquired to establish a robust training dataset. By embedding a squeeze-and-excitation (SE) attention mechanism into the conventional ResNet-18 architecture, the model’s capacity to capture and emphasize salient thermal features was significantly improved, resulting in more accurate and stable depth predictions. Experimental results demonstrate that the proposed SE-ResNet-18 achieves 93.77% accuracy within a ±1[Formula: see text]mm tolerance, outperforming the baseline ResNet-18 network by a substantial margin. This solution is fully automated in its predictive analysis and noncontact in its sensing modality. It shows strong potential for practical implementation in real-world structural health monitoring and provides a foundation for future research on field-scale applications and model generalization under varying environmental conditions.

Abstract - Reinforced Cement Concrete (RCC) has been widely used as a construction material globally for the past century, and in India, its utilization has significantly increased over the last 50–60 years. During this period, a large number of infrastructural assets, including bridges, buildings, and stadiums, have been constructed, serving as lifelines for society. However, RCC structural elements are often subjected to damage during their service life due to overloading, faulty design, poor workmanship, chemical attacks, and adverse environmental conditions. Repairing and rehabilitating such damaged structures without demolition is crucial for extending their service life and ensuring safety. This study investigates the strengthening of damaged RCC columns using jacketing techniques, incorporating both mineral admixtures (silica fume) and chemical admixtures. Silica fume, used as a supplementary cementation’s material at 25 % replacement by weight of cement, was incorporated into the concrete mix to enhance mechanical properties and durability. Concrete specimens were cast and tested to evaluate compressive strength, split tensile strength, and flexural strength, and the results were compared with conventional concrete. Additionally, non-destructive testing (NDT) was performed on structural elements before and after rehabilitation to assess the effectiveness of the strengthening methods. The results indicate that the inclusion of silica fume significantly improves the mechanical performance of the concrete on Cubes, cylinders and prisms. While the jacketing techniques effectively restore the structural capacity of damaged RCC members. This research demonstrates a practical and economical approach for the repair, retrofitting, and rehabilitation of RCC structures, ensuring enhanced durability and service life without the need for demolition. Keywords: RCC, Jacketing, Silica fume, Compressive strength, Flexural strength, Non-destructive testing, Structural rehabilitation.

The growing demand for concrete due to rapid urbanization necessitates large-scale cement production, contributing significantly to CO₂ emissions. As a sustainable alternative, Sulphur-Infiltrated Concrete (SIC) utilizes molten sulphur, an oil and petroleum industry by-product, to fill voids in porous concrete. This study explores the potential of SIC, focusing on its production process, mix design, mechanical performance, and microstructural characterization. Concrete specimens (150×150×150 mm cubes) with varying water-cement (w/c) ratios (0.50-0.70) and cement contents (235.71-330 kg/m³) were infiltrated with 99% pure molten sulphur at 140 °C. Experimental trials evaluated compressive strength using destructive and non-destructive methods, including Rebound Hammer and Ultrasonic Pulse Velocity (UPV) tests. Microstructural analysis was conducted using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) at 1-day and 7-day curing periods. Durability was assessed through carbonation testing and water absorption studies. The results showed increased early compressive strength, even with reduced cement content, with Trial 3 (w/c = 0.70) demonstrating superior performance due to enhanced sulphur penetration. Microscopic analysis revealed reduced porosity and improved bonding between sulphur and cement matrix. Water absorption tests indicated minimal absorption, confirming enhanced impermeability. Cost-benefit analysis indicates long-term economic viability. SIC demonstrates promise as an eco-friendly alternative for precast construction applications, offering dual benefits of waste utilization and reduced cement consumption.

The increasing accumulation of plastic waste has become a major environmental concern due to its non-biodegradable nature and harmful impact on ecosystems. At the same time, the construction industry continuously seeks innovative materials to enhance the performance and sustainability of concrete. This study focuses on evaluating the mechanical properties of concrete incorporating waste plastic fibres as a reinforcing material. Waste plastic fibres were collected, processed, and added to concrete mixes in different proportions to examine their influence on strength characteristics. An experimental investigation was carried out to determine compressive strength, split tensile strength, and flexural strength of the concrete specimens at various curing periods. The results were compared with conventional concrete to assess performance improvements. The findings reveal that the addition of waste plastic fibres significantly improves tensile and flexural strength while maintaining acceptable compressive strength. The fibres also enhance crack resistance, toughness, and ductility of concrete. The study concludes that waste plastic fibres can be effectively utilized as a sustainable construction material, reducing environmental pollution and promoting eco-friendly concrete production. This approach supports waste management efforts while improving the mechanical behavior of concrete. Keywords:- Waste plastic fibres, Fibre reinforced concrete, Mechanical properties, Compressive strength, Split tensile strength, Flexural strength, Sustainable construction.

This study assesses the electrochemical compatibility of steel reinforcement with molten sulfur in Sulfur-Infiltrated Concrete (SIC) through integrated electrochemical and compositional analyses. Twelve cylindrical concrete specimens (100 mm × 200 mm) with 10-mm-diameter Fe550D steel reinforcement embedded in them were prepared: six with sulfur infiltration and six without. Half-cell potential measurements were conducted on triplicate specimens from each series at 1-day and 28-day curing ages according to ASTM C876-15. These measurements were complemented by Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy (SEM-EDX) characterization at 28 days. The results show that sulphur infiltration does not adversely affect the electrochemical state of embedded steel reinforcement. SIC specimens exhibited corrosion potentials of −181 mV (1-day) and −211 mV (28-day) versus −193 mV and −237 mV for conventional concrete. Both specimen types remained within the low corrosion probability range (more positive than −350 mV versus CSE) according to ASTM C876 criteria, confirming that exposure to molten sulphur at 140°C does not initiate corrosion. SEM imaging revealed a modified pore structure with a sulfur coating on cement particles. EDX analysis confirmed a fivefold higher sulfur content in SIC (2.6 wt%) than in conventional concrete (0.5 wt%). These findings establish the electrochemical compatibility of sulfur infiltration with steel reinforcement and validate that the SIC process does not compromise steel passivity, making it suitable for reinforced concrete precast applications.

Marine concrete engineering faces severe service environment challenges, including high hydraulic pressure, large stress, and serious penetration. The evaluation of the durability and safety of these structures depends directly on the damage mechanism of concrete materials submitted to high hydraulic pressures. This paper introduced the experimental research on the mechanical properties and the damage mechanism of concrete submitted to high hydraulic pressures. The permeability tests were carried out on concrete specimens under the effect of different hydraulic pressures (1.2 MPa, 2.4 MPa, 3.6 MPa) and durations (10 d, 20 d, 30 d), after which the compressive strength, micro-cracks, and the ultrasonic velocity were obtained and analyzed. The results show that under the effect of sustained high hydraulic pressure, the micro-cracks in concrete increase, the density decreases, and the harmful pores expand, resulting in a degradation in the mechanical properties of concrete. The damage to concrete is more severe at the near end of the hydraulic head than at the far end. The pore water pressure decays gradually with depth inside the concrete and expands inward when the outer layer of concrete is damaged. The conclusions will provide a scientific basis for the safety evaluation of marine concrete engineering.

Waterproof dam concrete’s permeability stability in goaf waterlogged environments critically impacts coal mine safety and groundwater sustainability. Underwater immersion, weak infiltration pathways are formed at the joint interfaces of the composite structure (concrete-concrete), potentially triggering water damage incidents. Optimization research on interface anti-seepage performance is urgently required. This study focuses on the composite structure of waterproof concrete dams, analyzing permeability modification by nano SiO 2 /TiO 2 /Al 2 O 3 at varying percentages on bi-material specimens post-immersion. Gas permeability, Liquid-measured porosity test, Ultrasonic velocity, and SEM were performed to evaluate the permeability evolution and interface stability of nanomaterial-modified concrete after different days of water immersion. Results indicate that post 14-day immersion, the permeability of ordinary concrete monomer specimens (OC) and bi-material specimens (C-C) increased to 0.236×10 -5 μm 2 and 0.760×10 -3 μm 2 , respectively, corresponding to degradation levels of 220.5% and 88.5%. Moreover, the permeability of C-C remained two orders of magnitude higher than that of OC, and their degradation followed a three-stage pattern: rapid amplification, moderate development, and gradual stabilization. Nanomaterial incorporation suppressed permeability deterioration, particularly the 0.5% TiO 2 group, showing optimal performance. Post-immersion, the 0.5%TiO 2 group showed 0.236×10 -3 μm 2 permeability, representing a 69.0% improvement relative to the C-C. Other groups demonstrated modification effects of 55.9% for 0.5%Al 2 O 3 , 52.6% for 1.0%Al 2 O 3 , 42.1% for 1.0%TiO 2 , and 24.4% for 0.5%SiO 2 , while the addition of 1.0%SiO 2 exhibited no significant improvement. Liquid-measured and ultrasonic tests showed the 0.5% TiO 2 group had 16.4% lower porosity and 14.2% higher wave velocity post-immersion. SEM analysis demonstrated that nano-TiO 2 effectively suppressed the expansion of interface cracks, and image binarization processing revealed a 49.6% reduction in fracture surface porosity in the 0.5%TiO 2 group, resulting in a denser interface microstructure and enhanced permeability stability. This study establishes key technical foundations for optimizing composite structural materials for waterproof concrete dams, thereby enhancing permeability stability in underground storage facilities and related engineering structures.

This study experimentally investigated the shear mechanical properties of heterogeneous concrete surfaces during freeze–thaw cycles. Artificial concrete joint specimens with identical morphologies were subjected to direct shear tests under varying freeze–thaw cycles (0, 5, 10, 20, and 30 cycles) and normal stresses (2 to 4 MPa), and the changes in the porosity of the specimens were observed. The results demonstrated that an increase in the number of freeze–thaw cycles resulted in a continuous decrease in the peak shear strength, pre-peak shear stiffness, and residual shear strength of the structural surface, with reductions of 11.5–44.4%, 15.7–31.7%, and 14.5–38.5%, respectively; the increase in porosity exhibited a pattern of rapid growth initially, followed by a slower rate as the number of freeze–thaw cycles increased. The enhancement of normal stress can, to a certain extent, suppress freeze–thaw damage; however, its strengthening effect weakens as the number of freeze–thaw cycles increases. Based on the experimental data, the degradation models of peak shear strength, pre-peak shear stiffness, and residual shear strength considering the influence of freeze–thaw cycles, both the peak shear strength and residual shear strength models were developed based on the Mohr–Coulomb criterion. Strength and stiffness expressions based on porosity increments were also derived and a piecewise constitutive model capable of fully describing the entire shear process was further established. Model predictions showed good agreement with experimental data, with correlation coefficients exceeding 0.91, validating its high predictive accuracy. These findings provide a theoretical basis for the durability design and safety assessment of heterogeneous concrete structural surfaces in water conservancy projects within seasonal freeze zones.

Experimental study and deep learning model for evaluating the impact strength of a concrete U-shaped specimen retrofitted with a UHPFRC layer

To address the issue that open-pit blasting delay designs struggle to concurrently mitigate vibration and optimize fragmentation, this article proposes an interval-based delay optimization framework integrating theory and experiments.Unlike traditional fixed-value delay designs, this framework responds to the variability of blasting parameters and rock mass properties, determining a reasonable delay time interval rather than a single fixed value to realize synergistic control of vibration mitigation and fragmentation optimization. It adopts Hanukayev's theory for delay time calculation, the Swebrec function for fragmentation evaluation, and the “vibration reduction rate” for vibration assessment. Experiments were conducted on C50 concrete specimens using a 3-hole model. The results indicate that inter-hole delays of 3-4 ms and inter-row delays of 1-3 ms enable effective coupling control. Among all schemes, the optimal 3 ms/3 ms (inter-hole/inter-row) scheme achieves remarkable effects: it reduces the peak particle velocity (PPV) in the free surface direction and reverse direction by 70% and 54% respectively, while decreasing the average fragment size and large fragment size by 10% and 9.3% respectively. This research provides crucial theoretical support for safe and efficient mine blasting operations.

Fiber-reinforced polymer (FRP)-reinforced concrete columns have gained interest for use in corrosive environments due to their high tensile strength and corrosion resistance. This study aims to improve the compressive strength and deformability of FRP-reinforced concrete (FRP-RC) columns by investigating the mechanical behavior of FRP stirrups and longitudinal reinforcement. A mechanized FRP grid-cage confinement for concrete columns was advanced, and its axial compressive performance was experimentally evaluated. The results demonstrated that the FRP grid cage stirrups effectively limited concrete damage compared with glass FRP hoop-confined concrete specimens. Reducing stirrup spacing was found to be the most effective way to enhance the compressive behavior of FRP grid cage–confined concrete (FGCC). Furthermore, the effective confined area of FGCC was defined, and an existing model was modified. The updated axial load–strain model accurately predicted the compressive performance of FGCC.

This study presents a distribution-optimized mesostructure estimation method for statistically modeling near-surface aggregate size distributions in concrete by optimizing the spatial arrangement of polydisperse spherical aggregates with respect to formwork boundaries. The approach is based on minimizing the deviation between a generated cumulative aggregate volume function and an idealized linear target function corresponding to a constant area fraction along the specimen depth. To enable efficient computation for systems containing a large number of aggregates, grain size groups derived from the grading curve are represented using symmetric Beta distributions, allowing each group to be described by a single shape parameter. The resulting optimization problem is solved using a derivative-free Powell algorithm. The method inherently captures wall effects, leading to a migration of smaller aggregates toward the specimen boundaries to compensate for the geometric constraints of bigger aggregates. Experimental validation was performed for a single concrete mixture and specimen geometry by determining the depth-dependent mean bulk density of a concrete cube using incremental surface grinding combined with high-resolution 3D laser scanning. The optimized mesostructure shows strong agreement with measured density profiles for the investigated specimen. While the validation is limited to a single mixture and geometry, the results indicate that the proposed method is a computationally efficient approach for incorporating wall effects into mesoscale concrete models. Furthermore, increasing aggregate volume fractions intensify the near-surface accumulation of fine particles.

The freeze-thaw cycles lead to cumulative damage and gradual strength deterioration in concrete, which cannot be accurately represented by traditional empirical models. To address this issue, shale-based lightweight structural concrete (LSC) specimens with four strength grades (LSC20-LSC50) were subjected to basic mechanical performance and freeze-thaw cycle experiments. The study investigated the patterns of mass loss, relative dynamic elastic modulus, and loss of compressive strength in LSC subjected to varying numbers of freeze-thaw cycles. Furthermore, the correlation between the dynamic modulus of elasticity and compressive strength was examined. A Gamma process-based stochastic degradation model for the compressive strength of LSC was then developed. The results show that the compressive strength degradation of LSC under freeze-thaw cycles follows a monotonically increasing trend that gradually stabilizes, with low-strength LSC deteriorating faster than high-strength LSC. After 200 cycles, the compressive strength degradation of LSC30 and LSC50 was only 32.66% and 29.79% of that of their corresponding ordinary concretes (C30 and C50). The proposed Gamma process model showed high fitting accuracy for all strength grades of LSC (R2 > 0.96, RMSE < 0.25 MPa, MAPE < 11%). The research results provide a scientific basis for the structural design of concrete in cold regions.

The construction industry is a major contributor to environmental degradation due to the excessive use of natural resources such as cement and river sand. Cement production generates significant carbon emissions, while uncontrolled extraction of river sand leads to ecological imbalance. This study focuses on developing sustainable concrete by partially replacing cement with eggshell powder (ESP) and fine aggregate with manufactured sand (robo sand). Eggshellpowder, a bio-waste material rich in calcium carbonate (CaCO₃), was used as a cement replacement at levels of 0%, 3%, 6%, 8%, 10%, 12%, and 15%, while river sand was replaced with robo sand at proportions of 0%, 50%, and 100%. Concrete specimens were prepared and tested for workability, compressive strength, and split tensile strength at curing periods of 7, 14, and 28 days. The workability of concrete was assessed using the slump test, which showed a gradual decrease in slump values with increasing ESP and robo sand content due to higher water demand and angular particle characteristics. However, all mixes remained within acceptable workability limits for structural applications. The mechanical properties indicated that the inclusion of ESP improves the microstructure of concrete by acting as a filler material and enhancing particle packing. Robo sand further contributes to strength improvement due to better interlocking between particles. The optimum performance was observed at 10% ESP and 100% robo sand replacement,achieving a maximum compressive strength of 41 MPa at 28 days. Beyond this level, a reduction in strength was observed due to decreased cementitious content. The study concludes that the combined use of ESP and robo sand can produce sustainable and high-performance concrete, reducing environmental impact and promoting eco-friendly construction practices.. Keywords:Eggshell Powder (ESP), Robo Sand, Sustainable Concrete, Compressive Strength, Flexural Strength, Split Tensile Strength, M30 Concrete

This study investigates the enhancement effect and modification mechanism of nickel-coated carbon fiber (NCF) on the piezoresistive performance of concrete. Nickel-coated carbon fiber concrete (NCFC) and conventional carbon fiber concrete (CFC) were prepared with varying fiber content (0.1%–0.4% vol). The study tested the static mechanical properties, electrical conductivity, and piezoresistive responses of concrete specimens under various loading regimes. Microstructural analysis was conducted, and the piezoresistive response mechanisms of both concrete specimens were thoroughly examined by establishing a conductive network model. Results indicate that NCF effectively enhances both the static mechanical properties and electrical conductivity of concrete, with a percolation threshold of 0.266%, significantly lower than that of CF. Under direct compressive loading, NCFC03 exhibited peak resistance change rates of −41.7% and strain sensitivity of 133.8, markedly outperforming specimens with equivalent CFC content. Under various cyclic loading conditions, NCFC demonstrated more stable and pronounced piezoresistive responses.

Some of the problems created by concrete production in the world include depletion of natural resources and burning of fossil fuels with its attendant problems. Due to rapid industrialization and urbanization, there is incraease in the generation of glass wastes which poses great danger to man and his environment. To this end, this work is aimed at studying the engineering properties of concrete produced by replacing natural coarse aggregate (crushed granite) in concrete with glass waste to promote sustainability in concrete production and effective waste management. Sieve analysis, specific gravity and bulk density tests were conducted on the sand, crushed granite and glass waste aggregates used in this work. The various components of concrete were thouroughly mixed using a mix ratio of 1:1.92:3 and a water – cement ratio of 0.54. During concrete batching, crushed granite coarse aggregate was substituted with 0%, 10%, 20%, 30% and 40% glass waste by mass giving rise to 5 different concrete batches. Slump test was conducted on each concrete batch to determine the workability of the concrete. Concrete beam specimens of (150mm x 150mm x 450mm) size were produced from each concrete batch and cured in water for a period of 14 and 28 days after which they were tested for flexural strength. The results showed that workability of the concte increases as the glass content in the concrete increases. There is reduction in the flexural strength of the concrete as the glass content in the concrete increases, however the strength reduction rate was very minimal from 0% to 30% glass content in the concrete but beyound 30%, the strength reduction rate was high. Glasss waste concrete is recommended for light weight concrete applications due to their low unit weight.

Abstract The study examined the combined effect of the main compounds in Sulphate-Resistant Portland Cement (SRPC), represented by a Burnability Index (B.I.) (C3S/(C4AF+C3A)), on strength progression at different curing temperatures (7°C, 21°C, 34°C). 270 cubic concrete specimens with three different values of B.I. 2.08, 2.81, and 3.21 were applied to the compressive strength test at ages of 1, 2, 4, 7, and 28 days to monitoring the rate of strength progression (K-value) and determining the activation energy, following ASTM C1074 procedure. The study additionally examined the effect of cement quantity in concrete on strength progression by testing two concrete design strengths (20 and 35 N/mm 2 ). The results revealed that the concrete compressive strength reduced with the increase of B.I. in cement, especially at the age of 28-day. This reduction was more pronounced in concrete that contained a higher cement quantity (35 N/mm 2 strength). The B.I. has a significant influence on K-value at low curing temperature (7°C); while this influence decays with higher temperature (34°C). In addition, the increase of B.I. in cement raises the activation energy of concrete, specifically in higher-strength concrete.

Fatigue damage is a critical factor for the long-term service performance degradation of concrete structures. Nevertheless, the mesoscopic fatigue process is still debatable due to material heterogeneity and the complex internal damage progression. To further investigate the internal damage mechanism of concrete under fatigue loading, this study quantitatively monitors the dynamic internal strain evolution of concrete prismatic specimens during uniaxial compression high-cycle fatigue by designing and embedding aggregate sensors (EAS). The results indicated that EAS may effectively reflect concrete cracking, and the approach can properly capture the internal strain field redistribution features of concrete. Significant internal strain localization was observed during fatigue damage. The turning points in strain evolution, which correlate with the stages of stable propagation and microcrack initiation, were identified. Furthermore, the evolution of internal strain effectively characterized the alteration of stress transfer routes induced by crack propagation. Based on failure modes and mechanical analysis, the synergistic driving mechanism of fatigue damage involving crack growth, interfacial friction and stress field evolution was investigated. The difference in concrete damage under fatigue and monotonic loading due to changing mesoscopic crack propagation was defined, establishing a mechanical foundation for exploring concrete fatigue damage processes. The EAS monitoring method used in this study not only gives a viable approach for the fatigue damage analysis of concrete structures, but it also offers a new viewpoint and data support for comprehending the mesoscopic fatigue mechanism of concrete.