The post-crack flexural performance of fiber-reinforced concrete (FRC) is commonly assessed using simple beam specimens such as the ASTM C1609/C1609M, Standard Test Method for Flexural Toughness of Fiber-Reinforced Concrete (Using Beam with Third-Point Loading), third-point-loaded beam test. Like most beam-based test methods for FRC, the performance revealed by this test method exhibits high variability. An investigation based on variance-covariance analysis has been undertaken to examine the sources of variability in this test method and identify the true variability in FRC once extraneous test-related sources of variability have been isolated. This analysis has determined that friction in the supporting rollers and the location of the crack relative to the center of the beam are the main test-related sources of variability in FRC performance assessment using the ASTM C1609/C1609M test method. Given that the apparent magnitude of flexural strength also increases with friction, it is advisable to place limits on the maximum acceptable magnitude and variance in roller friction during a beam test so that the apparent variability in the output can be moderated. Control of the location of the crack in a third-point-loaded beam is more difficult and may not be desirable when seeking a representative estimate of mean flexural performance.
An integrated multiscale framework combining hydration kinetics and lattice modeling was established to investigate the microstructural evolution of cement paste. To overcome the inherent overestimation of pore connectivity in traditional models, a nucleation-and-growth mechanism coupled with a small capillary pore redistribution algorithm was incorporated into the generation of representative volume elements featuring polydisperse particles. This approach ensures that the simulated pore network characteristics, such as pore size distribution and percolation threshold, closely align with authentic microstructures. Experimental validation using nuclear magnetic resonance confirms the accuracy of the simulated porosity development. Quantitative structural analysis revealed that, in systems with low water-to-cement (w/c) ratios, connectivity reduction accelerates and tortuosity increases rapidly as hydration progresses, whereas high w/c ratio systems exhibit significantly more gradual variations. Furthermore, both connectivity and tortuosity demonstrated strong correlations with capillary porosity but negligible direct dependence on initial w/c ratios. The derived fitting curves for these structural parameters provide a robust mechanistic basis for durability assessment and service-life prediction of cementitious materials.
In this study, calcium sulfoaluminate cement (CSAC) was used as a more sustainable material to stabilize high plastic clayey soil compared to ordinary Portland cement (OPC). Both CSAC and OPC were used and studied as soil stabilizers. The percentages of both cements used were 2.5%, 5.0%, and 7.5 % by dry weight of soil and cured for 0, 7, 14, and 28 days in a water bath. The clayey soil was characterized by using the Atterberg limit, specific gravity, and miniature Proctor test. Samples for the unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were prepared at optimum moisture content and maximum dry density. The stabilized clay samples were tested for UCS and UPV tests as per American Society of Testing and Materials guidelines. Results showed that both types of cement improved the strength of the clayey soil with curing periods. The UCS test showed that samples prepared with CSAC were stronger without curing, but OPC-treated samples showed higher strength after a curing period. The UCS value reached a maximum of 1,758.16 kN/m2 for 7.5 % CSAC-treated samples at 28 days of curing, whereas the UCS value reached up to 3,261.22 kN/m2 for OPC-treated samples. The UPV test also showed that the addition of both types of cement to clayey soil samples increased its strength. The UPV value for untreated soil was 990.5 m/s, whereas CSAC-treated samples showed an increase between 1,275.13 and 1,647.8 m/s. The OPC-treated samples had an increase between 1,355.25 and 2,043.63 m/s. All OPC-treated samples had higher UPV values than CSAC-treated samples.
The accelerating deterioration of road infrastructure, exacerbated by increasing traffic loads and climate variability, necessitates sustainable and intelligent rehabilitation strategies. Simultaneously, the environmental footprint of conventional bitumen underscores the need for eco-friendly alternatives. This study explores an integrated approach to sustainable pavement rehabilitation by combining waste-modified asphalt mixtures with an artificial intelligence (AI)-driven road defect management system. VG-30 bitumen was modified using lignin and waste engine oil (WEO), both individually and in hybrid formulations, to evaluate their effects on physical, thermal, and mechanical properties. Lignin improved stiffness, softening point, and rutting resistance, whereas WEO enhanced ductility and low-temperature flexibility. Hybrid mixes such as L20EO6 and L30EO9 demonstrated a balanced response, mitigating the brittleness of lignin and the excessive softening from WEO. All modified binders satisfied storage stability and thermal safety requirements. The study also developed a threetier AI framework for automated pavement inspection and maintenance prioritization. Using a curated data set of manually annotated images, a YOLOv7 model was employed for real-time detection of potholes, cracks, and rutting, whereas U-Net segmentation quantified defect severity based on area and geometry. The models achieved high accuracy, with YOLOv7 reaching 96.8 % mAPat0.5 and U-Net providing an average Intersection over Union of 0.85. The results demonstrate that hybrid lignin-WEO-modified asphalt mixtures can offer both environmental advantages and improved mechanical performance, whereas the AI-based framework enhances efficiency in defect detection, classification, and maintenance planning. The integration of sustainable materials with intelligent defect prioritization presents a feasible solution for cost-effective and environmentally conscious pavement management in resource-constrained regions.
The alteration in microstructure or phase composition of concrete subjected to aggressive surroundings results in the reduced working life of concrete structure. The diffusion of ions in concrete subjected to aggressive surrounding mainly chloride and sulfate are not uniform and depends on various parameters that make complex variations in the microstructure or phase composition along the depth of concrete, which may affect the further ingress behavior of ions and reaction mechanism. This study reported the change in microstructure or phase composition along the depth of concrete subjected to aggressive solutions containing chloride and sulfate. For this purpose, chloride diffusion and microstructure analyses were performed on various concrete mixes along the depth and exposed to chloride (3% NaCl: 3NC) and chloride with sulfate (3% NaCl with 4% Na2SO4: 3NC with 4NS) solutions. From the result of chloride ingress test, the existence of NS in surrounding solution retards ingress/diffusion of chloride ions into the concrete. The microstructure analysis revealed non-uniform distributions of key phases, including calcium hydroxide (CH), ettringite (E), and calcium chloroaluminate (CCA), within the concrete matrix. The distribution patterns, which varied with the depth of concrete and type of exposure solutions and binder used, are described comprehensively. CH content decreased closer to the exposure surface and increased with greater depth intervals, while E was more prominent at intermediate depths compared to lower and higher levels. CCA content was slightly higher at lower depth intervals. Notably, CCA was more prevalent in ordinary portland cement with 20 % fly ash concrete (O20FAC) at lower depths, while E content exhibited differences between binder types and exposure solutions, with implications for concrete performance.
