Full Time-Domain Investigation of the Cracking Behavior of PVA Fiber-Reinforced High-Titanium Slag Concrete Using DIC Technology: Material Optimization, Performance Assessment, and Mechanism Analysis

The incorporation of high-titanium slag may reduce the crack resistance of concrete. To promote the recycling of industrial solid waste while maintaining structural integrity, this study investigates the use of high-titanium slag as a replacement aggregate in concrete, supplemented with polyvinyl alcohol (PVA) fibers to enhance toughness, crack resistance, and flexural and tensile properties. Semicircular bending (SCB) specimens were subjected to loading, and their strain and displacement fields were monitored in the full time domain using digital image correlation (DIC) technology. Multiple indicators were proposed to evaluate the crack resistance provided by the fibers. Scanning electron microscopy (SEM) was employed to observe the micromorphology of the fibers and the cementitious matrix, revealing the mechanisms underlying the enhanced crack resistance. Results demonstrate that with 0.5% vol. PVA fiber addition, the peak load capacity increased by 17.2%, total fracture work improved by 52.6%, and the failure duration extended by 1.30 s. Quantitative DIC analysis revealed that fiber reinforcement reduced maximum strain concentration by 83.8% (from 5.204 to 0.843%) and decreased lateral displacement difference across cracks by 46% (from 0.35 to 0.19 mm). The enhanced performance is applicable within the tested fiber content range (0–0.5% vol.) and is particularly effective for concrete mixtures where high-titanium slag replacement exceeds 50% of total aggregate volume. However, the crack resistance improvement may be constrained by fiber dispersion quality and interfacial bonding strength. This study not only facilitates the high-value utilization of industrial solid waste, but also significantly improves the crack resistance of concrete, offering broader potential for the application of high-titanium slag in construction materials.