Quantifying surface damage of concrete subjected to freeze-thaw cycles and bending stress using line laser scanning technique

This study investigates the surface damage evolution of low-heat cement concrete (LHCC) and P·I cement concrete (PICC) under the combined effect of bending stress and freeze-thaw (FT) cycles, using a self-invented stress-FT coupling test system. The line laser scanning technique (LLST), an innovative non-contact and non-destructive testing method, is employed to quantify multiple surface damage parameters with considerable precision. The surface flatness and average vertical displacement obtained by LLST show strong consistency with traditional scaling weight measurements, confirming the accuracy and effectiveness of LLST. The experimental results demonstrate the exceptional superiority of LLST, and also reveal that the bending stress-FT synergy accelerates damage rate by 200% compared to FT cycles alone, with stress contributing over 50% of total damage. Moreover, LLST demonstrates exceptional capability in detecting the localised extreme damage (LED). The variation coefficient is introduced to quantify the discrepancy between global damage and LED. A difference exceeding 500% highlights that LED can escalate to unpredictable structural consequences, such as sudden brittle fracture without any macroscopic warning signs. These advancements establish LLST as an effective tool for real-time structural health monitoring, particularly for critical infrastructure in cold regions where coupled stress and FT threats exist.