Time-Dependent Influence of ASR and Cracking on the Physical and Mechanical Properties of Laboratory-Accelerated Reinforced Slabs with Distinct Exposure Conditions

The impact of alkali-silica reaction (ASR) on the physical, mechanical, and structural behaviour of ASR-damaged structures in service is time-dependent. While destructive examinations of ASR-damaged structures in service offer a valuable snapshot of the structure’s condition at a particular point in the ASR deterioration process, they cannot provide a complete understanding of how the propagation of ASR cracking affects the physical, mechanical, and structural behaviour of the structure over time. To better understand the influence of ASR on structures affected by this deleterious reaction, it is essential to conduct laboratory experiments that simulate the progress over time. These experiments can provide insights into the impact of ASR cracking on the physical and mechanical behaviour of reinforced slabs. To assess ASR-affected bridge slabs in Denmark, it is crucial to consider the time-dependent impact of external alkali supply in the assessment methodology. While the equivalent Na₂O content in older Danish bridge slabs is believed to be below the threshold value for initiating ASR, it is essential to recognize that external alkali sources, such as de-icing salts, may be critical for initiating ASR damages in reinforced bridge slabs in service. To address this gap, this study aims to improve understanding of the time-dependent influence of ASR on the physical and mechanical properties of reinforced slabs through accelerated laboratory exposure. Seven reinforced slabs were cast and stored under accelerated conditions, with three exposed to saturated NaCl solution from the top surface to simulate external alkali supply, two with initial high alkali content boosted by NaOH, and two as control slabs. Internal and surface expansion measurements were periodically taken, and cores were drilled and tested in compression. Fluorescent epoxy was impregnated into the cores to evaluate ASR crack extent and orientation.