Evaluating ASR Physicochemical Process Under Distinct Restraint Conditions for a Better Assessment of Affected Concrete Infrastructure

Abstract

Over the last decades, researchers have proposed a number of tools for the condition assessment of concrete infrastructure affected by alkali-silica reaction (ASR). Amongst those, increasing attention has been given to the Stiffness Damage Test (SDT), Damage Rating Index (DRI), and Residual Expansion (RE) laboratory test procedures that aim to determine the cause and extent (i.e., diagnosis) of damage along with the potential of further deterioration (i.e., prognosis) of affected concrete. Yet, most of the data gathered so far while using the aforementioned tools has been obtained on laboratory test specimens presenting distinct conditions from affected structural members in the field, especially regarding restraint effects. This work aims to understand the impact of restraint on ASR-induced expansion and damage. Thirty-two 450 mm by 450 mm by 675 mm concrete blocks with various reinforcement configurations (i.e., unreinforced, 1D and 2D reinforcement) and incorporating highly reactive coarse and fine aggregates (i.e., Springhill coarse and Texas sand) were manufactured and stored in conditions enabling ASR-induced development (i.e., 38°C and 100 R.H). Two expansion levels were selected for analysis (i.e., 0.08% and 0.15%); once reached, cores were extracted from three different directions (i.e., longitudinal, transversal and vertical) of all blocks and mechanical (i.e., SDT and compressive strength), microscopic (i.e., DRI, scanning electron microscope, etc.) and expansion (i.e., RE) test procedures were conducted on the concrete cores. Results suggest that the presence of restraint influences the induced expansion, resulting in an anisotropic response of the specimens. Furthermore, similar to the expansion behavior, an anisotropic distribution of induced damage and mechanical properties reduction are observed for the restrained concrete blocks in which the restraint configuration seems to significantly affect ASR-induced damage development and features. This led to the observation of a higher number of damage features, ASR development and mechanical properties reduction in cores obtained from unrestrained directions. Yet, some anticipated results from the current research will be studied in detail in the near future where the reliability of the existing techniques (i.e., residual expansion and soluble alkalis) for appraising ASR potential for further induced development and distress (i.e., prognosis) in affected concrete presenting distinct restraint scenarios will be evaluated.