Moisture dynamics and influence on alkali-silica reaction induced expansion: A comprehensive laboratory study

Moisture availability is crucial for initiating and progressing alkali-silica reaction (ASR) in concrete. As a result, moisture control has often been adopted as a mitigation strategy in maintaining ASR-affected concrete. Selecting effective maintenance strategies requires a deep understanding of the moisture dynamics between internal moisture in concrete and its environment, and influence on ASR, which remains incompletely explored. To evaluate this interplay, 180 concrete cylinders incorporating a reference reactive aggregate (i.e., Spratt) were manufactured and stored at distinct conditions: i.e., three different temperatures (21°C, 38°C and 60°C) and five relative humidities (100% RH, 90% RH, 82% RH, 75% RH, and 62% RH). The internal and external relative humidity, length, and mass change were monitored for up to a year. Results indicate that the amount of water used for cement hydration is sufficient to trigger the reaction, regardless of the subsequent exposure condition. However, the rate of ASR-induced development is influenced by the internal relative humidity, which changes with time based on the external relative humidity and temperature. Additionally, the minimum moisture (i.e., RH threshold) required to cause significant deleterious effects from ASR was assessed and confirmed to be temperature-dependent.