Case Study: LMDC’s Alkali Silica Reaction Prognosis Approach Applied to an Hydroelectric Dam

A promising prognosis approach developed at the Laboratoire des Matériaux et de la Durabilité de Constructions (LMDC) based on the reactive silica consumption kinetics was applied to an hydro-electric dam located in province of Quebec, Canada. Accelerated expansion tests in immersion conditions (1N NaOH solution) were carried out on mortar specimens of three different sizes made with unreacted rock material (metagrauwacke) crushed into four different particle sizes. The optimal combination of aggregate size (600–1180 µm) and mortar bar size (252 × 25 × 285 mm) for this aggregate was determined based on expansion results measured after 546 days. Accelerated tests in similar conditions with unreacted rock material and two gradations (5–20 and 20–40 mm) of aggregates recovered from the dam’s concrete and crushed to optimal aggregate gradation showed results well aligned with the reactive silica consumption model implied in LMDC’s method. LMDC’s testing method appeared effective in consuming reactive silica. However, mechanism of consumption of the reactive silica in site conditions differs from those of the accelerated expansion tests in alkali rich immersion conditions.