Question

Damage due to alkali silica reaction (ASR) occurs due to a reaction between rebars and concrete pore solution (the remaining mixing water left in the void system in concrete).

True or False

Answer 1

Alkali-Silica reaction as the name suggests occurs between the silica present in aggregates and the high alkalinity of the cement mix.

The aggregates containing reactive silica are very common( Eg: quartzite, chert, strained quartz crystals, opal, etc) which react with the excessive Hydroxyl ions in cement paste ( OH-1) to form a matrix. The ASR reaction causes the expansion of concrete leading to the generation of internal stress, causing micro-cracks in the concrete and eventually failure of concrete due to the spoiling of concrete. ASR reactions are more prominent when the concrete is exposed to moisture such as in retaining walls and bridge piers etc.

Hence the above statement is false as ASR is a reaction between excessive alkalinity in cement paste and reactive silica present in aggregates