Alkali Silica Reaction (ASR)

ASR is caused by chemical reaction between alkalis and certain reactive silica minerals which form a gel. The gel absorbs water, causing expansion which may damage the concrete and adjacent structures. Alkalis are most often introduced by the portland cement within the pavement. ASR cracking may be accelerated by chemical pavement deicers. Visual indicators that ASR may be present include: 1 Cracking of the concrete pavement (often in a map pattern). 2 White, brown, gray or other colored gel or staining may be present at the crack surface. 3 Aggregate popouts. 4 Increase in concrete volume (expansion) that may result in distortion of adjacent or integral structures or physical elements. Examples of expansion include shoving of asphalt pavements, light can tilting, slab faulting, joint misalignment, and extrusion of joint seals or expansion joint fillers. Because ASR is material-dependent, ASR is generally present throughout the pavement section. Coring and concrete petrographic analysis is the only definitive method to confirm the presence of ASR. The following should be kept in mind when identifying the presence of ASR through visual inspection: 1 Generally ASR distresses are not observed in the first few years after construction.  In contrast, plastic shrinkage cracking can occur the day of construction and is apparent within the first year. 2 ASR is differentiated from D-Cracking by the presence of cracking perpendicular to the joint face.  D-Cracking predominantly develops as a series of parallel cracks to joint faces and linear cracking within the slab. 3 ASR is differentiated from Map Cracking/ Scaling by the presence of visual signs of expansion.

How to Count

No other distresses should be recorded if high severity ASR is recorded.