Durability of High Performance Concretes: Alkali – Aggregate Reaction and Carbonation
The degradation of concrete due to alkali – aggregate reactions was identified for the first time in the USA in 1940. Then cases were detected in many countries, and in France recently, in dams, bridges, roads, buildings. A humid environment, a high concentration of alkalis in the interstitial liquid phase of concrete, and alkali reactive particles in the aggregates are the main factors responsible for alkali aggregate reactions. The pore solution squeezed from cement pastes, mortars and concretes can be considered as a soda or potash solution with traces of calcium and sulfate. The rate of reinforcement corrosion depends then on the electrical resistivity of the concrete. Contradictory results have been published on the resistance of silica fume concretes to carbonation. The carbonation depth is equal or superior to that of normal concretes and more particularly when curing time is too short in silica fume concretes.