ASR pessimum behaviour of siliceous limestone aggregates

Siliceous limestone aggregates have “pessimum” behaviours similar to those observed for pure siliceous aggregates such as flint or opal. For high alkali contents concretes based on fine and coarse reactive siliceous limestone aggregates swell less than concretes based on fine reactive siliceous limestone aggregates and non-reactive coarse aggregates. The reduction of the swelling is more significant for a “micritic” limestone containing highly reactive free silica than for a “sparitic” limestone containing less reactive free silica. The consumption of a part of the alkalis by non-expansive processes such as chemical sorption on silanol sites of reactive silica and pozzolanic C–S–H is expected to explain the reduction of the swelling.