Alkali silica reaction – the mechanism leading to concrete deterioration

Abstract

The alkali-silica-reaction (ASR) leads to severe deterioration of concrete structures worldwide. The general principle of the reaction is known. However, the mechanism generating pressure and cracking is still debated. The mechanism commonly presented is water uptake of the ASR products that leads to swelling and pressure. In addition to hygric swelling, osmotic pressure has been also attributed for aggregate cracking and concrete expansion. Crystallization pressure is seldom associated with ASR in spite of the fact that it is an accepted mechanism for other types of damage in building materials. This paper reviews and discusses the different mechanisms considered for concrete deterioration induced by ASR. The reaction sequence and the composition of the ASR products are presented as well, because they are the basis for the discussion on the mechanism of pressure generation.