Internal sulfate attack in mortars containing contaminated fine recycled concrete aggregates

Abstract

Internal sulfate attack can be caused by the gypsum residues present in fine recycled aggregates (FRA). As opposed to the better known external sulfate attack or Delayed Ettringite Formation (DEF), the sulfates in this context are provided by a gypsum contamination of the aggregates. Mortars made with contaminated FRA were subjected to different conditions, to assess which parameters had an influence on the sulfate attack reaction. Their mechanical properties and microstructure are investigated. Results showed that gypsum content, porosity, temperature and alkalinity influenced the consequences of sulfate attack. However, the gypsum size distribution and cement type did not.