Effect of aggregate particle size and composition on expansion of mortar bars due to delayed ettringite formation

The effect of aggregate composition and particle size on the expansion of mortar bars, due to delayed ettringite formation (DEF), was evaluated by heat-curing mortar bars made with basalt, dolostone, granite, limestone, siliceous limestone, and pure crystalline quartz. Subsequent to heat curing, the mortar bars were subjected to 3 thermal cycles to accelerate the formation of DEF. They were then stored in lime water for 59 days and length change was monitored. Only mortar bars made with quartz aggregate showed significant expansion. Expansion was found to be inversely proportional to the particle size of the quartz aggregate. The amount of ettringite formed in the mortar bars was shown to be proportional to their rate of expansion. (C) 1998 Elsevier Science Ltd