ABSTRACT Title of Thesis: THE INFLUENCE OF EXPOSURE CONDITIONS ON DELAYED ETTRINGITE FORMATION IN MORTAR

The objectives of this research were to experimentally study the influence of exposure conditions on delayed ettringite formation (DEF) in mortar specimens, and to explore the complex processes of expansive cracking associated with DEF. Different exposure conditions were investigated while other parameters such as water-to-cement ratio, fine and coarse aggregates, cement and curing conditions were kept constant in order to study the influence of storage conditions on mortar damages associated with DEF. Mortar bars and cubes were prepared using Portland cement ASTM Type III, Frederick sand and ordinary tap water. The specimens were steam-cured and then subjected to the Duggan heat cycle to introduce microcracks. Control batches of mortar mixes with no additional potassium (K2O) content and sets with additional potassium increasing the overall potassium level to 1.5 % K2O by weight of cement were prepared. Increasing the potassium level has a deleterious effect on the specimen expansion and causes deterioration in compressive strength. Length change measurements according to ASTM C490 and weight changes of the mortar bars were constantly monitored during th