Influences of external chlorides and synthetic zeolite on delayed ettringite formation

Abstract: Investigations were conducted to evaluate the effects of synthetic zeolite additive and sea salt on the potential for delayed ettrintite formation (DEF) in heat cured cementitiuos systems. Mortar prisms 25x25x285 mm were prepared at water-cement ratio (w/c) = 0.5, using CEM I 42.5 N,R. Sulphates were introduced into the mixtures by adding 2%, 3% and 5%SO3. Also, a commercially available synthetic zeolite additive PWC was added to cement at proportions of 1%, 0.5% and 2.5%PWC. The mortar specimen were heat-treated at 95oC then stored in water, seawater or 0.5M, 1.0M, 1.5M and 2.0M NaCl solutions, and monitored for expansion of the prisms over a period of three months..