Calcium Hydroxide Saturation Factors in the Pore Solution of Hydrated Portland Cement Fly Ash Pastes

The portlandite saturation factors in the pore solution of hydrated portland cement paste and changes related to the addition of two types of fly ash have been studied. Small additions (15 wt%) of fly ash increase portlandite supersaturation at early ages, whereas larger additions reduce it, relative to the plain cement. At later ages, portlandite undersaturation is observed despite the continued presence of free portlandite in the paste as observed by SEM.