Ettringite in hydration of portland cement concrete and its occurrence in mature concretes

摘要

Ettringite is a normal product of cement hydration, and persists indefinitely in the hydration products of many cements. Because small crystals are unstable relative to larger ones, it tends to recrystallize in any available cracks or other spaces. This process occurs in both damaged and undamaged concretes, irrespective of the curing temperature, and the presence of ettringite is therefore not an indication of distress. Cracks at aggregate interfaces or elsewhere are a feature of distress, but crystals of ettringite or other phases within them are recrystallization products and their presence does not shown what has caused the cracks to form.