With the Fall season underway in the northern hemisphere, concrete producers and contractors readily understand that the setting rate and strength development of cementitious mixtures will be delayed as concrete and ambient temperatures drop. These delays in set and strength gain can be offset with the use of set accelerating chemical admixtures. The performance requirements of such admixtures are clearly stipulated in various regional nation standards such ASTM C494, where two types of set accelerating admixtures are desribed, Type C and Type E. Compositionally, set accelerators fall into two classes: chloride or calcium chloride-based, and non-chloride. More importantly, it is very important to understand corrosivity of an admixture over the dosage range recommended by the manufucturer. My next posting will provide further guidance on the use of set accelerating admixtures.