Q.: If I use a retarder does the strength stay the same?
A.: Modern retarders generally affect the setting time but have no great effect on the strength. They frequently contain materials that compensate for the early loss in strength which the concrete would suffer if these materials were not included in the retarder formulation. The ultimate strength of the concrete is generally the same or possibly even a little better than concrete without a retarder. The article "Admixtures and the Contractor" in Concrete Construction magazine for July 1966, page 263, gives further information.