Effects of Large Retarder Overdose on Concrete Strength Development

Abstract

Retarders are used to delay the setting time of concrete. Retarder overdosing is not an uncommon problem, but its effects are not well understood. In this study, laboratory tests were conducted to determine the effect of retarder overdosing on the setting time and strength of concrete, using both cubes, and cores from a large specimen. It was found that overdose levels of 3 times the normal dosage had little effect on setting and strength development. Also, concrete with even 6 times the normal dosage of retarder did eventually set and gain strength. Tests were also conducted to determine cement setting time under different temperature and surface drying (wind) conditions, in order to make inferences regarding strength development of concrete surfaces compared to interiors.