Use of maturity methods to estimate the setting time of concrete containing super retarding agents

摘要

In this study, we examine a method for estimating the setting time of concrete containing super retarding agent (SRA) under various curing temperatures. To estimate the setting time, the equivalent age method using the apparent activation energy (E_a), proposed by Pinto et al., is applied. Increasing the SRA content leads to considerable retardation of the initial and final sets of concrete, whereas increasing the curing temperature shortens the initial and final set times regardless of the SRA content. E_a values at the times of initial and final sets obtained using the Arrhenius function differ for different mixtures. They are estimated to be in the range 30-35 kJ/mol for the control mixture, which is similar to or slightly lower than the results of a previous study, but are in the range 20-40 kj/mol in concrete containing SRA, which is lower than that for conventional concrete. We apply E_a according to the SRA content to Freisleben-Han-sen and Pedersen's equivalent age function and find that the equivalent age is nearly constant regardless of the curing temperature. This implies that the concept of maturity can be applied to the estimation of the setting time of concrete containing SRA. The setting time estimated using the equivalent age according to the SRA content and curing temperature is presented herein. A good agreement is observed between the estimated setting time and measured setting time. Thus, the method for estimating the setting time suggested by Pinto is applicable to the region of concrete containing SRA.