Book Description

Water bath methods for accelerating the strength development of portland cement concrete were investigated in a two phase study as follows. Phase I - Participation in a cooperative accelerated strength testing program sponsored by the American Society for Testing and Materials. The three methods studied consisted of; (1) curing immediately after casting in 95°F water for 24 hours, (2) curing in boiling water for 3 1/2 hours, commencing 23 hours after casting, and (3) curing in boiling water for 15 hours commencing after the concrete reached a penetration resistance of 3500 psi (fixed set). Phase II - A study of the effects on the results of the fixed set accelerated curing methods of curing water temperatures from 95°F to 212°F. Also considered were certain heat transfer parameters relevant to strength development. The major conclusions were: Phase I 1. The fixed set boiling method is the most efficient and reliable of those studied. 2. Water bath accelerated curing is more efficient for high than for low strength concretes. 3. Water bath and standard moist curing produce strength results of about equal reproducibility. Phase II 1. Accelerated curing efficiencies are directly proportional to the total relative amounts of heat released by the concretes during accelerated curing. 2. Boiling (212°F) water is not conducive to optimum curing efficiency. 3. Optimum water bath temperatures for accelerated concrete strength development range approximately from 165° to 180°F. The duration of accelerated curing is not critical for the fixed set boiling method.