Study of a Method of Immediate Estimation of Concrete Strength

Abstract

The method of immediate estimation of concrete strength using rapid hardening process is a method which can estimate concrete strength within about 1.5 hr after getting a sample from fresh concrete by means of compression test of rapidly hardened specimens. The rapidly hardened strength of specimens can be obtained by using the combination of the addition of accelerator and the high temperature curing. The strength of rapidly hardened mortar specimens which are obtained by wet-screening of concrete is clearly dependent on the water-cement ratio of concrete. Thus, there is a high correlation between the 28-day strength of concrete and the strength of rapidly hardened mortar specimen. The coefficient of variation of the ratio of estimated strength at 1.5 hr to the actual 28-day strength of normal concretes was about 10 percent regardless of the brand of ordinary portland cement used in the laboratory test. Practicability of this method was ascertained at the field test using a portable curing chamber and a compressive test apparatus. /Author/