Commodity Rebound Method To The Study Of The Strength Curve

Concrete structures exist everywhere in the world. Many of them collapsed partly or wholly which caused many casualties Occuring and mush property losing. The cause is usually that the concrete strengths are not enough to support themselves safely. Hence, to ascertain concrete strengths of structures is very important.This article states that the concrete strengths of structure body, specimens cured under standard condition and the same condition as structure are different each other, although they are made of the same concrete mix. So the concrete strength of specimen cured under each of the two conditions is not equal to the one of the structure body. The concrete strength of core drilled from structure body is the closest one to the concrete strength of structure body, but core testing is rarely used with to ascertain concrete strength of structure bodies because of difficulties to operate and bad effects to the bodies.Rebound method to ascertain concrete strength structure bodies by has many advantages: Instruments are light, Operation is simple, It can be used everywhere at any time, and so on, but traditional curve for ascertaining concrete strength by rebound method is not right for commercial concrete owing to its characteristics. So we studied a method to ascertain concrete compressive strengths of commercial concrete structure bodies by rebound. First, by testing rebound value, carbonated depth and compressive strength on each of cubic specimens cured under the same condition as structures in a wide range of strength: C15-C80, we have established a regressive equation about relationship "rebound-carbonation-strength" of the specimens.Next, in consideration of fact that strengths of specimens do not represent perfectly the ones of concrete structures because of differences of curing conditions and molding methods, we did tests on concrete structures bodies of rebound value, carbonated depth and compressive strength of core drilled from the same place where the rebound value and carbonated depth were measured. By comparing these results with those on cubic specimens, we found correlative factor, and then got a new equation which satisfies to ascertain the concrete strengths of structure bodies practically.The achievements in the study might be an important basis for establishing local and national curves to ascertain concrete strengths of structures by rebound method.