혼화콘크리트의 비파괴 실험에 의한 강도 추정에 관한 연구

Abstract

This study made member specimen for taking specimen, core with the concrete mixing normal concrete, admixture and conducted the same air curing as field conditions. After performing destructive and nondestructive test by age, estimate expression was suggested by analyzing correlations between compressive strength, rebound number and ultrasonic pulse velocity and the results are as follows. 1) As a result of measuring compressive strength by age, it was found that core specimen showed higher compressive strength than specimen. In comparison between upper and lower cores of member specimens, compressive strength of lower core specimen was higher because of moisture and decline of aggregates after pouring concrete. 2) As a result of measuring rebound number and ultrasonic pulse velocity by nondestructive test according to age, it was found that added value of ultrasonic pulse velocity was too smaller than that of rebound number. It was because capillary air gap from evaporation in the inside of concrete made ultrasonic pulse detour and its increase was small. 3) As a result of applying measurements of rebound number and ultrasonic pulse velocity to existing suggestions, it was known that existing suggestions by rebound number method were similar in expression from Japanese Materials Academy, that from U.S Army Laboratory, and existing suggestions by ultrasonic pulse velocity were similar in expressions from Japanese Architecture Society and J. Pysziak and those by mixed methods showed similar trends at expressions from Japanese Architecture Academy and compressive strength. 4) As a result of estimation by regression analysis, in single method, ultrasonic pulse velocity showed higher coefficient of determination than rebound number and complex method showed higher coefficient of determination than complex method, and it is judged that reliability of complex method has higher reliability of complex method. 5) As a result of comparing error rate of existing expressions and this estimation expression, error rate of this estimation is reduced compared to existing expressions and has higher reliability. 6) This study suggested estimation expression of age up to 180 days, but for the security of higher reliability, experiment through long-term age is needed. 7) When conventional concrete expression is applied to admixture concrete, error rate occurs and then this study suggests the following estimation expressions depending on types of admixture concrete.