MECHANICAL PROPERTIES OF 80 TO 180MPa CLASS HIGH-STRENGTH CONCRETE AT THE AGE OF 20 YEARS

Abstract

 In the late 1980's, a national project of super high-rise reinforced concrete buildings using high strength and high quality concrete and reinforcing steel was promoted by the Ministry of Construction of Japan. The project was simply referred to "New RC". This project aimed at producing high strength and high quality concrete of the specified from 30 to 120MPa and high strength and high quality reinforcing steel bars of yield strength from 400 to 1200MPa.
 After that many experimental data and knowledge of high strength concrete were provided by many researchers. In the middle of 1990's, high strength concrete of the specified 60MPa Class had been used for high-rise reinforced concrete buildings. And high strength concrete of the specified 100MPa Class had been used for high-rise reinforced concrete buildings in the late 1990's. However, long term data of high strength concrete that cannot obtain by accelerating tests was not collected sufficiently.
 This paper deals with long term data of high strength concrete. Mechanical properties of 80 to 180MPa class high strength concrete at the age of 20 years were examined. Conclusions are as follows. (1) Long-term strength development ratio of sealed specimen and core specimen of mock up column using high strength concrete are increased when water-binder ratio becomes low.(2) Drying shrinkage ratio of 80 to 180MPa class high strength concrete increases between the age of 10 years and the age of 20 years.(3) Core strength and rebound number of mock up column with 80 to 180MPa class high strength concrete are also increased by increase of the age.(4) Elastic modulus and poisson's ratio of 80 to 180MPa class high strength concrete at the age of 20 years can be estimate by conventional estimate equation.(5) Carbonation has not occurred to surface of mock up column with 80 to 180MPa class high strength concrete at the age of 20 years.