Strength of High-Performance Concrete in Columns—Factors and Effect of Placing Method


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Title: Strength of High-Performance Concrete in Columns—Factors and Effect of Placing Method

Author(s): J. R. Casas, R. Gettu, L. Agullo, and B. Toralles-Carbonari

Publication: Special Publication

Volume: 189


Appears on pages(s): 451-553

Keywords: compressive strength; core strength; high=performance concrete; reliability

Date: 1/1/2000

The influence of the type of placing of concrete (free fall or compacted layers) in vertical elements on the mean value of the compressive strength, as well as its variability is investigated in the present work, with comparisons of normal (NSC) and high-performance (HPC) concretes. The experimental program consists of the fabrication of NSC and HPC columns with steel reinforcement placed under two extreme conditions, and the extraction and testing of cores from different heights. From these results, the corresponding strength reduction factor to be applied to concrete is obtained for NSC and HPC with the condition that the same safety level is to be obtained in both cases. The study covers the range of target reliability indices from 3.5 to 5. The extreme values of the sensitivity factor of the random variable concrete strength are also considered. The main conclusion that can be drawn is that the reduction factors used in design codes or normal concretes do not apply to HPC since its final strength is more sensitive to the placing conditions. However, due to the limited number of tests performed, further and more extensive results are necessary to calibrate a value of the strength reduction factor for the design codes.