EFFECT OF CONSTRUCTION PRACTICE ON ENTRAINED AIR OF CONCRETE

KATSUHATA Toshiyuki, KOGA Hirohisa, WATANABE Hiroshi, WATANABE Kenji

doi:10.14250/cement.68.291

Generally, air-entraining agent is used for improving the freeze-thaw resistance of concrete. Entrained air exists as independent microscopic bubbles in fresh concrete. Air-voids less than 0.3mm in diameter and its homogeneous distribution are effective for improving the freeze-thaw resistance. However, unsuitable concrete works, for instance exceeded vibration of fresh concrete at compacting work and unsuitable mix proportions can cause the loss of microscopic bubbles and affect the freeze-thaw resistance of hardened concrete. In this study, the effect of segregation of fresh concrete due to unsuitable works and mix proportions on the air-void distribution of hardened concrete was investigated. Various mix proportions of concrete were prepared and the effect of unsuitable concrete works, exceeded impact due to free fall from the height of 4.0m without shooter and exceeded horizontal move using internal concrete vibrator was discussed. As a result, it was confirmed that air-void diameter and air content in hardened concrete was influenced by concrete works and mix proportions. Total amount of microscopic bubbles below 0.3mm in diameter were reduced by unsuitable concrete works and the loss was significant in the mix proportions whose unit weight of water were high. When conventional concrete whose slump was 8cm was used, while the loss of microscopic bubbles due to 4.0m free fall was not significant, the loss of microscopic bubbles by exceeded vibration was remarkable. From these results, it was confirmed that the suitable viscosity of cement mortar is important to eliminate the risk of deterioration by freeze-thawing.

EFFECT OF CONSTRUCTION PRACTICE ON ENTRAINED AIR OF CONCRETE

Bibliographic Information

Search this article

Description

Journal

References(2)*help

Keywords

Details 詳細情報について

Export

Report a problem