INFLUENCE OF MAXIMUM TEMPERATURE, R₂O AND SO₃ CONTENT IN CONCRETE ON DEF EXPANSION AND EXPANSION START TIMING AT LONG TERM AGE

Abstract

We have already studied the occurrence condition of expansion due to delayed ettringite formation（DEF）on the concrete with wide range of R₂O and SO₃ content and unified material conditions. We showed that the result at the age of 200days supported the threshold values of the maximum temperature of concrete to prevent DEF cracking proposed by JCI “Guidelines for Control of Cracking of Mass Concrete 2016”. In this study, we investigated the occurrence of DEF expansion at long term age and examined the reliability of JCI guidelines. The result of 600days supported the proposal by JCI guidelines. However, at the maximum temperature of 70℃, it expands in the wide range of R₂O and SO₃ in 600days, so it is necessary to widen the range of R₂O and SO₃ that should limit the maximum temperature to 65℃ or less. We investigated the influence of R₂O and SO₃ content on DEF expansion, respectively. In this result, concrete with both high R₂O and SO₃ content expanded early and concrete with either small R₂O or SO₃ content expanded late. In the case of a high R₂O content, it did not expand at 200days, but at 600days it showed a large expansion.