INFLUENCE OF MAXIMUM TEMPERATURE OF CONCRETE AND R₂O AND/OR SO₃ CONTENT ON DEF EXPANSION

Abstract

In this study, the influence of R₂O and SO₃ content independently added on DEF expansion was investigated assuming mortar portion of concrete with unit cement content of 300kg/m³. Two types of cement（HPC and OPC）was used and the mortars were affected by high temperature at 70, 80 and 90℃. The result of the limit values obtained in this study almost agrees with the content indicated by Guidelines for Control of Cracking of Mass Concrete（2016）JCI, and it supports the proposal of the limit values of concrete temperature to prevent the DEF cracking. However, in the range where the limit value is 65℃, when the R₂O content is high, it is necessary to lower SO₃ content from 17kg/m³ to 15kg/m³. In OPC mortars, the composition range of R₂O and SO₃ where expansion occurs is smaller than HPC. As the R₂O and SO₃ content increase, the expansion of DEF tends to increase. When the SO₃ content is large, it expands regardless of the R₂O content. When the salt type of R₂O and SO₃ is changed, there is a small difference in the final expansion, the influence of the difference in chemical species on the DEF expansion is also small.