Soundness evaluation of concrete with MgO

A new test method - delayed autoclave expansion test - has been used in this study to evaluate the soundness of concrete that contains intrinsic dead-burnt MgO and adscititious lightly burnt MgO. The autoclave expansion value and strength of that concrete were investigated and the relationships between the expansion or strength and the soundness were discussed. The results of this study showed that it was unsuitable to apply a standard for the soundness evaluation of cement with MgO to that of concrete. Unlike the MgO content upper limit 5% in cement, more than 5% in concrete is acceptable. The soundness of concrete can be evaluated on the basis of expansion rate or strength changes after autoclave and it will be better to use changes in strength to express the volume soundness of concrete.