Based on the experimental results of strength developments of high strength mass concrete using low-heat type cement, rational corrections of proportioning strength are investigated. Differences in strength between concrete in structures and standard cured specimen increased in proportion to specified design strength. In case of using rich-Belite Portland cement applying to high strength concrete, the age for proportioning strength of concrete cannot be extended to 91 days. And corrections of proportioning strength in term of the effect of high temperature curing in an early age are proposed in regard to rich-Belite portland cement and substituting fly-ash for 40% of normal portland cement.
