This paper is to validate the effect of the application of improvement binary blended cement with the combination of OPC, FA and coarse particle cement on the reduction of hydration heat for field application. Mat foundation at the basement floor of steel reinforced concrete building constructed at Seoul OO project is considered for field application of the improvement binary blended cement. Slump, air content and chloride content met the target values. Compressive strength also satisfied the design strength at 28 days. According to temperature history, crack occurrence index at the center section in A, B and D placement zones had over 1.5, which can be protected from crack, while crack occurrence index at C placement zone had around 1.2~1.5, which requires proper crack prevention measures. However, there are no significant crack induced by excessive hydration heat to be observed at the concrete after placement based on visual survey. Accordingly, it is thought that the application of improvement binary blended cement studied in this paper is valid to control the hydration heat of the mass concrete.