The purpose of this study is to obtain the thermal expansion of air dried high-strength concrete, from 20℃ to 100℃ and then from 100℃ to 30℃, under constant compressive stress including tri-axial loading in which maximum compressive stress is below the one third of strength. The conclusion is the following; In the heating and cooling process, the thermal expansion of high-strength concrete under multi-axial constant stress is smaller than that of free expansion. The strain of this concrete can be obtained as the sum of elastic deformation, free thermal expansion and creep strain. The creep strain of concrete at any temperature can be obtained by using "Time Temperature Equivalence Principle."
