Abstract: In an attempt to overcome the difficulty of determining the thermal expansion coefficient of dam concrete at early age by standard test method, temperature-stress test (TST) was conducted. The early-age thermal expansion coefficients of fly ash concrete were determined by segmented linear fitting of the temperature difference and strain difference curves of conventional dam concrete dosed with 35% and 80% fly ash volumes. Results demonstrated that (1) the thermal expansion coefficients of the two kinds of concrete varied in the range of (20~30)×10^-6 /℃ at the stage of initial hardening, and tended to be stable in the range of (4.6~10)×10^-6/℃ at late stage. (2) The thermal expansion coefficient of high-volume fly ash concrete (80% fly ash concrete) is lower than that of reference concrete (35% fly ash concrete), which is conducive to crack resistance of dam concrete. (3) On the basis of the determined thermal expansion coefficients, a model of thermal expansion coefficient is proposed to better reflect the development law of thermal expansion coefficient at early age and to calculate the temperature deformations of the two kinds of concrete.

Key words: high-volume fly ash concrete, thermal expansion coefficient , temperature-stress test (TST), equivalent age, early age