Simulation analysis of the hydration heat of large diameter CFST arch and its effects on loading age

Abstract

The hydration heat of pumped concrete in large diameter concrete-filled steel tube (CFST) arches results in considerable temperature changes, which significantly affect the development of the mechanical properties of concrete during its hardening process, making it hard to determine the loading age. Based on the heat conduction theory and finite element method, the hydration heat temperature field of large diameter CFST arches during the period of construction was analyzed. Subsequently, the effects of hydration heat on the developments of compressive strength (fcu) and elastic modulus of concrete (Ec) were analyzed by using the equivalent age method. The results reveal that, because of the influence of the hydration heat, the developments of fcu and Ec are uneven along the radial direction of the arch cross section in the early stage, i.e. faster at the concrete center, and slower at the concrete edge. On the 5th day, the average values of fcu and Ec reach 81.6% and 90.3% of their characteristic values, respectively; the difference of fcu and Ec between the concrete center and concrete edge are 13% and 7.3%, respectively; and fcu, Ec of the concrete cross section tend to be uniform. Hence, in order to ensure structural safety, the loading age for large diameter CFST arches after concrete casting should not be less than 5 days at low ambient temperature.