Early hydration heat temperature field of precast concrete T-beam under steam curing：Experiment and simulation

Precast concrete T-beam steam curing can improve production efficiency, realize large-scale production of T-beams, and achieve better economic benefits. We performed tests and numerical simulations on a 30-meter-long full-size precast concrete T-beam to study the economical and reasonable steam curing scheme. The study found that in the early stages of steam curing, the temperature at the mid-span section increases faster than that at the end-span section. The highest temperatures of the tested beams were found in end-span section., and the core-surface temperature difference increased and then decreased, with the maximum temperature difference occurring at the junction of the top and web slabs of the concrete T-beam. To meet initial prestress tensioning requirements, the steam curing of increasing the temperature for 2 h to 50 ℃, keeping the temperature constant for 7 h, and cooling the temperature for 1 h is the most economical scheme, as seen from the comparison and analysis of the development law of concrete hydration heat temperature and the results of concrete test blocks under the same curing. Under this steaming scheme, the end-span section of the concrete T-beam reached a peak temperature of 68.5 °C at 14 h, and the core-surface temperature difference reached a maximum of 8.6 °C at 4.5 h; the peak temperature of the mid-span section was 60.2 °C, with a maximum temperature difference of 8.3 °C. In order to accurately predict the law of T-beam concrete temperature development under steam curing, two subprograms, HETVAL and UMATHT, were compiled on the ABAQUS secondary development platform. When calculating by natural age t, the maximum differences between the measured peak values and the peak values calculated by HETVAL and UMATHT were 30.0% and 27.7%, respectively. After considering the equivalent age te of concrete, the maximum differences between the measured peak values and the peak values calculated by HETVAL and UMATHT were 8.2% and 1.9%, respectively. Therefore, the UMATHT subprogram, considering equivalent age and hydration degree, can accurately predict the development of the concrete hydration heat temperature field under the steam curing process.