Effect of volume-to-surface area ratio and heat of hydration on early-age thermal behavior of precast concrete segmental box girders

Abstract

This paper presents the findings of an investigation on early-age thermal behavior of concrete segmental box girders using finite element (FE) analysis. A FE segmental box-girder diaphragm model was created to evaluate the effect of its flanges, webs, volume-to-surface area ratio (V/A), and heat of cement hydration on the temperature development of the segment at an early age. Isothermal calorimetry testing was conducted on the cementitious materials of four normal and a high-strength concrete mix designs to obtain the heat of hydration and temperature rise, which then were used in the preprocessing of the FE schemes. Based on the investigation on 3 different model shapes consisting of the full-, no-flange-, and core-segment models, the no-flange-segment model was selected as the simplified and representative model for segmental box-girder diaphragms in thermal analysis. Additionally, a parametric study on various V/A of the no-flange- segment model indicates that the segmental box-girder diaphragms are considered mass concrete when using high-strength concrete regardless of the V/A, and measures should be implemented to prevent unexpected thermal cracking.