Effect of volume-to-area ratio and heat of hydration on temperature development of segmental bridges and drilled shafts

It is known that whenever fresh concrete is used in the construction of large homogeneous structures, consideration is always given to the amount of heat that will be generated. Temperature difference per unit distance between one point and another in a structure is called a thermal differential. Temperature differentials are produced when the heat being generated in the concrete is dissipated to the surrounding environment causing the temperature at the surface of the concrete to be lower than the temperature at the interior of the concrete. This temperature drop at the surface results in the contraction of the concrete creating tensile stresses in the surface that can induce thermal cracking. If thermal cracking does occur, it can ultimately affect the ability of the concrete to withstand its design load, and allow the infiltration of deleterious materials which undermines durability.;The Florida Department of Transportation (FDOT) has identified two structures which show susceptibility to thermal cracking commonly observed in mass concrete. These structures are: segmental bridge pier sections and drilled shafts.;This dissertation presents the development of a finite element model used for the prediction of temperature development curves of concrete segmental bridges and drilled shafts.;The segmental bridge model developed was used to evaluate the effects of the extremities, volume-to-area (V/A) ratio and heat of hydration on temperature development. Results show that use of local V/A ratio, focused on core of segmental bridge, is more adequate in classifying a segmental bridge section as mass concrete. The drilled shaft model developed was used to evaluate the effects of V/A ratio and heat of hydration on the temperature development of drilled shafts.;Results show that predicted maximum temperatures and maximum temperature differentials of tested models are greatly influenced by the heat generated due to hydration of concrete mix used. Furthermore, it was found that maximum temperature differential values exceeded limits set by FDOT in structures with V/A ratios less than 1.0 ft.;It is recommended that FDOT classify and treat all segmental bridge sections and drilled shafts as mass concrete structures regardless of V/A ratio or minimum dimension.