102 Transportation Research Record: Journal of the Transportation Research Board, No. 2508, Transportation Research Board, Washington, D.C., 2015, pp. 102–110. DOI: 10.3141/2508-13 A spreadsheet program based on a two-dimensional (2-D) finite differ- ence method was employed to analyze the thermal behavior of two bridge pier caps, and analysis results were compared with recorded concrete temperatures from the field. Tests were performed in the laboratory to determine the rate of heat generation of the identical concrete mixtures used in the construction. The activation energy of each mix design was determined following the ASTM C1074 procedure to implement the equivalent age concept to the temperature predictions. Results showed that concrete temperature time histories at the center and the side surface of the bridge pier caps could be predicted reasonably well by using the 2-D finite difference model. This spreadsheet can be a use- ful tool to help engineers make critical decisions, such as formwork removal time, insulation practices, and precooling and postcooling methods, and minimize the risk of early-age thermal cracking in mass concrete structures. In recent years, it has become a common practice for contractors to use concrete with relatively high cement content to increase the rate of strength gain, to reduce formwork removal time to acceler- ate construction schedules. Concrete placements of large structures with an increased amount of cement contents result in higher peak temperatures as well as higher temperature differentials between the concrete surface and the interior, showing a thermal behavior similar to the mass concrete concept described by the American Concrete Institute (1). It is well known that high thermal differentials can result in large temperature-induced stresses and increases the risk of early age cracking. Therefore, prediction of the temperature rise in mass concrete has always been a common concern for both researchers and project engineers. The most important properties for temperature prediction inside the concrete element other than the cement hydration are the thermal properties of the aggregates, geometry of the structure, formwork, insulation materials, and ambient settings (2, 3). Several empirical or numerical methods are being used to predict the maximum temperatures and temperature differentials in mass concrete structures. Among them, the finite difference method (FDM) and the finite element method, are the most widely used tools for solu- tion of this problem. Some of the prediction models using commer- cial software programs, such as CTL 3-D thermal modeling software (4), TNO DIANA thermal and structural analysis models (5–7 ), and other models that can be found in the literature (2). Additionally, the Schmidt Method has been a well-known finite difference solution, calculating the temperatures for single nodes and different time inter- vals. ACI 207.2R provides example computations of how to use the Schmidt Method to calculate the temperature rise and the gradients. Another method suggested by the American Concrete Institute, known as graphical solution, was developed based on empirical results for different types of concrete containing 376 lb/yd 3 (222 kg/m 3 ) cement to predict maximum temperature in mass concrete using several charts and equations (8). Furthermore, a software program was developed at the University of Texas at Austin, with features such as concrete mixture proportioning, thermal analysis, crack prediction, and chloride diffusion service life, where FDM is being used to perform thermal analysis in mass concrete elements (9). This paper presents the comparison of the experimental find- ings with the thermal analysis based on FDM developed by Ballim (10). The analysis uses a spreadsheet program that can solve two- dimensional (2-D) mass concrete temperature development problems. Additionally, temperature time histories data collected from two bridge pier caps were presented in comparison with FDM analysis results. This study shows that the temperature predictions can be correlated reasonably well with the field data, and analysis results show that the largest temperature differential occurs at edges of the midsection of the pier caps. BASIC PRINCIPLES FOR TEMPERATURE PREDICTION MODEL Thermal behavior of hardening concrete element can be described by the partial differential equation shown as ɺ G ( 1) 2 2 2 2 2 2 c T t k T x T y T z p ρ ∂ ∂ = ∂ ∂ + ∂ ∂ + ∂ ∂       + where ρ = density of concrete, c p = specific heat, T = temperature, t = time, k = concrete thermal conductivity, x, y, and z = coordinates of structure, and G . = rate of internal heat generation. Numerical Prediction Model for Temperature Development in Mass Concrete Structures Tahsin Alper Yikici and Hung-Liang (Roger) Chen Department of Civil and Environmental Engineering, College of Engineering and Mineral Resources, West Virginia University, P.O. Box 6103, Morgantown, WV 26506-6103. Corresponding author: H.-L. Chen, roger.chen@mail.wvu.edu.