Effect of Early Age Strength on Cracking in Mass Concrete Containing Different Supplementary Cementitious Materials: Experimental and Finite-Element Investigation

This paper presents the findings of an investigation using the finite-element method to predict the distribution of temperatures within a hydrating massive concrete element. The temperature distribution produced by the finite-element thermal analysis of the model is used in the finite-element structural analysis to quantify the maximum allowable internal temperature difference before cracking will initiate in the concrete. To verify the results obtained in the finite-element model, four different mixes of concrete, typical for use in mass concrete applications in Florida, were produced and each mix was used to make two large-scale $1.07\mathrm{m}\times 1.07\mathrm{m}\times 1.07\mathrm{m}$ ($3.5\mathrm{ft}\times 3.5\mathrm{ft}\times 3.5\mathrm{ft}$) concrete blocks. The mechanical and thermal properties of early age concrete used values obtained experimentally from the concrete used to construct the four sets of blocks. The temperature distributions produced by the model were shown to be very similar to those measured in the experimental blocks. Results suggest that reliance on a limiting maximum temperature differential to control cracking in massive concrete applications should be supplemented with a requirement for the presentation of an analysis showing the calculated stress response to the predicted temperature distribution within the concrete to ensure that the induced tensile stresses will not exceed the tensile strength of the concrete.