Determination of Properties of Concrete Used in Thermal Studies for Lock and Dam Number 2, Red River Waterway.

Abstract : Two concrete mixtures, one containing and one not containing fly ash, were tested to determine pertinent physical properties for use in a finite element method (FEM) analysis of concrete thermal conditions during the construction of Lock and Dam No. 2 on the Red River Waterway. The overall objective of this testing and analysis was to develop construction procedures aimed at eliminating thermally induced concrete cracking during construction of the structure. The concrete mixtures tested were selected to be representative of those which will be used in the project. Aggregates and cements were from suppliers who could be expected to participate in the actual construction. The testing program included determination of ultimate strain capacity, compressive strength, splitting tensile strength, modulus of elasticity, Poisson's ratio, thermal diffusivity, specific heat, adiabatic temperature rise, and coefficient of linear thermal expansion. The strain capacity data presented are somewhat unique in that the two concrete mixtures evaluated more closely resembled structural concretes than typical mass concretes. A limited investigation of the effect of the size of the concrete specimens on their strain capacity was also conducted. Strain capacities were seen to decrease with specimen size for specimens in the range from 18 by 18 in. by 96 in. to 6 by 6 by 36 in This decrease may have been the result of one or more of the following: (a) differences in instrumentation used to measure strains; (b) differences in setting and curing temperatures as well as thermally induced strains for the larger beams; and (c) a greater probability of flaws in the larger cross sections of the larger beams.