Dynamic and static determinations of Young's modulus and Poisson's ratio were made on concrete cylinders to establish a relationship between the two methods when applied to concrete test specimens. Three curing conditions, three sizes of cylinders, and two strengths of concrete were used;the cylinders were tested at 2, 4, 7, 12, and 24 weeks from the casting date. Dynamic values were calculated from the fundamental transverse, longitudinal, and torsional frequencies of the specimens. Static values were obtained by the NCEL compressometer-extensometer, surface-mounted strain gages, and an NCEL-developed hoop transducer.nThe static test results were not influenced by the cylinder size, and no difference could be found between the dynamic results for the 4- by 8- and 4- by 12-inch cylin¬ders. However, the dynamic results for the 6- by 12-inch cylinders gave slightly lower values of E (0.16 x 106 psi or 3.4%) than the two smaller cylinder sizes.
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