Seismic techniques, including the Spectral-Analysis-of-Surface-Waves test, direct and interval compression wave tests, and resonance tests, provide reliable techniques for determining the elastic properties of portland cement concrete (PCC). These techniques can be applied to pavement structures, such as slabs, and to laboratory specimens, such as cylinders. The nondestructive nature of these tests makes them ideal for monitoring PCC from the earliest stages of curing and continuing throughout the life of the structure. Elastic properties, typically expressed as Young's modulus and shear modulus, provide an easy way to compare the similarity of laboratory specimens with each other and with the structures they are intended to represent. The results of different seismic tests on curing slabs and field-curing cylinders demonstrate the applicability of the tests and show that, in these tests, the field-cured cylinders did not obtain the stiffnesses of the slabs. Small-strain static tests performed on cylinders are also shown to be consistent with moduli determined by dynamic (seismic) tests on the same cylinders when both types of tests are performed at similar strain levels. However, these small-strain moduli are shown to be about 10 percent greater than Young's moduli measured in conventional static tests at 40 percent of the unconfined strength, because of the decrease in modulus with increasing strain. (Author/publisher)
Abstract