Quality Control of Portland Cement Concrete Slabs with Wave Propagation Techniques

Coring is normally done to monitor the thickness and quality of port-land cement concrete (PCC) slabs during construction. Because this procedure requires a considerable amount of time, it is done at widely spaced intervals. As a result, the most critical points, in terms of strength or thickness, are sometimes not tested. Their repeatability and extreme sensitivity to the properties of surface layer enable wave propagation techniques to be used for quality control. The main advantage of these techniques is that they are nondestructive. Fortunately, these techniques have been automated in the last few years. Two seismic devices (seismic pavement analyzer and a portable version of it called the Lunch Box) have been used extensively for quality control. With them, slabs can be tested at closely spaced points and at a fraction of the cost and time of coring. The main tests used are the impact echo for determining the thickness of the slab, the ultrasonic body wave for determining the modulus, and the ultraso...