ONE-SIDED STRESS WAVE VELOCITY-MEASUREMENT IN CONCRETE

Measurement of the velocity of stress waves in concrete provides valua ble information on the state of the material. Recently, a number of pa pers have been published on wave velocity measurements in concrete whe n access to only one surface of the structure is possible, such as for the case of concrete pavements. In this paper, the existing one-sided methods for stress wave measurement in concrete are reviewed. Then, a modified method for one-sided stress wave velocity determination in c oncrete is introduced; the novel aspect of the modified technique is t he data collection and processing system, which more accurately determ ines the arrival of the generated longitudinal and surface waves. The modified method, which is demonstrated on a variety of materials inclu ding steel, PMMA, and concretes of varying composition, is shown to be superior to existing one-sided techniques. Using the developed techni que, the significant effect of the moisture content gradient within co ncrete on one-sided velocity measurements is demonstrated. Finally, on e-sided velocity measurements are shown to be useful for monitoring th e strength gain of early age concrete.