Using ultrasound to monitor stiffening process of concrete with admixtures

A nondestructive one-sided wave reflection factor (WRF) test was applied to concrete with a variety of admixtures, including an accelerator, silica fume as replacement, a superplasticizer, and a retarder. This paper presents the results. The WRF test is sensitive to the presence of admixtures. In addition to WRF tests, dynamic modulus tests were performed on normal- and high-strength concretes. The results from these tests are correlated with the results from the WRF tests. A new, objective method for determining the time of occurrence of critical points on the WRF curve was developed. The critical WRF points were found to correlate well with critical points in set time and cement hydration processes.