Ultrasonic Testing to Determine Water-Cement Ratio for Freshly Mixed Concrete

The objective of the research presented here was to find promising directions for the development of ultrasonic test method(s) for the direct, instantaneous determination of the water-cement ratio (W/C) in fresh mortar or concrete. The importance of W/C is related to potential strength development and, to a certain extent, the durability potential of the hardened concrete. Since previous efforts during the past 50 years have been unsuccessful in testing fresh concrete due to the complexity of the problem, innovative, high-risk/high-gain methods were selected in the present work. The methods are considered innovative since a literature search detected no sign that they have been used for testing fresh concrete before. The following test methods were tried out for testing fresh concrete: • ultrasonic methods used regularly for testing hardened concrete; • solidification of the fresh mixtures by freezing or heat treatment or accelerating admixture + heat treatment before testing; • use of high-intensity stress waves by lithotripter; • the direct contact method. None of these methods produced a satisfactory solution for the instantaneous determination of the water-cement ratio, although interesting side results were obtained. It is hoped that both the positive and negative results presented will help researchers in their work on ultrasonic testing of concrete.