Evaluation of the hydration of concrete mixtures by ultrasonic testing

Proper evaluation of the hydration process of concrete mixtures is essential and useful to assess the quality of concrete mixtures and cement mortars used for the repair of structures. Currently the penetration resistance test is widely used to evaluate the strength development of fresh mortar and concrete. Ultrasonic through transmission and wave reflection methods are reliable alternative techniques for evaluating the strength development in concrete mixtures. Experiments demonstrate the accuracy of the above mentioned methods. The ultrasonic waveforms were continuously examined during the tests and compared with the strength development obtained from the standard penetration resistance test. The test results are analyzed and it is shown that the ultrasonic wave velocity and reflection coefficient have a strong linear relationship with the strength development. Additionally, a rapid increase in the wave velocity and frequency amplitude may be utilized as a tool to indicate a beginning of the strength in the fresh mixtures. The results show that using the ultrasonic testing techniques is a promising way to evaluate the strength development in early age concretes and mortars.