Mechanical properties of old concrete using destructive and ultrasonic non-destructive testing methods

This paper examines the variation in properties of a specific type of 28-year-old concrete, the characteristics of which were known at 7, 28, 36 and 90 days. Beyond the destructive tests (compression, splitting tension and bending), the concrete was studied with non-destructive ultrasound testing. Moreover the relationship between the compressive strength of this concrete and the ultrasonic longitudinal wave velocity, as well as the dynamic modulus of elasticity were determined. The objective was to control changes in the quality of concrete over a long period of time and to contribute to the development of a non-destructive method for the determination of concrete strength in structures. The presented approach, that seems promising for such development, uses the velocity of ultrasonic waves in concrete.