1. Scope

Keywords

Rationale

The proposed test method is similar to the impact-resonance method in ASTM C215 (Test Method for Fundamental Transverse, Longitudinal, and Torsional Resonant Frequencies of Concrete Specimens), the main difference being that the proposed method uses the microphone of a smartphone of tablet computer rather than a sensor attached to the specimen to monitor the vibrational response. Thus, the proposed method requires little specialized equipment and little specimen preparation to measure resonant frequencies. The specimen is not damaged during a measurement and can be tested repeatedly over time to track property development. Resonant frequencies can be measured for the transverse (flexural) or longitudinal mode of vibration by changing the location of the impact. The resonant frequencies can be used to determine the dynamic modulus of elasticity using the equations in ASTM C215. For cylinders made from a given concrete mixture and exposed to comparable curing conditions, there is a unique relationship between the resonant frequency and the compressive strength. Once that relationship has been determined experimentally, the development of compressive strength of concrete cylinders made from that mixture can be estimated by measurement of the resonant frequency. Finally, given an experimentally derived mixture-specific relationship between resonant frequency and compressive strength, the method can be a useful adjunct to compression testing for investigating unexpected compressive strength test results.