Strength-related testing of concrete using microwave signals

摘要

An apparatus is disclosed for testing concrete having an unknown water/cement ratio and an unknown compressive strength. The apparatus includes a transmitter assembly for transmitting microwave signals at one or more predetermined frequencies. A receiver assembly receives each microwave signal reflected from the concrete under test. The reflected microwave signals, together with the transmitted microwave signals, are used to determine a reflection coefficient magnitude for the particular microwave frequency. A processing unit uses the reflection coefficient magnitude to determine a value related to concrete strength. In one embodiment, the processing unit relies on a logarithmic function that correlates the reflection coefficient magnitude and a water/cement ratio. A value related to the compressive strength of the concrete can also be obtained using the value of the water/cement ratio or the value of the reflection coefficient magnitude.