Concrete dielectric properties investigation using microwave nondestructive techniques

The paper deals with dielectric properties of concrete and the effect of frequency, curing time and water to cement (w/c) ratio, concrete compression strength, steel fibre concrete and moisture content on the dielectric properties. The concrete dielectric properties such as transmission coefficients, reflection coefficients, dielectric constants and loss factors; were investigated using microwave nondestructive testing (MNDT) technique. The MNDT system consists of transmit and receive horn lens antennas, a vector network analyzer, mode transitions, and a printer. The horn lens antennas are used for minimizing diffraction effects due to the edges of the sample. Electromagnetic waves at microwave frequency range 7.0-13.0 GHz using free-space microwave method was used for measuring dielectric properties of concrete. Concrete specimens were prepared using different w/c ratios and different compressive strengths. Concrete dielectric properties were measured and correlated with compressive strength and w/c ratio of concrete, curing time. The experimental results indicate that microwave non-destructive technique has correlated well with to determine the compressive strength and w/c ratios of concrete. The results also show the potential to be used to determine the percentage of fiber. This technique is easy to adapt for in situ measurements.