Comparison of Results of Impedance Spectroscopy Methods with Results of Impact-echo Method in Investigation of High-temperature-degraded Concrete

The growth in the transport industry results in more accidents, which often include fire in locations with the concrete structures, which also effects its lifetime and its functionality. After any case of fire loading it is required to verify structure's condition. One way how to assess the risks connected with further usage of the structures after being exposed to the fire is the non-destructive testing. This paper is dealing with non-destructive measurement of changes of electric parameters of the cement based mortars subjected to the high temperatures. Prismatic samples with dimensions of 40×40×160 mm were prepared from water, Portland cement CEM I 42.5 R and quartz sand (in a ratio 1:3), with water/cement ratio 0.46. Samples were intentionally degraded by high temperature in range of 200–1200 °C (200 °C step) and the changes in bulk density, flexural tensile strength and electric properties (loss factor tan δ (f), the imaginary component impedance ImZ (f) and the real part of component impedance ReZ (f) were monitored. Two methods were used for testing of electric properties – Impedance spectroscopy and Impact-echo method. The obtained results were compared and suitability of used methods was assessed.