The applicability of pulse phase thermography (PPT) for the investigation of structures is studied systematically on concrete test specimens and on a plastered sandstone column. In the test specimens, voids and delaminations are implemented in different depths and with different sizes, modelling real voids, honeycombing and debonding. Delaminations of plaster in concrete and masonry and behind tiles on concrete are investigated. PPT is based on the frequency analysis of the cooling down process of actively heated surfaces. Therefore, it is contactless and thus completely non-destructive (if overheating of the surface is prevented), fast and allows the inspection of large surface areas. The interpretation of amplitude and phase images gives semi-quantitative information about the observed defects. The phase images provide a deeper probing up to 1015 cm in relation to the interpretation of the thermograms and to the amplitude images. In addition, the influence of surface inhomogeneities and non-uniform heating is reduced.
Impulse thermography is an active method for quantitative investigations of the near
surface region of various structures. It has recently been applied and optimized to applications in civil
engineering. For quantitative analysis of data recorded on the building site, the problems are manifold.
Here, the influence of the different surface properties on the detection and characterization of voids
and honeycombing simulated by polystyrene cubes and cubes prepared of porous concrete are
demonstrated.