Reliability of Impact-echo Method as a Tool to Detect the Reinforced Concrete Element Corrosion

One of the heaviest problems of reinforced concrete structures consists in the steel armature corrosion. The steel armature condition affects, above all, the properties of horizontal structures. It is to be noted that the corrosion process itself may not be observable from the outside in many cases. This is why studies of non-destructive methods allowing the researchers to detect the degree of corrosion for the built-in armatures are being paid much attention currently. The armature corrosion is particularly dangerous in the cases where the concrete cover layer is not disintegrated. This corrosion type is not due to the concrete being attacked by its environment, but, rather, to the concrete – in a modified chemical form – having attacked the steel armature. Whereas the strength of concrete increases in time, its ability to protect the armature, based on a process called the concrete passivation, decreases in time. The reduction of the protecting capacity is connected with the natural carbonation of insufficiently dense concrete, in consequence of atmospheric carbon dioxide absorption. Featuring the capacity to increase the concrete strength and corrosion resistance, the carbonation bereaves – at the same time – the concrete of its capacity to protect the steel armature. The acoustic emission method, providing for a continuous internal structure damage evolution and degree detection, appears to be a convenient method to monitor the internal building structure condition.