Identification of the degree of fibre-cement boards degradation under the influence of high temperature

This paper presents an original methodology for identifying the degree of degradation of fibre-cement boards caused by high temperature. The methodology enables the reliable and automated identification of the degree of degradation on the basis of parameters determined using non-destructive methods. The methods include: the ultrasonic method, the acoustic emission method together with the analysis of the results by artificial neural networks, and the optical method using a scanning electron microscope. First, fibre-cement boards are preliminarily tested by means of the ultrasonic method. Thanks to this method boards in which structural changes likely took place are simply and quickly singled out to be subjected to more thorough testing using the acoustic emission method, which is the principal method in the methodology. The optical method is an auxiliary method used mainly to verify the results yielded by the other two methods. The investigations carried out by the authors have shown that the identification of the degree of fibre-cement board degradation solely on the basis of bending strength (MOR) is insufficient. It should be noted that the methodology was verified in practice through experiments carried out directly on the production line.