Non-Standard Methods for Assessing the Quality of Intumescent Coatings
The main most frequently used structural materials are monolithic reinforced concrete, steel profiles and lightweight thin-walled building structures, which in case of fire at temperatures above 500 °C lose their mechanical properties, deform, and collapse. To protect the load-bearing structures from dangerous deformations for a certain time before the start of extinguishing a fire, various fire-retardant materials are used, among which thin-layer intumescent coatings occupy a special place. Serious problems with the quality of intumescent coatings are associated with the use by manufacturers of paint components (often counterfeit products of low quality) that do not correspond to those stated in the certificates. In these cases, the intumescent coating does not guarantee the formation of a high-quality protective layer of the coke foam in case of fire. Standard methods for assessing the quality of such coatings allow to assess appearance, thickness, and adhesion of the coating prior to coke foam formation. However, it is required to check directly on the object the additional non-standard parameters of the intumescent coatings: intumescence coefficient, appearance and strength of the coke foam. Ways are described related to the implementation of measuring the structural and mechanical properties of the coke foam: intumescence coefficient, penetration and shear-breakout strength. It is proposed to measure the strength characteristics of the coke foam by the penetrometry method on an original installation (analogue of a cone penetrometer). The proposed measurement method is simple, demonstrative and does not require expensive equipment. The dependence is revealed concerning the strength of the coke foam on its density, which is determined by the intumescence coefficient at all other things being equal. The higher the intumescence coefficient, the lower the density and strength of the coke foam. Therefore, high values of the intumescence coefficient do not guarantee the reliability of fire protection. It is recommended to set normatively limit values for the intumescence coefficient, which will differ for different compositions of the intumescence paints.