Coated building materials: Determination of water absorption/desorption (NT BUILD 342)

Abstract

1. SCOPE

This NORDTEST method specifies a procedure for the determination of water absorption and desorption through paint coatings on building materials. The testing of water absorption/desorption is carried out by comparative testing of treated and untreated specimens.

2. FIELD OF APPLICATION

The test method can be carried out on both unexposed and exposed (e.g. to ageing procedures or alkaline treatment/ultra-violet radiation), treated specimens. The method is suitable for comparing performance levels of paint coatings on specified substrates. The paint coating must be applied to blocks of a rigid substrate. The substrate used in the testing shall, if possible, be comparable to the substrate the paint coating has been developed for and is applied to in practice. Usually concrete (water/cement ratio = 0.37) and bricks are used as substrates; concrete representing a compact and relatively slow absorbing building material and bricks representing a porous and relatively fast absorbing material. The problems concerning water which has entered the building-material by other routes than through the paint coating (e.g. through unprotected cracks and joints) are not within the scope of this test method. Testing of water vapour diffusion can, for example, be carried out according to ASTM E 96-80, procedure b.