Evaluation of two test methods for the strain measurement of interior paints

Abstract

The appearance of structural cracks is nothing unusual neither in old nor in new buildings. The causes of these cracks range from improper selection and use of materials to faulty design, and can have serious consequences. In buildings in which the structural integrity is not endangered, cracking, especially in interior spaces, constitutes a significant impairment of the building's serviceability. The repair costs for these cracks are often considerable. Fortunately, a cost-effective and lasting solution to this cracking problem can be found in the use of more elastic interior paints. In order to utilize this solution, it is essential to know the elastic properties of the paint; however, manufacturers often fail to provide adequate information in this respect. In addition, the European market lacks standardized procedures for quantitatively determining the elasticity of paint. By combining two independent mechanical test methods, it is attempted to obtain a quantitative determination of the strain of interior paints. The suitability and relevance of the test methods used is discussed on the basis of the results obtained. The tests used are the classical tensile test in accordance with DIN EN ISO 6892-1 and a modified 3-point bending test based on DIN EN ISO 178. In order to determine the strain, optical deformation analysis by means of digital image correlation (DIC) is used for both test methods.