Risk related to the assessment and verification of the constancy of performance of construction products. Analysis of the results of the tests of cementitious adhesives for ceramic tiles commissioned by Polish construction supervision authorities

The paper analyzes the results of adhesion tests of cementitious adhesives to ceramic tiles, commissioned by construction supervision authorities in 2016-2020. A significant number of the tested cementitious adhesives did not meet the acceptance criteria. Following legal regulations, their manufacturer was obliged to withdraw the product from the market immediately. When assessing the compliance of the results with the requirements, the simple acceptance rule is applied. It means that the product is considered compliant only if the result met the threshold requirements. The results variability estimated from the measurement uncertainty is not taken under consideration. Possible situations in which the manufacturer correctly assessed and verified the constancy of performance [AVCP] of the cementitious adhesive, but the laboratory assessment was negative due to not including the variability resulting from measurement uncertainty, or the specificity of the multi-stage research methodology were discussed. The analysis of the test results was carried out according to the division into C1 and C2 class cementitious adhesives, and also according to the division into notified laboratories, where the tests were performed. When analyzing the number of products that meet or not the requirements, significant differences were found between laboratories carrying out tests commissioned by construction supervision authorities.