## 4 Discussion  
At the beginning of the considerations on the results of the analysis of cementitious adhesives for ceramic tiles, performed in notified laboratories at the request of construction supervision authorities, it is worth noting that the final product conformity assessment is performed using the simple acceptance principle. This means that the product is considered compliant/non-compliant with the obtained test result if this result (without taking into account the variability resulting from the measurement uncertainty) meets the requirements. There is one more critical issue at the beginning of considering the results of laboratory tests ordered by construction supervision authorities. Considering how complicated the adhesion measurement is and how many factors are not precisely defined in the measurement method, there is a distinct possibility of a dispute between the manufacturer and the construction supervision authority. Figure 8 shows the percentage of cementitious C1, C1T, and C1 TE adhesives that met/did not achieve the minimum tensile adhesion strength of 0.5 N/mm\({}^{2}\) required by EN 12004 for four different conditioning methods. Figure 7: Mean values and measurements uncertainty of initial tensile adhesion strength (**A**), tensile adhesion strength after water immersion (**B**), tensile adhesion strength after heat ageing (**C**), and tensile adhesion strength after freeze-thaw cycles (**D**) for C2 TES1 cementitious adhesives for ceramic tiles. Legend: (—) dashed line represents threshold level acc. to EN 12004, * no data available. In the case of cementitious adhesives of types C1, C1T, and C1 TE, most samples did not meet the required tensile adhesion criterion of not less than 0.5 N/mm\({}^{2}\) after thermal ageing (57%, 50%, and 25%, respectively). The required adhesion of not less than 0.5 N/mm\({}^{2}\) after immersion in water was not met by 25% of cementitious adhesives type C1, 15% of C1T, and 7% of C1 TE. After determining the initial tensile adhesion strength and adhesion after the freeze-thaw cycles, a smaller share of adhesives not meeting the requirements of 0.5 N/mm\({}^{2}\) was observed. In the case of the determination of initial tensile adhesion strength, all 16 tested samples of C1 TE adhesives met the adhesion criterion of not less than 0.5 N/mm\({}^{2}\). All 12 samples of C1 adhesives achieved the required value of at least 0.5 N/mm\({}^{2}\) adhesion after the freeze-thaw cycles. Figure 9 shows the percentage of cementitious adhesives for ceramic tiles type C2, C2T, C2 TE, and C2 TES1, which met/did not meet the criterion of tensile adhesion strength not less than 1.0 N/mm\({}^{2}\) in various conditioning conditions before the measurement. Figure 8: Percentage of cementitious adhesives for ceramic tiles type C1, C1T, and C1 TE, which met/did not meet the criterion of tensile adhesion strength of not less than 0.5 N/mm\({}^{2}\) (under different environmental conditions). At the beginning of the discussion of the results obtained for the class's adhesives with increased parameters (C2), it is necessary to note that in the case of cementitious adhesives of C2 and C2T type, the sample population was small. In both cases, it was only n = 8. Such a small abundance of the examined sample may indicate an incomplete overview of the situation. Thus, the obtained results may not be fully representative. The largest share of C2, C2T, C2 TE, and C2 TES1 cementitious adhesives which do not meet the criterion of tensile adhesion strength not less than 1.0 N/mm\({}^{2}\) was observed for samples stored in water: 62% for C2, 59% for C2 TE, 46% for C2 TES1 and 12% for C2T. After determining the adhesion of cementitious adhesives after immersion in water, the measurement conditions with the largest share of samples not meeting the 1.0 N/mm\({}^{2}\) criterion are the measurement of the tensile adhesion strength after thermal ageing. In the case of thermal ageing, a 62% share of samples not meeting the requirements for C2 adhesives was observed, and a 48% share for C2 TE adhesives.