Combining ultrasonic testing, infrared thermography, and stereoscopy to unveil characteristics of the adhesion capacity of metakaolin plastering mortars

[Display omitted] •Combining UT, IRT, and stereoscopy, aspects of mortar adherence are unveiled.•The velocity of incident ultrasonic waves helps calculate Young's Mortars modulus.•IRT investigates the mortar's ability to transfer water molecules to solid substrates.•Stereoscopy revealed aspects of homogeneity of the adherence area. In the present work, characteristics of the adhesion capacity of metakaolin plastering mortars are unveiled by combining ultrasonic testing, and infrared thermography (IRT), associated with stereoscopy. The investigation was carried out for plastering mortars with metakaolin incorporated by adding and partially replacing the Portland cement, in which incorporations of 5%, 10%, and 15% were employed. Scanning Electron Microscope (SEM), and Energy Dispersive Spectroscopy (EDS) were employed to investigate the morphological characteristics of the metakaolin mortars' surface. In addition, flexural strength tests were also performed to evaluate mechanical behavior. The SEM, and SEM/EDS results revealed aspects of the incorporation of metakaolin in the plastering mortars and revealed the formation of Portlandite, Ettringite, and the CSH phases. Considering the flexural strength behavior, only the plastering mortar with 10% incorporated metakaolin has a better mechanical performance than the reference mortar. Further, the propagation velocity of incident ultrasonic waves was useful in calculating Young's modulus, which is associated with the adhesion capacity of the plastering mortars, due to its mechanical response to the test. Furthermore, the IRT results revealed a significant water absorption by the substrate when a layer of roughcast was applied before the metakaolin plastering mortar. When the plastering mortars are directly applied to the concrete substrate, a smaller ability to transfer water to the solid surface is verified. These adhesion behaviors are associated with the capacity of the system to transfer water to the substrate. Finally, stereoscopy results showed heterogeneity in the interface area between the mortar directly applied to the concrete surface and homogeneity in the interface between the mortar and roughcast/concrete surface, corroborating previous results. In conclusion, the ability of metakaolin plastering mortars to transfer water molecules to solid substrates can be unveiled by combining ultrasonic testing, IRT, and stereoscopy, and this is particularly useful in explaining it’s adhesion property, as shown