A microstructural approach to adherence mechanism of poly(vinyl alcohol) modified cement systems to ceramic tiles

PVA is a water soluble polymer used as cement modifier. An important modification observed by addition of PVA is the increase of the bond strength between cement paste and aggregate. The purpose of this work was to investigate the effect of PVA on the mechanism of adherence of cement pastes to ceramic tiles. Pastes with and without PVA were applied on the back side of porcelain tiles and after 56 days the microstructures of the interfaces were evaluated by SEM. The mode of rupture changed from mostly interfacial failure to a mixed-mode interfacial-cohesive failure for the paste with polymer addition in which was observed the reduction of the thickness of the porous transition zone between tile and paste bulk. Also, in plain paste the formation of a duplex film (CH plus C-S-H) in contact with tile surface was observed while in modified paste a single layer of C-S-H was identified.