Interaction between two anti-graffiti treatments and cement mortar (paste)

Much of the twentieth centuryʹs built heritage is made of concrete, which is particularly susceptible to graffiti “attacks”. Since the traditional methods used to remove spray paint are not particularly effective on this type of material, the adoption of preventive measures by applying a new type of protective treatments, known as anti-graffiti coatings, may be a good way to tackle the problem. The present study aimed to evaluate the physical properties of a cement mortar coated with two such products and to study the possible molecular interactions between the coatings and the cement paste. Neither product induced chromatic changes on the surface of the material, while both made it water repellent. 29Si MAS NMR analysis detected a lower Q1/Q2 ratio, indicative of a longer chain length, in the C–S–H gel in the cement paste mixed with the anti-graffiti products.