Use of waste latex paints in adhesive mortars for ceramic tile applications

Waste latex paints (WLPs) require appropriate economic and environmental disposal solutions. This investigation assesses the suitability of WLPs in cementitious mortars used as ceramic tile adhesives, including compliance with EN 12004 specification. The WLPs contained vinyl acrylic copolymer latex concentrations and extender/pigment powders. Results showed that such additions should be limited to a maximum of 50% of the tap water since higher ratios could increase the mortar cohesiveness and detrimentally alter cement hydration reactions. The slips of ceramic tiles applied onto WLP-modified mortars remained within the specified EN 12004 limitation. The thixotropy and bond strengths determined under different exposure conditions (i.e., ambient, open time, water immersion, or heat aging) are affected by the WLP type, reflecting the relevance of tracing the origin and properties of expired paints. The relative improvements in the bond are attributed to the presence of latex and the ultrafine extender/pigment powders that refine the cement-sand interfacial zones.