Value-added waste latex paints in masonry cement for plastering applications

Polymeric latexes are commonly used in cement-based plastering and rendering works. This paper assesses the effect of recycled polymers obtained from waste latex paints (WLPs) on flowability and mechanical properties of masonry cement (MC) mortars, including whether such performance would be similar to that induced by virgin polymers. Three MC classes prepared with different cement-to-limestone ratios are produced in compliance to relevant EN 413-1 and ASTM C91 specifications. The WLPs were not obtained from waste collection sites, rather produced to monitor constituents and properties prior to use. Test results showed that water retention and rheological properties of mortars containing virgin or recycled polymers are remarkably higher than unmodified mixtures. The mechanical properties of WLP-modified mortars including compression, flexure, and pull-off adhesion strength were pretty similar, or even higher than equivalent mixtures containing virgin polymers. This was attributed the presence of ultrafine pigment and extender particles that improve packing density and infer nucleation benefits for the growth of additional hydrates. The dry curing regime applied for virgin and recycled polymer-modified mortars is particularly advantageous in construction sites, as this reduces the hassle of moist curing normally required for unmodified plasters while securing higher resistance against sorptivity and shrinkage cracks.