SPEC MIX® IWR Masonry Mortar (Integral Water Repellent) is specially formulated to reduce water penetration, shrinkage and efflorescence of masonry mortar joints while meeting ASTM C270 requirements. SPEC MIX IWR Masonry Mortar incorporates a proprietary, dry polymeric integral water repellent admixture during the SPEC MIX manufacturing process, assuring the designer, specifier, owner, and contractor the mortar on their project will repel moisture, while maintaining optimal workability and flexural bond strength.