Protectosil® CHEM-TRETE® PB VOC is a clear, penetrating, breathable water repellent for use on concrete, brick, concrete masonry units and some natural stones. It is especially suited for making porous substrates, such as split-face block, water repellent in order to stand up against wind-driven rain. By penetrating into the substrate and chemically bonding with silica to form a permanent attachment of the water repellent molecule, Protectosil® CHEM-TRETE® PB VOC prevents water and waterborne contaminants from entering the substrate and causing premature deterioration. It also reduces problems such as efflorescence, leaching, acid rain deterioration, scaling, dirt buildup, staining, the corrosion of reinforcing steel and mildew.