Concrete structures are subject to physical or chemical attacks by various substances, including water, acids, alkalis, salt solutions, and organic chemicals. Damage may vary in intensity from surface discoloration or roughening to catastrophic loss of structural integrity due to acid attack. Guide to Selecting Protective Treatments for Concrete, ACI 515.2R-13, addresses the effects of various substances on untreated concrete and provides recommendations for protective treatments. More exotic treatments, such as lead sheet, glass, or metalizing are included, but not usually called for except in extreme or unusual circumstances. Because various treatments provide different degrees of protection, product producers should be consulted for each application. Available in hard copy or electronic format at www.concrete.org.