Older concrete surfaces exhibit patterns of weathering and soiling that are similar to those observed on limestone and marble buildings. In fact, the chemistry of all of these calcium-rich construction materials is related. HCT, developed for the preservation treatment of deteriorated carbonate stone, is an aqueous solution of ammonium hydrogen tartrate. It converts the acid-soluble calcium carbonate in the concrete’s surface into calcium tartrate tetrahydrate, a stable compound that is not attacked by environmental acidity. Concrete surfaces treated with HCT show resistance to sulfuric acid at a pH as low as 2. An added advantage of the HCT is it enhances the attachment of catalyzed alkyl silane water repellents, and promotes the spreading of water-borne paints and coatings.