Fortunately most concrete in service is not subjected to chemical attack. Concrete is generally less able to resist successfully corrosion of this kind than disintegration by other forces. By chemical attack is meant leaching and acid or sulfate attack. Although concrete is often disfigured by deposits of efflorescence [1] as lime water leach reaches outside surfaces, very little good-quality concrete has actually been destroyed or made unserviceable by leaching of lime from internal or external surfaces. In addition to good workmanship, probably the best initial correctives are either an ample cement content with a low-water content and water-cement ratio or a cementitious mixture of portland cement and a good, active pozzolanic material to minimize permeability. Acid attack is commonly encountered in sewers above the flow line, on floors of food processing plants, and elsewhere. In the case of sewers, attack on concrete is by sulfuric acid; little can be done about it directly but much can be done to prevent it by proper sewer design. The lactic and acetic acid attacks are milder and can be minimized by good workmanship, good concrete, and a good pozzolanic material added to the cement to make the lime less subject to attack by acids.