A composition that can be used as an additive to paints, adhesives and resins to provide a prolonged effectiveness to kill microorganisms exposed to the coating is disclosed. The biocidal coating is comprised of a calcium hydroxide particulate that is within the matrix forming material (e.g. paint, adhesive, resin, etc.). The calcium hydroxide is hygroscopic and attracts waters at a surface of the biocidal coating to limit conversion of the calcium hydroxide particulate at the surface to calcium carbonate in order to maintain a high alkalinity of the biocidal coating. The calcium hydroxide particulate is produced through calcination of crushed limestone, hydration, and then grinding and classification to a particle size less than 25 microns. The calcium hydroxide particulate is then mixed with water in a desired ratio prior to adding to the matrix forming material. The mixture is then applied shortly after mixing.
