derived from concrete, mortar or lime, which can be mistakenly assumed to be efflorescence. Calthemites are usually deposited as calcite which is the most stable polymorph of calcium carbonate (CaCO3). Protecting against efflorescence The only way to completely and permanently prevent (both primary and secondary) efflorescence in cementitious materials is by using special admixtures that chemically react with and bind the salt-based impurities in the concrete when hydrogen (H) is present. The chemical reaction in these special additives fuses the sodium chloride on a nanomolecular level, converting it into non-sodium chemicals and other harmless matter that will not leach out or migrate to the surface. In fact, the nanotechnology in these additives can be up to 100,000 times smaller than even the smallest cement particles, allowing their molecules to literally pass through cement minerals or sand particles and ultimately become part of the cement or sand with which they react. And since they require the presence of hydrogen they stop reacting as the concrete dries out and begin reacting again when the concrete is exposed to moisture. It is also possible to protect porous building materials, such as brick, tiles, concrete and purely against efflorescence by treating the material with an impregnating, hydro-phobic sealer. This is a sealer that repels water and will penetrate deeply enough into the material to keep water and dissolved salts well away from the surface. However, in climates where freezing is a concern, such a sealer may lead to damage from freeze/thaw cycles. And while it will help to protect against efflorescence, it cannot permanently prevent the problem. Efflorescence can often be removed from concrete using phosphoric acid. After application the acid dilution is neutralised with mild diluted detergent, and then well rinsed with water. However, if the source of the water penetration is not addressed efflorescence may reappear. Common rebar protective measures include the use of epoxy coating as well as the use of a slight electrical charge, both of which prevent rusting. One may also use stainless steel rebar. Certain cement types are less resistant to chlorides than others. The choice of cement, therefore, can have a large effect upon the concrete's reaction to chlorides. Today's water repellents help create a vapor permeable barrier; liquid water, especially from wind driven rains, will stay out of the brick and masonry. Water vapor from the interior of the building, or from the underside of pavers