Concrete hardeners are a permanent, transparent sealer that protects underlying concrete from damage caused by chemicals and contaminants. Liquid concrete hardeners create a chemical reaction when applied to concrete, penetrating pores. Hardeners act as a strong adhesive for different floor coverings and surface treatments. Also, they prevent newly poured concrete from curling, a distortion of a slab into a curved shape by upward or downward bending of the edges. Hardeners are applied to new or existing slabs.