A dilemma sometimes faced by concrete floor contractors and owners is what to do about a recently installed or existing industrial floor that has a weakened surface. Obviously, removing and replacing the concrete is not a favorable option, because it is disruptive, labor-intensive, and costly. A simpler, less expensive option is to use a liquid chemical treatment to harden and densify the concrete surface.


Liquid floor hardener formulations vary from manufacturer to manufacturer, but they usually contain inorganic compounds that undergo a series of complex chemical reactions with the available lime in mature concrete. Most liquid floor hardeners contain inorganic compounds that are water soluble and comply with today's environmental, health, and safety regulations.


As soon as a liquid floor hardener is applied to a concrete substrate, a chemical reaction takes place between the inorganic compounds and lime (whether hydrated or unhydrated) in the pores of the concrete matrix. The primary product of this reaction is a mixture of dicalcium and tricalcium silicate compounds, which hydrate (react with water) even further to produce a chemical compound called calcium silicate hydrate, or tobermorite gel.


Ideally, concrete floors should be treated with liquid floor hardeners at least seven to 14 days after placement, or after the cement has had sufficient time to hydrate. Liquid hardeners can't penetrate a membrane-forming curing compound. If a curing compound has been used, be sure to remove it before applying a liquid hardener.