The Difference Between Densifiers and Sealers
A beautifully finished decorative concrete floor must go through a fairly involved process to achieve the intended outcome. From the “pure” pour through the glossy finish, concrete needs to be chemically altered before a floor is ready for prime time. Densifiers and sealers are applied to decorative concrete flooring at different stages and serve different purposes.
The Building Blocks of Concrete
Portland cement is the basic ingredient of concrete. Concrete is formed when portland cement is combined with water. Cement and water form a paste that coats and binds with sand and rock. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete.
The longer the concrete is kept moist, the stronger and more durable it will become. The rate of hardening depends upon the composition and fineness of the cement, the mix proportions, and the moisture and temperature conditions. Concrete continues to get stronger as it gets older. Most of the hydration and strength gain take place within the first month of concrete’s life cycle, but hydration continues at a slower rate for many years.
Densifiers: Chemically Hardening Concrete Flooring
Calcium Hydroxide is left over from the cement paste hydration process. If left untreated, calcium hydroxide reacts with carbon dioxide in the air and turns into chalky dust. Dust ends up on everything. For years, the only remedy to sealing concrete floors was to cover them with a film or membrane. Products included acrylics, urethanes, epoxies and waxes. These treatments were a temporary method of sealing concrete. They are subject to delamination, scratching, chipping and wear. Eventually, they have to be replaced.
Densification – Hardening From the Inside Out
A concrete floor is usually between 4-6” inches thick. Most of the wear takes place in the top 1/16th-inch wear zone of the concrete. That’s where the concrete is most vulnerable. Densification is not a topical layer that seals the surface of a concrete floor. Densification is the application of a liquid silicate hardener to a concrete surface to create a chemical reaction. The densification reaction process fills in the natural pores and voids in the concrete through a process of crystalline growth. The concrete is densified internally and inorganically. The same reaction also hardens the concrete and locks up the dust.
What remains is a crystalline-densified version of the concrete that was there in the first place. Because the chemistry is inorganic, there is nothing to wear out, scratch or peel. The seal is the result of an ongoing chemical reaction that takes several months to complete.
Once densification takes place, foreign matter such as oil, alkali, free lime and traffic scum are easily removed with regular cleaning. A regular maintenance program is highly recommended to remove surface contaminants. Any acids or other corrosive materials should be removed immediately from the floor.
