What is a concrete densifier, and what is the best concrete densifier? According to the Internet, “A concrete densifier is a chemical applied to a concrete surface in order to fill pores, increasing surface density. Chemical densifiers are used on polished and non polished slabs to reduce dusting and wear; on polished concrete surface densifiers help concrete take a better polish and make the surface less permeable to liquids so the slab does not require sealing.”
Now lets explore this: Why would you need a concrete densifer in the first place? Concrete is composed of three ingredients, Portland cement, aggregate and water. It may seem simple but concocting the exact ratio of these three components is tougher than you think. If the proportions are even slightly off it will result in weakened concrete that will begin to deteriorate. After concrete is poured it solidifies and hardens through a chemical process called hydration. Water reacts with the cement and causes all of the ingredients to bond together. If too much water was added to the mix and the water-cement ratio is off, the aggregate will begin to separate from the cement paste. If water is not fully absorbed through hydration some of it may evaporate as it hardens resulting in bleeding that will reduce the final strength of concrete. A mix with too much water will also experience increased shrinkage and visible cracks which will also affect the strength of concrete. That being said when you buy a home that already has a poured concrete basement, driveway, patio etc. you do not know what the water-cement ratio was when poured. In most cases since the ratio is so difficult to perfect it is adequate to assume your concrete will weaken with time.
By applying a concrete densifier you are permanently closing the pores in the concrete thus in fact hardening the concrete and making it stronger. There are a few types of concrete densifiers on the market today. The oldest and most popular being silicate based densifiers. They can include sodium silicates, potassium silicates, lithium silicates or a combination. Silicate densifiers are chemically reactive sealers that penetrate and react with calcium silicate hydrate or C-S-H. C-S-H is the same material that is produced in the reaction between Portland cement and water giving concrete much of its original strength. When a densifier is applied to the surface of concrete the silicate begins to immediately react with the calcium hydroxide. Not only does densifying begin but the once empty pores of the concrete are filled creating a tougher, stronger concrete slab. But beware silicate sealers are known to leave a white residue called carbonation on the surface (When silicate left on the surface that did not penetrate reacts with carbon dioxide in the atmosphere.) This is often times difficult to remove. A newer technology on the market is a colloidal silica densifier. It is claimed that colloidal silicas are the silicates of the future since they have a low viscosity, penetrate deep and also react with lime found in concrete. Since colloidal silicas have the ability to bond to itself (silicate sealers cannot do this) it can densify stronger and has the ability to bond to cement products not made from regular Portland cement. It is claimed colloidal silica is safer to use than traditional silicates and since there are small amount of metallic salts compared to silicates, there will never be whiting left on the surface. Application is quicker (the slab is dry in 1-2 hours vs. 6-24 hours.) But which densifier is the best choice?
Our take : Best Concrete Densifiers
When it comes to silicate sealers we feel the best densifier and hardeners are lithium based. Since lithium silicates will react with calcium hydroxide present in concrete to produce the same molecule that concrete naturally forms to hold itself together (C-S-H) we feel this is the strongest, most durable densifier. They have a faster dry time than sodium silicate densifiers and they are a cost effective solution to harden concrete.
