Choosing which concrete densifier to use for polished concrete floors isn’t always a straightforward task. The choices have also expanded. We have moved from sodium and potassium to lithium silicates and colloidal silica. Each of the silicate densifiers has a different way of bonding with the silica resulting in a different molecule size.
In theory, any of the silicate-based densifiers do the job on any concrete surfaces, but molecule size plays a role. The smaller molecules give a better sheen and combine better with smaller amounts of free limes. Larger molecules do a better job on weaker concrete surfaces with greater porosity but give a duller sheen. The depth that the densifiers penetrate into the concrete also varies with molecule size. Thus, the type of silicate used depends on the concrete’s properties and the effect you want to achieve.
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Sodium silicates have the largest molecules of silicate sealers. They react well with larger amounts of free lime but give a lower sheen. The sodium and potassium silicate also raise the pH of concrete during the chemical reaction. Increased pH forces residual salts and other impurities to the surface.
Lithium silicate has smaller silicate atoms. As a result, more silicate bonds with lithium per volume. The result is that you have the same effect from spraying less liquid over the concrete surface. The smaller silicate atoms also give a higher density and strength to the finished product. Lithium silicate also provides the best sheen for decorative concrete floors. Because of the lower pH, there is less chance of bloom. There’s less residue to dispose of after the application of lithium silicate.
Benefits of Using Densifiers
Using silicate densifier and concrete sealers has many benefits beyond providing a superior finish and strengthening the concrete. Unlike other surface treatments and water repellants, the silicate penetrates the concrete, changing the molecule structure. The increased abrasion resistance makes concrete surfaces treated with a densifier ideal for high-traffic areas. The smoother concrete surface also makes polishing a high sheen easier and makes the floor easy to clean and maintain. The reduced porosity contributes to the longevity of the concrete. The last benefit is that the concrete’s chemical reaction within the concrete is ongoing. This reduces dusting and continually increases its strength.
For most applications, especially where the concrete floor’s strength is known, lithium silicate densifiers give the best benefits. Sodium silicates work better with weak, porous concrete to achieve similar effects. For applications where the initial pour’s strength or quality is unknown, a blend of lithium and sodium or potassium silicates covers most bases. Sodium silicates give a matt finish, whereas lithium-based densifiers give a more reflective surface. The sodium-based silicates give a slower action, and the lithium densifier has a faster reaction with the concrete. Both densifiers achieve the same effect, but sodium is best for porous concrete, and lithium works better for dense concrete.