Improving concrete polishing.

Your article "Using Liquid Hardeners to Enhance the Diamond Polishing Process" (September, p. 44), though commendable for addressing the topic, falls far short of an accurate description of the process.

As the article states, silicates have been used for years, but the author is really

describing the early stage curing/densifying process of a basic densifier, a product that is good only for curing and dust proofing. Concrete polishing, when performed correctly, with the right product and knowledge, has evolved immensely from this basic step. In the mid-1990s, we at Advanced Floor Products used a product (our own silicate) to densify and dustproof, but we added the mechanical steps of diamond grinding and polishing, and developed a patented method for delivering a hardened, densified, and polished concrete surface on existing industrial floors that were dusting and spalling from hard-wheeled forklift traffic. Today this process, known as the RetroPlate System, is used worldwide on both existing and new concrete, whether raw or in conjunction with acid staining (without the need for topical sealers), dry shake hardeners, integral colors, or cementitious terrazzo. The difference in the end product, when done correctly, is a stronger, denser floor with clarity to the polish, as opposed to just "gaining reflectivity." This superior result is due to the combination of our modified densifier and the mechanical action of the diamond polishing process.

Two main ingredients are needed to deliver a lustrous, long-wearing polished concrete floor: the contractor must have not only the equipment to grind and polish but, just as important, 1) the knowledge and experience in creating "proper scratch patterns" and 2) the proper product for the chemical reaction, along with the proper time to deliver the product to the floor.

When it comes to choosing the proper product, you have a variety (silicates, siliconates, and silicate/siliconate blends, to name a few), with a variety of results. The two main product groups used, with possible modification by the manufacturer, are silicates (RetroPlate) and siliconates (L&M). Some main differences are:

* Siliconates are very different from silicates. Siliconates have one silicon, one carbon, and three oxygen atoms. The silicate molecule has one silicon atom and four oxygen atoms. In concrete, when the lime and clays react, they form inorganic aluminosilicate polymers. The strength and physical characteristics of the resulting material are determined by the configuration of the component molecules. The strongest and most stable molecular structure is the three-dimensional tetrahedron, the configuration achieved with silicates. It is physically impossible to obtain three-dimensional bonding if one of the oxygen atoms is replaced by carbon, as is the case with siliconates. This translates into a weaker two-dimensional structure than the stronger three-dimensional structure achieved with silicates.

* Siliconate reacts more quickly at the surface than silicate. You get a quicker initial hardening with siliconate, but you do not get the same depth of penetration, densification, and crystallization as with the silicate.

* According to the manufacturer, the siliconate always requires "a two-coat application," while the silicate generally only requires one application to achieve its stated results. (An extremely porous slab may require an additional application of both products to receive optimal results.)

* Both products provide a minimum 10-year warranty, though the siliconate requires maintenance with a specified cleaner in order for the warranty to be in effect.

* Based on independent testing of both manufacturers' products, the siliconate (depending on which formulation) achieves an increase in abrasion resistance of between 50% and 56%, while silicate has shown an increase of up to 400% in abrasion resistance. (Again, your article's reference to "can increase the surface abrasion by 25% or more" alludes to basic densifiers, not patented systems such as RetroPlate's, which incorporates mechanical grinding and polishing).

Despite the author's conclusion that the process "can't improve the quality of the concrete," when done properly, with both the proper products and methodology, concrete polishing systems do improve the quality of the concrete. From independent testing we know that we increase the abrasion resistance up to 400%, we increase the impact resistance up to 21%, we increase the reflectivity up to 30%, we meet OSHA and ADA for SCOF, we are UV stable, and we have been proud to qualify for use in LEED projects all the way to the top--platinum. If that isn't improving the quality of the concrete, then we have a lot of customers who are lying to us and to themselves!

Peter Wagner

Marketing Director

RetroPlate

pbwagner@retroplatesystem.com