It's turning into a big box world. The Home Depot, the nation's second largest retailer, plans to build 500 more stores between now and the end of the decade, bringing its total number of outlets to 2600. With each store averaging 105,000 square feet, than means the Atlanta-based home improvement retailer alone plans to add more than 52 million square feet of space in the next three years.
That is a lot of floors that must be coated. These retailers spend big money to install and maintain these exposed concrete floors. To make the concrete more abrasion-resistant and easier to maintain, the specs usually call for a densifier to be applied, either at the time of placement or toward the end of construction.
Sodium and potassium silicates and the newer nano-lithium silicates are generally used for this purpose. While these materials harden well, environmental concerns are causing the big box companies to focus more attention on nano-lithium silicates.
Sodium and potassium silicates must be rinsed with water after application, or the residue will turn crusty white and mar the floor's appearance. This rinse water is very alkaline and some municipalities are requiring it to be put into barrels and disposed of as hazardous waste. Nano-lithium silicates do not need to be rinsed off after application, saving labor and waste disposal fees.
For example, Costco, a higher end big box retailer catering to small businesses, has more than 500 stores in the United States, Canada, Great Britain, and Asia. Ferguson Construction was awarded the contract for the 140,000-square-foot Marysville, Wash., store completed in 2006. The concrete sealing contract was awarded to a small Utah contractor, Silkote, which selected nano-lithium Pentra-Sil (NL) by Convergent Concrete Technologies, from the spec.
As soon as the trowels came off each pour of 20,000 to 30,000 feet, Silkote sprayed on nano-lithium Pentra-Sil (NL) at a rate of about 500 square feet per gallon. Then, the bondbreaker/curing material was applied right over the top of that application, and the joints were cut.
This early application has several important advantages. First, the slab is clean, ensuring excellent nano-lithium penetration and reaction. Second, the slab is denser and harder during the construction process, protecting it from damage and serious staining. Third, the final clean-up is much easier because dirt, debris, and staining are kept from the substrate. The result is a better looking finished product with lower application and clean-up costs.
At the end of construction, the slab was scrubbed clean and a final coat of another nano-lithium product by Convergent, Pentra-Guar (HP), was applied using a microfiber pad followed by high-speed burnishing. This product is a concrete-hardening, micro-coating that provides a high shine and excellent stain protection to the floor. It is nearly odorless, dries quickly, and the floor is ready for use in hours.
Despite some scheduling and weather problems, the results were positive and Costco managers were pleased, said Rick DeAlba, Ferguson's project manager.
In fact, Costco is using nano-lithium on a variety of other projects in the United States, the Caribbean, and Japan. Ikea has used it in Europe, and Wal-Mart has done some work with nano-lithium in Mexico over the last few years. Large developers such as Panattoni, IDI, Lauth, and First Industrial have also begun using nano-lithium with good results.
This grinding process can create anything from a matte to a brilliant glass-like sheen, depending on the customer's preferences and budget.
Moving toward diamonds
Diamond polished concrete has also become a strong player in this area the last five or six years. This process usually involves densifying the concrete with sodium potassium, or nano-lithium silicate and then grinding the concrete with metal-bonded diamonds followed by resin-bonded diamonds. HTC has a line of diamond-impregnated pads that seem to work well and are becoming popular.
Depending on the condition of the concrete to start with, the cost can range from 60 cents per foot for a couple of passes with a polishing pad to more than $6 per foot for a mirrorlike finish.
Anyone attending World of Concrete the last few years has noticed the explosion of companies producing diamond-polishing equipment and materials. The performance and sophistication of the equipment has come a long way since the early days of diamond pads placed under buffing machines. Several nationwide contractors, including Centimark, Diamashield, and Perfect Polish specialize in polishing for big box retailers. There are also some smaller regional contractors who do fine work.
Stain resistance and shine durability can be problems with polished concrete. The perception of polished concrete is that it will be sealed too, but that is not the case. And generally, the higher the sheen, the less durable the gloss will be. Some anti-stain treatments are solvent-based and high in VOCs, making them less popular to environmentally sensitive retailers.
However, nano-lithium Pentra-Guar (HP) is very hard and provides good stain protection with none of the environmental issues. This material is a maintenance product that needs to be periodically re-applied. It acts as a good sacrificial coat to protect finely polished concrete, and is rapidly gaining acceptance in the marketplace.