Sure Hard J17

Installing and maintaining common flooring materials—such as vinyl composite tile, carpeting, and terrazzo—add significant environmental and financial costs to a structure over its lifespan. Structural concrete that is already in place can double as finish surface, creating attractive flooring that mitigates those life-cycle impacts.

Polished concrete floors combine diamond stone-polishing technology and silicate chemical treatment to create a highly durable, nearly maintenance-free surface that does not require repeated applications of VOC-laden waxes or other potentially hazardous coatings. Pioneered in Sweden in the 1990s, polished concrete is created by grinding concrete until level and smooth, adding silica-based densifiers, and polishing using increasingly finer abrasives. The silicates fill the pores and react with the concrete to make it dense and less porous. This concrete can then be polished to the desired sheen to create a finished product. Low long-term maintenance costs—no maintenance beyond regular cleaning should be needed—help make polished concrete among the least expensive flooring options available.

Three of the most common densifiers in North America are sodium and lithium silicates and colloidal silica. Sodium silicate is inexpensive but requires rinsing after densification, generating alkaline wastewater that has to be disposed of appropriately. Lithium silica requires no rinsing and cures quickly. Colloidal silica (nanoparticles of amorphous silica suspended in solution) penetrates deeply and is more reactive than either sodium or lithium.

GreenSpec generally does not encourage the use of nanomaterials, but colloidal silica is approved by the FDA as an anti-coagulant in food and has been used extensively in industry since the 1950s. It should react completely with the concrete and not present a hazard. Overall, evidence suggests it is relatively safe, though all densifiers have to be handled and applied appropriately.

GreenSpec lists concrete polishing systems and supporting products, including water-based, zero-VOC densifiers.

GreenSpec also lists pigments, including recycled materials and mineral byproducts of industry, and concrete stains—typically a blend of acrylic polymers and pigments; surface-applied dyes that can be mixed or diluted to create custom colors; and color hardeners, blends of pigments, silica sand, wetting agents, and portland cement that are worked into freshly placed concrete to densify and color the surface.