Q: We have a hospital expansion project and are considering polished concrete as the flooring material throughout. Our issue on this project is moisture (about 92% internal relative humidity after eight months), so the sheet vinyl originally installed has failed. I've been looking online for information about whether polished concrete can be used and have found plenty of corridors and public spaces, but patient areas seem tougher to find. Our client's main concern is infection control, so wondering if you know of any research on the topic? If polishing won't work, our next investigation will be a poured epoxy resin.

A: Polished concrete is great for many applications, especially public areas because it is low maintenance and beautiful, but it is too permeable for use in patient areas. Although the densification achieved in the surface with materials such as lithium silicates reduces the porosity, a hard-troweled concrete surface is less permeable than a polished one, because the densified layer was removed during polishing. Polishing leaves an open surface susceptible to bacterial contamination. This openness is another advantage of polished concrete because it allows the floor to breathe, releasing the water vapor within the concrete—the same water vapor that debonded your sheet vinyl. There are some sealers that could work on a concrete floor—Acryl-iCon, which has been used successfully in food processing plants—but most hospitals use seamless flooring in patient care areas, such as epoxy resin you mentioned. Polyaspartic coatings might also work—some have been shown to be able to remain bonded at internal relative humidity levels as high as 98%.