There was a statement in the course presentation that the industry recommendation for the water/cement ratio for concrete floors should not be higher than .50 - where does this come from? I need to justify this criteria to my structural engineer. Just because I read on the course does not mean too much to him. Is there any ASTM or other american standard that state that? Thank you, Marieta

Hello Marieta! Thanks for supporting our Online Learning Center. I have received a response from Armstrong regarding your question: "[You can find the information in] ASTM F-710 "Standard Practice for Preparing Concerte Slabs to Recieve Resilient Flooring" statesthe water/cement should be 0.40 - 0.45. Armstrong's F-5061 Guaranteed Installation Systems states a water/cement ratio up to 0.50. The flooring industry has accepted a water/cement below 0.50. Anything higher will compromise the compressive strength and permeability of the slab. Water /cement ratios higher will require longer wet cure times and will take longer to dry to the limits necessary to install resilient flooring materials." I hope this information helps. Please let us know if you require any further assistance. -- Mark Hennyey, Content Manager, AEC Daily

The course was great! I have 3 questions. I noticed that the word permeable was used quite a bit in this course.Can you use the term porous and permeable interchangeably? I also wondered about the term subfloor. I read an article in one of the flooring magazines and it referred to the top layer that would receive the floorcovering as "substrate". Can the terms subfloor and substrate be used ineterchangeably? One last question. You mention Porland latex patches and Calcium Sulafte patches. I wondered where the Premixed Latex acrylic copolymer patches fit in. Would they have the same drawbacks as the Calcium sulfate patches? Thanks, Jane

Can you use the term porous and permeable interchangeably? No, they have a separate meaning. Porous means that a substrate has the ability to absorb moisture. Permeability is the rate in which moisture passes through a membrane, such as a vapor retarder. Can the terms subfloor and substrate be used interchangeably? No, the term substrate is the surface in which you are bonding to and while the subfloor may be concrete if there is a residual on the surface of the concrete that is the substrate. Porland latex patches and Calcium Sulfate patches. I wondered where the Premixed Latex acrylic copolymer patches fit in. Would they have the same drawbacks as the Calcium sulfate patches? There are basically two types of floor patching materials Portland cement-based (cementitious) and gypsum-based (calcium sulfate). The additives such as copolymers and/ or latex can be added to either. The additive will give the patch more flexural strength and lower compressive strength. The key is to know if the patch is either cementitious or gypsum. Gypsum is no longer a recommended patching compound for concrete.