Rodney van：

Hi John, certainly this terminology and description of concrete is a first for me. What would the three definitions be?

WILLIAM NIX：

Owner, Salesman,Estimator, Designer, Project Manager, Working Foreman & Mentor at WKN RESTORATIONS

When tooling concrete a bull float or light fresno trowel will produce a soft finish, light hand trowel will produce a medium finish, and a power trowel will produce a hard finish. There are other variables such as water ratio and curing methods that matter also and of course the psi design of the mix.. The hardness of the concrete determines the selection of tooling towards grinding and polishing.

Jay Barstow：

Technical Director at AeroFlor Coating Services

Yes, and that's why everyone needs a Mohs hardness tester. Never "assume" in contracting! There are national maps indicating "average" hardness ... they are NOT written by the hand of God! Hardness is also a function of finishing and curing.

Jason Walker：

Owner at The Polishing Spot

In cincinnati the residential seems soft around 3000 to 4000 psi. The commercial end of it is harder from 4000 to 6000 psi. A lot of the newer slabs we have done are starting to water cure from 30 to 60 days. This makes it very hard. I also think the newer concrete made with flyash is harder. It also seems like the older concrete produces a deeper shine.

Jay Barstow

Technical Director at AeroFlor Coating Services

Sometimes Linkedin just chaps my resins!!! I had written MUCH more and it just didn't show up ... what's up with that (AKA WTF!)? Concrete ready mix plants don't always use regional aggregate, it's a commodity and is sometimes imported from other parts of the country. I've had jobs side by side (but a few years apart) with hardness on BOTH sides of the scale. Finish techniques, curing regimen, age, aggregate source, can ALL affect hardness. Sometimes finishers think they're doing the customer a service by making their concrete "ring" by using a high angle of attack on their trowel machines ... this is NOT a good thing for coatings. I try to get to the finishing guy before he starts and ask him to keep his blades as flat as possible to maximize porosity and minimize surface hardening. BTW, the one exception I've seen to concrete all over the map is S. Florida ... soft soft soft soft soft (relatively)!