I'M GLAD YOU ASKED

Great question - here's the answer.

You are close. Those do look like floor buffers for a waxed floor, and they work the same way for much the same purpose. They are concrete polishers or smoothers and they work just like a buffer, except that instead of having buffing brushes on the bottom, they have metal blades much like a ceiling fan. These scrape and smooth the concrete, and once it has cured somewhat, they can smooth and polish it to a point where it is extremely smooth and shiny.

The plan right now is to leave part of the floor upstairs as smooth, polished and stained concrete. That is what C.E. has requested for some of the space up there rather than carpet or vinyl tile of any type.

O.K., now I have another question about the concrete. I saw both upstairs and in the new parking lot a bunch of rods and some sort of white things. What is that all about?

Another great question.

Concrete has some inherent strength of its own, but it needs help. We have bones in our arms to help the muscles and the concrete needs bones too. The only difference is, it can't grow its own. Instead, engineers call for a skeleton in the concrete of reinforcing bars or rebar. Depending on the thickness, the expected weight a floor has to hold and so on, different size rebar is called for.

In a floor or slab, like the parking lot, the rebar is laid in a grid and wired together at every intersection with baling wire. Then, the white things you saw, called chairs, are placed under the rebar to suspend it in the middle of the concrete layer. This elevates it so it is totally surrounded and lends strength to prevent bending in both directions throughout the entire thickness of the slab.

Thanks for asking.

I'M GLAD YOU ASKED

Good Question - Maybe not the answer you want.

The concrete takes time to "cure". Normally, engineers do not want any heavy weight, like cars driving on it, for at least two weeks. They really do not want that kind of weight for 28 days, which is the official length of time it takes to fully cure.

The reality is, it depends. During a concrete pour, a number of plastic cylinders are poured from the different batches of concrete, set aside under the exact same conditions to cure, and then destructively tested. The cylinder of concrete is slipped out of the plastic sleeve and it is put in a big hydraulic press and squeezed until it breaks. Technicians watch to see how much pressure it takes to break it at each of the test dates, which are spread out over the entire cure time, and from the results determine whether it is fully cured or not.

If the engineers and the Project Superintendent, together with his boss, the General Contractor all give the O.K. then they will take the barricades down and we can park there. If they are still up, then they do not think it is cured enough and we might find ourselves with tire tracks in the concrete. Not a good scene.

Sometimes we just have to be patient, but it sure is hard.

November 8, 2004