Expert: Dan Griffin - 4/26/2010

Question
QUESTION: (my son wrote you but out of town?) We are having a temo sunroom built 27x14.9 feet/and foundation being poured soon- using 4000psi with fiberglass additive to prevent cracking- as an 80+ young senior I wondered if their plan of having cocreate joints two (2) aprox 9 feet apart for the 14.9 feet across and then one joint all the way across 27 feet in middle make sense? I'm worried re how look as I cant afford any flooring and will be left as is.

Does it make a difference if the pump cocreate in or use wheel barrels and several men?

ANSWER: Terry, the joint pattern sounds great to me.  Now the choices - you can have the joint tooled with a jointer or saw cut after the concrete has set.  Either one can be quite effective and I would rely on the finisher to perform the joint he feels would work out better which will probably be a saw cut.  The saw or the jointer MUST penetrate the top at least 1/4 of the depth - about 1"+ for a 4" slab, which requires a deep keel on the edger.   He may suggest tooling the short joints and making the saw cut later.  If he plans to saw, the cut needs to be made very early, preferably the same day the concrete is poured.  This cut tells the concrete where you would like it to crack, hopefully in anice straight line.  Make sure they plan on curing the concrete.  If you are leaving it exposed it, it will be fine to use curing compound.  

The fiber mesh will leave fuzzy hairs standing up in the concrete.  These will wear off with time, but talk to your finisher about singeing them off with a torch.

---------- FOLLOW-UP ----------

QUESTION: Excellent and Blessings- Q: How could I "test" my concreate to find the true PSI after they are done? So I would kw I didn't get ripped off or a bad batch?

Answer
Terry, you can ask to see or have a copy of the ticket to show what was ordered.  The truck usually gives multiple copies.  The back of the ticket should show how much water was added at the site, though this often does not happen.  It sounds as if you have a competent finisher.

Commercial work uses test cylinders, but the cost is not warranted for your project.  There is a test called a Swiss hammer test, but, again, I don't feel the cost is justified for your work..