I should have used different wording but the principles I have posted regarding concrete and reinforcing steel are elementary engineering topics. Any engineer would agree 100% with what I have posted. Sometimes I get frustrated for actually trying to explain and describe engineering science in an effort to educate people over "this is how we do it here" attitude. I run into this routinely with concrete contractors telling me they have done it that way for 30 years and truth is they have been doing it wrong for 30 years. There is a tremendous amount of knowledge that can be learned from contractors and I am a good listener and always consider their point of view. However that said, I am an engineer and base my opinions on proven science developed over decades by research institutions. Every project I develop and oversee I am responsible for. If the concrete doesn't perform as intended I am the individual they come to court over seeking a large settlement. Because of this I am only allowed to deal in facts and science as established by the industry. Many building codes were developed "because that is how it has always been done". Doesn't make them right but they need to be followed until someone challenges them or when the codes are updated. The statement I made regarding "they aren't real engineers" is probably from my personal frustrations as anybody and everybody loses the term "engineer" without the proper credentials and professional registrations. Something that takes 8 years to obtain then listen to janitors being called xxx engineers is disheartening. Sorry for the rant and I will keep my "educating" to myself.
Merry Christmas!
Thank you for taking the time to share your knowledge with us. I might be one of those guys who has been doing it wrong. I do a fair number of pads using 2x4s as forms, that gives me a 3 1/2 inch thick pad. I've worked in CA and TX. I've been a helper and I've tied rebar on dozens of houses in CA that where inspected to meet code and the rebar was all set on plastic chairs to keept he rebar in the middle fo the concrete. This was always stressed to me as the only way to do this by everyone I've ever been involved with.
Wire was never allowed on a house.
Fiber was never a substitute for rebar.
On the flat, rebar is to hold the concrete together when it cracks. so the crack doesn't get bigger and move up and down. It is not to make concrete stronger. 3,000 psi is plenty for any residential floor, so the goal is not to increase the psi, but to minimalize cracking so the floor remains flat and level over the decades.
Where am I wrong?
You suggested useing fiber instead of wire or rebar. I don't believe that fiber is a substiute for either, and I don't believe that it increases the psi of concrete. A dry mix is important, but it wont increase psi. A wet mix will lower psi, so you want it dry so that the mix cures to it's maximum strength. Not to increase anything.
As a remodeler, I repair houses and modify them on a regular basis. In every case that I cut out concrete with wire, I find the wire either under the concrete, or at the very bottom of it. I have never found wire in the middle of the concrete!!!!! Has anybody?
If what you are saying is true about requireing 3 inches of concrete above the rebar, then would it be true with wire as well? In my experenice, the big cracks in concrete always happen when their isn't any rebar or the wire is at the bottom of the pad.
Are we comparing apples to apples? Are you talking about adding strength or decreasing cracking for a residential floor?
My comments and advice is to help to achieve the best, longest lasting floor possible. If I'm wrong, then I will admit it, apologize, and bow out.
Eddie
