Fiber in concrete

I've heard many good things about fiber, never heard a downside. Helps avoid cracjing.

You need reinforcement for concrete that might come under tension as tensile strength of concrete is only about one eighth that of compressive strength. Number he is quoted must be compressive strength. Apparently there are some advantages of fiber over rebar. I would tend to take the advice of the concrete man.

I live in an area where most of the concrete men are just local rednecks. They are very good at digging out footers and pouring the concrete, but do not have the engineering education . It will look like an execellent job, but I am just not sure about how long it will last or hold up. The more I read, the less I understand about the concrete..Just like many things, too many opinions by too many that claim to be experts.

My back gound is electronic engineering,so tend to look at most thing as an engineer would. What looks good and like it would work sometimes is the wrong way to go.

Fiber might help a little but it is no replacement for steel.

Do they plan to put in at least one solid rebar for grounding purposes? Bend it if necessary and leave maybe 3" sticking out to connect ground wire. The NEC says at least 20' so it should be wired to at least one other piece. There's an article here about just leaving some rebar sticking out of the concrete.

It's also called a Ufer ground after the man who invented it. It's better than a ground rod if done properly.

I have heard of the Ufer ground. However I do not want any rebar sticking out of the concrete. It tends to swell up and bust up the concrete.

It does not matter anyway as there is not going to be any electricity going to the building. It is going to be about 70 feet from the house. If I do want to power up something, I will just run a dropcord from the house to it. I had thought of putting some powered doors on it, but it would have been about $ 2000 more not counting on having to run the electrical service to it. I am thiking of getting a propane or propane/gas generator and leaving it out there, but I have a 3.5 kw one I could roll out there if I really wanted to.

I did have another thougth of powering the roll up doors with a battery and solar charger.

But presumably they do know what has happened with most of the work they have done.

When I built my house on a bare block of land, doing almost all the work myself, the operation selling the mesh for the slab would give you the design of the slab for free if you sent them a copy of the house plans. I just followed the instructions they sent me to the letter. And had the hilarious result of the local council telling the local builders to have a look at my slab before the concrete was poured, because that is how it should be done.

They didn't bother with bar chairs which are little bits of reo made into a 4 legged thing that holds the mesh up from the ground so that the mesh is at the right height in the concrete. They are a bit time consuming to use, you use a tool that wraps wire around it and the mesh to keep it in place.

In those days there were no plastic bar chairs.

They builders do it the other way, use tool with a hook on the bottom of it and lift the mesh once the concrete has just been poured, The building inspectors hate that because there is no way to check that the mesh is in the right place.

Another option is to put at least 20' of copper wire in the concrete. It has to be at least #4 or larger. One could easily bring that up inside of where the walls will be. And, of course, you can always put in the old, faithful ground rod if you change your mind. We had to install ground rods or their equivalent on center pivots even if they were going to be powered by a generator and not connected to commercial power. The generators would be there constantly though. I don't know if that would apply to your situation.

I'm a retired chemist and did a lot of work with composites but am not familiar with cement except as a home owner. The cement guy may not know that much but did talk about compressive strength which I would think few would know about. Irregardless, I think most agree that you are better with reinforced concrete.

I do not know the fine points of the NEC but just to run some power for a couple of hours I am not going to worry about it.

I worked around enough electricity at a large plant and dealt a lot with

If at some later date I decide to run perment power to the garage I will make sure it meets the NEC.

For now it is going to be mainly storage. My wife just bought a small car so she could drive it better than our larger Toyota Camry. I have a truck that I do not drive very much unless I want to haul something so it may sit for a week or two. That goes in the two car size garage along with my riding lawn mower and other yard items that is about to over flow two smaller buildings

I have not researched what the numbers really mean, but anyone that works with concrete will know there are several strengths and that is how you order it. The 3500 mix is usually the standard for 4 to 6 inch garage floors and driveways at peoples homes. For the simple slabs like I want, I guess most anything would work for a while, but I would like to make sure it will hold up for many years.

A friend has a garage and the ground/rock base under it has sunk down in parts as you can tell as you go across it. So far it has held up and not cracked and sank down. As I am going to have about 4 feet of rocks or something under a good portion of the slab I do not want to take a chance of it breaking and falling in or down for an inch or three. Along with the fiber he did say something about putting in some rebar. I doubt he will put in very much,but I thought I read somewhere years ago that it really needs about 10% rebar. That is a lot.

Sometimes even the concrete pros get mixed up. A friend had a retaining wall about 6 feet high and 20 or 30 feet long built. The concrete that filled the blocks had something added to it to slow down the curing and something else for strength. Whatever they did, that concrete did not cure correctly and after 2 months you could push the cinder blocks out by hand if not for the rebar that was vertically in them. The wall had to be taken down and rebuilt at the expense of the concrete company.

They typically turn that rebar up inside a wall. The other option is a short piece of #4 copper. This is a UFER in a Florida building (code now).

It doesn't even need to be 20' of #4, Just enough to get from a concrete listed acorn on the rebar up to where you can connect it to your service disconnect enclosure bus.

From what I read you are correct. That strength is standard for home owners and can go up to 10,000 psi for industrial use. Steel, glass, Kevlar can go considerably higher and their tensile strengths even go much higher. That is why you add fibers of steel or other materials to concrete as its tensile strength is only 10-20% of its compressive strength.

There is still a lot of 2500 or 3000 PSI concrete used but the 3500 is usually made with pea gravel so you can pump it and that makes it more attractive. Most concrete gets pumped from what I see here. In round numbers one extra bag of portland (94# more per yard) adds 500 PSI. It is a little more complicated than that but not a bad rule of thumb. My policy has been, much greater than 2 yards that you can't place directly from the truck, I am getting a pump. Obviously for tie beam and cell pours, you get a pump.