Concrete Question

[Duffster]

I am planning to pour 5" of 4,000 psi, will that be good for a drive?

Scott

With a rebar grid it would be perfect.:thumbsup:

 

[luscsmith]

Should I drop the fiber and spend the money for extra cement?

Scott

 

[Duffster]

If I was pouring a drive for you I would pour 5" of C4 (~4500psi.) with #3 rerod 2' o.c. both directions place on 1.5" plastic chairs. I would place a second mat of bar in the corners setting on 3.5" chairs.

Fiber is a waste of money and looks like crap IMO.

 

[NC tractor driver]

Unless the steel is pre-stressed (Pulled and held in tension while the cement hardens), the only thing the steel does is keep the broken concrete sections reasonably together.

What pre-stressing does is place the concrete in compression so that when it is loaded none of it goes into tension and fails. Concrete is great in compression, but will fail under tension.

 

[luscsmith]

Thank youal very much. I just returned rom the hardware store with my wire meh and rebar, hope they start monday.

Scott

 

[Duffster]

Many years ago my steel supplier showed me a diagram in one of his engineering and steel sizing books.

It showed that if you poured a 8" x 8" x 8' column of concrete and laid it on its side supported only at its ends it would fail under its own weight.

Now that same column with 2 properly placed #4 (1/2") rerods laid on its side and supported at the ends would hold up (this is the part I don't remember, too many years ago) alot of weight point loaded at the center of the span.

So steel in concrete is everything.

 

[beppington]

Many years ago my steel supplier showed me a diagram in one of his engineering and steel sizing books.

It showed that if you poured a 8" x 8" x 8' column of concrete and laid it on its side supported only at its ends it would fail under its own weight.

Now that same column with 2 properly placed #4 (1/2") rerods laid on its side and supported at the ends would hold up (this is the part I don't remember, too many years ago) alot of weight point loaded at the center of the span.

So steel in concrete is everything.

But ... Would that 8 x 8 x 8 column survive if fiber was use in the concrete?

I doubt it, just asking. I agree with those that say use steel. I don't trust little fibers in concrete.

 

[Duffster]

But ... Would that 8 x 8 x 8 column survive if fiber was use in the concrete?

I doubt it, just asking. I agree with those that say use steel. I don't trust little fibers in concrete.

I doubt it too.

 

[Steve_Miller]

Many years ago my steel supplier showed me a diagram in one of his engineering and steel sizing books.

It showed that if you poured a 8" x 8" x 8' column of concrete and laid it on its side supported only at its ends it would fail under its own weight.

Now that same column with 2 properly placed #4 (1/2") rerods laid on its side and supported at the ends would hold up (this is the part I don't remember, too many years ago) alot of weight point loaded at the center of the span.

So steel in concrete is everything.

You are absolutely correct. We build concrete arches (up to 84' spans), bridges up to 55' span, concrete pipe up to 12' diameter and steel is everything, no steel and most of it would probably collapse from it's own weight. Fiber adds strentgth but not as much as steel but you'll be hard pressed to get any kind of finish to it as the fibers tend to stick out of the concrete like loose threads.
Home : Shaw Pipe

Steve

P.S. Image #12 on the photo gallery of the arches shows a partially finished steel grid in one of the arches.

 

[crbr]

I am having a concrete drive poured and would like to know if I can substitute rebar and/or wire with thicker higher psi concrete with fiber.

Thanks, Scott

Not with any successful expectations. Fiber is for prevention of reduction of surface shrinkage cracking. It will not substitute for much of anything in the manner of primary reinforcement. As a Civil Engineer, I have worked in concrete many years with research on this issue. Take it or leave it. Your concrete will be the proof in the pudding.

Steel in concrete is indeed the essential reinforcement. Wire mesh is a waste of money.