Cracked Concrete

I wouldn't want to be in a space under cracked concrete.

That's why I need to repair it!

Concrete cracks are contraction cracks, not expansion cracks. Poured Concrete is never larger than the day that it is placed. Why not apply a membrane such as Bituthene to the surface? It is flexible, adheres to most surfaces, and creates a waterproof membrane that is impenetrable. It can be placed in such a way as to create a flashing by simply allowing it to extend up the face of the surrounding walls and under whatever siding is in place. If the surface has to support foot traffic, then you need a tougher but similar material.

If cracks are not to wide (over 1/2 inch) a good silicone caulk should work.

oilcan13

Thank you Roy. What is the name of the resin you use?

Hi! Xperimentor

Assuming that you do not have any structural integrity issue but shrinkage cracks, try the following.

On the underside, cut a groove across the length of the crack.

Fill the groove with Nitomortar AP to seal.

On the top side, install nozzles for injection.

Use low viscosity epoxy resin Nitofil LV. Use a hose to inject resin from the gun to the installed nozzles.

You can download the data sheets for the products from the web.

You will find this very interesting.

I hope the WWF was placed on chairs and not directly on the plastic sheet. The concrete is surprisingly thin, I looked up shutterboard and it is substantial.

I would recommend covering the roof with a membrane. The concrete is thin and will probably have further cracks. If water gets down to the plastic, it must migrate to find a place from which to drip. That water, in migrating, could then caused the WWF to rust.

If it was just an ordinary roof, I wonder why the concrete, the shutterboard with a tar or membrane would have been adequate, unless there are conditions there, of which, i am unaware.

BTW, WWF = welded wire fabric.

The WWF, which I think we refer to as wire re-inforcing here, WAS placed directly on the plastic! Is that incorrect? By chairs do you mean some kind of support? I assume you don't mean table chairs. We use concrete for strength. Close to hurricane strength winds are common here.

I have done some re-thinking.

I think that the concrete is not there as a structural element, but was intended as a continuous membrane to shield against water and wind uplift. The wire reinforcing is probably what is known as "shrinkage reinforcing". When concrete cures, it shrinks and so the shrinkage reinforcing is placed to reduce or even up the shrinkage.

Reinforcing must be completely surrounded by concrete to develop the bond between the concrete and the steel to transfer the forces. Best is if it is placed on supports, but the contractors prefer to either lay the WWF down, place the concrete and then go around "lifting" the WWF to the desired depth; or place the concrete then the WWF and "walk it down" to the desired depth. This is true whether for structural or shrinkage use.

Several good epoxy crack filler/sealers have been suggested by others and these may do the trick. Then see how it goes.

There are probably good local reasons for the type of construction that I would not know about. If you want more on the concrete as a structural element, you must consult someone with local credentials.