2-3 years ago I saw a system on A Bob Vila show wherein tension cables were embedded in a concrete slab to strengthen it and prevent breaking/cracking on un-stable ground. I really need to track down this system to re-pour the slab under my house. Can anyone please tell me whay the system is,and more important how to find the manufacturer/dealer to get info on it.
Thanks In advance ... Gary

Concrete works quite well in compression, holding up a load directly above it, but by itself it doesn't work well at all in tension, the forces exerted by bending and pulling. In order to make a slab that could span a certain distance without the normal "frame" designed into it on the bottom side, engineers came up with the idea of embedding steel cables in conduit in slabs to compensate.

Basically, the cables and conduit are formed in the concrete slab as if they're held at both ends, with the middle part hanging in a curve as gravity would form it, but all parts are within the limits of the slab. As the slab cures, one end of each cable is anchored in the slab, and the other end is pulled (in tension) by a machine made specially for the purpose. Engineers calculate the necessary tension under which the cables need to be stretched before the pulling end is also anchored. The theory is that the upward forces provided in the slab by the curved cables, now stretched under tension, will counteract the downward forces of gravity and the weight of the concrete when the slab is installed with supports only on the ends, and not under the entire slab...like a bridge.

Thanks for your explanation. Do you happen to know who makes/distributes the equipment and cables for this system ?

Sorry, I've never had the need to look for a contractor who could do that, or a establishment that could provide the equipment. But if I had the need, I might start by calling the closest ready-mix concrete company. They might not have the know-how, but they might be able to give you a lead.

michealholigan.com
They built a huge house and used this design for the slab. There may be info on that site.