Rebar, Wire Mesh and Fiber: What a Slab Actually Needs

Summary:

Cesar explains what reinforcement does and, just as importantly, what it doesn't do. ACR uses rebar in its work and fiber in the concrete mix, but he is direct that reinforcement does not prevent cracking. Concrete moves, and it will crack. What reinforcement does is hold the slab together through that movement, keeping any crack tight and the two sides level with each other rather than separating and lifting. That is the difference between a hairline a homeowner barely notices and a genuine problem. He also emphasizes placement: rebar lying flat on the ground at the bottom of a pour contributes very little, because it needs to sit up within the slab to work. Homeowners cannot verify this after the pour.

Answer:

Reinforcement is what holds the slab together, and we put it in. On our work we use rebar, and we use fiber in the concrete. What people misunderstand is what it's actually for. Reinforcement doesn't mean your concrete will never crack. Concrete moves, and it's going to do what it's going to do. What reinforcement does is hold everything together when it moves, so if something does open up, it stays tight and the two sides stay level with each other instead of separating and one side lifting. That's the difference between a hairline you barely notice and a real problem you have to fix. What matters just as much is where it sits. If rebar is laying flat on the dirt at the bottom of the pour, it's not doing much for you at all. It needs to be up in the slab where it can actually work. That's a thing you can't check after the concrete is down, which is why I tell people to ask about it before.