The next stage in the evolution of building with concrete is also a wonderful innovation. “pre-stressed” concrete is another solution to the problem that concrete is stronger in compression than in tension. To make pre-stressed concrete, you start by laying out the rebar in sections where you will pour the concrete with the ends of the rebar sticking out. Then, just before pouring the concrete, you put the re-bar under tension, pulling it from the ends. After the concrete sets hard, you release the tension. the re-bar pulls the concrete, putting the entire slab under compression. Then when you use it to bridge over a gap, any resulting tension is partly mitigated by the pre-existing squeeze.
The next stage in the evolution of building with concrete is also a wonderful innovation. “pre-stressed” concrete is another solution to the problem that concrete is stronger in compression than in tension. To make pre-stressed concrete, you start by laying out the rebar in sections where you will pour the concrete with the ends of the rebar sticking out. Then, just before pouring the concrete, you put the re-bar under tension, pulling it from the ends. After the concrete sets hard, you release the tension. the re-bar pulls the concrete, putting the entire slab under compression. Then when you use it to bridge over a gap, any resulting tension is partly mitigated by the pre-existing squeeze.