why does rebar and remesh make concrete so much stronger?
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Concrete is very strong in compression – when it’s squeezed.
It is very weak in tension – when you try to use it to pull.
The rebar or mesh carries most or all of the load when the structure demands that the material used have some tensile strength.
Different designs can mean that the rebar may put a large amount of compression on the structure by itself, squeezing it together, if it is properly designed. This can make the whole structure very strong.
Concrete by it self is very strong when it’s compressed. Look at old Roman structures, the design of the buildings and the large amount of concrete made it so that the material it self only had to worry about compression. The weakness of concrete is its sheer factor. Basically when it gets pulled it starts to crumble. This is where rebar comes in. Steel and other metals have incredibly good sheer capacity but tend to be weaker with compression. This is why we put rebar/remesh in concrete so that they can work together to handle compression forces and sheer forces.
If you are curious on a more in-depth and easy to follow video practical engineering did an incredible video describing the in and outs of concrete.
Concrete by itself is incredibly strong under compression but very weak under tension. The addition of steel reinforcement adds this tensile strength, making it perfect for building applications.
Rebar and remesh make concrete stronger because they are made of steel, which is strong in both compression and tension. Concrete is strong in compression but weak in tension, so rebar and remesh help to distribute the load evenly and prevent the concrete from cracking.
Concrete does great supporting heavy things but no good at keeping things from pulling apart. Rebar won’t stretch and crumble like concrete so the two work well together making it great at building stuff.
It’s the skeleton of the concrete. Imagine how much less good your body would be without a skeleton.
It changes the failure of concrete from brittle to ductile failure. Something people miss in their explanations about tensile strength is that the component materials still have their individual qualities in their finished product. It does not average into an amalgam that has both qualities. This is to say that if you have two blocks made of the same concrete and one has rebar they will still crack at the same load (barring rebar at certain tensile rigidity ratios compared to the concrete). The difference is that once the concrete cracks the rebar kicks in and now the cracks form slowly. This is an important thing in engineering because a common saying is
>It’s not about if it will fail but when
And having failures occur slowly over time rather than all at once is valuable.
Worth noting too even in a simply driveway slab where there is no tensile (pulling apart) forces, you still need reinforcing. This is because concrete shrinks just a tiny bit as it sets. This causes uneven tensile stresses across the slab, even in a flat on ground slab. So the steel mesh is used to prevent or at least control the cracking
Second part of this is the jointing you see in most larger slabs. There is a limit to how much stess the reinforcement can manage, so engineers leave deliberate weak points in the slab so the concrete can crack in a controlled location, hidden out of sight. The stronger the reinforcing you use, the fewer joints are needed. If you don’t want to use reo, then just make the joints very close together (like every metre or 3′).
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