Concrete and steel expand to almost the same amount when they are heated. Explain why you think this is lucky?

While making a bridge or a building, the first thing that comes to our mind is that these are always made by the combination of concrete and steel. Concrete is cheap, but it has the property of breaking when it is twisted or under tension. Steel is expensive, If we made the whole thing with it, it will cost a lot. To provide strength under a reasonable cost, we use the combination of concrete and steel. Another postive point which they have together is that they both expand equally under heat, because they have the same coefficient of thermal expansion. It proves really useful, because if they had different coefficients of thermal expansions, one would expand more than the other, which will create tensions in the mixture and would break it easily. In the case, many cracks would start to appear in the bridge or buildings, which will eventually break them.

it's a b and