The title is the question.
Maybe it’s the cheapest thing with the right properties, but can’t it be painted with something a little more reflective, that won’t absorbe so much heat from the sun?
In: Technology
It’s not the only one used. In addition to asphalt concrete, we also use dirt, gravel, chip seal (little bit of asphalt thrown on gravel), cement concrete, cobble stones, and paving stones.
Dirt obviously quickly deforms and get ruined in rain. Gravel is better, but still get deformed over time and loose rocks get thrown. Chip seal is a little better for the loose rocks, but still not that durable.
Cobble stones are expensive to install. Also very loud for vehicle traffic. Formed paving stones even more expensive.
So this leaves concretes as the best options. Strong, durable, flat and relatively quiet. Somewhat cheap to install. No loose stones to throw.
Of this we have cement concrete and asphalt concrete. Cement concrete (aka concrete) is aggregate (stones) glued together with Portland cement. Asphalt concrete is aggregate glued together with bitumen/ tar.
Cement concrete is strictly speaking better. It’s more durable, deforms less, longer lasting. It is however more expensive and louder (thanks to expansion cracks). It’s also not as dark, though still gets hot in the sun. You wouldn’t want a pure white surface, that would be horribly blinding. Try driving in snow on a sunny day. Not fun. You need to make cement obviously, which isnt cheap, and takes energy. A very large source of CO2 emmisions actually.
Asphalt concrete is cheaper to install. Arguably more expensive in long run. You just get bitumen from the ground, as a byproduct of oil extraction. The bitumen is also very recyclable, you just heat it and do it again. It’s also much easier to install that pouring cement concrete. The downside it is weaker. Heavy vehicles will eventually leave ruts in it. It doesn’t last as long. Contrary to the premise of your question, its actually great in hot climates. It’s cold climates that asphalt gets torn apart in. The hot surface in the sun is a minor issue, really only if people are walking bare foot or with dogs on it.
There are other concretes. Say polymer concrete. You could theoretically make a road out of this. But not going to beat the other two if you’re making a highway. Will we eventually find a better one? Maybe.
So asphalt is just the sweet spot of durability versus cost. Want more durability, cement concrete. Want less, chip seal or gravel. Want to look fancy but cost a lot and be less useful? Stonework.
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