Why do some roads use asphalt under concrete pavement?

[Jayne_Monie]

I've noticed that many highway projects now use a layer of hot mix asphalt before pouring concrete, and sometimes another layer of asphalt is added on top later.

 

[randdyarroyo]

The asphalt layer acts as a smooth, stable base for the concrete. It helps create uniform support, improves drainage, and reduces the risk of cracks caused by uneven settlement. If the concrete eventually wears out, adding a new asphalt overlay is often faster and less expensive than replacing the entire pavement.

 

[Theoeni1]

It's actually a smart design. The asphalt underneath acts as a smooth, flexible base that improves drainage, reduces stress on the concrete, and helps prevent cracking. If the concrete eventually wears out, adding a new asphalt overlay is often faster and more cost-effective than replacing the entire concrete slab. Pretty neat engineering!