We have seen plastic roads, and we have seen roads made out of steel fibers and bacteria; so why not try and use rubber as a road construction material? Surely it would be cheaper and less catastrophic in case of an accident!
The idea might sound enticing, but it breaks down if you take factors like friction, abrasion, brittleness and thermal expansion into account.
Starting with friction, since both tires and the road will be made out of rubber, there would be an extreme amount of friction as the coefficient of friction for rubber on rubber is 1.16. This would make movement nearly impossible, consuming a whole lot fuel and at a lot lesser speeds. Making tires out of cement or ceramic would be difficult too due to machining constraints, and the brittleness of the material, meaning the cars in The Flintstones are probably only feasible in the cartoons.
Pic Credits: newsworks
Now coming to the feasibility of the roads itself, since they are made out of rubber, they would abrade quickly due to rubber’s poor abrasion and wear resistance. This would lead to higher maintenance costs and frequent relaying of roads. High abrasion rates would also pose safety issues, like the prospect of hardened rubber chunks flying after breaking off and leaving massive Moon’s craters.
Rubber has a high thermal coefficient of expansion which means it will expand at elevated temperatures. This would render the road useless in high temperatures, and would also cause cracking and creation of discontinuities with inhomogeneous thickness.
The converse would also be troublesome; a very low temperature would make the polymer extremely brittle and highly prone to cracking and falling part.
Rubber is also not hydrophobic, neither does it have a lattice structure that can allow seeping in of water in its voids and pores. This would lead to water drainage issues after a shower and extremely slippery surfaces due to the ever present layer of moisture on the roads.
Finally, rubber has a relatively poor strength and moduli meaning it can withstand only limited loads. This is why every vehicle needs customized rubber tires and making a one fit all rubber road for everyone would mean exuberant costs and highly redundant use of the material.
So that is why we do not make roads out of rubber. Can you think of any other reasons? Let us know in the comments section.
