What is the purpose of paving bituminous surfacing over concrete structures?

The use of bituminous surfacing over concrete structures (e.g. existing concrete roads) is widespread to improve the skid-resistance and the general appearance of roads on one hand, and to avoid the pre-mature
failure of concrete surface by frost spalling in cold countries on the other hand.

In designing the bituminous surfacing over concrete, there are several areas to which engineers should pay attention. Firstly, the laying of thin bituminous material over the joints or existing cracks of concrete structure would lead to reflective cracking because the thermal movement of concrete induces swift formation of cracks in bituminous surfacing. Past research demonstrated that with the adoption of minimum thickness of 100mm bituminous surfacing the occurrence of reflective cracks would be delayed when compared with the use of thinner surfacing. Secondly, sufficient adhesion between concrete and bituminous surfacing has to be achieved. Therefore, it is recommended to apply a layer of tack coat on the concrete surface to promote bonding.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.