Q. Illustrate Bituminous surfacing over concrete structures?
Usage of bituminous surfacing over concrete structures (for instance existing concrete roads) is widespread to improve the skid-resistance and general appearance of roads on one hand and to avoid the pre-mature failure of concrete surface by frost spalling in cold countries instead.
In designing the bituminous surfacing over concrete, there are numerous areas to which engineers must pay attention. Firstly laying of thin bituminous material over the joints or existing cracks of concrete structure will cause reflective cracking because the thermal movement of concrete persuades swift formation of cracks in bituminous surfacing. Past research confirmed that with the adoption of minimum thickness of 100mm bituminous surfacing the occurrence of reflective cracks would be delayed when compared with the usage of thinner surfacing. Secondly sufficient adhesion amid concrete and bituminous surfacing has to be achieved. So it's suggested to apply a layer of tack coat on the concrete surface to promotebonding.