Question

Would a sub-base layer be served as a drainage layer to take away water from pavement?

Answer

As well providing load distribution in post-construction stage and working platform in building stage, sub-base can as well serve as the drainage layer to get rid of water coming from the pavement. For broad layers of road pavement, it is as that water leakage from pavement is not important and therefore sub-base layer chiefly serves to support traffic stresses. Still, for thin pavement layers, water penetration is quite significant and as a result sub-base might also act as drainage layer to eliminate this water.