Optimum binder material in bituminous pavement
The amount of binder to be added to the bituminous mixture cannot be too much or too little. The principle of designing the optimum amount of binder material is to incorporate a sufficient amount of binder so that the aggregate is completely coated with bitumen and the spaces within the bituminous material are sealed. As such, the durability of bituminous pavement can be increased by the impermeability achieved. In addition, a minimum amount of binder is required to prevent the aggregate from being pulled out by the frictional actions of vehicles plying on the carriageway.
However, the binder content cannot be too high as this will result in instability of the bituminous pavement. In short, the incorporation of excessive binder material reduces the resistance of bituminous pavement to deformation under traffic load.