Components of road structure:
1: sub – Grade
2: Sub – Base
3: Base Course
4: Binder Course
Sub-grade is the the natural surface of the road, which is very important for road and this is lowest layer of the road.
Sub Grade construction:
this is the natural surface of the soil. therefore if the bearing capacity of soil is good so we have should not do any change in sub grade. but if the bearing capacity of soil is low than we have to up the sub grade level up to 60 cm (2ft) from the flood level. and we have to used the cheap materials in the sub grade just for making surface if the bearing capacity is good.
Sub Base :
Sub base is the one of the main load bearing layer of the road. which role is to spread the total load of the sub base to sub grade. and this is also the important layer of the road. And we have to used the good quality of materials in the sub base. because when the sub base is not good so the road will be not work for long time.
construction Sub Base:
The sub base can constructed above the sub grade. and the thickness of the sub base should be from 3 inch to 6 inch or 7.5cm to 15cm.
the base course the pavements layer of material in asphalt road. and this layer in between the sub base and binder course. when the sub base designed than we directly construct the base course on above this.
Construction of Base Course
we have to use the strong materials in this layer of the road. and the bottom layer essentially comprises of unbound mixture from course and fin aggregate , and also used to crush sand, to get the desire load bearing capacity and absorb the upcoming traffic load.and we have to use the good quality of materials in the base course construction.
Binder Course :
in road structure the binder course are the different combination of aggregate and binders. and the binder course is layer which bind all the materials in road structure. which are present in the base course , sub base and sub grade. in binder course we can bind the materials with asphalt (bitumen). and binder course is suitable for a wide range of of used from heavy duty of road pavement to car parks and also for race road etc.
Surfacing is the waterproof layer of road, which protect the underlying pavement. and also increase the skid resistance of road. the surfacing prevent the road from the cracks . and its anti- glare surface during the wet weather and surfacing can increase the reflexive surface for the night driving.