How Roads Are Built

Roads are much more than what you see on the surface. There’s a lot going on underneath the few inches of asphalt that we drive on every day.  Before you can even begin to paving a road, about six months of prep work needs to be done.  This includes initial planning, design, soil testing and any road prep work the existing road may need like crack sealing, grinding, potholing, etc…   
Roads are built up on several layers consisting of subgrade, aggregate base and asphalt layer.  The thickness of each of these layers will vary depending on existing condition of the subgrade, the amount of traffic and weight load that is anticipated, and more.  Learn more about what these various layers consist of and what role each play in building a good road.  
Subgrade – the natural ground, graded and compacted, on which pavement is built. In some instances if subgrade is very poor, cement, lime or better soils are mixed in to improve the subgrade. 
Aggregate Base – Since subgrade soils may be soft and unstable, an aggregate base often helps ensure the stability of the pavement surface. The base is made up of various rocks and minerals compacted to ensure the stability of the pavement surface above. Although the aggregate base may be hidden from sight, it remains a critical part of the pavement structure.
Asphalt – The uppermost part of the road that comes in contact with your car’s tires is made of asphalt. Asphalt is a mixture of crushed rock, sand, and gravel combined with a binder which holds together the various aggregates.  Asphalt not only creates a smooth driving surface but also helps prevents the entrance of water into the sub layers beneath the road.