Lean concrete base is used under the foundations to provide a level surface, where main foundation (raft, isolated or any other type) can be placed. Lean concrete base is an example of rigid pavement. Rigid pavements are typically constructed using a portland cement bound surface layer over one or more support layers over a prepared natural earth subgrade. The bound layers may be conventional dense-graded asphalt, lean concrete, or cement-treated; or opengraded asphalt or concrete designed to promote lateral drainage within the pavement structure.