Rigid versus Flexible Pavement Design

Generally when discussing the topic of pavement there are two main categories to consider, rigid and flexible. As with most things in engineering there are pros and cons to each of these types and one may be selected over another depending on the specific needs of a project. Some main points to consider when weighing the two types are:

Rigid pavements are typically distribute wheel loads over a wide area of the subgrade as shown on the left side of the exhibit below and consists generally of cement concrete and may be reinforced with steel. Other rigid pavement characteristics include:

  • Design life typically 30+ years
  • Equivalent unit cost approximately $6 – $8 per SF
  • Lower maintenance costs
  • High flexural strength
  • Strength of road less dependent on strength of sub-grade
  • Low ability to expand and contract with temperature and therefore need expansion joints
  • High ability to bridge imperfections in sub-grade

Flexible pavements typically distribute wheel loads to lower layers of the pavement section as shown on the right side of the exhibit below and consists generally of bituminous material. Other flexible pavement characteristics include:

  • Design life typically 10 – 20 years
  • Equivalent unit cost approximately $2 – $3 per SF
  • Costs tied closely to price of oil
  • Higher maintenance costs
  • Low flexural strength
  • Strength of road highly dependent on strength of sub-grade
  • High ability to expand and contract with temperature and therefore do not need expansion joints
  • Low ability to bridge imperfections in sub-grade