Concrete Mixture

Overlay mix designs are typically similar to conventional paving mixes. There are, however, a few unique considerations that may require a special mix design.

• Thin concrete overlay designs may call for the incorporation of fibers into the overlay paving The use of fibers is accommodated by both the ACPA and BCOA-ME methods for the design of thin bonded overlays of asphalt or composite pavements.
• For bonded concrete overlays of existing concrete pavements, the use of a concrete mix with similar thermal properties as the existing pavement is recommended to minimize the shear stress at the new and old concrete interface.
  
  

Since thin overlays are often used as rapid rehabilitation solutions, narrow time-to-opening windows may require the use of special concrete mix designs. In this case, the agency should prescribe a mix design for the overlay that provides the needed strength (or other performance measures) at a specified time.