Q: What can be done to make concrete pavements give a smooth ride for a longer time?

A: The best insurance is to provide a uniformly stable foundation. Based on field studies sponsored by the American Concrete Paving Association, Phil Fordyce, an Engineering Consultant, has prepared a list of procedures to provide uniformly stable foundations:

Excavate clay cuts as soon as possible.

  • Utilize selective grading and cross hauling to get the most unstable, expansive soils into the bottom of fills or along fill slopes and the more stable soils in the upper part of the subgrade in both cuts and fills.
  • Compact subgrades at controlled moisture contents. For embankments more than six or eight feet high moisture contents slightly lower than the AASHO T99 optimum may be permitted, but it is still essential to compact the upper 2 1/2 to four feet of all subgrades to slightly more than T99 optimum.

Mr. Fordyce describes these methods for getting reasonably uniform, stable subgrades as being an economic bargain.