Illinois interstates, especially the ones in and around Chicago, are some of the most heavily traveled in the country. The pavement on these interstates will experience over an estimated 100 million equivalent single-axle loads (ESALS) over a 20-year design life. Now, the Illinois Department of Transportation (IDOT) has its sights set on extended-life concrete pavement with a design life of 30 to 40 years.

IDOT routinely uses continuously reinforced concrete pavement (CRCP) as its preferred interstate pavement type. CRCP is, simply, concrete pavement that is reinforced with longitudinal steel reinforcing bars over the entire pavement length. No transverse joints are required. The reinforcing steel controls the width of transverse cracks and keeps them tightly closed. Transverse cracks form due to material and environmental factors, and do not impair the structural integrity of the pavement.

The CRCP on many heavily traveled interstates in Illinois has exceeded its original 20-year design life with little or no damage. Because of this success with CRCP, IDOT believes that designing and constructing with more stringent material and construction specifications will ensure that a substantially longer design life can be achieved.

An accelerated testing program, primarily funded by IDOT and conducted by the University of Illinois at Champaign-Urbana, is being undertaken to develop an optimized CRCP design that can withstand heavy loading throughout its extended design life. The objectives of the accelerated testing program are to determine:

  • The required design steel content percentage to achieve the desired crack width and spacing
  • The required slab thickness of the pavement section
  • The ideal depth of steel from the pavement surface
  • The effect of uniformly induced crack spacing on performance
  • The necessity of using two layers of reinforcing steel

This photo gallery shows the test pavement construction and instrumentation, and the mechanical testing device that will perform the accelerated testing. Please visit this site again for updates about the testing program and results of the study!
  Test Pavement Construction >>