Improving Resilient Modulus (MR) Test Procedures for Unbound Materials

The Mechanistic-Empirical Pavement Design Guide requires that the resilient modulus of the subgrade be used to design the pavement thickness for both asphalt concrete and portland cement concrete(PCC) concrete pavements. Due to the complexity of the test, test results have been inconsistent. For example, data to date has shown that: (a) Two different laboratories testing split samples of the same soil or aggregate layer get widely different results. (b) Two technicians on the same equipment would also get widely different results. (c) Repeated tests on the same sample by one technician on the same equipment would not always produce consistent results. The resilient modulus of a soil or unbound aggregate material is the recoverable stress/strain relationship of the soil. The greater the resilient modulus of the soils is, the "stiffer" the soil will be, and the greater the strength will be for supporting transmitted wheel loads. This parameter is considered to be the best indicator of a subgrade's strength since the test replicates the dynamics of moving wheel loads. This pooled fund study has three primary goals to: (1) reduce the variability currently associated with resilient modulus testing of unbound materials; (2) conduct a precision and bias study of the test procedure; and (3) provide assistance to states to properly equip and setup a laboratory for successful resilient modulus (MR) testing.

Language

  • English

Project

Subject/Index Terms

Filing Info

  • Accession Number: 01495907
  • Record Type: Research project
  • Source Agency: Federal Highway Administration
  • Contract Numbers: TPF-5(177)
  • Files: RiP, USDOT
  • Created Date: Oct 22 2013 1:02AM