Volume 35, Issue 6 (November 2012)
An Assessment of Resilient Modulus Testing: Internal and External Deflection Measurements
The long-term pavement performance (LTPP) resilient modulus test protocol specifies the use of external linear variable differential transformers (LVDTs) to measure the material’s response, whereas the Mechanistic-Empirical Pavement Design Guide (MEPDG) requires input for resilient modulus based on the test results using internal LVDTs. Given this discrepancy of data, the relationship between resilient modulus determined from internal and external measurements was studied for a variety of materials using the NCHRP Project 1- 37A resilient modulus test protocol and recording deformation data both with internal and external LVDTs. Resilient moduli determined from internal deformation measurements shows to be higher than those from external measurements, whereas the ratio of external to internal resilient modulus decreases with increasing internal resilient modulus because of an increasing effect of machine compliance as specimens become stiffer. Furthermore, the relationship between internal and external resilient modulus depends on the material type.