Nebraska LTAP


Date of this Version


Document Type



Bruce Barrett, B., Troxel, K., Dresselhaus, B., and Hansen, D. (2021). Measuring Foundation Course Modulus Using Falling Weight Deflectometer, Light Weight Deflectometer, and Dynamic Cone Penetration. NDOT Research Report.


Phase I results showed that FWD, LWD, and DCP provided valid results and trended with each other at the stations all three tests were run. This gives confidence that any test method is reliable when used on an exposed bituminous foundation course.

The results of Phase I and Phase II indicate that using FWD testing after concrete is built does not provide an accurate modulus of the foundation course. As demonstrated through the statistical analysis, foundation course moduli cannot be reliably calculated by using FWD on top of doweled concrete pavements and back-calculated using Darwin software or ME Design. Additionally, the COV Phase I data reveals a significantly larger variance than Phase II across the test area proving that uniformity of the foundation course cannot be determined by FWD testing after the concrete pavement is placed.

DCP showed an approximate 50% reduction in the penetration of the foundation course when constrained by concrete in place. However, only a limited number of tests using DCP after the pavement was placed were conducted and therefore no conclusion can be drawn at this time.