HWD Test Procedure and Results


HWD Test Procedure

Heavy Weight Deflectometer (HWD) measurements were taken at the slab centers on the TT sections. The HWD testing was conducted with a four-drop loading sequence beginning with an approximate 12,000-lb seating load. The subsequent loads were approximately 6,000, 9,000, and 12,000 lbs. At each load level, surface deflections were measured using eight geophones positioned at: -12, 0, 12, 24, 36, 48, 60, and 72 inches, respectively. The HWD loading plate was offset from the slab center by two feet (in the South direction) to facilitate measurements on all geophones within the slab dimensions.




HWD Test Results


The P-401 AC overlay modulus values reduced from Phase I throughout Phase II. Specifically, the average P-401 modulus value from RCOD Phase I was approximately 985 ksi, whereas the RCOD Phase II pre-trafficking and post-trafficking values were 848 ksi and 389 ksi, respectively. The average modulus values for Phase III pre-trafficking were similar to those for Phase II post trafficking and can be found in Appendix F. Specifically, the pre-trafficking Phase III average modulus value was 654 ksi. This average value is most likely too high due to an outlier value of 1157 ksi calculated for the  TT4 test location. Excluding the outlier value, the analysis reduced the average modulus to 554 ksi, which is a noticeable reduction between Phase II and III. The P-401 AC overlay modulus values for the measurements taken post Phase III trafficking once again decreased, to 389 ksi. The number of cracks noticed prior to Phase III trafficking was 60, which was a 30% increase than what was documented post Phase II trafficking. The pre-trafficking reduction in stiffness may have been a result of the cracking that had occurred in the P-401 AC overlay. It also was observed that the P-154 subbase layer experienced some densification between RCOD Phase I and RCOD Phase III. This may have been a result of some preliminary compaction in this layer after exposed to traffic loading in RCOD Phase I. Regarding the other pavement layers (P-501 and Subgrade), all backcalculated modulus values were relatively similar between the different phases. It was also observed that the subgrade modulus values appeared greater than expected.










HWD File Downloads

HWD Test Date

File Download

March 2, 2022

Zip File

March 19, 2022

Zip File


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