Density Gauges: Nuclear Face-Off

Nov 02, 2010

My previous job was at a third party QC lab working with contractors and state agencies. For this trip to Jericho Rd. in Kane County 46 miles west of Chicago, I was able to bring a TransTech PQI 380 to do comparison testing along side Curran's QC. State Testing had QC technicians on both jobs running nuclear gauges.  The mix being placed was a PG58-22 9.5mm N30 with 35% FRAP. A 5 pass roller pattern was used. The N30 without Evotherm had an average density of just below 93% while the N30 with Evotherm had an average density of 94.8%.  Three different comparisons were performed on the N30 with Evotherm:

  1. A comparison between the non-nuclear PQI 380 and Troxler's 3440 taken at the same spot on the mat.
  2. A progression of density after each pass with the roller. Both times the N30 with Evotherm maxed out after five passes.
  3. A comparison of the PQ1 380 and both nuclear gauges. In Illinois the QC/QA program requires an official test every .5 miles. The test consists of five readings in a diagonal pattern starting with the first just off the edge and each one after that two feet over and two feet up. Richard Hankins with Midland Standard was QA for Kane County. 

Based on feedback from State Testing and the tests that I took, higher densities were achieved using Evotherm J1. We all know the cost savings and incentives with higher densities not only in the short term but also in the long term with longer road life. If there are any questions about these graphs or how the PQI works please feel free to ask.


Author: Rob Bach