Q&A from Asphalt in Depth’s WMA session

Jun 13, 2011

I’ve listed a few of the questions asked during the Q&A session that I thought were interesting.

Q1. Any problems with over compaction?
A1: If so, I wouldn’t contribute it to WMA.

Q2: Any problems with PG 76-22?
A2: Mike Law had no problems using Evotherm with PG 76-22. It was the best WMA job they had.

Q3: Is there a need or benefit to adding lime or LAS?
A3: Brad said he thought it was dependent on the aggregate and not the WMA. Mike Law said he had to add LAS because they had a 5-6% drop in TSR between design and field TSRs using Foam.

Q4: What type of additional equipment is needed for foaming?
A4: Matt Corrigan did not know many manufacturers that made lab foamers. He did mention Wirtgen.  He said that the foaming manufacturers need to work on getting better equipment available because right now it is kind of limited. Additional laboratory testing equipment is not needed with Evotherm technology.

Q5: Are there issues with blending of RAS in WMA?
A5: Matt Corrigan says that there could be some issues with blending of RAS since the binder is so oxidized and that we need to spend some more time researching that area. Brad Bradford said that it is being successfully done now, but those contractors are not pushing the envelope on dropping the temperature.

Q6: Can you run HMA in a plant set up for foam and if so, is it still WMA?
A6: Brad has seen some tender mixes foaming at 325.  It can still be used as a compaction aid if run between 290-300.

Q7: How do you determine the right amount of water to add to your mix?
A7: (This actually stumped all four of them for a second) Matt Corrigan said that the manufacturer typically has guidelines of water to add based on the temperature to use, although he has never seen any foaming jobs under 270-275 with out seeing problems.

Author: Jenna Michael