SUPERPAVE Digest 232
Topics covered in this issue include:
3) Compaction
by
5) Re: Compaction
by "ERVIN DUKATZ" <>
6) Re: Compaction
by "Kenneth Hobson" <>
7) Re: Compaction
by "Kenneth Hobson" <>
· To:
· Subject: Compaction
· From:
· Date: Wed, 25 Aug 1999 19:15:50 EDT
We are currently supplying a Dot project with both 19mm & 12.5mm mixes. The
best compaction the Dot can record in the field is mid 80's, but core results
come in at 91,92 (borderline). I wasn't involved with the design process,
but have my own ideas as to why the contractor cannot achieve compaction. 1.
too much natural sand. 2. over asphated appearence due to high M/F acting as
an asphalt extender. Am I wrong in my thinking that even a bad mix can be
compacted in the confines of the gyrotory compactor? Lab figures are on the
money. Also the rolling pattern seems to be all over the place.
· To: <>
· Subject: Re: Compaction
· From: "ERVIN DUKATZ" <>
· Date: Wed, 25 Aug 1999 18:37:26 -0500
yes, you can get passing densities in the gyratory compactor on a "poor" mix. For a test, compact the mix at placement thickness and see what happens to the voids. Also, check the slope on your compaction curve. High rates of compaction are usually bad news. Also.check Nint on the product samples.
· To: <>
· Subject: Re: Compaction
· From: "Kenneth Hobson" <>
· Date: Wed, 25 Aug 1999 19:06:22 -0600
> We are currently supplying a Dot project with both 19mm & 12.5mm mixes.
The
> best compaction the Dot can record in the field is mid 80's, but core
results
> come in at 91,92 (boarderline). I wasn't involved with the design process,
> but have my own ideas as to why the contractor cannot achieve compaction.
1.
> too much natural sand. 2. over asphated appearence due to high M/F acting
as
> an asphalt extender.
How are you getting the field densities? Was a trial mix done? Was a test
strip done? What weather conditions existed at the time? What were the mix
temperatures at mixing, delivery and compaction. Were "enough" rollers
available at the site? What was the experience level of the laydown crew?
Was a MTV used? What was the DP ratio? If you plotted the field gradations
on the 0.45 power chart how did it compare to the mix design. What kind of
rollers were used? Was a tenderness phenomenon experienced? Was
segregation a problem? What speed was the roller operating? What frequency
was the vibratory roller using? Was a rice's test run to verify Gse? Maybe
an aggregate source changed at the quarry.
Am I wrong in my thinking that even a bad mix can be
> compacted in the confines of the gyrotory compactor? Lab figures are on
the
> money. Also the rolling pattern seems to be all over the place.
Exceptions in the field include: Poor Subgrade, Temperature problems,
inproper laydown techniques, moisture in the aggregate, slippage caused by
insufficient lift/layer bonding, marginal mix design, and inproper lift
thickness just to name a few. I think rolling patterns pretty well tell you
the story. Unless the Nini, Ndes and Nmax were changed I don't think lab
molds are the problem.
If your lab molds are coming out ok I would say something is happening
between plant production and laydown. Where it happens is the big question.
If your cores absorb too much water, are you using the parafin method to
obtain densities?
Kenneth Hobson
Bituminous Branch Manager
Oklahoma DOT
SUPERPAVE Digest 233
Topics covered in this issue include:
2) Re: Compaction
by
· To:
· Subject: Re: Compaction
· From:
· Date: Thu, 26 Aug 1999 14:19:36 EDT
Your comment about making assumptions seems to make sense about a whole lot
of things involved with Superpave besides a compaction slope...