SUPERPAVE Digest 448
Topics covered in this issue include:
1) RAP Use
by Chris Lange <>
2) Re: RAP Use
by "R. Irving" <>
- To: Superpave Group <
- Subject: RAP Use
- From: Chris Lange <
- Date: Mon, 26 Feb 2001 12:51:48 +0200
Good Day All,
RAP Use In HMA
Much Asphalt (Pty) Ltd is a major manufacturer of HMA in the Southern Africa region. I read an article "RAP Research Wraps Up" by Rebecca S. McDaniel in the NCSC News brief (vol2, number3 - Fall 2000 Page 6). The research being carried out is extremely interesting. Perhaps there are people out there that could assist us with the situation documented below:
We have approx. 150 000 tonnes of RAP on one stockpile. The material in this
stockpile were accumulated over 20 years. It consists of approx. 10
different mixes (gradings) and about 5 different grades of binder - 40/50
pen, 60/70 pen, 80/100 pen, bitumen rubber and latex modified binder.
Currently we hire a dozer to rip the material up, and add it through a
special RAP Addition system at the Astec plant. We add a max. of 15% RAP to
virgin material.
The problems we experience are as follows:
1. High Marshall Stability - approx. 5-7 kN higher than normal.
2. Difficulty in processing the RAP - big lumps of material causing
blockages etc.
3. Variability of mix grading
I am particularly interested in the experiences with RAP in conventional
mixes, as well as those with bitumen rubber mixes, as well as the processing
procedure of the RAP.
We would appreciate any assistance that you may be able to offer.
Looking forward to hearing from you shortly.
Chris Lange
Tel ++ 27 (0) 41 364 1116
Cell ++ 27 (0) 82 775 2750
Fax ++ 27 (0) 41 364 1584
Much Asphalt (Pty) Ltd
PO Box 10065
Linton Grange
6015
Port Elizabeth
South Africa
- To: <
- Subject: Re: RAP Use
- From: "R. Irving" <
- Date: Mon, 26 Feb 2001 13:18:07 -0600
To: Chris Lange
Here in Louisiana we are allowed to use up to 20% RAP in our binder course mixes only we run our through an astec plant also. We are required to scalp over a 2" screen so we use a lump breaker that is in line on the RAP system to break any lumps over 2" in dia. I don't know why you are getting such a big jump in Marshall stability in Marshall mixes, I have experienced a small rise in Marshall stability but not as you have maybe it is due to the different mixes and AC's in your stock pile, Here we are required to keep our RAP piles from different sources separate and do a separate mix design when ever we change RAP sources. That would probably account for your variability of mix grading. I don't know if this has helped or not. If you wish to discuss it more contact me at and I will be happy to talk with you about it or send you any inf. I have on RAP use here.
Thanks
Robert Irving
Coastal Asphalt LLC
SUPERPAVE Digest 449
Topics covered in this issue include:
1) Re: RAP Use
by "Ervin Dukatz" <>
- To: <
- Subject: Re: RAP Use
- From: "Ervin Dukatz" <
- Date: Tue, 27 Feb 2001 08:29:14 -0600
I would suggest after getting the RAP out of the pile that it be crushed to at least 100% passing the 2 in (50 mm) size. We have found that a jaw or horizonal impact crucher works well fro crushing the RAP. Then if you are still having gradation problems, screen the RAP into plus and minus 3/4 in. (19MM) sizes.
The aged and RAP with modified binders will stiffen the mixes. If this is a concern as it appears to be from your question, extract the binder from the mix and test it. If the RAP binder is as stiff as it appears to be from your description you may need to use a softer grade of asphalt in your RAP mixes. I would suggest using the SHRP binder tests to grade the recovered binder.
Erv Dukatz
Mathy Construction/MTE