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RE: Granular Layer over Vapor Retarder[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Granular Layer over Vapor Retarder
- From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
- Date: Mon, 21 Feb 2005 17:22:19 -0500
- Cc: "Hoskins, Kevin" <HoskinsKM(--nospam--at)cdm.com>, "Shah, Chandrakant" <ShahCA(--nospam--at)cdm.com>
Gail, I agree with you in that the ACI 302 recommendations do not provide adequate information on gradations and enforceable specifications for fill to be placed above vapor retarders. I have been considering the use of "aggregate base course" material of the type typically used by DOT's for base course below pavements. This material is generally readily compactable and is well graded.
Based on a review of various DOT specifications for "aggregate base course", I have developed a proposed gradation specification below; however, the ranges for each sieve size have been adjusted to accommodate a range of gradations from various specifications, so this does not match any "single" DOT gradation. The intent is to have a well graded granular material that easily compacts. The maximum size is based on my own preference. Following is the proposed wording:
"A 4-in layer of readily compactable, well-graded, crushed rock or crushed gravel shall be placed over the vapor barrier before setting reinforcing steel for the concrete placement. The crushed rock or crushed gravel, combined with fine aggregates as needed, shall conform to the following gradations:
Sieve Designation Percent Passing (by weight)
No. 4 30-70
No. 8 (or No. 10) 20-70
No. 40 10-50
No. 200 3-15
The liquid limit of the material passing the No. 40 sieve shall not exceed 30 and the plasticity index shall not exceed 6."
I would like to get some feedback on this proposed gradation.
William C. Sherman, PE
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