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Re: Granular Layer over Vapor Retarder

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Rick,

You brought out an important aspect of design process:
material availability. Thanks.

Rajendran

--- Rick Stone <rstone(--nospam--at)madisonconcrete.com> wrote:

> 
> Gail knows how I feel about putting anything over a
> sheet material---it is a
> pain in the butt, expensive because it is labor
> intensive, etc.
> 
> But anyway---when you specify a gradation, I suggest
> you look carefully at
> what is available in the market where the project is
> located; many quarries
> run only what they have demand for every day, and
> when you ask them for
> something different, the answer is either:
> 	No. We do well enough with our bread and butter
> runs, we don't want
> to reset our screens.
> 	Yeah, we have something like that, but only about
> 235 tons. You said
> you needed 1200 tons? Oh, well, sorry. We got that
> gradation once by
> accident when some screens jammed. It's been in a
> pile in the back for 5
> years; glad to get rid of it. Too bad we only have
> one fifth of what you
> need. Any more? No. (see above)
> 	Well, we could re-set our screens for that, but
> you'll have to wait
> about 6 months because we are trying to stay up with
> our orders for #57, #8,
> etc.
> 	
> We recently saw a specification for a layer using
> NJDOT I-3 material. It is
> a material set at 60-100 at 3/4 in sieve, 30-100 at
> No. 4, 5-35 at No. 50,
> 0-8 at No. 200. Sort of like masonry sand only a
> little more coarse. And, of
> course it was completely unavailable from any quarry
> in a 100 mile radius of
> the site. 
> 
> The A/E was very confused; they had developed the
> specification based on
> recommendations of the Geotechnical Engineer. (As an
> aside, the A/E was from
> Chicago, the GE was from Michigan, and they admitted
> that they knew nothing
> of the availability of materials for the local
> market, they looked at the
> NJDOT manual and found something they thought looked
> pretty good so they
> specified it. NJDot basically says that they have
> gradations that they think
> are good ideas but that particular gradation was
> "not one in  popular use"
> as the district engineer we contacted could not
> recall ever seeing it used
> on roadway or storm projects)
> 
> Yes, it was available, but not within the time frame
> that the project
> required (the 2 quarries that were willing to run it
> had specifiec windows
> when they would consider doing it, related to
> re-setting their screen
> sets)and both were more than 100 miles away; and the
> cost was 4x that of  a
> more available material on top of the trucking
> costs.
> 
> We suggested a PaDOT 2A layer (100 at 2in, 52-100 at
> 3/4, 36-70 at 3/8,
> 24-50 at No.4, 10-30 at No. 16, 0-10 at No. 200)from
> a quarry 32 miles
> distant.
> And it was accepted. We gave back a negotiated
> credit of a couple of bucks a
> ton.
> 
> So---check your desired gradation with local
> suppliers, and if it is an
> unusual one, manage the expectations of your client
> (Architect, Owner,
> GC/CM) that there is a premium involved.
> 
> By the way, the same thing applies to special
> gradations for aggregate for
> concrete. Quarries think as described above, and
> plants often only have
> limited silos or bins, so "custom" aggregate runs,
> while possible, are
> difficult. We have been told point-blank that it is
> not worth their while to
> empty their bins of "standard" (say, #57)aggregate
> to re-fill with a custom
> blend when they make out fine with profits from
> their everyday 3,4,and 5 ksi
> mixes. It is just not worth it to them.
> 
> 
> 
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