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Re: Slab on Grade and the Green Code

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Hello Chuck,

Can you explain the problems created by use of sand?

Also I would like to better understand what a Class II base
gradation spec looks like.  Is this a typical subbase course
under a roadway, or is it a typical base course under a
roadway, to is this a base for concrete pipe trench installations?

Thank you,

On 5 Dec 2013 at 8:39, Chuck Utzman wrote:

> Oshin
> My standard detail is a 5" slab w/ #4 at 12"oc on a heavy duty vapor
> barrier over 2" of compacted Class II base, over 5" of drain rock.
> This assembly was the recommendation of an ASTM working group headed
> by Tom Butt around 2000. Placement directly on a sand layer is the way
> the old-school slab finishers like it because it allows the concrete
> to be placed slightly wet & finished quickly with less shrinkage
> cracking. The sand layer creates a number of problems. However,
> placement directly on the membrane does need a wet cure to mitigate
> shrinkage. YMMV Chuck Utzman, PE
> On 12/5/2013 8:15 AM, Oshin Tosounian wrote:
>> Does anyone have a resolution to a conflict between the Green
>> Building Code and the standard slab on grade base requirements,
>> usually recommended by the soils engineer? The GBC requires the
>> concrete to be placed directly on the vapor barrier which is
>> directly placed over a 4" base of gravel. The standard practice and
>> most soils engineers' recommendations is the placement of concrete
>> over a sand base with the vapor barrier in the middle of the sand
>> layer, then the gravel base.

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