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RE: Shotcrete

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I don't have any references for you; however, I do have some experience with
similar situations.  I think you need to look at the overall picture.  

Is the cover really needed? No.   

What is the negative effects if the cover is installed? Additional deadload
and project cost/time not to mention deteriorated client relations.

What are the benefits? Corrosion protection and possible aesthetics.

What are the alternatives? Do nothing; spray coat a epoxy coating to provide
the corrosion protection; plaster and paint.

The aforementioned is merely my perspective, some times you need to look at
projects from different ones.

> -----Original Message-----
> From:	Jason Kilgore [SMTP:jkilgore(--nospam--at)]
> Sent:	Wednesday, March 21, 2001 10:52 AM
> To:	seaint(--nospam--at)
> Subject:	Shotcrete
> I have a problem involving shotcrete in a renovation project, and the
> required cover for bars.  Are the minimum cover requirements different for
> shotcrete than for cast-in-place?  If so what are they?  Also, we'll be
> doing more projects like this in the future, so what is a good
> shotcrete/gunite reference to buy?
> Following is a description of the project and problem:
> -----
> I have a project where they're renovating an old warehouse and converting
> it
> into a mix of retail (1st floor) and loft apartments.  The building is a
> cast-in-place concrete frame with 20'x20' bays.  The floor is a two-way
> plate with drop panels and capitols.  The floors are 7" thick, with a 3"
> topping slab in some areas.  The drop panels are an additional 4".
> Column-band reinforcing is parallel to the grid lines.  Field reinforcing
> is
> at 45 deg., and is continuous over the entire floor.  As near as I can
> tell
> there is only one mat (bottom), but it is probably bent up at the columns.
> Over all, the building is in good shape.
> For the first floor slab, the reinforcing was placed on chairs directly
> over
> a foam insulation.  This insulation was removed as part of the renovation,
> which is where the problem lies.  During casting, the chairs sank into the
> insulation, and the bottom layer of bars in the bottom mat is exposed for
> about 75% of the floor.  About half of the bar diameter is exposed over
> the
> majority of this area, with occasional spots with full exposure (you can
> see
> the second layer).  There is full coverage at the drop-panels.  All the
> bars
> are in good shape with no major corrosion.
> The building was used as a warehouse with varying storage requirements for
> several decades (from light boxes to 2-ton boxes of metal gears, with lift
> traffic).  There is no obvious cracking.
> The contractor wanted to leave is as is.  His reasoning was a) leave well
> enough alone and b) it will add a huge unexpected cost to the owner to fix
> it.
> We specified meeting ACI-318 requirements of 3/4" min. cover.  The
> contractor then wanted to do a single pass of shotcrete (about 1/2").
> We're
> still sticking to the 3/4", but the contractor and owner are screaming
> about
> the cost and time of installing the required mesh that 3/4" would require.
> Does anyone out there have any experience in this?
> ----
> Jason W. Kilgore, P.E.
> Leigh & O'Kane, L.L.C.
> jkilgore(--nospam--at)
> (816) 444-3144