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)leok.com]
> Sent: Wednesday, March 21, 2001 10:52 AM
> To: seaint(--nospam--at)seaint.org
> 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
> 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
> at 45 deg., and is continuous over the entire floor. As near as I can
> 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
> 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
> majority of this area, with occasional spots with full exposure (you can
> the second layer). There is full coverage at the drop-panels. All the
> 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
> 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").
> still sticking to the 3/4", but the contractor and owner are screaming
> 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.
> (816) 444-3144