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Re: Shotcrete

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Hi Jason :

Here are some ACI specs that might be of good use for you:

ACI 506R-90
ACI 506.2-95
ACI 506.4R-94

In ACI 506R-90 (5.4.1), it is stated that reinforcement in shotcrete is
designed  using the same criteria as in reinforced concrete. I think having
such specs are very important in your case.

Wael Shabana, P.E.

----- Original Message -----
From: Jason Kilgore <jkilgore(--nospam--at)>
To: <seaint(--nospam--at)>
Sent: Wednesday, March 21, 2001 5:51 PM
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
> 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").
> 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.
> jkilgore(--nospam--at)
> (816) 444-3144


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