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Following are some frequently asked questions about our medium of work...
(Information from Gunite: A Handbook for Engineers by
T.F. Ryan, Cement and Concrete Association, 1973)
What is gunite?
"Gunite can be defined as mortar or concrete conveyed
through a hose and pneumatically projected at high velocity onto a
surface. The force of the jet impacting on the surface compacts the
material. Normally the fresh material in place has zero slump and can
support itself without sagging. Gunite can also be placed overhead in
thicknesses of up to 50mm (2 in) at a time.
There are two different [gunite] processes in use, namely
the 'wet mix' process and the 'dry mix' process. The latter is more
successful and more generally used" (p. 6).
What can it be used for?
- "New structures (particularly curved or folded
sections). Examples are roofs, walls, prestressed tanks, reservoirs,
swimming pools, tunnels, sewer and shaft linings.
- Coatings to brickwork, concrete, rock, or steel for protection or
appearance.
- Encasement of structural steel for fireproofing and strengthening.
- Strengthening of concrete structures, slabs, concrete and masonry
walls, masonry and brick arches.
- Repair of deteriorated concrete structures such as bridges,
reservoir linings, dams, tunnels, cooling towers, chimneys and marine
structures. General repairs to spalled concrete on old reinforces
concrete buildings. Repairs to masonry and concrete structures damaged
by earthquake or fire.
- Refractory linings to chimney stacks, furnaces, boilers, cupolas,
etc.
- Abrasion-resistant coatings to coal or aggregate storage hoppers,
spillways, slipways" (p. 7).
Why is gunite used in underground tunnels?
"The purpose of lining rock tunnels in gunite is threefold:
1) To prevent water penetrating into the tunnel from the rock;
2) To prevent air and water vapor penetrating into the clay-filled fissures
in the rock, causing the clay to swell and thus promoting rock falls;
3) To form an arch to hold the sides and roof against any movement."
What are some of the credentials of Gunite Construction Company?
- The US Department of Transportation bestowed upon us a rating of No. 10,
which is the highest rating that they give for a company like ours.
- The Pittsburgh Testing Laboratory tested a sample of our material; it gave
an average 7-Day Compressive Strength of 10,900 psi and a 28-Day C.S. of
13,960 psi; average 7-Day Flexural Strength of 4580 psi and 28-Day F.S. of
5530 psi.
- The Pittsburgh Testing Laboratory also tested some of our gunite
panels. Three 3"x3" cubes were cut from each slab and the
following results obtained: the first specimen withstood a unit load of 8030
psi on average, while the second specimen withstood a unit load of 9840 psi
on average.
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