This
Article provides introduction, information, guidance for selection and
application of both of the technologies Gunite
and shotcrete in detail. Both of the terms Gunite and Shotcrete stands
for the method of application of concrete by exerting pressure force with it. There
is a lot of confusion between both of these methods, which are briefly cleared
in this post
Define
Gunite and Shotcrete ………???
Gunite
is simply a process which deals with spraying of concrete. Spraying of concrete
generally may be done by means of both Gunite as well as Shotcrete. The term Gunite
stands for the process in which dry mix is generally used. The Gunite is also
named as Dry Mix Process of
spraying concrete. Dry mix process or Gunite involves mixing of the cement and
the aggregates in a Dry rig or bin etc and then pumping the same through a hose
pneumatically (using compressed air by a compressor) under high pressure to the
nozzle (the spray gun).water is introduced to the mix at the nozzle (by means
of water feeding line) just before the mix get out of the nozzle at a high
velocity on the surface to be treated.
Shotcrete,
when talking about the term shotcrete it is nearby similar to the term Gunite. Both
of these terms differ only due to type of process of carrying out work.
Shotcrete is the process in which the mix of cement and aggregate is made in
presence of water. It is also named as the Wet
Mix Process. Here wet mix process involves the spraying of the premixed
concrete or mortar at a high pressure and at a high velocity which eliminates
the need of adding water at the nozzle of the spray gun. Here we have both of
the terms well explained.
Differentiate
between Both Gunite And Shotcrete…..?????
Both
of the terms stands for the same work, but the only one thing which causes
difference is the process of working only nothing else. As described earlier Gunite
is the process in which contents are mixed in their dry form and then water is
added while dispatching the mix through the spray gun. At the same time
shotcrete is the process of mixing all elements of concrete including water
earlier. In Gunite aggregate size is limited to the size of sand particles
where in shotcrete
Shotcrete
or Gunite was invented by CARL AKELEY, who received a patent on precess in
1911. Originally the concrete mixture made up of cement, aggregates are
thoroughly mixed dry pumped to the position. At the nozzle water is then added
to the mix, which is named as dry mix.
In
1950 it becomes possible to add water into the mix first, then pump the “”wet
mix”” only adding air at the nozzle This was important for two reasons. The
amount of water can be controlled properly and on other hand it was possible to
add the aggregates having larger particles then sand. Today shotcrete
become a generic term which includes both of the processes. However some pool
industries refer Shotcrete for Wet Mix
and Gunite for Dry Mix.
Which one
is the better SHOTCRETE OR GUNITE……?????
While
we are talking about best one then I will say that both of them have their own strong
as well as weak points. This one is the harder question to answer because it
depends on several variables. As per theory Dry mix must be strong but at the
same time it depends on the nozzle man because of addition of quantity of
water. If the nozzle man is not a skilled person, he may add either too much or
too little quantity of water which directly affects the quality of work and
properties of concrete.
On
the other side there is the problem termed as “Rebound”. Rebound refers to the aggregate, which bounces or
deflects off of the receiving material and lands in areas other than intended.
When the small piece of sand is in mixture, it is combined with the moisten
cement and if properly placed will added strength to the structure. If on the other hand, bounces off something
hard, such as the wooden form or a piece of the steel reinforcement, the cement
is likely to adhere to the hardened surface, but the sand, now mostly stripped
of the binding agent falls elsewhere. This rebound must be gathered up and
removed, not allowed to become part of the structure.
In summary, Gunite or the dry-mix should be stronger, but the
margin for error is too great in my opinion. Having seen too many failed
dry-mix applications, I much prefer to use a shotcrete
or wet-mix process in the construction of pools and spas.
At
the end, it’s much more important to choose the
right or more suitable process (dry-mix or wet-mix) for a particular work and
ensure that the same is properly & skillfully implemented rather than
bothering too much about whether to call it dry-mix shotcreting or guniting.
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nice and informative article! wow!!
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