MagicMtnDan
08-10-2005, 06:59 AM
Which is best?
Here's what I've been told:
* Gunnite is mixed on-site by the contractor.
* Shotcrete is pre-mixed by the manufacturer.
* The difference, as I've been told, is that shotcrete is more consistent and gunnite quality will vary with the contractor.
Sounds like shotcrete is the better way (and more expensive). Is that right?
Found this online (http://www.itsa.info/Shotcrete.shtml ):
Concrete is the material that gives a thin-shell it's rigidity. While the concrete can in theory be entirely mixed and applied by hand, that seldom is economical. There are two popular methods of applying the concrete to the structure of the building: shotcrete and gunnite. The end result is the same in each case--concrete provides tremendous compressive strength while the rebar provides the tensile strength. But the means of handling the materials is slightly different.
Shotcrete is typically applied with a pneumatically driven pump. Concrete that is either site-mixed or delivered from a redi-mix plant is poured into a large hopper, from where it's pumped through a hose and sprayed by high air pressure (100-120 psi) and air volume (185 cfm or so) against the formwork. The best of the professional systems are able to move 6-to-12 or more yards of low-slump concrete (2" slump or less) through 2" hoses to produce a wall in excess of 4000 psi, though individual contractors will have their own specifications and preferences. Most concrete plants should have a recipe for a shotcrete mix that they can prepare at a moment's notice.
Gunnite is an equally suitable method of applying concrete. It is most frequently used when building swimming pools, and differs from shotcrete in that the ingredients are dumped separately into the gunnite truck, and then pumped through hoses, where they mix at the nozzle and project onto the wall. This method is not inherently better or worse than shotcrete--each work well as long as the rebar is properly encased.
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Hey Roz, I got the excavator's info and will PM it to you later today. (He's got 18 years of experience and is great to work with).
Here's what I've been told:
* Gunnite is mixed on-site by the contractor.
* Shotcrete is pre-mixed by the manufacturer.
* The difference, as I've been told, is that shotcrete is more consistent and gunnite quality will vary with the contractor.
Sounds like shotcrete is the better way (and more expensive). Is that right?
Found this online (http://www.itsa.info/Shotcrete.shtml ):
Concrete is the material that gives a thin-shell it's rigidity. While the concrete can in theory be entirely mixed and applied by hand, that seldom is economical. There are two popular methods of applying the concrete to the structure of the building: shotcrete and gunnite. The end result is the same in each case--concrete provides tremendous compressive strength while the rebar provides the tensile strength. But the means of handling the materials is slightly different.
Shotcrete is typically applied with a pneumatically driven pump. Concrete that is either site-mixed or delivered from a redi-mix plant is poured into a large hopper, from where it's pumped through a hose and sprayed by high air pressure (100-120 psi) and air volume (185 cfm or so) against the formwork. The best of the professional systems are able to move 6-to-12 or more yards of low-slump concrete (2" slump or less) through 2" hoses to produce a wall in excess of 4000 psi, though individual contractors will have their own specifications and preferences. Most concrete plants should have a recipe for a shotcrete mix that they can prepare at a moment's notice.
Gunnite is an equally suitable method of applying concrete. It is most frequently used when building swimming pools, and differs from shotcrete in that the ingredients are dumped separately into the gunnite truck, and then pumped through hoses, where they mix at the nozzle and project onto the wall. This method is not inherently better or worse than shotcrete--each work well as long as the rebar is properly encased.
----------------------------------------------
Hey Roz, I got the excavator's info and will PM it to you later today. (He's got 18 years of experience and is great to work with).