A week or so ago, during a Precon meeting, I was asked by the City of Seattle if I cared if some of the shotcrete nozzle men or Blow-pipe men were trainees. Without knowing any code requirements on the subject, I said that I did not care as long as they did it right.
It was interesting to me that the City of Seattle asked and recorded the names of all shotcrete workers. Now as I review the shotcrete shop drawings, I see that all nozzle men and Blow-pipe men are listed along with years of experience and state they meet or exceed the ACI Qualification requrements. Apparently there is a certification we can request: https://www.shotcrete.org/ASAcertification.htm
Does anyone have further knowledge on the subject of certification or on the design considerations and limitations of using shotcrete applications in lieu of pouring?
1 comment:
Shotcrete is useful in many respects, but has some caveates...
The advantages are that you have no form or only 1 sided form depending on the topography; Also the application is rapid, and the prep start to finish is more rapid than formed concrete.
Some caveates are that shotcrete is not as dense as poured concrete. Also where the lift joints occur, there may not always be a 100% bond, and ground water could seep in more readily than otherwise. The finish is also rougher than with a formed wall...
Regarding certification, i think these are spelled out be the city, and are required to ensure that the correct techniques are used to place concrete in the various areas/formats and rebar configs that come up.
Placing shotcrete can be dangerous too because of the high pressure hose - grade prep and staging areas for the nozzlemen etc are important to prevent on site drama...
Rebar splices are considerations in shotcrete - bars are to be orientated behind a bar rather than to the side of the bar - also sometimes non-contact splices are used.
Another areas is the testing of the consolidation aspects of shotcrete - must designate a sacrificial area to core-drill and view the concrete consolidation and check for voids behind rebar (check shooting techniques)...
I'm not aware of any other over-riding design considerations...?
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