This is a question directed at either those who have a background in building pools (waste !) or those who watched the shotcrete sub-contractor shoot their pool.
Did the shotcrete sub-contractor reuse the shotcrete rebound, or was the rebound hauled away as debris?
Evidently the reuse or recycling of shotcrete rebound is very common among shotcrete contractors who mainly work on residential pools. Very common, and a very bad practice. Here are some relevant quotes from an expert on both pools and shotcrete.
Aside from it being a waste product of pneumatic application, what’s wrong with using rebound as a structural material?
Think of a baseball that’s coated with cement and thrown very fast against a rigid wall. The result is that the baseball ricochets off the rigid wall but, as this happens, a substantial amount of the cement that coated the ball becomes splattered against the wall. The ball, now lacking a good part of its cement coating, falls to the most convenient landing spot.
Similarly with gunite and shotcrete, a portion of the high velocity shot material— primarily the larger aggregates—ricochets or rebounds off the receiving surface and lands on the nearest horizontal plane.
The key point of this comparison is that, like the ball, the “rebound” aggregate has lost a substantial amount of its cement and is therefore no longer viable as a structural material. This is so widely recognized that, in fact, uniform building codes do not permit the use of rebound in structures.Not using rebound as a structural material is a baseline workmanship principle that should never be violated, but, unfortunately, that’s just not the case in a large number of (mostly residential) swimming pool/spa projects.http://www.shotcrete.org/pdf_files/Spri ... yMix%2EpdfThe good news is that the fix is simple: don’t use rebound or trimmings to form steps or benches anywhere in a pool/spa shell—end of discussion!
The bad news is that this practice is so common in the industry that it’s hard to imagine things changing without some sort of concerted information campaign and increased education in workmanship and good construction practices. The simple fact is that there is a right way to apply shotcrete and that guidance in doing so is available from the American Concrete Institute (ACI) and the American Shotcrete Association (ASA).
Even Ben Powell of Pool Forum/Pool Solutions did not like the idea of reusing shotcrete rebound when he was musing about his dream pool. http://www.poolsolutions.com/letter.html
All gunite rebound would be discarded.
I would be interested to hear stories or anecdotes of how the shotcrete guys did your pool. Thanks!