PoolQ The company installing our pool ran short of wet mix by about 4 yd3 (3 m3). The pressure truck left, leaving one finisher behind. It was about an hour before the last of the material arrived and what had already been placed had pretty much set. He added about 20 gal. (76 L) of water so he could get it in place. The fully exposed areas, I feel, would be OK. However, the long tapered overlays concern me for strength; it seems like more of a patch. Since it was not shot in place to compress and integrate it, will it bond and strengthen properly?
Proper shotcrete placement of concrete depends on high-velocity impact of the concrete materials for full consolidation. Though not clear from your inquiry, it sounds like the additional concrete was just dumped in place without high-velocity impact. Thus, you simply have normal cast concrete that would require some type of external vibration to densify and properly consolidate the concrete. The bond of cast concrete would be inferior to the bond from shotcrete since you do not have the high-velocity impact driving the cement paste into the previously shot material. Also, adding 20 gal. of water at the site would substantially weaken the concrete from the original design strength of the concrete mixture. Further, feathering edging in a joint is not recommended since you end up with a very thin overlay at some point that may tend to spall or delaminate much more easily at the thinner section. A better approach when running short of concrete is to stop and prepare a joint for later shotcreting. For best bond, joints should be cut at a 45-degree angle, roughened, and then cleaned and wetted immediately before shooting.
Thus, answering your final question, in summary the bond will be reduced, and with the higher water content, the concrete will be weaker than properly shotcreted concrete.
