Generally, the interface between sequentially placed layers of shotcrete is not considered a cold joint because the shotcrete abrasion, velocity of impact, and high paste content make excellent bonding conditions. Cores taken through layers of shotcrete on shotcrete often show that it is virtually impossible to ascertain one layer of shotcrete from the next. Please refer to ACI 506R, “Guide to Shotcrete,” for information on joints in shotcrete.