Shotcrete compressive strength should be tested using cores from test panels. Shotcrete cannot be shot into closed cylinder forms and be representative of the in-place shotcrete. ASTM C1140-11 and C1604-05(2012) provides the panel configuration and compression testing requirements. However, if using the wet-mix process for shotcreting and one wants to verify the compressive strength, air content, or temperature of ready mixed concrete materials as delivered, rather than as shotcreted in place, samples can be taken from the truck before pumping. These cylinders would follow ASTM C31-15 for making and curing concrete test specimens.