The number of construction projects using wet-mix instead of dry-mix shotcrete continues to grow, primarily because wet-mix shotcreting can achieve a higher production rate. Contractors using this concrete placing method have a number of pump options. But what's the best pump type to own or rent? The answer depends mainly on the volume of concrete to be placed.

For high-volume applications, use larger pumps that are fed by a truck mixer. These pumps typically are equipped with swing-tube valves, 6-inch-diameter pump cylinders, and 5-inch-diameter outlets and have outputs up to 40+ cubic yards per hour for conventional pumping. When the pumps are used for wet shotcreting with a 2-inch-diameter hose, line reducers at the pump outlet cut the output to about 20 cubic yards per hour--still more than enough capacity for jobs ranging from ground support to swimming pools. For low-volume applications requiring average placement rates of only a few cubic yards per hour, consider using a scaled-down swing-tube pump with 3-inch-diameter cylinders and a 3-inch-diameter swing tube and outlet. These smaller dimensions produce less output loss when reducing the line size to 2 inches.