One person says one thing about where to sample the concrete to make test cylinders of pumped concrete and another says something else. Is it correct to sample from the truck chute or the end of the pump line?
It depends on why you are testing the concrete. ASTM C 94, "Standard Specification for Ready Mixed Concrete," requires taking samples from the discharge chute of the truck mixer (but not from the first or last 15 percent of the load). The purpose of these samples is to determine whether ready mixed concrete is acceptable. If you are interested in knowing the quality of the concrete going into the structure, the proper place to sample it is at the end of the pump line. The concrete usually has some differences in properties (such as slump, air content and compressive strength) when it reaches the end of the hose from the properties it had when discharged from the chute. The mixing that has taken place in the pump hopper and hose is likely to improve the uniformity and strength of the concrete. On some jobs test cylinders are made from concrete sampled at both the end of the chute and the end of the hose.