How should samples of freshly mixed concrete be taken in the field to provide information on concrete in the structure?

Q. How should samples of freshly mixed concrete be taken in the field to provide information on concrete in the structure?

A. Samples should be taken as close to the point of placement as possible. Many times they are obtained at the point of discharge of the concrete from the mixer. Other points of sampling may be specified, such as the discharge of a concrete pump. Samples should be taken from several points in a batch in sufficient quantity so that, when mixed together, an excess of material will be available for the required number of specimens. The test sample should be protected carefully from loss of moisture and should be remixed and handled to the minimum degree necessary. Improper sampling leads to misinformation on the properties of concrete (ASTM C172).

References: SP-1(02); ASTM C172

Topics in Concrete: Concrete Fundamentals; Testing of Concrete