Sampling Fresh Concrete

Sampling Fresh Concrete

It is very important that the concrete put into the moulds should be a representative sample of the concrete that is going into the works. A sample of the concrete should be taken either as the concrete is being discharged from a mixer, or from a stationary lorry or heap; the latter method is less satisfactory.

The quantity of concrete required should be 10 kg for making each 150 mm cube, but in no case should the quantity of concrete sampled be less than 20 kg. Each sample should consist of at least six increments when it is taken from a heap or lorry, and at least four increments when taken from a chute or conveyor.

Sampling from Heaps or Lorries

The increments should wherever possible be distributed through the depth of the concrete as well as over the exposed surface. Care should be taken not to take any from the edge of a pile where large particles of aggregate may have gathered through segregation.

Sampling from Falling Streams, Chutes or Conveyors

When sampling from a falling stream, increments should be taken by passing a scoop through the whole width and thickness of the stream in a single operation. Alternatively, the entire stream may be diverted so that it discharges into the container.

Whichever way the samples are taken, the parts must be thoroughly mixed together so that the whole sample is uniform. If the sample is in a barrow, the remixing can be done in the barrow with a shovel or a sampling scoop; alternatively, and especially if the sample is in a bucket, it can be tipped over a non-absorbent base and then thoroughly mixed together.