How many portions are required when sampling concrete from a revolving truck mixer?

When sampling concrete from a revolving truck mixer, the requirement is to take two or more portions. This is necessary to ensure that the sample accurately represents the entire batch of concrete in the mixer. By taking multiple portions, the variance within the concrete mix can be accounted for, which helps in achieving a more reliable and homogeneous sample for testing.

Sampling from just one portion would not provide a valid representation of the entire load, as the components of the mix may not be uniformly distributed due to the mixing process or due to segregation that may have occurred during transport. By collecting at least two portions, one can effectively reduce the potential for errors and inconsistencies during testing, leading to more reliable results when determining the properties of the concrete.

In regard to higher numbers such as four or five portions, while taking more portions can offer even finer granularity and potentially improve the representativeness of the sample, the minimum standard is set at two to achieve the balance between practicality and reliability in typical sampling conditions.