Sampling from a paving mixer requires how many portions of the pile to be combined?

The correct answer is that five portions of the pile should be combined when sampling from a paving mixer. This method ensures that the sample collected is representative of the entire batch. Sampling multiple portions helps to account for variability in material composition that may exist throughout the pile, which can occur due to factors like uneven mixing or segregation of materials.

By combining five portions, the sampling process increases the reliability of the results, allowing for a more accurate reflection of the overall material quality. This practice aligns with standard procedures in construction and materials testing, where the objective is to ensure consistency and reliability in the materials used. Variability is minimized with the larger number of portions, thereby increasing confidence in the test results that will follow.

In contrast, sampling only one, three, or seven portions may not provide the same level of representativeness, as fewer portions could miss important variations within the pile, and while sampling more than five can add complexity without significant additional benefit. Hence, five portions strike an effective balance between thoroughness and practicality for ensuring quality control in paving operations.