What is a requirement for acceptable sand used in the sand cone?

The requirement for acceptable sand used in the sand cone method pertaining to bulk density variation is that it should not exceed 1%. This specification is crucial because the accuracy of the sand cone test depends on the consistent properties of the sand used for determining the density of the material being tested.

Using sand with a bulk density variation greater than 1% could lead to significant errors in the calculation of the in-place density of the soil or aggregate material, which is a key factor in assessing the compaction and stability of the construction site. Consistency in the density of the sand ensures that the measurements taken are reliable and valid, leading to more accurate results that are essential for quality assurance in construction practices.

The other options relate to various forms of density measurement that are not as critical for this specific test. For instance, while moisture content can affect the density of the sand, it is not a requirement for the sand itself to have varying moisture content, as this could also introduce variability in the testing process.