Unless gradation samples are really what, the test results are not effective?

For test results to be effective in assessing the characteristics of aggregate mixture, the gradation samples must be truly representative of the material being evaluated. A representative sample accurately reflects the variability of the entire batch of materials, including different sizes, shapes, and distributions of particles. If the samples are biased or disproportionately reflect certain particle sizes or characteristics, the analysis may lead to incorrect conclusions about the quality and performance of the aggregate mixture.

When gradation samples are representative, the test results can confidently inform decisions regarding mix design, performance predictions in the field, and compliance with specifications. Conversely, if the samples are not representative, all associated test results—including gradation, density, and performance metrics—are rendered less reliable, potentially affecting project outcomes. Therefore, ensuring the samples are representative is of utmost importance in obtaining valid results in aggregate testing.