What does D1140 determine regarding soil composition?

The answer focuses on the objective of ASTM D1140, which is to determine the amount of material finer than a 75-micrometer sieve in soils through a washing process. This method is commonly used in geotechnical engineering to evaluate the fines content in soil samples. The quantification of fines is essential because it influences various soil properties, including permeability, compressibility, and shear strength.

The washing process specifically helps separate the finer particles from coarser ones, allowing for accurate measurement of the percentage of material that can pass through the 75-µm sieve. Understanding the fines content is crucial for soil classification and can impact the selection of suitable materials for construction projects.

Other options, such as determining the compaction rate, organic content, or moisture retention capacity, represent different tests and ASTM standards that are designed for those specific purposes. However, D1140 specifically addresses the quantification of fine particles within a soil sample, making option B the right choice.