An alternative method for determining particle-size distribution of forest road aggregate and soil with large-sized particles

Measurement of particle-size distribution (PSD) of soil with large-sized particles (e.g., 25.4 mm diameter) requires a large sample and numerous particle-size analyses (PSAs). A new method is needed that would reduce time, effort, and cost for PSAs of the soil and aggregate material with large-sized particles. We evaluated a nested method for sampling and PSA by comparing it with the methods that follow the American Association of State Highway and Transportation Officials (AASHTO) standard T88-00 and the American Society for Testing and Materials (ASTM) standard D422-63. Using 33 forest road aggregate samples from the Clearwater National Forest in northern Idaho, the nested method required much less laboratory time and effort and resulted in similar PSA values, except for the 0.149 mm (No. 100) sieve, where the smallest particle-size fraction (PSF) values (1.30% and 1.39%) were observed. The nested method shows great potential for determining PSDs of the soil and aggregate material with large-sized particles and should be tested on other forest soils and road aggregates. The nested sampling and analysis method allows for the same number of samples to be collected but requires less laboratory time, making it more efficient and economical for testing the soil and aggregate material with large-sized particles such as forest road aggregate.