Precision Estimates of AASHTO T 304, AASHTO T 96, and AASHTO T 11 and Investigation of the Effect of Manual and Mechanical Methods of Washing on Sieve Analysis of Aggregates

This digest summarizes key findings of research conducted in Task Order #2 of National Cooperative Highway Research Program (NCHRP) Project 10-87, “Precision Statements for AASHTO Standard Methods of Test,” by the American Association of State Highway and Transportation Officials (AASHTO) Materials Reference Laboratory. The Digest updates precision estimates of AASHTO Standard Test Methods T 96, Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Testing Machine; T 304, Uncompacted Void Content of Fine Aggregate; and T 11, Materials Finer Than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing. The report also examines the significance of the difference between variability of percent passing No. 200 sieve of 300-g and 500-g fine aggregate samples measured according to AASHTO T 11. In addition, the report evaluates the effect of manual versus mechanical washing, by comparing the results of sieve analysis of Proficiency Sample Program samples, washed manually or mechanically prior to being tested according to AASHTO T 11, T 27(Sieve Analysis of Fine and Coarse Aggregates), or T 30 (Mechanical Analysis of Extracted Aggregate).