Volume 4, Issue 5 (September 1976)
An Evaluation of a Proposed Test Method for Determining the Maximum Dry Density of Dense Graded Aggregate
A unique compaction test method similar to ASTM Test for Moisture-Density Relations of Soils, Using 10-lb (4.5-kg) Rammer and 18-in. (457-mm) Drop (D 1557-70) was developed and evaluated in the course of a National Cooperative Highway Research Program study of density standards for field compaction of granular base and subbases conducted at Clemson University. The new test method, called the Marshall Hammer Compaction Test, utilizes a standard 1/30 ft3 (944.64 cm3) mold as specified in ASTM Test D 1557-70, Method C, but the 10-lb (4.53-kg) Marshall hammer is substituted for the 10-lb (4.53-kg) Proctor hammer. Also, forty blows for each of the five layers are used to provide a total compaction effort of 90 000 ft-lbs/ft3 (4362.6 kN·m/m3) for the new test.
Laboratory density tests were performed using ASTM Test D 1557-70, Marshall hammer, and a combination procedure to determine the effects of additional energy and confinement on density produced. Four materials were tested with these procedures, and the densities were compared. Gradation tests were also performed to determine the extent of the degradation produced by the additional compaction energy. The laboratory densities were compared with densities obtained from full-scale prototype test pit constructions using the same materials.
Results from this study showed that the Marshall hammer procedure produced densities that were on the average 3 lb/ft3 (48 kg/m3) higher than those produced using ASTM Test D 1557-70. A comparison of the laboratory densities with the field densities showed that ASTM Test D 1557-70 obtained maximum dry density results which were 96.7% of the test pit densities while the Marshall hammer procedure obtained 99.0%. If a specification of 98% of maximum field compaction is required, as in some control-strip, compaction-control procedures, then the Marshall hammer procedure would provide an adequate target density at a specification level of 100% or less.