COMPARISON BETWEEN COMPACTION OF SUBBASE MATERIAL BY PROCTOR TESTS AND SUPERPAVE GYRATORY COMPACTOR

Proctor impact compaction tests represent the most commonly used laboratory method to determine the maximum dry unit weight and optimum moisture content of soils. One shortcoming of the Proctor test is that it uses impact loads to compact the soil in a stiff non-yielding mold. This technique may not accurately simulate modern field compaction methods so, a more appropriate method of compacting soils in the laboratory is needed. The research presented herein explores the feasibility of using a superpave gyratory compactor (SGC) to compact subbase material. The subbase is brought from Badra area, east of Wasit governorate. Type (B) subbase is used in this research, with three percentages of aggregate passing sieve No. 4, (30, 50 and 60) %. Before the SGC tests were implemented on the subbase material, Proctor tests (ASTM D-1557) (ASTM D-698-12) were performed on it to obtain the optimum moisture content and maximum dry density.

It was concluded that the SGC is capable of achieving higher densities than the standard and modified Proctor methods even at moisture contents lower than optimum conditions. These density levels are similar to those achieved by modern heavy compaction equipment in the field. The dry density increases with the increase of the number of gyrations, so, the    higher the number of gyrations, the higher the dry density that can be achieved because as the gyrations increases the particles continued to rearrange themselves subsequently better interlock and maximum dry density were achieved. All samples achieved at least 90% of total compaction in the first 50 gyrations, although dry unit weights continued to gradually increase at a rather slow rate until compaction was terminated at 500 gyrations.