Evaluation of laboratory and field compaction of dense graded aggregate base

Abstract

The optimum compaction is required to provide an effective path to enter energy into unbound material under its Optimum Moisture Content (OMC). To achieve the optimum energy level, the relationship between OMC, Maximum Dry Density (MDD) and Compaction Effort need to be identified at field conditions. But it is difficult to conduct in field scenario and therefore those condition are simulated at laboratory condition to find above parameters. However understanding of the importance of this relationship is a question in local context. The information of current compaction practices were gathered by conducting questionnaire survey, while laboratory and field studies were carried out to compare compaction behavior of Dense Graded Aggregate Base (DGAB) at different Moisture Contents (MC) and energy levels. Few number of impact compaction tests and vibratory hammer compaction test were conducted to compare with the field trial test results. The results of field trial study revealed that the higher compaction effort is needed, when compacting at moisture levels which is deviated from OMC. In addition to that Dry Density (DD) is rapidly increased when lesser number of roller passes are applied at MC which is closed OMC. The comparison of field and laboratory test results shows that the vibratory hammer test is suitable to obtain OMC and MDD for field compaction. Although compaction effort can be minimized when it compacts at MC close its OMC, common practice is achieving the required density at higher MC by applying an ineffective compaction effort while leading to segregate the DGAB layer. Therefore appropriate compaction effort should be identified prior to compaction for relevant MC in order to achieve an effective compaction.