Experimental comparative analysis of laboratory soils compaction methodologies

Proctor impact compaction represents the most common laboratory method adopted to determine the maximum dry density and the optimal moisture content of soils and aggregate mixes, for pavement sub-base and foundation layers. It has been proven that the result of in-situ roller compaction in terms of particles path distribution totally differs from what the Proctor impact compaction produces inside the steel mould. In fact, field compaction relies on a combination of superficial kneading, vibration and vertical pressure to achieve the densification of particles within the layer. This can be sufficiently reproduced, together with the obtainment of reference dry density, by means of the Gyratory Compactor (GC), which is also able to assess the compactability of the soil during the process. Variables within Gyratory Compaction of soils are: vertical pressure, number of gyrations as well as soil type and moisture content. These were explored as a prequalification procedure to define their effect on compaction of clayey soils prior lime stabilization. Proctor and GC compaction results for various soils were compared to define a methodology leading to the substitution of the traditional compaction method and to the use of GC for achieving better field compactions.