Analysis of the Effect of the Degree of Compaction on the Permanent Deformation of Recycled Unbound Base Layers

The accumulation of permanent deformation in unbound granular layers contributes to a significant part of the rutting damage in flexible pavement systems. Generally, adequate compaction ensures good performance and limited accumulation for any soil or granular materials. Because pavement materials are required to be compacted close to their maximum dry density, the effect of the degree of compaction is well acknowledged but not yet entirely understood. A laboratory study on permanent deformation with cyclic triaxial was conducted on granular base materials consisting of a 50–50% mix of virgin aggregates and recycled asphalt pavement aggregates. A new analysis approach was developed to infer permanent deformation model parameters using angles of the strain accumulation with respect to the number of load cycles at reference values. The approach was used to quantify the combined effect of stress and degree of compaction on the performance of unbound recycled granular materials.