ABSTRACT
The large use of Mechanical-Empirical (M-E) pavement design methods requires an extensive know-how concerning the structural behavior of the materials used in the pavement layers, especially regarding the fatigue and permanent deformation performances. Cement-Bitumen Treated Materials (CBTMs) have been used with great success for several years; however, their structural design with an M-E approach is often complex due to a lack of reliable performance models.
In recent years, the researchers investigated the fatigue performance of this type of material but, to date, no reliable model has been defined concerning the evolution of permanent deformation over time.
In order to properly describe the rutting behavior of these materials, an extensive in-field and laboratory test campaign has been conducted on specimens that were collected directly from two trial sections laid down over a cement-stabilized subgrade in a motorway construction work zone. The permanent deformation characterization in the CBTM was based on laboratory test measurement complying with the EN 12697-22:2007 “Test methods for hot mix asphalt—wheel tracking”. In a first set of tests, the specimens were analyzed by implementing the procedure provided by the EN standard and subsequently loads and temperature were changed in order to understand the dependence of the permanent deformations evolution with load repetitions on these factors.
The results obtained in the experiment allow to define a model to estimate the CBTM rutting evolution with traffic over time, and the effect of temperature and applied load.
