ADVANCED TESTING AND THEORETICAL EVALUATION OF BITUMINOUS MIXTURES FOR FLEXIBLE PAVEMENTS

Autore Tesi: 
Andrea Grilli
Email: 
a.grilli@univpm.it
Dottorato di Ricerca in: 
Strutture e Infrstrutture
Ciclo e A.A.: 
VI ciclo
Anno di corso: 
2004/08
Tutor: 
Prof. Canestrari F., Prof. Virgili A.
Coordinatore: 
Prof. Santagata F. A.
Sede Amministrativa: 
Università Politecnica delle Marche, Ancona
Dipartimento/Istituto (sede amministrativa): 
Istituto di Idraulica ed Infrastrutture Viarie
Facoltà (sede amministrativa): 
Facolt di Ingegneria
Argomento della Tesi: 
It is well known that cracking and permanent deformation in asphalt pavements and their related degradation processes can be caused by traffic loading and temperature variations. Moreover, these distresses are often accelerated by water damage mechanisms that generally affect mixture cohesion and/or adhesion between binder and aggregate interface. Nowadays, the increasing traffic, higher axle loads and reduced road maintenance budget, force engineers to seek long lasting materials and reliable testing methods for the design and rehabilitation of asphalt pavements. This thesis focuses on both long-term and durability performance of asphalt pavements. In this context, on one hand the increasing interest in the use of high performance materials, like geosynthetics, drove to determine whether these products act as reinforcement and enable longer service life. On the other hand, a lack of reliable test method for the water sensitivity evaluation of asphalt mixtures led to develop a new experimental method to investigate water and temperature cycle effects in flexible pavements. In order to improve the knowledge on pavement reinforcement use, the Part I of this research project proposes an overall testing protocol analysing shear behaviour, fatigue performance and permanent deformation resistance of geosynthetic-reinforced asphalt pavements. Geosynthetics could not act as a reinforcement product if they are a cause of separation between the layers at the interface. For this reason, this study concerns a better understanding of reinforcement systems behaviour and their effects on mechanical properties of the interface. To this purpose the interlayer direct shear test ASTRA (Ancona Shear Testing Research and Analysis) is used to provide more details regarding the comprehension of the interlayer shear resistance. As previously mentioned, the present work even compares the behaviour of reinforced and unreinforced double-layered prismatic specimens under repeated loading cycles in both controlled deflection and controlled load modes. proposed to simulate the permanent deformation evolution curve and the number of loading cycles corresponding to the flex point of the permanent deformation evolution curve was selected as failure criterion. On the other hand, pavement durability may be improved not only by using high performance materials but also by selecting adequate combinations of materials to resist against repeated loading and to mitigate the effects of environmental factors such as water and temperature cycles. For this reason, the Part II of this thesis regards the development of a versatile test method which simultaneously couples both dynamic loading and environmental factors. Tests were carried out on differently compacted specimens with three different approaches: traditional (Indirect Tensile Test), empirical (Cantabro) and innovative (Coaxial Shear Test). In particular, the Coaxial Shear Test (CAST), designed at EMPA since 1980s, is used to determine the evolution of mechanical properties under repeated loading cycles and, in the last years, also combining water action and temperature cycles. Preliminary findings led to concentrate on developing of an effective performance related procedure to characterize water sensitivity of asphalt mixtures with respect to fatigue performance with CAST. In this sense, an elasticity-based damage model has been applied to determine the damage evolution in fatigue test with and without temperature cycles. By evaluating the damage factor evolution the influence of water and temperature cycles on the damage process can be highlighted.
Societa' Italiana Infrastrutture Viarie - S.I.I.V. - Cod.Fis. 93024730421