Analisi sperimentale e modellazione reologica della lavorabilità dei conglomerati bituminosi

In recent years pavement engineering has considerably evolved from many perspectives, with a general improvement of field performance. This improvement should attributed to the development of new materials and technologies and to a more careful management of resources in every stage of infrastructure life, from design to maintenance, through construction. The laying and compaction of hot-mix asphalt (HMA) is one of the most important issues to be taken into account since it is a stage that can negatively influence the whole life of a pavement. It is advisible to pay attention to the workability properties of HMA because only with the control of these and with a careful study of the factors that affect compaction it is possible to prevent unexpected performance problems during service life. This research work is set in this general framework, trying to give a further contribution to the actual knowledge of HMA workability. The aim of the research is to analyse critically the factors that affect compaction of HMA by means of laboratory investigations carried out with a SUPERPAVE Gyratory Shear Compactor. The study has been structured in different levels through which the influence of individual parameters on HMA compaction has been evaluated. This has been done by considering different mixture structures (i.e. different composition of the mixtures) and by taking into account the effects caused by variations of temperature and binder type. Part of the research has focused on the development of a rheological model for the simulation of the laboratory compaction process of HMA. This has lead to the detailed analysis of the effects caused by the various parameters on compaction. When considering final results. It can be pointed out that the workability factor k was observed to be independent from temperature and binder type. On the contrary, it proved to be sensitive to variations of the bitumen content and of the percentages of the fine aggregate fractions. In particular, workability was directly influenced by variations of filler content and of the quantities of aggregate material associated to sieves with an opening of 0.400, 0.180 and 0.075 mm. By increasing the filler content, workability increases; by increasing the quantities of fine material associated to the abovementioned sieves, workability is reduced.. This is due to the fact that more dense structures are obtained with the consequence of encountering a greater difficulty in reorganising and redistributing aggregates in the bulk of the mixture. Variations of the autocompaction parameter C1 were also analysed. It was thus observed that such a parameter depends only upon the coarser aggregate fractions, and more specifically upon the maximum aggregate size. Only minor effects caused by variation of the binder content were noted. In the rheological modelling of the compaction process it was observed that the employed parameters are dependent upon a series of factors which are linked to the composition of the mixtures, to test conditions (especially to temperature) and to the level of compaction (number of gyrations and compaction pressure)

Design and Construction of a Full-Scale Test Section with Asphalt Rubber Gap-Graded Wearing Course Mixture

A full-scale test section with asphalt rubber gap-graded wearing course mixture was designed and constructed on a major infrastructure as part of a regional research and implementation project. Standard and performance-related laboratory tests were carried out in order to select constituent materials, define the job-mix formula and monitor construction operations. Gaseous emissions of the bituminous mixture sampled during laying were analyzed to assess the potential risks to which labourers are exposed during paving. Environmental compatibility was also evaluated by performing laboratory leaching tests. Based on the results obtained in the investigation, technical guidelines were validated and enhanced

Design and Construction of a Full-Scale Test Section with Asphalt Rubber Gap-Graded Wearing Course Mixture

A full-scale test section with asphalt rubber gap-graded wearing course mixture was designed and constructed on a major infrastructure as part of a regional research and implementation project. Standard and performance-related laboratory tests were carried out in order to select constituent materials, define the job-mix formula and monitor construction operations. Gaseous emissions of the bituminous mixture sampled during laying were analyzed to assess the potential risks to which labourers are exposed during paving. Environmental compatibility was also evaluated by performing laboratory leaching tests. Based on the results obtained in the investigation, technical guidelines were validated and enhanced

Experimental Investigation for the Analysis of Cold-Recycled Bituminous Mixtures

The Authors present the results obtained in a experimental investigation carried out to provide technical support to the construction of a cold-recycled bituminous sub-base layer of a major Italian motorway. Compliance of the employed materials and of the resulting recycled mixture to requirements set in Technical Specifications and to the adopted job-mix formula were verified by means of laboratory tests. Field observations focused on the evaluation of the void content of the compacted sub-base layer and on its stiffness evolution in the short term curing phase. Finally, mix design was carried out by following a procedure based on the use of the gyratory shear compactor and on the optimization of the composition of the fluid phase. The procedure was validated by performing volumetric and mechanical tests both on the optimized mixture and on a mixture prepared according to the job-mix formula

Rutting Behaviour of Wearing Course Mixtures in Severe Temperature and Loading Conditions

Following the construction of a major motorway pavement in Northern Africa, relevant rutting phenomena were observed after opening to traffic. Preliminary investigations showed that permanent deformations were limited to the upper wearing course layer which was designed according to set requirements. In order to define the most appropriate rehabilitation strategy, investigations were carried out by focusing on the volumetric and mechanical properties of the employed wearing course mixture. Compaction properties were assessed by making use of a gyratory shear compactor and of a rubber-wheeled roller. Moreover, simulative wheel-tracking tests were carried out in severe temperature and loading conditions. Additional tests were performed on an alternative bituminous mixture containing polymer granules. Based on the obtained results the possible causes of the above described distress phenomena were identified and the use of the alternative bituminous mixture as a technical solution to adopt for rehabilitation was considered

Mechanical Characterization and Influence of Water on WMA by Adding Synthetic Zeolite

http://www.ljmu.ac.uk/BLT/PEAT/90854.ht

FULL PERFORMANCE EVALUATION OF RUBBERIZED WEARING COURSES FOR SUSTAINABLE ROAD PAVEMENTS

This paper reports the results of an experimental study focused on the performance evaluation of rubberized bituminous mixtures for pavement wearing courses. The investigation aimed to identify materials which exhibit a satisfactory balance in terms of durability, skid resistance and noise reduction. Rubberized mixtures considered in the study were of the gap-graded and open-graded type, prepared by employing an asphalt rubber binder containing crumb rubber from end-of-life tires. Following a preliminary mix design phase, optimized mixtures were used for the construction of full-scale trial sections with the subsequent field and laboratory evaluation of their performance-based properties. Experimental results revealed that when compared to reference porous friction mixtures containing polymer-modified bitumen, rubberized mixtures may exhibit lower stiffness losses during freeze-thaw cycles and a better behaviour in terms of emission of rolling noise, while still guaranteeing satisfactory skid resistance levels