6533b857fe1ef96bd12b49bf

RESEARCH PRODUCT

SURFACE AND MECHANISTIC PROPERTIES OF RECYCLED BITUMINOUS MIXTURES

subject

description

EXECUTIVE SUMMARY Problem Often, when the characteristics of a bituminous mixture are analised, there are major differences between in-lab and in-situ results. This is due to the fact that the procedures and techniques implemented during the design phase (in lab) may be different from those used on site. Then, is very important to be able to predict the main properties of a mixture particularly when innovative materials are used. For example, when crumb rubber is used, phisical and volumetric properties of mixes may change over time, in particular due to the swelling phenomenon that it alters different properties of the mixture (e.g., viscosity). This study aims to investigate the main aspects of road pavement design in order to improve the performance of innovative mixes. Objectives and scopes The main objectives of this thesis are: • Ob. 1 – To set up models for the prediction of surface characteristics of conventional and innovative road pavements. • Ob. 2 – To design innovative bituminous mixtures with crumb rubber. • Ob. 3 – To analyse the consequences related to Life Cycle Cost Analysis deriving from the application of different pavement design methods. Description This thesis intends to investigate the superficial and mechanical properties of conventional and innovative road pavements. The thesis contains a collection of experiments related to: i) laboratory-based study of the surface properties of road pavement; ii) laboratory-based study of the mechanical properties of road pavement and; iii) determination of expected life and pay adjustment. Conclusions The main conclusions of this thesis are: • Macro- and microtexture test can be explained and predicted based on simple physical and geometric models. In lab- measures can be related to the corresponding measures on real pavements. • The variation of viscosity over time is linked to the swelling process of the rubber. The order of components in the asphalt plant does not have significant effects on viscosity. • Short-time oven aging (STOA) and interrupted compaction process entail a worse compaction of mixes. • CRT2 mixes are usually easier to compact and are the most resistant to permanent deformation. • STOA effects are more evident than interrupted compaction effects in terms of compactability, workability, stiffness and rutting. • Rubberised mixes are easier to compact, when STOA process is applied. They have higher stiffness and a better resistance to permanent deformation. • Regard to the variables under investigation (e.g., AV), AASHTO, KenPave, MnPAVE and, M-EPDG have a similar trend in terms of expected lives.