EVALUATION OF THE AGEING EFFECTS ON THE PERFORMANCE OF NON-BITUMINOUS BINDER FOR PAVING APPLICATIONS

Sustainability has been the new global purpose from the last decades due to environmental concerns about the use of non-recoverable natural resources. The interest in using bio-materials in constructions and, in particular, in pavement engineering has grown significantly, heading us to concentrate on finding recoverable materials with the highest performances. Roads are mainly composed of asphalt mixture, a combination of aggregates and bitumen, generally petroleum-based. Nowadays the tendency is to abandon these petrochemical products in a favour of environmental friendly materials, called BioBinders. In this thesis, two different binders were studied and compared: a non-modified, neat and petroleum-based binder, defined as a target, and a bio-materials recently introduced in the market: BioPhalt®. The last is a non-bituminous binder, produced from pine derivatives and by-products of the papermaking industry. As the common binders, these biomaterials are subjected to ageing: change in mechanical, physical and chemical properties with time due to traffic loads, environmental conditions (e. g. temperature) and UV radiation. The bitumen hardens and loses the initial viscoelastic properties, consequently the road become stiffer and more prone to deterioration: small cracks evolve in large cracks and potholes and other distresses start to form on the pavement. These effects undermine the lifetime of the infrastructure and the safety of the users. Indeed, more investigation on this field are needed in order to govern this unpleasant effect of oxidation, polymerization and volatilization of bitumen. This thesis presents the results from a laboratory study on the effects of aging on the properties of the two binders. Performance parameters and chemical characteristics were studied under several ageing conditions: neat, short term ageing and long term ageing. Both binders were aged artificially and then tested according different procedures that simulate performance characteristics (rutting, fatigue and cracking at low temperature) and chemical ones. All the tests have been performed on both standard and bio bitumen in order to make the comparison between the two possible. All the collected data were analysed and compared, using the standard bitumen as guideline: in these way it has been possible to clearly understand the differences between the two materials and to highlight the advantages and drawbacks of BioPhalt®. It has been already proved that BioPhalt® has:- greater rutting resistance than the target bitumen, but only for short term ageing, while for long term the situation is totally the opposite;- excellent resistance to low temperature cracking and fatigue, since the material has greater viscous component;- a strong inclination to oxidation.This laboratory investigation states that aged BioPhalt® is a promising alternative to standard bitumen and, with further studies, it will be possible to replace the petroleum-based material with this renewable resource.