Polymers and crumb rubber modified binders play an important role in the manufacturing of asphalt mixtures in order to achieve more durable, safer, more comfortable and more sustainable pavements. Actually, the use of modified binder is compulsory for surface layers in highways.

This project studies the properties (characteristics and rheology) of different polymer modified bitumen and crumb rubber modified bitumen, and the mechanical behavior and fatigue performance of asphalt mixtures manufactured with them.

Thus, it is planned to achieve some environmental, energetic and social goals such as:

• Reduce energetic consumption

• Reduce gas emisions during the manufacture and transportation of hot asphalt mixtures with modified bitumens

• Reduce environmental impacts through the decrease of the use of quarries

• Increase road users comfort and safety, due to the reduction of maintenance operations and works frequency

• Collaborate to the attainment of a more sustainable society

Bitumens

Based on two types of modified binders: polymer modified bitumen (BM3c) and crumb rubber modified bitumen (CRMB), 6 modified binders with diferent contents of poymer and rubber are going to be studied.

Hot bituminous mixtures

In order to analyze the influence that the modified bitumens can have in the performance of asphalt mixtures, two mixes for surface layers are studied: BBTM11A (a discontinuous mixture) and PA16 (porous asphalt). These mixes will be manufactured using the same aggregates, being the bitumen the variable to considerer.

The project methodology is divided into two stages. The first one consists of the study of bitumens; while during the second stage the mechanical behavior of the asphalt mixtures with the different modified bitumens will be analyzed.

1st Stage: Bitumen study

In order to characterize bitumens, their penetration, softening point, fragility point, elastic recovery, ductility, viscosity and storage stability are going to be measured. In addition, the UCL method has been undertaken to study the cohesion, aggregate-binder adhesiveness, thermal sensitivity and ageing resistance of the binders.

The change of bitumen properties due to aging will also be analyzed through the RTFOT and RTFOT+PAV and the repetition of the characterization tests to the aged bitumens.

Finally, a rheological study of the bitumens is going to be performed using the Dynamic Shear Rheometer (DSR) and the EBADE test.

2nd Stage: Hot bituminous mixtures study

For the study of the influence of modified bitumens in the behaviour of hot bituminous mixtures, the following tests are going to be fulfilled:

• UNE-EN 12697-12:2009. Determination of the water sensitivity of bituminous specimen

• UNE-EN 12697-22:2008+A1:2008. Wheel tracking (only for BBTM11A)

• UNE-EN 12697-26:2012. Stiffness (only BBTM11A)

• UNE-EN 12697-17:2006+A1:2007. Particle loss of porous asphalt specimen (only for PA16)

• UGR-Fact: A test developed at the University of Granada which allows the analysis of cracking propagation in asphalt mixtures at different phases (initiation, progression, and failure).

Under development.