Contribuição ao estudo das propriedades reológicas de ligantes asfálticos modificados com montmorilonita.

Abstract

Research related to the improvement of performance in asphaltic mixtures aims to reduce the permanent deformations, increase the fatigue life and increase the durability. Thus, it has been used techniques in order to modify the asphaltic binders using polymers, fillers, fibres and, most recently, nanomaterials, which have presented technical and economic viability for this use. The aim of this research is to study the incorporation of pure montmorillonite and montmorillonite modified with distearyl dimethyl ammonium chloride (Praepagen WB) and cetrimonium chloride (GENAMIN) to the asphaltic binder type PAC 50/70 and compare its behaviour to the binder type 55/75 E. The montmorillonite was added in the percentages of 2%, 3%, 4% and 5%, pure and modified by the two salts (Praepagen WB and GENAMIN). The study was divided into three parts: in the first part it was performed the characterization tests, such as penetration, softening point and viscosity; in the second part, rheological tests were performed and in the third part the best percentage was chosen. The physical characterization of the asphaltic binder with addition of the modifiers presented increase in viscosity and, consequently, higher stiffness. In rheology, it was obtained for montmorillonite a not so expressive increase in machining temperature, opposed to the mix with Genamin at 5%, in which there was expressive increase using PAC 50/70; in PG, there was no major variations, meaning that there was no benefit from the additions. However, there was increase in the performance of the binder regarding oxidation. The modifier agents contributed to the short-term aging resistance. The mixture with 4% of WB and Genamin presented reduction in the phase angle values, indicating a slight increase of elasticity if compared to PAC 50/70. For the fluency and multiple stress creep recovery (MSCR) tests there was increase related to elastic properties. The montmorillonite, GENAMIN e Praepagen WB can be used with a performance grade of 64oC for a standard level of traffic. It is possible to accept that the content of 5% of Genamin can be used as a modifier agent of PAC and that it is capable of promoting improvement in rheological properties of asphalt cements.