Evaluation of rheological behavior of asphalt mixtures modified with triblock polymers grafted maleic anhydride and montmorillonite clay

Abstract

This work presents an investigation of the incorporation of maleic anhydride (MAH)-grafted triblock copolymers and montmorillonite clay (Mt) as modifiers of asphalt. A series of unmodified copolymers styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), or styrene-ethylene/butylene-styrene (SEBS) with clay were prepared by direct mixing of all components. Subsequently, they were compared with their grafted-MAH copolymer counterparts. The asphalt blends were characterized with respect to their rheological, morphological, and physical properties. Experimental results revealed that SBS and SIS grafted-copolymer composites increase the softening point by 1.5%-7%, while the penetration decreases by 2%-15% in comparison to the homologous nongrafted polymers.The improvement can be directly linked to the continuous network polymer in the asphalt blends. The combined use of styrene-isoprene-styrene-g-MAH (SISg-MAH) copolymer and clay impart higher elastic behavior than that of the other blends. G 0 increases about 95% in comparison to that of SIS/Mt, while the complex viscosity is three decades larger in the low frequencies region. Elevated rutting resistance temperature (>100 C), tanδ <5, reveals a solid-like behavior with no Newtonian plateau. SEBS-g-MAH/Mt presents diminished rheological properties with respect to those of SEBS/Mt due to poor dispersion and agglomeration of clay particles in the polymer and asphalt matrix.