A method for NaA zeolite synthesis from coal fly ash and its application in warm mix asphalt

Fly ash (FA) can be a powerful substitute for conventional sources towards synthesis of zeolites, a class of aluminossilicates that can be used as additives in the production of warm mix asphalt (WMA). The use of zeolite has proved to enhance asphalt workability by water releasing. In this work, it is presented a new synthesis route for zeolite NaA based on fly ash as the primary source of silica and alumina, in which different sources of fly ash were applied. The composition of FA samples was determined by means of X-ray fluorescence (XRF) and the zeolite synthesis was confirmed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The rheological properties of the pure and modified asphalt cement (AC) assessed by a dynamical shear rheometer (DSR) did not show significative differences. The mechanical tests of tensile strength (TS), resilience modulus (RM), dynamic creep (DC) and pull-off tensile strength (POTS) for mixtures with modified AC showed subtle positive differences when compared to mixtures with unmodified AC.