Effect of coal fly ash treatments on synthesis of high-quality zeolite A as a potential additive for warm mix asphalt

Abstract

An experimental investigation on the synthesis of zeolite A, based on the treatment of fly ash and controlled extraction of silica and alumina from coal fly ash, combined with the adjustment of the reaction mixtures aiming minimum amount of secondary phases, is presented herein. The precursor samples of fly ash and the obtained zeolites were widely characterized considering different techniques including powder X-ray diffraction, infrared vibrational spectroscopy, scanning electron microscopy, and thermogravimetric analysis. A new pore characterization technique that combines experimental CO₂ isotherms at 273 K and molecular simulation was specially developed for this system. The synthesized zeolites presented zeolite A as the major phase, with high crystallinity and low degree of defects in the supercages. The treated fly ashes affected the synthesis yield and the properties of the obtained zeolites, which proved to be efficient in decreasing the viscosity of the modified asphalt cement, during heating, contributing to improve its workability.