Pozzolanic reaction of fly ash modified by fluidized bed reactor-vapor deposition

This study aimed to introduce fluidized bed reactor-vapor deposition (FBR-VD) into the modification of fly ash (FA) using the activators of NaOH, Na2SO4, and NaCl. The compressive strength, non-evaporable water and the hydration degree fly ash (HDFA) were investigated. The scanning electron microscopy (SEM), and the X-ray powder diffraction (XRD) Rietveld analysis were also conducted. The results demonstrate that FBR-VD can benefit the compressive strength when the dosage rates of NaOH, Na2SO4 and NaCl are 0.1%, 0.5%, and 0.5%, respectively. The non-evaporable water and HDFA also increased at certain activator dosage rates. A modification layer consisting of nanometer-scale crystals forms on the surface of the FA beads, with NaOH or Na2SO4 applied. NaOH can react with FA and promote its pozzolanic activity. Na2SO4 and NaCl can benefit the HDFA by remaining undissolved, to increase their concentration around FA. The enhanced HDFA is also proved by the consumption of Ca(OH)2.