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

Abstract This study aimed to introduce fluidized bed reactor-vapor deposition (FBR-VD) into the modification of fly ash (FA) using the activators of NaOH, Na 2 SO 4 , 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, Na 2 SO 4 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 Na 2 SO 4 applied. NaOH can react with FA and promote its pozzolanic activity. Na 2 SO 4 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 .