Microstructure and performance of fly ash micro-beads in cementitious material system

To exploit the advantages of fly ash in cementing materials to the full, in this study, the micro-constitution of fly ash beads was investigated; the effects of micro crystalline and non-crystalline phases inside fly ash on the performance of cementing material were discussed, also including technical ways to bring these advantage effects into play. It was found that the sinking beads, were hollow and containing a mass of smaller round spheres or even nano-spheres. A large quantity of interlaced nano micro-crystal fibers constitute the basic frame work of the bead wall, and the active silicon-aluminum matrix fills the gaps among the micro-crystal fibers. The silicon and aluminum matrix is active, which could react with Ca(OH)2 produced during the hydration of cement clinker minerals, while nano-crystals that fly ash particles containing are inert. Super-fine grinding can break the out-shell of fly ash beads, releasing the nano-spheres and really improving the active and micro-aggregate effects of fly ash micro-beads. Meanwhile, the reinforcing fiber effect of micro-crystals inside fly ash particles will be developed and enhancing the flexural strength of cementing materials at later age.