The Performance And Leaching Toxicity Of Cement Containing Pretreatment Fly Ash

With the sharply develop of economy, the discharge of solid waste in China showed a steep rising trend, including urban construction waste, industrial waste, municipal solid waste, et al. Most of the solid waste contains heavy metal element. At present, many countries have extensively study, with the various methods to deal with the solid waste. The incineration method is better. The fly ashes increase annually with the development of society and the increasing municipal solid waste. The treatment and ultimate safe disposal of solid waste fly ashes has become a problem to be solved. The cement solidification has been widely used, because it's low-cost, simple treatment process and operation and fixed heavy metal very well.This article based on "National Natural Science Foundation of China (51002110)" the subject of "heavy metals in MSWI fly ash cement clinker study on occurrence mechanism of migration". MSWI fly ash was for the subject investigated of this dissertation. Water, phosphoric acid and phosphate solution as pretreatments was researched. The best of the conditioning regimen was found during different concentrations, temperature and pretreatment of curing time on curing through the heavy metals leaching toxicity. Studied on pretreatment of fly ash on hydration heat of cement water requirement of normal consistency, setting time, chemical shrinkage, compressive strength and effect of curing. To explore the mechanism of pretreatmented ash on hydration and curing of cement. Main work and achievements are as follows.Research showed that, the result of alkalinity k which calculated by the chemical composition of ash was same to the pH of which determined by PHC-3S instrument, in laboratory conditions. We used Laser particle size Analyzer to analysis the ash particles. We also used XRD,SEM to analysis the ash. We used the ICP-AES to detect the heavy metal concentrations during the experiment.The results of heavy metals leached concentration are not obvious different among different concentrations, different temperature and different time of water, phosphateacid and phosphoric pretreatmented ash. The leaching of concentrations of pretreatmented samples are lower than the blank, which achieve national emission standards. The pretreatmented ash in cement solidification experiment showed: water requirement of cement and setting time are increase with increased content of ash. The ash after pretreatmented effect is smaller than the blank on water requirement of cement normal consistency and setting time.The compressive strength of cement is not much difference among the fly ash content of10,20and30. The compressive strength of cement are significantly reduced, when the addition is more than30%. The compressive strength of cement is still more than5MPa, when the content of pretreatmented ash less than70%. The pretreatmented ash had a great influence on hydration heat of cement. The volume of slurry is shrinkage without fly ash. But the volume slurry is expansion after adding fly ash.