Investigations On The Cementing Mechanism Of Fly-ash From Power Plants And Its Hydration Reaction Kinetics Performance In Mine Filling

As one of the best effective and broadest mining method used by metal mine, for using up much cement as the cementing materials and makes the mining cost high, the filling mining used in underground mine becomes the fatal technology problem. The solid castoff — fly ash discharged by fire power plants in our country has over a hundred million tons, it piles up on ground and pollutes environment. So, developing all-round use fly ash has important strategic means to environmental protect and resource compositive applications. The dissertation has studied fly ash roundly and systemically aiming at its potential cementing performance and it can be developed a broader coming and cheaper filling cementing material.(1) Compositive using basic theories knowledge, such as sonochemistry, colloidal chemistry, thermodynamics, phase analysis, the paper has studied the filling material hydrating reaction mechanism on fly ash ,cement and tailings and the probability used as cementing agent in mine cementing filling from fly ash's physical performance, chemical component, activating mechanism and the forming process of filling materials frame.(2) Recuring XRD and SEM to observe and analysis filling materials and composing component and microcosmic frame of filling body, the paper opens out the filling body's microcosmic configuration: it is a three-phase and a great deal of holes system forming from tailings, non-hydrating fly ash, water and a little of air.(3) The fly ash's activeness can be activated by activators. Joining lime, gypsum and CaCl₂ may increase fly ash's activeness clearly and improve filling body's intensity.(4) According to the characteristic fly ash , cement and tailings system hydrating process, the paper builds up a physical model of fly ash , cement and tailings hydrating reaction. Thereundering the model and using TG, DT, SEM, EDT, XRD et al and filling body's intensity, combining the hydrating theories of cement and lime, the paper open out the hydrating system of fly ash, cement and tailings is a grading, multilayer process.(5) Using Ca(OH)2 as the bridge the fly ash and cement reaction in filling slurry to build the model of hydration reaction kinetics matchs case the true reaction. From the model, to increase the reaction degree of fly ash and the thickness of filling slurry are the key to improve the intensity of filling body. Especially, when the thickness of filling slurry rises from 65% to 70%, the reaction degree in system rise 25%, and the fly ash 55%; when thickness rise to 75%, the reaction degree rise 58% and the fly ash 1.5 times.(6) Under the function of activators, the hydrating reaction performance of fly ash is an absorbing by stage. Activators work by ions independently, OH" and Na+ can enhance the network tetrahedron broken ability of vitreous body in fly ash, and Ca2+ and SO42" promote the forming of hydrating products. The absorption of Ca(OH)2 by fly ash is imbalance. One of the reasons is the dissolving out of Ca2+, and the other is the transition of hydrating products and the difference in Ca2+ and OH" content in hydrating products.(7) The paper educe the conclusions: the fly ash in mine filling can not only advance the filling body's intensity, improve the filling body's frame, but also decrease the sieve rate in filling body, reduce the draining cost under well, lessen the filling pollution to under well environment.(8) The industry test make know: the fly ash filling body is more advantageous to its intensity advance in the moist environment in well, and can save a great deal of dosage of cement to reduce the filling cost.This study lays the foundation of the farther use of artificial pozzolana including fly ash, smelt slag et al, and break a new path for the fly ash's compositive utilization. So, the study has prominent economical and social benefit.