| Fly ash is an industrial waste from the coal-consumed power plant. This thesis concerns contemprary research and application of fly ash, especially its application in constructional material. Research shows that fly ash has poor activity, and carbon residue in fly ash at the same time serves as an obstacle to its better application in constructional material. By optimizing compound activators, and choosing the better ways to remove carbon residue, mortars of fly ash are analyzed and reserached with the help of XRD, SEM and mechanical testing instruments.Floatation method, and activation combining mechanical activation, chemical activation and steam curing, are adopted in this thesis to effictively exploit the potential activity in fly ash. Floatation method is much more effective than high temprature method in removing carbon residue. Besides, the former is energy-saving and environmentally-friendly. This method can also grind fly ash to finer grains so as to destory its hard surface and enhance its activity. Finer fly ash will be able to mix up well with the compound activators, thereby improving its ability to dissolve in water. The selected compound activators will maximize the activity in fly ash. Meanwhile, The optimization of curing conditions will help its solubility in water.The result shows that the compression strength of the fly ash mortars ,with incorporation of 75% fly ash, can reach 41 Mpa, and it reachs the advanced international standard when floatation method is employed, and fly ash is ground for 2 hours by fine ball milling and for 30 minutes by mixing milling, with lime being applied, the temperature being 60 degrees for 28 days. An anylasis of the fly ash gel by XRD show that this product contains large amounts of calcium silicate hydrate, monocalcium aluminate hydrate and ettringite. A SEM job about the micro constitution of the hydration product shows that fly ash mortar has transformed into the fly ash gel with an interwoven continous constructure.
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