Solid Sulfur Ash Characteristics And Its Composite Cementitious Material Performance

In China, compreshensive resourse utilizationg of industrial waste is one of the most important measures for achieve the "green" economy and the sustainable development of industry. Sulfur ash is one of the main products by the thermal power plants after they have controled the emission of sulful dioxide. containing some burnt clay minerals, and similar with ash at chemical composition, suitable for the building materials' raw material. But there are some different problms,such as the great quality difference, containing minerals and residual lime which will lead to the poor stability in the complex binding materials. In current the utilization of sulfur ash at a low level, which was treatmented by heap or landfill.At present the application of sulfur ash is mainly refer the utilization of fly ash, and its application on the potential impact of buliding materials has not been fully demonstrated. The main purpose of this study is using sulfur ash largely in industry.on the one hand that will be help to reducing the cost of desulfurization after improving their industial added value, then promoting the measures for desulphurization in thermal power intustry in our country, at the other hand,that could be effectively reduce environmental pollution in cement and concrete industry, and achieve green production.For the lack of systematic research and specific issues when Sulfur ash was used in complex binder systems at high volume, this paper have studied the physical and chemical properties of sulfur ash, the mechanical properties and durability of the composite cementitious material which use the sulfur ash as mineral admixture, and on the basis of this study proposed the application of different threshold quality of sulfur dust (maximum security content).The main contents include:1. This paper mainly analysis the resource charateristics of sulfur ash produced in different regions' thermal powers, such as Yunnan, Hebei, Henan and other places.The data shows:Desulfurization of sulfur ash from the high coal region of southwest was significantly higher than other areas, the sulfur content in the ash (as SO3 weight) about 12%, in Central and Northern areas of low sulfur coal, the sulfur sulfur ash were lower.the sulfur ash's loss ignition is a large amount, the ash's minerals is mainly composed of CaCO3, SiO2, Fe2O3, and CaSO4(AnhydriteⅡ-E), and the particle surface of ash is loose, irregular surfaces and holes in internal dents.2. The paper has studied the basic physical and mechanical properties of the sulfur ash, in which the sulfur content≤13% and the dosage ranges form 15% to 45%.With the increase of content, the water demand of the composite material is increase.with the reduction of sulfur duet in ash, water demanding appears to be decreasing trend, ranging between 0.4%～3%, all of the sulfur ash has some regarding efffect.For mechanical property, when the content is 15%, the adhesive material's activity coefficients R>1, in which the sulfur ash content is 10%～13%, the 7d activity coefficients ranged from 0.7 to 0.9. At age for the 28d, the coefficient was the highest, all>1, the maximum activity coefficient is 1.31 when the group of sulfur content 10% and 45% content. From the actual bending, compressive strength, when the sulfur content of 10% of the highest intensity, in which content is 15%, the 28d flexural, compressive strength, respectively 8.94Mpa and 55.6Mpa, When sulfur content of 7%, in which the content is 45%, the intensity of the lowest, respectively 6.39Mpa and 32.9Mpa.3. The paper selected the expansion and the remaining elongation after dry up as the two indicators for research the deformation property of the composite material.The expansion of the composite material is greater than the expansion of Pure Portland cement. With the increase of content, the expansion rate increases what basically achieve the stable at 28d. When sulfur content≥10%, content from 30% to 45%, the expansion rate increase sharply. When the sulfur content is 13%, and content is 45%, the expansion of the composite material beyond the safe rang. The higher sulfur content, the greater remaining elongation, and the expansion can be converted into prestress to long compensate for the contraction.4. At durability, this paper selected the resistance to sulfate erosion and the frost as the two indicators to measure the tolerance of the composite material.With the increase of the sulfur ash's content, the resistance of sulphate erosion of the composite material decrease. When the sulfur content is 5%, the safe content of the corrosion resistance of ash is about 40%; When 7%, the safe content is about 35%; When>10%, the safe content is about 30%. Every sulfur ash all can improve the quality of the resistance of frost. With the increase of the sulfur content, the improved effect is gradully increased. When the sulfur content is 13%, the most obvious improvement's ash content is about 30%.5. Comprehensive the above results, the threshold for application of ash was analysisedoWhen using 52.5 strength portland cement clinker and sulfur ash to product the meeting requirements of eco-cement, mixed ash with sulfur content≤5%, the safe content should be≤40%, that is 42.5 strength cement; when 7%, the safe content should be≤35%, and when content≤31%, that is 42.5 strength cement, when content between 31% to 35%, that is 32.5 strength cement, the safe content of the sulfur≥10% ash is slightly larger than 30%, that is 42.5 strength cement. Compared with ordinary cement, the eco-cement has a long-term strength, shrinkage compensated, good forst resistance, effective resistance to sulfate erosion and other advantages.6. Finally, the paper tried to alkaline test on the composite material.when NaOH as activating agent, the composite material has obvious effects of the mechanical property, the effect is s better than the other complex containing Na-doped alkaline substances stimulate class'effection, but worse than the effection of the NaOH single doped.