工农业废弃物在混凝土中的资源化再利用

发布时间：2018-12-13 20:09

【摘要】：近年来绿色混凝土和材料可持续发展的概念,受到人们越来越多的关注。实现混凝土的绿色化和可持续化的一个重要途径就是减少水泥的用量、利用工农业废弃资源替代,这不仅有益于生态环境,同时实现了非再生性资源的可循环利用和有害物质的从低排放。已有研究表明,粉煤灰、硅灰、矿渣等工业废渣作为混凝土矿物掺合料使用减少了对环境和土地的污染,降低了混凝土的成本,而且从某些方面弥补水泥混凝土的性能缺陷,满足现代混凝土工程的设计和要求。为此本文通过试验测试了稻壳灰、磨细稻壳灰、钢渣、赤泥粉几种工农业废弃物作为矿物掺合料取代水泥质量分数10%～30%得到的混凝土的宏观力学性能、耐久性能和微观形态,同时将这几种工农业废弃物分别与粉煤灰、硅灰二元复掺取代10%～30%的水泥,得到二元复掺混凝土的各项性能,从宏观和微观两个层面上对掺有工农业废弃物的混凝土进行了较为综合和深入的研究。研究表明,磨细稻壳灰的掺入会降低混凝土水化产物的比表面积,提高混凝土内部的孔隙率,但孔隙趋向封闭,从而导致稻壳灰混凝土的抗氯离子渗透性随掺量增加而提高。当磨细稻壳灰以10%的质量分数取代水泥可以得到高强度高耐久性的混凝土,此时稻壳灰主要发挥了微集料效应和活性效应。钢渣可以看做活性较低的胶凝组分,水化活性比水泥低,但10%掺量的钢渣由于其微集料效应使混凝土的各项性能有所提高,20%掺量的钢渣各项性能与普通硅酸盐混凝土相似。稻壳灰、钢渣和硅灰的二元复掺混凝土均可提高材料的强度和耐久性。赤泥单独作为矿物掺合料可以得到有色混凝土,由于赤泥的高碱性提高了混凝土水化产物中氢氧化钙的含量,降低了混凝土的各项性能。同时赤泥的高碱性对硅灰、粉煤灰的二次反应活性有激发作用,赤泥和硅灰、粉煤灰的二元复掺改善了赤泥混凝土中氢氧化钙的定向取向,提高了混凝土的力学性能和耐久性,当赤泥和粉煤灰以1：3的比例作为复合矿物掺合料可以最有效地改善混凝土的力学性能和抗氯离子渗透性。SEM微观测试结果表明,混凝土宏观力学性能的变化都是微观结构的变化在宏观上的反应,微观结构的变化规律与宏观力学性能相符。
[Abstract]:In recent years, more and more attention has been paid to the concept of sustainable development of green concrete and materials. An important way to realize the greening and sustainability of concrete is to reduce the amount of cement and substitute the waste resources of industry and agriculture, which is not only beneficial to the ecological environment. At the same time, the recycling of non-renewable resources and the emission of harmful substances are realized. Studies have shown that the use of industrial wastes such as fly ash, silica fume and slag as admixtures for concrete minerals reduces environmental and land pollution, reduces the cost of concrete, and makes up for the performance defects of cement concrete in some ways. Meet the design and requirements of modern concrete engineering. In this paper, the macroscopic mechanical properties of concrete obtained by using rice husk ash, fine rice husk ash, steel slag and red mud powder as mineral admixtures to replace 10% cement mass fraction have been tested and tested in this paper. The durability and micromorphology of these industrial and agricultural wastes were mixed with fly ash and silica fume to replace 10% cement, and the properties of binary mixed concrete were obtained. The concrete mixed with industrial and agricultural wastes is studied comprehensively and deeply from macro and micro level. The results show that the specific surface area of concrete hydration products will be reduced and the porosity of concrete will be increased, but the pores tend to be closed, which leads to the increase of chloride permeability of rice husk ash concrete. When grilled rice husk ash replaces cement with 10% mass fraction, the concrete with high strength and durability can be obtained, and the rice husk ash mainly exerts the microaggregate effect and active effect. Steel slag can be regarded as a less active gelling component. The hydration activity is lower than that of cement, but 10% steel slag can improve the properties of concrete because of its micro-aggregate effect. The properties of 20% steel slag are similar to those of ordinary silicate concrete. The strength and durability of rice husk ash, steel slag and silica fume can be improved. The red mud can be used as mineral admixture alone to obtain colored concrete. Because of the high alkalinity of red mud the content of calcium hydroxide in concrete hydration product is increased and the properties of concrete are reduced. At the same time, the high alkalinity of red mud can stimulate the secondary reaction activity of silica fume and fly ash. The binary admixture of red mud, silica fume and fly ash improves the orientation of calcium hydroxide in red mud concrete, and improves the mechanical properties and durability of concrete. When the mixture of red mud and fly ash is used as compound mineral admixture at 1:3, the mechanical properties of concrete and the resistance to chloride ion permeability can be improved most effectively. The results of SEM microcosmic test show that, The change of the macroscopic mechanical properties of concrete is the reaction of the changes of the microstructure in the macroscopic, and the law of the change of the microstructure is consistent with the macroscopic mechanical properties.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528

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