【作者】 张鹏；

【导师】 韦江雄；

【作者基本信息】 华南理工大学 ， 材料学， 2016， 硕士

【摘要】 目前,我国氧化铝工业每年排放大量的固体废弃物赤泥,赤泥既占用了大量土地,又会对土壤、水源、大气等造成污染。现阶段对赤泥的利用主要是应用到生产建筑材料、回收有价金属和环境保护中吸附材料等领域,但是由于赤泥碱性强、金属含量低等问题,处理成本过高,可利用领域狭小,难以做到循环经济的效果,目前国内外尚无有效的大规模工业化处理方法,因此赤泥利用率低。本文研究了赤泥种类、辅助性胶凝材料和水玻璃掺量及模数对赤泥基碱激发胶凝材料组成结构的影响,确定了赤泥基碱激发胶凝材料的基本配比;在此基础上研究了在不同养护制度下赤泥基碱激发胶凝材料的性能及反应产物;最后制备了赤泥基碱激发胶凝隔热保温砂浆,本文的具体研究内容如下:(1)研究了赤泥种类、辅助性胶凝材料(粉煤灰和矿渣)和水玻璃掺量及模数对赤泥基碱激发胶凝材料组成结构的影响。烧结法赤泥碱激发材料具有良好的力学性能(免煅烧,不掺任何辅助性胶凝材料情况下3天达36.3MPa),而拜耳法赤泥碱激发材料却难以凝结硬化。在常温养护条件下碱激发粉煤灰早期强度低且发展缓慢,不宜和烧结法赤泥组成碱激发材料;矿渣掺量越多,赤泥基胶碱激发材料的强度越高(特别是早期强度)。赤泥基碱激发胶凝材料的早期强度随着水玻璃模数和掺量的增加而增强,但是随着龄期延长强度影响幅度逐渐减小。基于以上研究结果,确定了赤泥基碱激发胶凝材料的基本配比:原状烧结法赤泥70%,矿渣30%,激发剂水玻璃模数为2.4,掺量为5%(以Na2O计)。基于以上配合比,在常温养护环境下,赤泥基碱激发胶凝材料的胶砂3天抗压强度大于40MPa,28天抗压强度大于60MPa。水玻璃激发赤泥基碱激发胶凝材料初凝时间大约为30分钟,终凝时间约为40分钟。水化热反应速率曲线有两个放热峰:第一个峰为7分钟左右,是原料的溶解放热峰;第二个峰为50分钟左右,是碱激发反应放热峰,碱激发反应速度快,主要放热反应在5小时内完成。(2)研究了不同养护温度对赤泥基碱激发胶凝材料性能的影响。研究结果表明,提高养护温度和延长较高温度下的养护时间都可以促进硬化体结构致密,提高早期强度。当养护温度为20℃~60℃时,赤泥基碱激发胶凝材料的早期强度随着养护温度升高而增加,提高养护温度可以促进凝胶产物形成,并使产物结构致密,强度大幅提高。养护温度对赤泥基胶凝材料早期强度的提高作用较有效,随着龄期延长,不同养护温度下其后期强度趋近一致。养护制度不会使赤泥基碱激发材料的反应产物发生改变,反应产物均为无定形非晶态物质,包括水化硅酸钙(C-S-H)和水化硅铝酸钠(N-A-S-H),以及发生了Al取代Si形成水化硅铝酸钙(C-(A)-S-H)凝胶产物。(3)研究了骨料、水玻璃、乳胶粉及水灰比对赤泥基碱激发隔热保温砂浆性能的影响。骨料主要影响赤泥基碱激发隔热保温砂浆的干密度和导热系数;水玻璃影响隔热保温砂浆的强度发展;可再分散乳胶粉不能有效提高隔热保温砂浆的强度,但是可以改善砂浆的可变形能力和耐久性;水灰比可以改变水玻璃的浓度,进而影响赤泥基碱激发胶凝材料的激发效果和力学强度。基于以上研究结果,得到赤泥基碱激发隔热保温砂浆的最佳配比如下:赤泥基碱激发材料100g,水灰比1.8,膨胀珍珠岩量100g,乳胶粉4g,水玻璃掺量60g。基于以上配比制备的隔热保温砂浆符合国家标准Ⅱ型保温砂浆技术要求。更多还原

【Abstract】 In present, as a type of solid waste, large amounts of red mud are annually generated by alumina industry in our country. Red mud occupied a lot of ground, and also causes environment pollution to soil, groundwater resources and air. Currently, the main applications of red mud are building materials, utilization in recycling valuable metals and absorbent materials for environmental protection fields. However, due to the high alkalinity,low metal content of red mud, the processing cost is very high; it is difficult to achieve the effect of circular economy and there is no effective way to deal with large-scale industrialization, thus the abundant red mud discharged from alumina industry was mostly left unemployed. In this thesis, the influence of red mud types, supplementary cementitious material and content and modulus of water glass on the composition and structure of red mud based alkali activated cementitious materials was investigated, and its basic mixture was determined; based on this, the performance and reaction products of red mud based alkali activated cementitious materials cured under different curing systems was also investigated.Finally, the thermal insulation mortar based on red mud based alkali-activated was prepared.The specific research results included:(1) The influence of red mud types, supplementary cementitious material(Fly ash and slag)and content and water glass modulus of water glass on the composition and structure of red mud based alkali activated cementitious materials was investigated. Alkali activated sintered red mud cementitious material presented good mechanical properties(3 days compressive strength was up to 36.3MPa without calcination and supplementary cementitious materials);however, it was difficult for alkali activated Bayer red mud cementitious material to set and harden. Under the room temperature curing, the early strength of alkali activated fly ash was low and the strength development was slow, indicating that fly ash was not suitable for preparing alkali activated sintered red mud cementitious materials. On the other side, a higher mechanical strength(especially the early strength) was related to a higher content of slag in red mud based alkali activated cementitious materials. The early strength of the red mud based alkali activated cementitious materials increased with the increase of the modulus and content of water glass; however, the influence of water glass on the strength decreased withthe curing age. Based on the above results, the basic mixture of red mud based alkali activated cementitious materials was determined: 70 % original sintered red mud, 30 % slag, and 5 %water glass with a modulus of 2.4. By using this mixture,when cured at room temperature, red mud alkali activated cementitious materials present a 3 days compressive strength higher than40 MPa, and 28 days compressive strength higher than 60 MPa. The setting time of red mud based cementitious material activated by water glass was about 30 minutes, and the final setting time was about 40 minutes. There were two main exothermic peaks on the heat release curve: the first peak at about 7 minutes was the dissolutions material exothermic peak of raw materials; the second peak at about 50 minutes was alkali activated reaction exothermic peak;the alkali activated reaction rate was fast and the main exothermic reaction was completed within 5 hours.(2)The effects of curing temperatures on the properties of red mud based alkali activated cementitious materials were studied. The experimental results indicate that increased curing temperature and extended curing time of the higher temperature lead to a denser structure of reaction products and improved early strength. When the curing temperature was in the range of 20℃-60℃, the early strength of red mud based alkali activated cementitious materials increased with the increase of curing temperature, increasing the curing temperature can promote the formation of reaction products, thus leading to a denser structure and significantly increased strength. The beneficial effect of curing temperature effect was more obvious for the early strength of red mud based alkali activated cementitious materials, when the curing age was extended, the later strength was similar at different curing temperatures.The curing system didn’t change the reaction products of red mud based alkali activated cementitious materials, the reaction products were amorphous substances, including hydrated calcium silicate(C-S-H) and hydrated sodium silicate(N-A-S-H), in some regions, Si was replaced by Al to form hydrated calcium alumino-silicate gel products.(3) The effects of aggregates, water glass, emulsion powders and water/cement ratio on the performance of the red mud based alkali activated thermal insulation mortar were investigated.The dry density and thermal conductivity of thermal insulation mortar were mainly influenced by the aggregates; the strength development of thermal insulation mortar was influenced by water glass; Re-dispersible emulsion powders didn’t effectively increase the strength ofthermal insulation mortar, but improved the deformation capacity and durability of mortar; the water/cement ratio changed the concentration of water glass, then influenced the activation effect and mechanical properties of red mud based alkali activated thermal insulation mortar.Based on the above results, the optimum mixture of red mud based alkali activated insulation mortar are as follows: 100 g red mud based alkali activated cementitious materials, water to cementitious materials ratio of 1.8, 100 g expanded perlite, 4 g emulsion powder, 60 g water glass. The prepared red mud based alkali activated thermal insulation mortar conform to the technical requirements of national standard II thermal insulation mortar.更多还原