【作者】 焦向科；

【导师】 张一敏；

【作者基本信息】 武汉理工大学 ， 矿物加工工程， 2012， 博士

【摘要】 地聚物是一种由Si04四面体和A104四面体通过共用氧原子交替键合而形成的新型无机胶凝材料。它一般以工业废渣为原料制备而成,且工艺过程简单,因此具有很好的发展前景。随着石煤提钒行业的快速发展,会产生大量的尾矿,这不仅占用土地,而且会引起二次环境污染。石煤提钒尾矿(以下简称为“提钒尾矿”)中Si和A1含量较高,因而有可能作为制备地聚物的硅铝原料。但由于提钒尾矿和传统的制备地聚物的硅铝原料(如偏高岭土和粉煤灰)相比,它的Si含量远高于A1含量,且活性较低,所以目前利用提钒尾矿为基质制备地聚物的研究很少。本研究首先分别通过湿法加碱煅烧、干法加碱煅烧和干法机械球磨的方式对原提钒尾矿(RVT)进行活化预处理,并通过碱溶浸出实验、X射线衍射(XRD)和傅立叶红外光谱(FTIR)和扫描电镜(SEM)对活化前后提钒尾矿的活性进行判断。实验结果表明,湿法加碱煅烧的方式最能有效促进提钒尾矿中晶态组分的分解,从而最能有效提高提钒尾矿的活性。再将选取的活化提钒尾矿(AVT)分别与铝质校正料(包括铝酸钠、偏高岭土、粉煤灰、铝酸盐水泥)复合,与碱硅酸盐溶液(通过硅灰与氢氧化钠溶液反应得到)混合制备地聚物。此外,考虑到在多数研究中作为激发剂的“碱硅酸盐溶液”具有腐蚀性而不利于地聚物的实际应用,所以同时以原提钒尾矿(RVT)为基质制备类地聚物水泥固体粉料。以抗压强度为考察指标,通过正交实验针对利用每种铝质校正料(或钙质原料)制备的地聚物试样的配方进行优化,并通过蒸压养护的方式进一步提高优选试样的抗压强度。通过SEM、ESEM、 FTIR、ATR-FTIR、27Al MAS-NMR、XRD和TG-DSC对早期地聚合反应过程和水化产物的微观结构进行了表征。结果表明,蒸压养护可以有效改善地聚物试样的微观结构和抗压强度；FTIR和27Al MAS-NMR分析结果共同说明在地聚合反应过程中A104四面体键接在Si04四面体上,形成三维网络结构；ESEM和ATR-FTIR原位在线分析表明对提钒尾矿的加碱煅烧活化过程可以提高早期地聚合反应的速率和程度,从而改善试样后期的微观形貌和抗压强度；以矿渣(KZ)为钙质原料制备的类地聚物水泥固体粉料砂浆试样的抗压强度普遍高于以钢渣(GZ)为钙质原料制备的类地聚物水泥固体粉料砂浆试样的抗压强度；XRD、TG-DSC和FTIR分析说明类地聚物水泥的水化产物中同时存在铝硅酸盐凝胶和水化硅酸钙(CSH)凝胶,而且适量CSH的存在可以改善试样的微观结构,提高其早期强度。对优选地聚物试样和普通硅酸盐水泥(OPC)砂浆试样的耐久性能及热稳定性能进行了研究。它们的耐久性能包括以下几方面：抗化学侵蚀性能、抗冻性能、抗渗性能。它们的热稳定性能通过煅烧之后试样抗压强度和微观结构的变化来评价。结果表明,部分优选地聚物试样的耐久性能和热稳定性能与普通硅酸盐水泥砂浆试样相当或优于普通硅酸盐水泥砂浆试样。最后研究了抑制地聚物试样“泛霜”行为的措施。将泛霜最严重的试样分别在600℃下煅烧3h和在150℃下蒸压养护5h。考虑到“泛霜”是由于试样中的可溶性盐由结构内部迁移至试样表面而形成,所以将试样放在去离子水中浸泡一定时间后,通过浸出液中Na的浓度来判断泛霜程度。结果表明,通过煅烧预处理和蒸压养护均能有效降低浸出液中Na的浓度,从而有效抑制试样的“泛霜”行为。本研究证实了提钒尾矿可以作为一种良好的硅铝原料制备地聚物胶凝材料。更多还原

【Abstract】 Geopolymer is a new kind of inorganic cementitious material that consists of SiO4and AlO4tetrahedra linked alternately by sharing the oxygen atoms. It is usually prepared from industrial waste residue as source materials, and the production process is relatively simple. Hence, it has good prospects. With the rapid development of vanadium extraction from stone coal, large amounts of tailings of vanadium extraction from stone coal (called "vanadium-extraction tailings" for short) have been produced, which not only occupy vast land but also cause secondary environmental pollution. The vanadium-extraction tailings consist mainly of Si and Al, thus they might be utilized as source materials for geopolymer synthesis. However, compared with conventional aluminosilicate source materials such as metakaolin (MK) and fly ash (FA), the tailings contain markedly higher Si and lower Al contents, and their reactivity are low. Hence, the tailings have seldom been used as base materials for geopolymer synthesis.In this study, wet-alkaline roasting, dry-alkaline roasting and dry mechanical ball milling were employed as the pretreatment for activation of the raw vanadium-extraction tailings (RVT). Reactivity of the RVT and the activated vanadium tailings (AVT) were evaluated via alkaline dissolution tests, X-ray diffraction (XRD), Fourier transform infared spectroscopy (FTIR) and scanning electron microscopy (SEM). The experimental results showed that, the wet-alkaline roasting pretreatment was the best way to promote the decomposition of the vanadium-extraction tailings’crystalline structure, and thus it can enhance reactivity of the vanadium-extraction tailings most effectively.Combined with the aluminum correcting materials (including sodium aluminate, MK, FA and aluminate cement), the selected AVT were mixed with alkaline silicate solution (which was created by the reaction between silica fume and sodium hydroxide solution) to prepare geopolymer products. Moreover, considering that the "alkaline silicate solutions" used as activators in most studies were corrosive and unfavorable for the practical application of geopolymer, the RVT were simultaneously used as base materials to create the geopolymer cement powder. With compressive strength as the investigation index, orthogonal experiments were conducted to optimize the geopolymer composition for each type of aluminum correcting materials (or calcium-bearing source materials). For the optimal geopolymer samples, autoclaving process was adopted to further enhance their compressive strength. The early-aged geopolymeric reaction and microstructure of the hydration products were characterized by SEM, Environmental Scanning Electron Microscope (ESEM), FTIR, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectra,27A1solid Magic Angle Spinning-Nuclear Magnetic Resonance (27Al MAS-NMR), XRD and TG-DSC analyses. The results indicated that, both microstructure and compressive strength of the geopolymer samples can be effectively improved by autoclaving process, and the FTIR and27Al MAS-NMR analyses confirmed that during geopolymeric reaction the AlO4tetrahedra was linked to the SiO4tetrahedra, forming three dimensional network structure. Moreover, the ESEM and ATR-FTIR in-situ analyses revealed that the alkaline roasting process can enhance the rate and extent of the early-aged geopolymeric reaction, thus the later hardened mortar samples’ compressive strength and microstructure can be improved. The compressive strength of the geopolymer cement mortar samples which adopted ore residue (KZ) as calcium-bearing source materials were generally higher than those of the geopolymer cement mortar samples which adopted steel residue (GZ) as calcium-bearing source materials. The XRD, TG-DSC and FTIR analyses jointly confirmed that aluminosilicate gel and hydrated calcium silicate (C-S-H) gel coexisted in the hydrated products of the geopolymer cement powder, and the appropriate amounts of CSH can improve the microstructure and early compressive strength of the samples.Subsequently, the durability and thermal stability of the selected geopolymer samples and ordinary Portland cement (OPC) mortar sample were investigated. The durability included the following aspects:chemical errosion resistance, freeze-thaw resistance and impermeability resistance. The thermal stability was evaluated in terms of the change of compressive strength and microstructure after heat treatment. The results revealed that, durability and thermal stability of the partial optimal geopolymer samples were similar or superior to those of the OPC mortar samples.Finally, further studies were conducted to decrease the efflorescence behavior of geopolymer sample. The geopolymer samples with the greatest presence of efflorescence, were selected and subjected to calcination at600℃for3h and autoclaving process at150℃for5h, respectively. Considering that efflorescence was caused by the transportation of soluble salts from inner of the structure to the surface of the samples, the geopolymer samples were immersed in deionized water for certain period, and the extent of efflorescence was evaluated by analyzing the Na concentration in the leaching liquid. The results demonstrated that, by means of the calcination pretreatment and/or autoclaving process, the Na concentration in the leaching liquid can be significantly decreased, thus the efflorescence behavior of geopolymer sample can be effectively prevented.This study has confirmed that the vanadium-extraction tailings can serve as favorable aluminosilicate source materials for synthesizing geopolymer binder materials.更多还原