偏高岭土—粉煤灰基地质聚合物的制备及其性能研究

地质聚合物是一种具有特殊网络结构的新型无机非金属胶凝材料。为了改善地质聚合物的力学性能,采用粉煤灰作为主要原料,液体水玻璃和氢氧化钠作为碱激发剂,将偏高岭土作为填料替代部分粉煤灰,制备了应用偏高岭土的粉煤灰基地质聚合物。对偏高岭土-粉煤灰基地质聚合物进行了扫描电子显微镜、抗折抗压强度以及折压比等表征,研究了偏高岭土-粉煤灰基地质聚合物结构以及强度的影响。结果显示：在粉煤灰基地质聚合物中添加偏高岭土会加快强度的形成,并且提高了粉煤灰基地质聚合物的强度。     

碱激发剂对铸造粉尘-粉煤灰基地质聚合物抗压强度的影响

以粉煤灰和铸造粉尘为主要原料,以KOH、NaOH、Na2SiO3、K2SiO3和水玻璃为碱激发剂,制备地质聚合物.研究了不同激发剂对铸造粉尘-粉煤灰基地质聚合物抗压强度的影响.结果表明:不同浓度的NaOH和KOH溶液的激发效果较差,制备的铸造粉尘-粉煤灰基地质聚合物的抗压强度较低.NaOH和KOH溶液与K2SiO3溶液混配复合激发剂可提高铸造粉尘-粉煤灰基地质聚合物的抗压强度.水玻璃溶液激发效果最好,随着水玻璃溶液模数的增加,铸造粉尘-粉煤灰基地质聚合物的抗压强度逐渐提高;当水玻璃模数为1.2时,铸造粉尘基地质聚合物28 d抗压强度达到最大,为21.4 MPa;继续增大水玻璃模数,铸造粉尘-粉煤灰基地质聚合物28 d抗压强度趋于下降.     

粉煤灰基地质聚合物固化Pb2+的化学形态分析

本文采用连续化学萃取法,对比分析了粉煤灰基地质聚合物和水泥中Pb2+的化学形态及迁移规律.试验结果表明:中性环境下粉煤灰基地质聚合物与水泥对Pb2+的固化能力相当,但Pb2+的存在形态不同; 在加速试验条件下,粉煤灰基地质聚合物对Pb2+的捕集率超过水泥.试验环境由中性向酸性转化时,水泥固化体中Pb2+由Ⅴ型向Ⅳ、Ⅲ型迁移,粉煤灰基地质聚合物中Pb2+由Ⅴ型向Ⅱ型迁移.粉煤灰基地质聚合物与水泥固化Pb2+的固化机理与迁移规则存在差异.     

矿渣-粉煤灰地质聚合物制备及力学性能研究

以矿渣、粉煤灰为原料,以硅酸钠和氢氧化钠为激发剂,制备了矿渣-粉煤灰基地质聚合物,测试了不同配合比下矿渣-粉煤灰基地质聚合物的7 d、14 d和28d的抗压强度.结果表明:当水胶比为0.3,氢氧化钠和硅酸钠的质量比为0.63,矿渣与粉煤灰的质量比为2,标准养护条件下,矿渣-粉煤灰基地质聚合物的7 d、14 d和28 d龄期的抗压强度分别达到57.0 MPa、69.0 MPa和84.3 MPa.     

富镁镍渣-粉煤灰基地质聚合物的制备与性能表征

以工业固体废弃物富镁镍渣和粉煤灰为原料,以水玻璃和NaOH为碱激发剂,制备了一系列富镁镍渣-粉煤灰基地质聚合物。研究了不同粉煤灰掺量对地质聚合物力学性能的影响,并测定地质聚合物的线性收缩和碱溶出,通过XRD、IR、DTA等手段对产物进行表征。结果表明:富镁镍渣-粉煤灰基地质聚合物的强度随粉煤灰的掺入先升高后降低,当掺量为30%(质量分数)时,地质聚合物的抗压强度可达最高值22.15 MPa,较镍渣基地质聚合物强度提高42.2%;XRD分析表明富镁镍渣中MgO以镁橄榄石相存在,而非游离态,故地质聚合物具有良好的体积安定性。     

基于文献计量的粉煤灰基地质聚合物研究趋势

与普通硅酸盐水泥相比，粉煤灰基地质聚合物可大幅减少生产过程中的碳排放，提供了开发新型绿色高附加值产品的新途径。近10年来，粉煤灰基地质聚合物领域发文近6 000篇，有必要进行基于科学计量学方法的定量分析，为粉煤灰基地质聚合物研究及粉煤灰的绿色综合利用提供参考。本文检索Web of Science核心合集及中国知网学术文献总库中文献，基于CiteSpace分析发文群体和关键词，构建共现网络，分析研究趋势和热点。结果表明：2013—2023年粉煤灰基地质聚合物的研究热度持续保持；中、英文文献核心作者发文频次占比均超过5%,英文文献发文机构间合作更紧密；关键词共现图谱以及聚类和突现分析结果说明相关研究集中于力学性能和吸附性能，且后者逐渐成为近年的研究热点；粉煤灰基地质聚合物及其复合材料捕集CO₂气体和去除水体污染物的性能和机制仍为应用的热点课题之一。反应体系的化学组成是粉煤灰基地质聚合物力学性能和吸附性能区别于其他地质聚合物的主要因素，利用化学组成协同调控力学性能与吸附性能的研究是今后的一个主要发展趋势。     

粉煤灰基地质聚合物固化重金属离子的研究进展

本文简要介绍了粉煤灰基地质聚合物的反应过程、机理、产物,着重介绍了其在重金属离子固化方面的研究现状及主要成果,指出了当前粉煤灰基地质聚合物固化重金属研究中的不足并对其未来的研究进行了展望.     

碱激发粉煤灰-硅灰基地质聚合物的性能及表征

以粉煤灰(FA)和硅灰(SF)为主要原料制备碱激发地质聚合物胶凝材料,运用XRD、SEM、EDS及FTIR等测试手段研究了SF与FA的质量比(SF/FA)及不同碱激发剂(NaOH和KOH)对粉煤灰-硅灰基地质聚合物砂浆力学性能及组织结构的影响.研究结果表明,随着SF/FA的增大,碱激发粉煤灰-硅灰基地质聚合物的抗压强度和抗折强度逐渐增大,最高可分别达到23.89 MPa和6.60 MPa,NaOH的激发效果强于KOH.碱激发粉煤灰-硅灰基地质聚合物结构中新生成了菱沸石相和无定形N-A-S-H凝胶相,FA和SF反应不完全,结构中仍存在未反应的FA颗粒及SF颗粒.FTIR结果表明N-A-S-H相的存在,随着SF/FA的增大,碱激发粉煤灰-硅灰基地质聚合物中[AlO6]9-八面体和[AlO4]5-四面体发生了结构重组,配位状态进一步完善,且T-O-Si(T=Al,Si)发生了聚合,致使地质聚合物强度逐渐增大.     

粉煤灰基地质聚合物力学性能及碱渣改性机理

为探索粉煤灰基地质聚合物的力学特性,通过12组胶砂试样的抗折和抗压强度研究NaOH掺量、养护条件、龄期和碱渣掺量对力学性能的影响,对比不同因素下试样胶砂表面孔隙特征,分析了碱渣对粉煤灰基地质聚合物体系的改性机理.结果表明:1.NaOH溶液过剩使强度降低;高温养护能提高强度;粉煤灰基地质聚合物的养护不需要太大的湿度.2.碱渣掺量小于27％时,对粉煤灰-NaOH体系强度有显著的改性作用.CaCO3增大溶液碱性,减小胶砂流动性,影响地质聚合物的微观结构,有效改善体系收缩程度.3.可溶性含钙组分中Ca2参与生成C-SH凝胶,与地质聚合物协同作用提高胶结性,减小孔隙的连通性.     

铸造粉尘-粉煤灰基地质聚合物的力学性能和微观结构分析

以粉煤灰为主要原料,以铸造粉尘为掺合料,水玻璃溶液为碱激发剂,制备地质聚合物.研究了养护龄期和水灰比对铸造粉尘-粉煤灰基地质聚合物抗压强度的影响.结果表明,铸造粉尘-粉煤灰基地质聚合物的抗压强度随养护龄期的延长而增大,随水灰比的增大先增大后减小;当水玻璃模数为1.2,水灰比为0.4时,地质聚合物28 d抗压强度达到最大,为21.4 MPa.X衍射分析表明,形成的地质聚合物主要为无定形矿物相;红外光谱分析表明,地质聚合物中有较多的非晶态铝硅酸盐生成;SEM分析显示地质聚合物具有良好的致密结构.     

Synthesis and characteristics of fly ash and bottom ash based geopolymers–A comparative study

The research was carried out to develop geopolymers mortars and concrete from fly ash and bottom ash and compare the characteristics deriving from either of these products. The mortars were produced by mixing the ashes with sodium silicate and sodium hydroxide as activator solution. After curing and drying, the bulk density, apparent density and porosity, of geopolymer samples were evaluated. The microstructure, phase composition and thermal behavior of geopolymer samples were characterized by scanning electron microscopy, XRD and TGA-DTA analysis respectively. FTIR analysis revealed higher degree of reaction in bottom ash based geopolymer. Mechanical characterization shows, geopolymer processed from fly ash having a compressive strength 61.4 MPa and Young's modulus of 2.9 GPa, whereas bottom ash geopolymer shows a compressive strength up to 55.2 MPa and Young's modulus of 2.8 GPa. The mechanical characterization depicts that bottom ash geopolymers are almost equally viable as fly ash geopolymer. Thermal conductivity analysis reveals that fly ash geopolymer shows lower thermal conductivity of 0.58 W/mK compared to bottom ash geopolymer 0.85 W/mK.     

Influence of new organic alkali activators on microstructure and strength of fly ash geopolymer

The fly ash geopolymer with improved mechanical properties was prepared by a new mixture alkali activator. In this paper, sodium tert-butanol, an organic strong alkali was used as an activator for preparing fly ash geopolymer to improve their mechanical properties. The effect of activator content and type on the macroscopic level of fly ash geopolymer was investigated experimentally by three types of activators: sodium tert-butanol, sodium silicate, and sodium tert-butoxide/sodium silicate mix activator. The microstructure of the fly ash geopolymer was characterized by ATR-FTIR, SEM-EDS, XRD, and Brunauer-Emmett-Teller (BET) physical adsorption method. The results showed that the new mixture alkali activator prepared by 5% sodium tert-butoxide and 10% sodium silicate improved the denseness and integrity of the microstructure of the fly ash geopolymer. Consequently, the mechanical properties of fly ash geopolymer are improved. The microscopic results demonstrated that the C–OH in tert-butanol after the hydrolysis of sodium tert-butoxide and Si–OH in the geopolymer can form C–O–Si bonds, forming a more complex three-dimensional network structure. This paper reveals the enhancement mechanism of organic alkali as activators for preparing fly ash geopolymer, and provides support for the subsequent development of organic strong alkali activators.     

Suitability of Sarawak and Gladstone fly ash to produce geopolymers: A physical,chemical, mechanical,mineralogical and microstructural analysis

Two types of fly ash sourced from Sarawak, Malaysia and Gladstone, Australia reflect differences in chemical compositions, mineral phase and particle size distributions. In this paper, the Sarawak fly ash was used to produce geopolymer in comparison to the well-developed Gladstone fly ash-based geopolymer. Characteristics of fly ash and mixtures proportions affecting compressive strength of the geopolymers were investigated. It is found that the variations of both fly ash types on particle size distributions, chemical compositions, morphology properties and amorphous phase correspond to the compressive strength. The results obtained show that after 7 days, geopolymer using Sarawak fly ash has lower compressive strength of about 55 MPa than geopolymer using Gladstone fly ash with strength of about 62 MPa. In comparison with Gladstone fly ash-based geopolymer, it showed that Sarawak fly ash-based geopolymer can be a potential construction material. Moreover, the production of Sarawak fly ash-based geopolymer aids to widen the application of Sarawak fly ash from being treated as industrial waste consequently discharging into the ash pond.     

室温碱激发低钙粉煤灰地质聚合物配比试验研究

为得到室温下粉煤灰与碱激发剂质量比、水玻璃与氢氧化钠溶液质量比和氢氧化钠溶液摩尔浓度对粉煤灰地质聚合物力学性能的影响,以低钙粉煤灰为原料,制备了地质聚合物胶凝材料。采用正交试验方法,分析粉煤灰地质聚合物抗压强度,探讨碱激发剂配比对粉煤灰地质聚合物力学性能的影响,结合SEM、XRD和FTIR对试样进行表征,并对该材料的应力-应变曲线进行了研究。结果表明:粉煤灰地质聚合物的抗压强度随着激发剂掺量的减少而增大,水玻璃在激发剂中的比值与粉煤灰地质聚合物的抗压强度呈现正相关,其中粉煤灰与碱激发剂质量比为1.8,水玻璃与氢氧化钠溶液质量比为2.5且氢氧化钠溶液的浓度为10 mol/L时,120 d龄期的抗压强度可达51.98 MPa。对应力-应变曲线分析得出,在一定程度上,激发剂的掺入量对粉煤灰地质聚合物的破坏应变和弹性模量有较大影响。SEM、XRD和FTIR分析表明随着养护时间增长,胶凝材料体系内结构更致密,生成了更多的硅铝酸盐凝胶。     

粉煤灰基地聚物的性能影响因素及其凝胶产物研究进展

粉煤灰基地聚物材料因绿色、低碳等优点受到建材行业关注。本文基于地聚物的形成及优势,分析了粉煤灰作为硅铝基材的优点,着重阐述了激发剂离子、养护方式和钙组分对粉煤灰基地聚物材料性能的影响,综述了粉煤灰基地聚物材料的凝胶产物变化及其反应机理研究进展。目前含钙固废作为添加物逐渐应用于改性粉煤灰基地聚物中,因此明确凝胶产物组成和反应机理将为粉煤灰基地聚物材料性能优化提供理论指导。     

Thermoelectric properties of geopolymers with the addition of nano-silicon carbide (SiC) powder

This paper investigated the effects of nano-silicon carbide (SiC) powder on the thermoelectric properties of both fly ash and metakaolin based geopolymer. The influences of different parameters, i.e., SiC dosage, alkali concentration and curing temperature, were investigated. Results showed that the addition of SiC powder effectively increased the Seebeck coefficient of geopolymers because of the quantum confinement effect. A higher alkali concentration is capable of increasing the Seebeck coefficient of both fly ash and metakaolin based geopolymer, while curing temperature has an insignificant influence on the Seebeck effect of metakaolin based geopolymer.     

粉煤灰地聚合物力学性能影响因素研究综述

粉煤灰地聚合物是以粉煤灰为硅铝质原料制备的,具有强度高、耐高温、耐腐蚀、有效固封金属离子等优点。但它固有的脆性以及需高温养护才能快速获得高强度的特点限制了其运用范围,而以纤维作为增强材料不仅可以提高粉煤灰地聚合物的强度,还可以改善其延性和韧性。本文主要从粉煤灰原料特性、碱激发剂、养护制度和增强材料四方面入手,重点阐述了粉煤灰粒径和化学组成,碱激发剂的种类、用量和模数,升温养护时间和初期养护温度对抗压强度的影响,以及纤维对粉煤灰地聚合物抗压强度和弯曲性能的影响。最后,根据现有的研究成果,对四种影响因素分别是如何影响粉煤灰地聚合物力学性能进行总结。     

Factors affecting the suitability of fly ash as source material for geopolymers

The suitability of fly ash stock piles for geopolymer manufacturing was studied. The results of chemical analyses, X-ray diffraction (XRD) and particle size distribution (PSD) of five sources of fly ash obtained from coal-fired power generating plants in the US are presented. Geopolymer paste and concrete specimens were prepared from each stock pile. The specimens were subjected to an array of chemical and mechanical tests including XRD, RAMAN spectroscopy, setting time and compressive strength. A correlation study was undertaken comparing the fly ash precursor chemical and crystallographic compositions as well as particle size distribution, with the mechanical and chemical characteristics of the resulting geopolymer. Factors inherent to the fly ash stockpile such as particle size distribution, degree of vitrification and location of the glass diffraction maximum were found to play an important role in the fresh and hardened properties of the resulting geopolymer.     

Mechanical properties and microstructure evaluation of fly ash - Slag geopolymer foaming materials

The existing fly ash-slag foaming geopolymer materials generally have the shortcomings of low fly ash content and low porosity. It is urgent to develop geopolymer foaming materials with high fly ash content and high porosity. Using fly ash and slag as the main raw materials, geopolymer foaming materials were prepared by alkali activation. The effects of activator content and sodium silicate modulus on the macroscopic mechanical properties, pore structures and microstructures of geopolymer foaming materials were studied. The experimental results showed that when the activator content was 21% (wt.) and the modulus of sodium silicate was 1, the specimen exhibited the best performance. The compressive strength of the specimen reached 2.18 MPa at 28 d, the porosity was 63.07%, and the average pore sizes of macroscopic pores were 920 μm. Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and Scanning Electron Microscopy and Energy Dispersive Spectrometer (SEM-EDS) analysis showed that when the content of activator was 21% and the modulus of sodium silicate was 1, the reaction grade of the system was the highest, reached 55.12%, meanwhile the main product Sodium silicate hydrate (N-A-S-H) gel produced the largest amount. The fractal dimension calculations showed that the spatial complexity of a specimen with large pores was greater than that of a specimen with small pores. This study can provide a basis for the design of geopolymer foaming materials with high proportion of fly ash and high porosity.