【作者】 刘帅；

【导师】 陈瑜； 袁庆莲；

【作者基本信息】 长沙理工大学 ， 工程硕士（专业学位）， 2018， 硕士

【摘要】 粉煤灰地聚合物具有许多优于传统胶凝材料的工程技术性能,突出的可持续发展属性,正成为国内外学者的研究热点。然而,这类材料存在诸如泛碱严重、韧性低及强度发展不稳定等缺点,制约了其在道路工程中的大规模应用。随着纳米技术的飞速发展,胶凝材料引入纳米组分,给建材行业带来了崭新的生命力。而有关纳米粒子在粉煤灰地聚合物中的改性作用,国内外鲜见文献报道。本文以粉煤灰为主要原料,成功制备粉煤灰地聚合物,选择两种不同类型纳米材料(纳米SiO2和碳纳米管),开展纳米材料对粉煤灰地聚合物流动度、凝结时间和力学性能等影响研究,并运用XRD、FTIR和SEM等测试手段进行微观结构综合分析,探究其对粉煤灰地聚合物的改性作用机理,主要研究结论如下:1、随纳米SiO2或碳纳米管掺量增加,体系的流动度和凝结时间显著减小。净浆流动度最低分别降为119mm和83mm,砂浆流动度为98mm和71mm;净浆的初终时间分别缩短至62min和65min,终凝时间减少到75min及81min。两种纳米材料均可有效增强粉煤灰地聚合物的抗折和抗压强度,纳米SiO2最佳掺量为2.0%,净浆28d抗折和抗压强度提升74.64%和47.60%。砂浆28d抗折和抗压提升42.20%和42.52%。碳纳米管最佳掺量为0.10%,净浆3d抗折和抗压强度提高127.92%和158.34%;砂浆3d抗折和抗压强度上升59.78%和129.05%。同时,分别在两种材料的最优掺量下,粉煤灰地聚合物的抗裂性能最优,泛碱程度最低,耐久性良好。2、两种纳米材料的掺入均不会对地聚合产物的种类造成显著影响,但纳米Si02会参与粉煤灰地聚合反应并改变地聚合生成物的含量,而碳纳米管则不会,碳纳米管通过纤维桥联和网状填充作用分布于反应物基体当中。3、基于以上研究,结合微观试验分析结果,提出两种纳米材料对地聚合反应的改性机理:纳米Si02颗粒分散于基体相中,为反应体系中凝胶相的形成提供形核位置,在其周围形成的离子富集区域,加速原材料中各相的溶出速率,加剧反应进行;碳纳米管可以很好填充粉煤灰地聚合物的微细孔,极大地密实其整体结构,同时其优异的力学性能和韧性,可以有效地凭其桥联和拔出作用防止和控制基体产生缺陷。更多还原

【Abstract】 Fly ash based geopolymer has many engineering performances over the traditional cementitious materials,and its outstanding properties in the sustainable development are becoming the research focus of scholars at home and abroad.However,this material has shortcomings such as severe efflorescence,low toughness and unstable strength development etc.,which restrict their large-scale application in road engineering.With the rapid development of nanotechnology,the introduction of nano-scale componets into the cementitious materials has brought new vitality to the building materials industry.However,there are few reports about the modification of nanoparticles in fly ash based geopolymer.Fly ash based geopolymer has been successfully prepared by using fly ash as the main raw material in this passage.Two different types of nano-materials(nano-SiO2 and carbon nanotubes)were selected to carry out the flowability,setting time and the microstructure of fly ash based geopolymer was analyzed by XRD,FTIR and SEM.The main conclusions are as follows:1.With the increase of nano-SiO2 or carbon nanotubes,the fluidity and setting time of the system decrease significantly.The minimum fluidity of the geopolymer paste is reduced to 119 mm and 83 mm,and the mortar fluidity is 98 mm and 71 mm;the initial setting time of the paste is shortened to 62 min and 65 min,and the final setting time is reduced to 75 min and 81 min.Both nano-materials can effectively enhance the flexural and compressive strength of fly ash based geopolymer.The optimum content of nano-SiO2 is 2.0%,and the flexural and compressive strength of the paste is increased by 74.64%and 47.60%in 28 day.The 28 day’s flexural and compressive strength of mortar increased by 42.20%and 42.52%.The optimum content of carbon nanotubes is 0.10%,the flexural and compressive strength of the paste increased by 127.92%and 158.44%in 3 day;the 3 day’s flexural and compressive strength of the mortar increased by 59.78%and 129.05%.At the same time,under the optimal dosage of the two nano-materials,the fly ash based geopolymer has the best crack resistance,the lowest efflorescence and the better durability.2.The incorporation of the two nanomaterials does not significantly affect the type of geopolymerization products,but the nano-SiO2 will participate in the geopolymerization and change the content of geopolymerization products,while the carbon nanotubes will not.The carbon nanotubes are distributed in the reactant matrix by fiber bridging and network filling.3.Based on the above research and the results of microcosmic test,the modification mechanism of two nanomaterials to geopolymerization is proposed:the nano-SiO2 particles are dispersed in the matrix phase to provide nucleation position for the formation of the gel phase in the reaction system.The ion enrichment region forms around it,accelerating the dissolution rate of each phase in the raw material and intensifying the reaction.Carbon nanotubes can be filled with fine pores of fly ash based geopolymer,greatly compacting their whole structure,and their excellent mechanical properties and toughness can effectively prevent and control matrix defects by their bridging and pull-out effects.更多还原