氧化石墨烯对水泥基材料结构与性能的影响
发布时间：2018-08-09 18:37
【摘要】：混凝土是应用最为广泛的水泥基复合材料,目前存在抗折强度低、韧性差、易裂缝等主要问题,影响了水泥基复合材料的使用性能和耐久性。针对这一问题,目前主要通过添加纤维增强材料来提高混凝土的整体强度和韧性,但是易裂缝问题依然存在,其原因是裂缝主要产生于混凝土中的硬化水泥石,添加纤维增强材料不能改变混凝土中起黏结作用的水泥石的结构和性能。前期研究发现氧化石墨烯(grahene oxide,简称GO)的高比表面积以及丰富官能团能够调控水泥水化产物形成规整性晶体,并使水泥石的力学性能特别是抗折强度有显著的提高,有助于从微观结构上解决水泥基复合材料的易裂缝问题。研究中也发现了GO的掺入使得水泥净浆流动性显著下降,并且GO在水泥浆体中存在着分散不均匀的问题,因此本论文针对GO掺入水泥基材料中存在的这些问题进行了研究,为GO在水泥基材料中的应用奠定基础。(1)采用对石墨进行氧化及超声波分散的方法制备了GO纳米片层分散液,并对GO纳米片层的含氧量、化学结构和纳米尺寸进行了检测与表征。石墨与氧化剂KMn O4质量比为1:6,氧化反应时间为12 h时,GO含氧量可达到31%左右,GO结构中含有羧基-COOH、羟基-OH以及环氧基-O-等基团;在固体状态下GO片层间距由0.35 nm扩大至0.84 nm;分散状态的GO纳米片层厚度为1.23 nm,片层大小为200 nm至500 nm。(2)系统地研究了GO掺量对水泥净浆流动度、硬化水泥石力学性能以及硬化水泥石微观结构的影响。研究结果表明随着GO掺量从0.01%增加到0.09%,水泥净浆流动度依次下降。GO掺量增加至0.03%时,水泥净浆流动度下降至160 mm以下;GO掺量增加至0.09%时,水泥净浆处于完全不流动状态。GO纳米片层分散液对水泥净浆流动性影响的规律为GO掺量每增加0.01%时,保持水泥浆体流动度在200 mm以上所需的聚羧酸系减水剂(polycarboxylate superplasticizer,简称PCs)掺量按照0.02%的比例增加。GO对水泥石力学性能的影响规律是随着GO掺量的增加,硬化水泥石的抗折强度与抗压强度均呈现先增加后下降的趋势,其最大抗压强度和抗折强度出现在GO掺量为0.01%时,在水化龄期为28天时的抗折强度、抗压强度分别为8.4 MPa和73 MPa。(3)采用分散剂对GO进行了分散并研究了分散剂对GO纳米片层分散液分散性的影响。发现PCs与十二烷基苯磺酸钠(sodium dodecyl benzene sulfonate,简称SDBS)复配分散GO的效果最好且最佳复配分散的固含量比为1:1:1。复合物GO/PCs/SDBS的吸光度值为0.62,均高于GO与PCs直接混合的吸光度(0.56)和GO与SDBS直接混合的吸光度(0.55)。GO/PCs/SDBS掺入水泥浆中可使GO纳米片层均匀分散,促使水泥水化产物形成密实规整的水化晶体,并优先出现在水泥石中的孔洞、裂缝、结构疏松等缺陷部分,使水泥石形成了密实的结构,GO/PCs/SDBS的掺量从0.01%增加至0.09%,微观结构中水泥水化产物越密实规整,并且使硬化水泥石的孔隙率下降、抗压强度和抗折强度显著提高,其中最大抗压强度和抗折强度出现在GO/PCs/SDBS掺量为0.07%时,在水化龄期为28天时的抗折强度、抗压强度分别为13.5 MPa和79 MPa。(4)提出GO纳米片层调控水泥水化产物的作用机理,GO纳米片层主要是通过调控水泥水化晶体的生长及形状达到对水泥石微观结构的控制,最终达到增强增韧水泥基材料的作用。本论文的创新之处在于得到了GO纳米片层对于水泥基材料流动性影响的规律以及制备了GO/PCs/SDBS复合材料,实现了GO纳米片层在水泥基材料中的均匀分散。研究结果对于提高水泥基材料的抗折强度及抵抗裂缝和延长使用寿命具有重要意义。
[Abstract]:Concrete is the most widely used cement based composite material. At present, there are many problems, such as low flexural strength, poor toughness, easy crack and so on. It affects the performance and durability of cement based composites. At present, the strength and toughness of high concrete are raised mainly by adding fiber reinforced material, but it is easy to crack. The reason is that the crack is mainly caused by the hardened cement stone in the concrete. Adding fiber reinforced material can not change the structure and performance of the cement stone in the concrete. The high specific surface area of grahene oxide (GO) and the rich functional groups can regulate the hydration production of cement. The mechanical properties, especially the flexural strength of the cement stone are greatly improved, which helps to solve the fracture problem of cement based composites from the micro structure. It is also found that the mixing of GO makes the cement paste fluidity significantly decrease, and the dispersion of GO in cement paste is not uniform. Therefore, this paper studies the problems existing in the GO doped cement based materials and lays the foundation for the application of GO in the cement-based materials. (1) the GO nanoscale dispersions are prepared by oxidation and ultrasonic dispersion of graphite, and the oxygen content, chemical structure and nano size of the GO nanoscale layer are detected. And characterization. When the mass ratio of graphite and oxidizing agent KMn O4 is 1:6, the oxidation reaction time is 12 h, the oxygen content of GO can reach about 31%. The GO structure contains carboxyl -COOH, hydroxyl -OH and epoxy group -O- groups. In the solid state, the interval between the GO lamellae of GO expands from 0.35 nm to 0.84 nm; the thickness of the dispersed nanoscale layer is 1.23 and the size of the lamellar is 200. Nm to 500 nm. (2) systematically studied the effect of GO content on the flow degree of cement paste, the mechanical properties of hardened cement stone and the microstructure of hardened cement stone. The results showed that with the increase of GO content from 0.01% to 0.09%, the flow degree of cement paste decreased to 0.03%, and the cement paste fluidity decreased to less than 160 mm; GO admixture was added to the cement paste. When the amount of the cement is increased to 0.09%, the effect of the cement paste in the complete non flow state of the.GO nanoscale dispersions on the fluidity of the cement paste is that the Polycarboxylic Water reducing agent (polycarboxylate superplasticizer, abbreviated as PCs) required to maintain the cement slurry flow degree above 200 mm (polycarboxylate superplasticizer, abbreviated as PCs) is added to the cement paste fluidity. The effect of adding.GO on the mechanical properties of cement stone is that with the increase of GO content, the flexural strength and compressive strength of hardened cement show a trend of increasing and then decreasing, and the maximum compressive strength and flexural strength appear at the age of 28 days when the age of hydration is 0.01%, and the compressive strength is 8.4 MPa and 73 MPa., respectively. (3) the dispersing agent was used to disperse GO and to study the effect of dispersant on dispersion of GO nanoscale dispersions. It was found that PCs and twelve alkyl benzene sulfonate (sodium dodecyl benzene sulfonate, for short, SDBS) were best used to disperse GO and the best compound dispersive absorbance value of 1:1:1. compound GO/PCs/SDBS was 0.. 62, the absorbance (0.56) and the absorbance of direct mixture of GO and PCs and the absorbance of GO and SDBS directly mixed with SDBS can make the GO nanoscale evenly dispersed, and promote the cement hydration products to form dense and regular hydrated crystals, and give priority to the holes, cracks and loose structure in the cement stone and make the cement. The stone formed a dense structure, the amount of GO/PCs/SDBS added from 0.01% to 0.09%. The cement hydration products are more dense and regular in the microstructure, and the porosity of the hardened cement stone is reduced, the compressive strength and flexural strength are significantly improved. The maximum compressive strength and flexural strength are now 0.07%, and the age of hydration is 2 at the age of 2. The flexural strength and compressive strength of 8 days are 13.5 MPa and 79 MPa. (4). The mechanism of GO nanoscale regulation of cement hydration products is proposed. The GO nanoscale is mainly controlled by the growth and shape of cement hydration crystals and the effect of reinforced toughening cement-based materials. The innovation is to obtain the regularity of the influence of the GO nano layer on the fluidity of cement based materials and the preparation of GO/PCs/SDBS composites. The uniform dispersion of the GO nanoscale in the cement-based materials is realized. The results are of great significance to improve the flexural strength of the cement-based materials and to resist the crack and prolong the service life.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
本文编号：2174951
[Abstract]:Concrete is the most widely used cement based composite material. At present, there are many problems, such as low flexural strength, poor toughness, easy crack and so on. It affects the performance and durability of cement based composites. At present, the strength and toughness of high concrete are raised mainly by adding fiber reinforced material, but it is easy to crack. The reason is that the crack is mainly caused by the hardened cement stone in the concrete. Adding fiber reinforced material can not change the structure and performance of the cement stone in the concrete. The high specific surface area of grahene oxide (GO) and the rich functional groups can regulate the hydration production of cement. The mechanical properties, especially the flexural strength of the cement stone are greatly improved, which helps to solve the fracture problem of cement based composites from the micro structure. It is also found that the mixing of GO makes the cement paste fluidity significantly decrease, and the dispersion of GO in cement paste is not uniform. Therefore, this paper studies the problems existing in the GO doped cement based materials and lays the foundation for the application of GO in the cement-based materials. (1) the GO nanoscale dispersions are prepared by oxidation and ultrasonic dispersion of graphite, and the oxygen content, chemical structure and nano size of the GO nanoscale layer are detected. And characterization. When the mass ratio of graphite and oxidizing agent KMn O4 is 1:6, the oxidation reaction time is 12 h, the oxygen content of GO can reach about 31%. The GO structure contains carboxyl -COOH, hydroxyl -OH and epoxy group -O- groups. In the solid state, the interval between the GO lamellae of GO expands from 0.35 nm to 0.84 nm; the thickness of the dispersed nanoscale layer is 1.23 and the size of the lamellar is 200. Nm to 500 nm. (2) systematically studied the effect of GO content on the flow degree of cement paste, the mechanical properties of hardened cement stone and the microstructure of hardened cement stone. The results showed that with the increase of GO content from 0.01% to 0.09%, the flow degree of cement paste decreased to 0.03%, and the cement paste fluidity decreased to less than 160 mm; GO admixture was added to the cement paste. When the amount of the cement is increased to 0.09%, the effect of the cement paste in the complete non flow state of the.GO nanoscale dispersions on the fluidity of the cement paste is that the Polycarboxylic Water reducing agent (polycarboxylate superplasticizer, abbreviated as PCs) required to maintain the cement slurry flow degree above 200 mm (polycarboxylate superplasticizer, abbreviated as PCs) is added to the cement paste fluidity. The effect of adding.GO on the mechanical properties of cement stone is that with the increase of GO content, the flexural strength and compressive strength of hardened cement show a trend of increasing and then decreasing, and the maximum compressive strength and flexural strength appear at the age of 28 days when the age of hydration is 0.01%, and the compressive strength is 8.4 MPa and 73 MPa., respectively. (3) the dispersing agent was used to disperse GO and to study the effect of dispersant on dispersion of GO nanoscale dispersions. It was found that PCs and twelve alkyl benzene sulfonate (sodium dodecyl benzene sulfonate, for short, SDBS) were best used to disperse GO and the best compound dispersive absorbance value of 1:1:1. compound GO/PCs/SDBS was 0.. 62, the absorbance (0.56) and the absorbance of direct mixture of GO and PCs and the absorbance of GO and SDBS directly mixed with SDBS can make the GO nanoscale evenly dispersed, and promote the cement hydration products to form dense and regular hydrated crystals, and give priority to the holes, cracks and loose structure in the cement stone and make the cement. The stone formed a dense structure, the amount of GO/PCs/SDBS added from 0.01% to 0.09%. The cement hydration products are more dense and regular in the microstructure, and the porosity of the hardened cement stone is reduced, the compressive strength and flexural strength are significantly improved. The maximum compressive strength and flexural strength are now 0.07%, and the age of hydration is 2 at the age of 2. The flexural strength and compressive strength of 8 days are 13.5 MPa and 79 MPa. (4). The mechanism of GO nanoscale regulation of cement hydration products is proposed. The GO nanoscale is mainly controlled by the growth and shape of cement hydration crystals and the effect of reinforced toughening cement-based materials. The innovation is to obtain the regularity of the influence of the GO nano layer on the fluidity of cement based materials and the preparation of GO/PCs/SDBS composites. The uniform dispersion of the GO nanoscale in the cement-based materials is realized. The results are of great significance to improve the flexural strength of the cement-based materials and to resist the crack and prolong the service life.
【学位授予单位】：陕西科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528
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