【作者】 王敏；

【导师】 王汝敏；

【作者基本信息】 西北工业大学 ， 化学， 2018， 博士

【摘要】 高性能水泥基材料因其所表现出的优异综合性能而被广泛应用于基础建设领域。然而,聚合物乳液改性水泥的机理研究却远远滞后于应用,利用化学分析的手段,有望对聚合物乳液改性水泥材料内部的化学反应进行研究;另一方面,氧化石墨烯（GO）是近年来新兴的一种二维材料,将GO用于改性水泥,有望制备出超高性能的水泥基材料;并且,GO片层结构上的活性基团给予了其良好的结构设计性,设计合成化学改性的GO,可以进一步研究其结构对水泥性能的影响。论文的主要研究内容及结果如下:（1）研究聚丙烯酸酯（PA）乳液改性水泥的性能;PA乳液会改善水泥的抗折强度、收缩率、保水性和粘度,会降低水泥的抗压强度。另外,7.5%的加入量为PA乳液作为改性剂增强水泥各项性能的上限,当PA乳液的加入量大于7.5%后,就会对水泥的引气性产生消极的影响,使其工作性降低。用傅立叶红外光谱（FT–IR）、X射线光电子能谱（XPS）、凝胶渗透色谱（GPC）以及pH计等分析方法研究PA乳液改性水泥体系内的化学反应。研究表明,整个体系内发生的反应可以分为三个阶段;第一阶段水化反应为主导反应;在第二阶段,PA乳液中含有的酯基会在水泥水化反应产生的富碱、升温体系中发生水解反应而生成羧基,这时水解反应占主导地位;第三阶段这些羧基会和水泥水化产生的Ca（OH）₂发生化学反应,生成Ca（HCOO）₂,这种化学反应会将不同的PA大分子链连接起来,反应的持续发生就会使PA大分子链形成以Ca²⁺相连的网状结构,这一阶段水化和交联反应占主导地位。（2）以丁苯（SBR）乳液和羧基丁苯乳液（XSBRL）为代表,研究聚合物乳液改性水泥的性能。聚合物乳液的加入可以改善水泥的抗折强度、粘度和收缩率等性能,聚合物乳液改性水泥存在最佳的加入量,超过了这个最佳掺量后,会对水泥的引气性产生消极的影响。含有可与水化产物反应的活性基团的聚合物乳液对水泥的抗折强度的增强作用更明显;但是聚合物乳液的加入会降低水泥的抗压强度。采用了差示扫描量热分析（DSC）、热重分析（TGA）、FT–IR、XPS以及扫描电子显微镜（SEM）等手段得到可以适用于任何聚合物乳液改性水泥的机理模型。当聚合物乳液链上不包含可与水化产物发生化学反应的基团时,改性机理只是物理机理,即聚合物乳液膜覆盖在水化产物表面以及填充在水泥的孔隙和裂缝中;当聚合物乳液链上包含可以于水泥XSBRL水化产物反应的活性基团时,改性机理包括物理和化学两个部分,物理机理和不含有活性基团的聚合物乳液相同,化学改性机理为活性基团与水化产物发生化学反应将聚合物乳液和水化产物连接起来,形成3D网状结构。（3）合成了GO,研究表明GO改性水泥具有优异的力学性能;然而GO会明显降低水泥净浆的流动度和粘度,这是由于GO纳米片层在水泥的表面具有非常强的吸附能力。GO在水泥表面为多层吸附,符合准二级动力学模型;吸附层厚度大约为10.16 nm,即约有12层GO纳米片层吸附在水泥的表面。并且GO在改性水泥的过程中也发生了化学反应,位于GO片层结构边缘的–COOH与水泥水化产生的Ca（OH）₂发生化学反应,将不同的GO片层连接起来,形成了一个3D网状结构,水化产生的晶体和凝胶则插入在这个3D结构中。（4）设计并合成了聚醚胺化学改性GO（GOM）,GOM可以有效的改善水泥净浆的流动度和流动度保持性,并且对水泥有一定的增韧作用以及对收缩率的改进作用。不同分子量的聚醚胺改性GO对水泥砂浆的改性效果不同,分子量为2000的M2070对流动度和流动度保持性的改善最佳。GOM在水泥表面的吸附符合准二级动力学模型,为多层吸附。在水泥的水化过程中,GOM主链的GO片层吸附在水泥表面,聚醚胺组成的长支链则会伸展在水里,这种吸附作用产生的静电斥力和位阻作用会减弱水泥颗粒相互之间的聚并现象,使水泥净浆具有良好的流动度,并且聚醚胺的分子量越大,吸附在水泥颗粒表面的GOM会越少,静电斥力和位阻作用也会越强,故而水泥的流动度和流动度保持性也越好。更多还原

【Abstract】 High performance cement-based materials are widely used in infrastructure due to their excellent comprehensive properties.However,the mechanism research of polymer latex modified cement lags far behind its application.It is necessary to use chemical analysis method to research the chemical reaction in the polymer latex modified cement system.Otherwise,graphene oxide(GO)is one of the research focuses material in recent years.GO as an additive to cement,can give some new properties to cement.Also,the presence of chemical groups is the starting point for binding the different polymer on the GO nanosheets.The design and synthesis of the new chemical functional GO can obtain a new additive for cement.And chemical functional GO can use to further study the influence of structure on the properties of cement.The main contents and results are summarized as follows:(1)Polyacrylate(PA)latex improved the flexural strength,shrinkage,water retention and viscosity,reduced the compressive strength of the cement.And the optimum content of PA latex in cement is 7.5%,when the content exceeded 7.5%,it will have negative influence on the workability of cement.The chemical mechanism in the polyacrylate latex modified cement system was investigated by Fourier transform infrared spectra(FT–IR),X–ray photoelectron spectroscopy(XPS),gel permeation chromatography(GPC)and compact p H meter.The hydration reaction can create a strong alkalinity,exothermic circumstance in the whole system.In this environment,the ester groups of the polyacrylate chains hydrolyzed to produce carboxyl groups.There is a large generation of carboxyl groups in the second stage,and the dominate reaction in this stage is the hydrolysis of polyacrylate latex.At the third stage;these carboxyl groups reacted with the hydration products of cement [Ca(OH)2] to generate a new product [Ca(HCOO)2].The chemical reaction between polyacrylate latex and cement generated a crosslinked network structure,in which Ca2+ served as the crosslinking points and linked different polyacrylate chains together.(2)With the addition of styrene butadiene latex and carboxylic styrene butadiene latex;the tenacity,shrinkage,water retention and viscosity modified cement increase at different degrees.The mechanism of polymer latex modified cement was investigated by differential scanning calorimetry(DSC),FT–IR,XPS and scanning electron microscope(SEM).Owing to the difference in polymer chains,most of the polymer latexes used in modified cement field can be classified into two kinds.Styrene butadiene latex was used to represent the first kind polymer latex with no active groups in their polymer chains,the mechanism of these polymer latexes modified cement just contained physical modification mechanism.The latex film covered the surfaces of hydration crystals and filled into the cracks and pores of cement thus could be able to give better performance to the modified cement.About the other,these polymer latexes with active groups which can react with hydration products to produce a 3D network structure in the modified cement system,such as carboxylic styrene butadiene latex.The mechanism of these polymer latexes included physical and chemical modification mechanisms.Meanwhile,the modification models of these mechanisms used in most polymer latexes have been put forward.(3)The graphene oxide(GO)nanosheets were compounded by the improved Hummer′s method.The introduction of GO nanosheets improved the mechanical properties of cement composites.But GO has the negative influence on the fluidity of cement,it is due to the strong adsorption ability of GO on the surface of cement.The adsorption layer thickness of GO nanosheets on cement was about 10.16 nm.It means that there are around 12 layers of GO nanosheets adsorbed on the cement surface.And the adsorption data was best fitted with the Freundlich adsorption isotherm model and described by the pseudo–second order kinetics model;the adsorption process contained the chemical reaction.The –COOH in the GO nanosheets reacted with the hydration product of cement(Ca(OH)2).The chemical reactions connected the GO nanosheets each other,producing a 3D network structure in the GO nanosheets modified cement.Moreover,the hydration products were also inserted into this 3D network structure.(4)The chemically functionalized nano–graphene oxide(GOM)was synthesized by the chemical reaction of polyether amine with graphene oxide(GO).The mechanical properties,rheological properties,dispersion effectiveness,slump retention behavior and the mechanism of GOM modified cement were also researched.The results show that GOM have the same toughing function for cement with GO.And GOM can increase the slump flow of cement.The slump flow,the dispersion effectiveness and slump retention of GOM modified cement increased with the increase of molecular weight of polyether amine.The experimental results were fitted better with the Freundlich model than the Langmuir model.The result implied that the adsorption of GOM on cement is mainly a multilayer type.And the adsorption kinetics of GOM on cement is fitted well with the pseudo–second–order.The main chain of GOM adsorbed on the surface of cement,and the branched chains stretched into the water.The electrostatic repulsive forces of adsorption layers and steric hindrance of branched chains endowed the good fluidity of cement.更多还原