白炭黑与聚羧酸减水剂相互改性及其对水泥基材料性能影响

发布时间：2018-03-27 07:24

本文选题：白炭黑　切入点：聚羧酸减水剂　出处：《西南科技大学》2017年硕士论文

【摘要】：减水剂是一种在维持混凝土坍落度不变的条件下,能减少拌合用水量的混凝土外加剂。其加入混凝土拌合物后对水泥颗粒有分散作用,减少单位用水量,改善混凝土拌合物的流动性或减少单位水泥用量。随着人们对工程质量要求的不断提高,减水剂已经成为现代水泥基工程材料不可或缺的"第五组分"。聚羧酸减水剂(PC)因其掺量低、减水率高而受到建筑工程界的高度认可,并已经实现大规模的生产和工程应用。尽管如此,PC的减水(分散)作用主要是靠碱性条件下水解出带负电荷的PC分子与带正电荷的水泥颗粒表面的物理吸附,这种物理吸附在高硫酸根、提高温度和带负电荷的硅酸根环境下作用较弱,这也使其应用普适性和稳定性受到限制;此外,PC的加入也会抑制水泥早期水化,对水泥基材料早期强度发展不利。近年来,纳米技术的快速发展同样引起了水泥基工程界的广泛兴趣,在较低的掺量范围内,纳米粒子可有效改善水泥基材料的工作性、力学性能和耐久性。特别是纳米级Si02,其表面具有大量活性硅羟基,可与其他材料表面的羟基发生缩聚反应;更重要的是,纳米级SiO2还具有诱导水泥水化和超级火山灰活性效应。然而,纳米粒子常以团聚体形式存在,难于在水泥基材料中均匀分散,需要与减水剂预先混合解聚。目前,聚羧酸减水剂性能提升和纳米粒子有效作用发挥同时成为水泥基工程材料领域需要重点解决的问题。基于白炭黑(纳米级Si02)的表面高活性硅羟基特性,其可能与PC分子链的羟基官能团发生缩聚反应,从而将纳米SiO2负载于PC分子链上(或将PC吸附于纳米SiO2表面),一方面提高PC的吸附性能,从而改善PC减水性和适应性;另一方面,能够有效实现纳米粒子的均匀分散,充分发挥其诱导水泥水化和超级火山灰活性效应。因此,本课题提出利用白炭黑与PC进行相互改性,并将其应用于水泥净浆和砂浆的制备,一方面保留PC的高效减水效应,提高水泥基材的工作性能;另一方面将白炭黑以较为均匀的方式引入到水泥基材料中,提高其物理力学性能。研究结果表明:相比于未改性PC,在一定条件下得到的白炭黑与PC改性产物,可以有效改善水泥净浆和砂浆工作性和力学性能。
[Abstract]:Water reducing agent is a kind of concrete admixture which can reduce the water consumption of concrete under the condition of keeping the slump of concrete constant. Improving the fluidity of concrete mixtures or reducing the amount of cement per unit. Water reducer has become an indispensable "fifth component" of modern cement based engineering materials. Polycarboxylic acid water reducing agent (PCP) has been highly recognized by the construction engineering because of its low content and high water reducing rate. However, the water-reducing (dispersion) effect of PC mainly depends on the physical adsorption of negatively charged PC molecules to the surface of positively charged cement particles under alkaline conditions. The effect of this physical adsorption on high sulphate, increasing temperature and negative charge silicates is weak, which limits its applicability and stability. In addition, the addition of PC also inhibits the early hydration of cement. In recent years, the rapid development of nanotechnology has also aroused wide interest in cement based engineering, and in the range of low content, nanoparticles can effectively improve the workability of cement-based materials. Mechanical properties and durability. In particular, nanoscale Si02, which has a large number of active silica hydroxyl groups, can be polymerized with hydroxyl groups on the surfaces of other materials and, more importantly, Nano-scale SiO2 also has the effect of inducing cement hydration and super pozzolanic activity. However, nanoparticles often exist in the form of aggregates, which are difficult to disperse uniformly in cement-based materials and need to be pre-mixed and depolymerized with water reducers. The improvement of properties of polycarboxylic acid superplasticizer and the effective action of nanoparticles have become important problems in cement based engineering materials field. It may react with the hydroxyl functional group of PC molecular chain, and then load the nanometer SiO2 onto the PC molecular chain (or adsorb PC on the surface of nanometer SiO2). On the one hand, the adsorption property of PC can be improved, and the water reducing ability and adaptability of PC can be improved. On the other hand, it can effectively realize the homogeneous dispersion of nano-particles and give full play to the effect of inducing cement hydration and super pozzolanic activity. Therefore, this paper proposes to use silica and PC to modify each other. It is applied to the preparation of cement mortar and mortar. On the one hand, the high efficiency water reducing effect of PC is retained to improve the working performance of cement substrate; on the other hand, silica is introduced into cement based materials in a more uniform way. The results show that compared with the unmodified PCs, the modified products of silica and PC under certain conditions can effectively improve the workability and mechanical properties of cement mortar and mortar.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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