聚羧酸减水剂与减缩剂的相容性研究

发布时间：2018-10-31 14:06

【摘要】：高性能混凝土由于其具有优良的工作性能、高强和耐久性好的突出优势而被广泛研究和应用。高效减水剂的应用是实现混凝土高性能化的必要技术手段，正是高效减水剂的应用使混凝土实现（超）低水胶比成为可能。然而高性能混凝土采用（超）低水胶比时，混凝土体积收缩显著，由此引起的开裂风险大大提高。因此研究改善高性能混凝土体积收缩导致开裂影响耐久性的相关问题迫在眉睫。减缩剂是一种能从本质上显著抑制混凝土收缩的化学外加剂，近年来受到越来越多的关注和重视，因此减缩剂的应用将来可能成为一种趋势。利用高效减水剂和减缩剂以实现高性能混凝土优良的工作性能和低收缩效果时，，两者将不可避免在混凝土中共同使用，因此研究高效减水剂和减缩剂共同使用可能引起的一系列相容性问题具有积极的理论价值和实际意义。本文对高效减水剂与减缩剂相容性的研究主要从两者共同使用时对减水剂塑化效果的影响、对减缩剂减缩效果以及对水泥基材料力学性能的影响来展开。在此基础上，采用紫外-可见光分光光度计（UV）、Zeta电位仪、荧光光谱仪、X射线衍射（XRD）及氮吸附分析仪等分析手段对聚羧酸减水剂与减缩剂相容性机理进行研究，结果表明：减缩剂对聚羧酸减水剂塑化效果基本不存在负面影响，对净浆流动度甚至有增大作用；聚羧酸减水剂与减缩剂同掺后对水泥基材料的减缩效果增强；减缩剂3.0%掺量下，减缩剂（SRA-SBT）与醚类聚羧酸减水剂（PC1）同掺后砂浆强度仅为单掺PC1组的78.6%，低于减缩剂（SRA-G）与PC1同掺组的强度，与酯类聚羧酸减水剂（PC2）同掺后的砂浆强度下降幅度均小于5%，且可以改善减缩剂内掺对砂浆力学性能的负面影响；减缩剂与聚羧酸减水剂同掺后混凝土强度较单掺减水剂组下降幅度小于7%，较与萘系减水剂同掺组高5MPa左右。由此可知，PC1与减缩剂SRA-G的相容性优于与减缩剂SRA-SBT的相容性，PC2与两种减缩剂的相容性均较好。采用UV、zeta电位仪及荧光光谱仪等分析手段，研究了水泥基材料对两者的吸附、两者同掺后对水泥浆体zeta电位以及对聚羧酸减水剂微结构的影响，发现减缩剂的加入会略微降低掺有聚羧酸减水剂的水泥颗粒表面zeta电位，但会明显降低掺有萘系减水剂的静电斥力，并且使聚羧酸的根均方半径增大且PEO支链得到伸展，有利于增加其空间位阻势能，从而可以适当增加聚羧酸减水剂的塑化效果。通过研究减缩剂存在下对孔隙溶液蒸发速率、砂浆和混凝土质量损失的影响，探讨两者同掺后引起水泥基材料减缩效果变化的原因。减缩剂主要通过降低溶液表面张力来实现对水泥基材料的收缩抑制效果；同时减缩剂能够增加溶液粘度并减小孔隙溶液的蒸发速率和在孔隙中的迁移速度，因此使水泥基材料质量损失速率降低，也能够在一定程度上降低其干燥收缩。采用XRD及氮吸附等分析手段，研究了两者同掺后对水泥石中氢氧化钙衍射峰强度、化学结合水含量以及水泥石孔隙结构发展的影响，探讨引起水泥基材料力学性能发生改变的原因。减缩剂对水泥水化的影响主要表现为不同龄期水泥石中化学结合水以及氢氧化钙含量的降低，当减缩剂掺量为3.0%时可使水泥石中30nm以上的孔隙显著增多，孔隙率显著提高，以上原因均可造成水泥基材料早期强度降低。
[Abstract]:High performance concrete is widely researched and applied due to its excellent performance, high strength and durability. The application of high efficiency water reducer is the necessary technical means to realize the high performance of concrete. It is the application of high efficiency water reducer to make concrete realize (super) low water cement ratio. However, when high performance concrete uses (super) low water cement ratio, the volume shrinkage of concrete is significant, thus the risk of cracking is greatly improved. Therefore, it is urgent to study the related problems of improving the durability of cracking caused by shrinkage of high performance concrete. Shrinkage-reducing agent is a chemical additive which can significantly inhibit concrete shrinkage from nature, and has attracted more and more attention and attention in recent years. Therefore, the application of shrinkage reducing agent may become a trend in the future. When the high-performance concrete excellent working performance and low shrinkage effect are realized by utilizing the high-efficiency water reducing agent and the reducing agent, both of the high-performance water reducing agent and the reducing agent will inevitably be used together in the concrete, Therefore, it is valuable and practical to study a series of compatibility problems which can be caused by co-use of high-efficiency water reducer and reducer. In this paper, the study of compatibility between high-efficiency water reducing agent and shrinkage reducing agent mainly affects the plasticizing effect of water reducing agent, the reducing effect of reducing agent and the influence on the mechanical properties of cement-based material. On the basis of this, the compatibility mechanism of polyacrylate water reducer and reducer was studied by UV-VIS spectrophotometer (UV), Zeta potential instrument, fluorescence spectrometer, Xray diffraction (XRD) and nitrogen adsorption analyzer. It is shown that the shrinkage reducing agent has no negative influence on the plasticizing effect of the polyacrylate water reducing agent, and even has an increasing effect on the fluidity of the net slurry; the shrinkage reducing agent of the polyacetal resin reducing agent and the reducing agent is enhanced with the reduction effect of the cement-based material; and the reducing agent 3 is used. The strength of the shrinkage-reducing agent (SRA-SBT) and the ether-like water-reducing agent (PC1) was 78.6% of the single-mixed PC1 group, lower than the strength of the reducing agent (SRA-G) and PC1, and the decrease of the strength of the mixed mortar with the ester polyacetal resin-reducing agent (PC2). It is less than 5%, and can improve the negative effect of the reducing agent on the mechanical properties of the mortar. The decreasing amplitude of the reducing agent and the water reducing agent in the same admixture with the water reducing agent is less than 7%, and the reducing agent is 5% higher than that of the water reducing agent. Therefore, the compatibility of PC1 with the reducing agent SRA-G is superior to that of the reducing agent SRA-SBT, and PC2 is compatible with the two reducing agents. The adsorption of cement-based materials on the two kinds of cement-based materials was studied by means of UV, zeta potential instrument and fluorescence spectrometer. The influence of the microstructure of water agent shows that the addition of shrinkage reducing agent reduces the surface zeta potential of the cement particle doped with the water reducing agent, but obviously decreases the electrostatic repulsion of the water reducing agent doped with the water reducing agent, increases the root mean square radius of the polyacetal resin and expands the PEO branched chain, which is beneficial to the increase. and the space position resistance potential energy is added, so that the polylactide can be appropriately increased. The effect of reducing agent on the evaporation rate, mortar and concrete mass loss in the presence of shrinkage reducing agent is studied. The shrinkage reduction effect of the cement-based material is realized mainly by reducing the surface tension of the solution, the shrinkage reducing agent can increase the viscosity of the solution and reduce the evaporation rate of the pore solution and the migration speed in the pores, the quality loss rate of the base material is reduced, By means of XRD and nitrogen adsorption, the effects of both the diffraction peak intensity, chemical bonding water content of calcium hydroxide and the development of cement stone pore structure in cement stone were studied. The effect of shrinkage reducing agent on hydration of cement is mainly shown as the decrease of chemical bonding water and calcium hydroxide content in cement stone at different age, and when the amount of shrinkage reducing agent is 3. 0%, it can make it more than 30nm in cement stone. the porosity is obviously increased, the porosity is obviously improved, and the above reasons are all
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TU528.042

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