聚羧酸减水剂的改性和性能研究

发布时间：2018-02-15 02:46

本文关键词： 聚羧酸减水剂衣康酸混凝土蔗糖 2-丙烯酰胺基-2-丙烷磺酸自由基聚合　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：聚羧酸减水剂是一种高性能减水剂,因其掺量低、分散性好、可设计性强等优点,被广泛用于世界混凝土市场。伴随着城市建设和基础设施建设的推进,中国市场也对聚羧酸减水剂提出了新的时代要求,开发新的聚合单体,探究新的减水剂合成方法是我们前进的方向。本论文实验内容依托中国高铁建设的推进,就高铁项目建设中常见的混凝土流动性差、坍落度保持度低和后期强度不足等问题展开研究。通过分子设计路线,在聚羧酸减水剂分子的主链上引入不同数量的羧基、酰胺基、磺酸基等基团,合成出新的聚羧酸大分子,以期改善聚羧酸减水剂的性能。主要研究工作如下:1、通过化学接枝的方法,将衣康酸分子接枝到聚羧酸分子的主链上,分别考察了反应温度、反应时间、反应物摩尔比、引发剂用量对产物性能的影响,并以水泥净浆流动度为考察指标确立了最佳合成条件。还分别考察了衣康酸改性减水剂、市售减水剂和未改性减水剂的混凝土性能,得出衣康酸改性的聚羧酸减水剂由于分子中的多羧基结构,水泥分散性明显优于未改性的聚羧酸减水剂,且已达到市售水平。后期的混凝土强度测试表明,掺加衣康酸改性减水剂的混凝土强度同龄期强度比未改性和市售减水剂高。因此,衣康酸改性聚羧酸减水剂具有很好的市场推广前景。2、通过化学接枝,将2-丙烯酰胺基-2-丙烷磺酸接枝到聚羧酸减水剂分子主链上,通过正交实验设计确定其最佳合成条件。通过水泥水化热测试和zeta电位分析探究了 AMP S改性聚羧酸减水剂的保坍机理—减水剂分子可优先吸附在水泥颗粒表面,有效的屏蔽了水泥水化的活性位点,从而使改性减水剂具有优良的分散保持性。通过混凝土强度测试发现,掺AMPS改性减水剂的混凝土 7d、28d强度比可分别达到80%和120%,比未改性和市售减水剂的强度表现都要好,说明AMPS改性的聚羧酸减水剂不仅可以提高混凝土的分散保持性,而且可以保证混凝土的后期力学性能。3、通过化学接枝将合成的一种新单体蔗糖酯引入到聚羧酸减水剂分子主链上,确定了各反应因素对减水剂性能的影响,得出最佳合成条件。通过zeta电位分析发现,改性后的减水剂分子可以更多的吸附在水泥颗粒表面,获得高减水作用。通过混凝土坍落度分析发现,改性后的减水剂其混凝土坍落度保持性更好。通过SEM分析发现,减水剂分子的掺入有利于针状氢氧化钙的生长,从而获得高强度混凝土。
[Abstract]:Polycarboxylic acid water reducing agent is a kind of high performance water reducing agent. It is widely used in the world concrete market because of its advantages of low content, good dispersion and strong designability. The Chinese market has also put forward new requirements for polycarboxylic acid water reducers. It is our direction to develop new polymeric monomers and explore new synthetic methods of water reducers. The experimental contents of this paper rely on the development of high-speed iron construction in China. In this paper, the common problems of poor concrete fluidity, low slump retention and insufficient later strength in the construction of high iron project are studied. Through the molecular design route, different amounts of carboxyl and amide groups are introduced into the main chain of polycarboxylic acid superplasticizer molecule. In order to improve the performance of polycarboxylic acid superplasticizer, a new polycarboxylic acid macromolecule was synthesized by sulfonic acid group. The main research work is as follows: 1. By chemical grafting method, itaconic acid molecule is grafted onto the main chain of polycarboxylic acid molecule. The effects of reaction temperature, reaction time, molar ratio of reactants and the amount of initiator on the properties of the product were investigated. The concrete properties of the water reducer and unmodified water reducer on the market show that the polycarboxylic acid superplasticizer modified by itaconic acid has better dispersion than the unmodified polycarboxylic acid water reducer because of the polycarboxyl group structure in the molecule. The strength of concrete mixed with itaconic acid modified water reducer is higher than that of unmodified and marketed water reducer. Itaconic acid modified polycarboxylic acid superplasticizer has a good market prospect. By chemical grafting, 2-acrylamido-2-propane sulfonic acid was grafted onto the main molecular chain of polycarboxylic acid superplasticizer. The optimum synthesis conditions were determined by orthogonal experimental design. The mechanism of AMP S modified polycarboxylic acid water reducer was investigated by hydration heat test and zeta potential analysis. The water-reducing agent molecule could be preferentially adsorbed on the surface of cement particles. The active site of cement hydration is effectively shielded, so that the modified water reducer has excellent dispersion and retention. The strength ratio of concrete with AMPS modified water reducing agent can reach 80% and 120 days respectively, which is better than that of unmodified and marketed water reducing agent. It shows that the AMPS modified polycarboxylic acid water reducing agent can not only improve the dispersion and retention of concrete, In addition, the mechanical properties of concrete can be guaranteed in the later stage. A new monomer, sucrose ester, is introduced into the main molecular chain of polycarboxylic acid water reducer by chemical grafting, and the effects of various reaction factors on the properties of water reducer are determined. Through zeta potential analysis, it was found that the modified water-reducing agent molecules could be adsorbed on the surface of cement particles to obtain high water-reducing effect. The slump analysis of concrete showed that the modified superplasticizer could be adsorbed on the surface of cement particles. Through SEM analysis, it was found that the addition of water reducer was beneficial to the growth of acicular calcium hydroxide, thus the high strength concrete was obtained.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528.042.2

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