【作者】 胡家兵；

【导师】 马保国；

【作者基本信息】 武汉理工大学 ， 材料学， 2012， 硕士

【摘要】 随着我国基础建设的全面发展,不仅促进混凝土需求量的增长,而且也推动着高性能混凝土技术的快速发展,在此前提下混凝土高性能化对高效减水剂的性能提出了更高的要求,传统减水剂已经不能满足现代混凝土的施工,因此,第三代聚羧酸系减水剂应运而生。本文依托于国家“973(2009CB623201)”子课题“现代混凝土胶凝浆体微观结构形成机理”,主要针对聚羧酸减水剂合成过程中出现的新技术、新单体原料,确定了醚类聚羧酸减水剂制备的最佳工艺,检测了合成减水剂的性能并表征了减水剂的分子结构,在此基础上针对C3A单矿早期水化特性和减水剂与水泥适应性不良问题,通过水化热、XRD、Raman、SEM等测试技术,研究了减水剂、减水剂与不同类型缓凝剂配伍对C3A-CaSO4·2H2O二元体系水化调控规律、作用机理及调控手段。主要工作及成果如下：1.研究了单因素对合成减水剂性能的影响,确定了最佳原料配比,检测了减水剂性能并征了分子结构：(1)确定APEG型减水剂合成工艺：n(APEG):n(MA):n(MAS)=1:3.5:0.6, APS含量为4%,在80℃下反应4h,保温1-2h,加碱中和即可。(2)确定TPEG型减水剂合成工艺：n(AA):n(TPEG)=5.0:1, H2O2占单体原料质量的2.0%,L-抗坏血酸与H202的摩尔比为3：4,3-巯基丙酸为1.0%,反应温度控制50℃以下,反应时间3h,保温1-2h,加碱中和即可。(3)使用红外光谱(IR)和凝胶渗透色谱仪(GPC)分别对所得醚类聚羧酸减水剂结构进行表征。结果表明,减水剂结构中引入了预期设计的官能团；根据GPC所测数据计算得出APEG/TPEG型减水剂重均分子量(Mw)、数据分子量(Wn)、聚分散系数(PDI)、主链长度(MCL)、侧链长度(SCL)依次为1.47万/10.3万g/mol、7540/84500g/mol、1.95/1.22nm、2.5/1.8nm、15.3/15.3nm。2.研究了不同掺量减水剂对C3A-CaSO4·2H2O二元体系的水化调控规律,并阐述其调控机理：(1)减水剂对C3A-CaSO4·2H2O二元体系的水化调控规律与其掺量有关。水化热研究表明,低掺量减水剂延缓和削弱水化热最高峰；高掺量减水剂促进水化放热速率,同时延峰效应消失；XRD、IR、Raman分析表明,低掺量减水剂在水化初期(1-2d)延缓AFt生成和石膏消耗,中期(2-7d)延缓AFt向AFm转变,而高掺量减水剂呈现相反作用,水化后期(28d)所有样品水化进程都相似；而SEM研究表明,减水剂的加入显著改变AFt晶体形貌,掺量0.1%样品中,AFt初期呈絮凝状,后期为短细杆状颗粒,且无花瓣状AFm出现；0.3%样品中,AFt初期为短棒状晶体,后期晶体逐渐长大相互搭接成致密的水泥石结构,有花瓣状AFm生成；0.5%样品中,AFt初期呈柔软的纤维状,后期转为定向排列的针状,有花瓣状AFm出现。(2)减水剂水化调控机理：减水剂对C3A-CaSO4·2H2O体系水化存在加速和延缓双重作用,由于掺量不同,延迟或者促进作用不同。掺量低时,吸附、络合占主导作用,从而延缓AFt形成及AFt向AFm转变的时间；掺量高时,分散占主导作用,因为减水剂的强分散作用而促进C3A水化及AFt向AFm转变的时间。3.研究了减水剂与不同类型缓凝剂配伍对不同含量C3A水泥体系和C3A-CaSO4·2H2O二元体系的水化调控规律,并获得调控方法：(1)减水剂与不同类型缓凝剂配伍对不同含量C3A水泥体系的调控呈现不同调控规律。对低C3A水泥而言,PP与减水剂配伍即能增加初始流动度又能抑制经时损失,而SJ、BS与减水剂配伍只具有较强抑制损失能力,不具有初始塑化效果；对高C3A水泥而言,PP与减水剂配伍降低初始流动性和增大经时损失,SJ与减水剂配伍具有优异的抑制损失能力,而BS与减水剂配伍具有辅助塑化效果同时又能抑制损失,有效解决减水剂与高C3A含量水泥相适性不良的问题。(2)减水剂与不同类型缓凝剂配伍对C3A-CaSO4·2H2O二元体系的水化调控规律与配伍的缓凝组分有关。水化热、XRD、SEM等测试分析表明：与空白样相比,减水剂与PP配伍增大水化放热速率,促进AFt生成及加速AFt向AFm转变过程,且水化产物中AFt初期大量簇拥堆积,呈现向外散射的针刺状,后期成为短棒状结构；而与SJ配伍对放热速率影响不大,但却延缓最高放热峰出现时间,且产物AFt初期为边界清晰,结晶程度较高的短圆柱状颗粒晶体,其密实程度比空白低,水化后期AFt转变为细棒状结构；与BS配伍极大的降低放热速率,使得最大放热峰不明显,同时延缓了水化产物AFt和AFm的生成,同时AFt初期呈现无定形状凝胶体,之后逐渐成为毛绒绒纤维状,后期转变为针状,相互搭建成结构致密的整体。更多还原

【Abstract】 With the all-round development of infrastructures in China, it not only accelerates the demand for concrete, but also promotes the rapid development of high-performance concrete technology. Meanwhile, high performance concrete puts forward higher requirements on the performance of superplasticizer, which has caused the traditional water reducing agent could not meet the reguests of the modern construction technology. Therefore, polycarboxylate superplasticizer of the third generation has come into being.The study is based on its sub-topics "Modern Concrete Gel Paste Microstructure Formation Mechanism" from the National973Project (2009CB623201). Focused on emergence of new technologies and new monomer raw materials, optical conditions for the preparation of ether-type polycarboxylate superplasticizer has been confirmed and performance and molecular structure of water reducer has been respectively tested and characterized. Besides, concerning the problems such as early hydration characteristics of C3A single mineral and poor adaptability between superplasticizer and cement, hydration regulation law, mechanism and control means of superplasticizer and the coordinating role of the different types of retarders and water reducer regulating C3A-CaSO4·2H2O binary system has been discussed by means of the heat of hydration, XRD, Laman, SEM etc. The main work and the conclusions are as follows:1.Researching on the influences of a single factor on the synthesis, confirming the optimal ratio of raw materials, testing the performance of superplasticizer and characterizing of molecular structure:(1)The synthetic condition of the APEG-type superplasticizer has been determined as follows:the mole proportion of the monomers APEG, MA and MAS is1:3.5:0.6, the content of initiator(APS) is4%, the temperature is80℃, and it reacts for4h.(2)The synthetic condition of the TPEG-type superplasticizer has been determined as follows:the mole proportion of the monomers TPEG and AA is 1:5, the mole ratio of L-ascorbic acid and H2O2is3:4, the mass ratio of oxidant (H2O2) is2%,3-thioglycolic acid is1%, the temperature is below50℃, and it reacts for3h.(3)The structure of the ether-type polycarboxylate superplasticizer is characterized by infrared spectroscopy and gel permeation chromatography. The results indicated that the expected functional group is introduced into structure. According to the measured data of GPC, the Mw, Wn, PDI, MCL and SCL of APEG and TPEG type superplasticizers are followed by14700and103000g/mol,7540and84500g/mol,1.95and1.22nm,2.5and1.8nm,15.3and15.3nm.2.Researching on the effect of different dosage of superplasticizer on the hydration of C3A-CaSO4-2H2O binary system and expounding the regulation mechanism:(1)The influence of superplasticizer on the regulation law of C3A-CaSO4·2H2O binary system is relevant to its content. Heat of hydration has shown that superplasticizer has delayed and weaked the hydration heat peak at low dosage, while promoting hydration heat rate and delaying effect vanished at high dosage. XRD, IR, and Laman analysis showed that superplasticizer delayed AFt generation and gypsum consumption at the early hydration and also delayed the transformation from AFt to AFm at medium-term hydration at low dosage, however, the opposite rule is concluded at high dosage, and hydration process of all samples are similar at28day. SEM studies indicated that superplasticizer significantly changed AFt crystal morphology on the whole. As far as dosage0.1%of the sample, AFt was flocculation at early stage, and then thin rod-shaped particles at later stage, in addition, detected no petal-like AFm. In terms of dosage0.3%of the sample, AFt displayed short rod-like crystals at the early, and then crystals gradually overlaped each other and growed into the dense structure of cement paste, moreover generated petal-like AFm. Concerning dosage0.5%of the sample, AFt is soft and fibrous stage at early stage, and then become aligned needle-shaped crystals latterly. Besides, appeared petal-like AFm.(2)The hydration regulation mechanism of superplasticizer: it played a dual role in the process of the hydration of C3A-CaSO4-2H2O binary system, that is delaying or promoting effect according to different dosage. When the content is low, adsorption and complexation exert the dominant role delaying the transformation time from AFt to AFm, in contrast to low content, when the content is high, dispersion plays a dominant role thus promoting change time from AFt to AFm.3.Researching on effect of superplasticizer and synergistic effect between different types of retarders and superplasticizer on hydration regulation law of different content of C3A-cement system and C3A-CaSO4·2H2O binary system:(1)As far as C3A-cement binary system, synergistic effect between different types of retarders and superplasticizer indicated different regulation law. Considering low C3A content cement, synergistic effect between PP and superplasticizer could increase the initial flow and inhibit flow-loss while synergistic effect between SJ, BS and superplasticizer have only excellent fluidity retention but not possess initial plasticizing effect. Referring to hige C3A content cement, the effect between PP and superplasticizer not only reduces the initial liquidity but also increases the loss, and the effect between SJ and superplasticizer has excellent ability to inhibit the loss, however, the effect between BS and superplasticizer owns auxiliary plasticizing effect and inhibit the loss, thus which can effectively solve adverse compatibility between superplasticizer and high C3A content cement.(2)As far as C3A-CaSO4-2H2O binary system, the regulation laws of synergistic effect between different types of retarders and superplasticizer is related to retarding components. Heat of hydration, XRD, SEM and other microscopic analysis indicates that: compared with blank samples, synergistic effect between PP and superplasticizer increases the rate of hydration heat meanwhile accelerates the generation of AFt and transformation from AFt to AFm and in the early hydration products, AFt are surrounded by a large accumulation and show the scattering of acupuncture shape and become a short rod-like structure at later stage. But the synergistic effect between SJ and superplasticizer has little effect on the heat release rate but has delayed the appearing time of the highest exothermic peak besides that, at the early hydratiob AFt has clear boundary and short cylindrical particle crystal with high crystallization then it transforms into a thin rod-like structure at the later stage. However, the synergistic effect between BS and superplasticizer greatly decrease the heat release rate even the maximum exothermic peak is about to disappear. At the same time, it also delays the formation of AFt and AFm. In addition, AFt shows amorphous gel shape at early term then gradually become fluffy fibrous shape and at later term transforms into the needle and build into a compact structure as a whole.更多还原