【作者】 谭洪波；

【导师】 马保国；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2009， 博士

【摘要】 聚羧酸减水剂是继木质素、萘系之后的新一代减水剂,以其优良的分散性和分散保持性及良好的力学性能在公路、铁路、水利工程、房建等领域得到了广泛应用,已成为未来减水剂的发展方向。本论文依托于国家“863“（2005AA332010）“高抗渗长寿命大管径隧道管片材料结构设计与工程应用”、国家“973”（2001CB610704-3）“化学外加剂对高性能水泥水化与结构的作用机理研究”、建设部软科学研究项目（2007-k4-3）“功能可控制型聚羧酸系高性能混凝土减水剂的研究”,主要针对聚羧酸减水剂合成及应用过程中存在的问题,进行了系统研究,确定了大单体及聚羧酸减水剂制备的最佳工艺条件;研究分析了分子结构对C₃A、C₃S及普通硅酸盐水泥水化历程的影响,实现减水剂的功能可控制;提出了优先吸附理论,制备了低成本高性能聚羧酸减水剂,并应用于商品混凝土;通过体积稳定性、水化热电性能及对水化产物的微观分析,研究了减水剂对水泥水化的调控机理。主要技术成果如下:1.研究了聚羧酸减水剂大单体制备工艺及减水剂合成工艺,确定了最佳工艺参数:（1）利用有机无机复合预处理的方法制备了甲基丙烯酸高效阻聚,克服了传统阻聚剂不稳定的缺点,使大单体酯化率可达到99%。（2）确定了中间大单体的最佳合成工艺:当催化剂掺量为5～6%;酸醇比为（1.15～1.2）:1;溶剂甲苯掺量为50%;温度控制为120℃。确定了聚羧酸减水剂合成的最佳工艺条件:引发剂用量为5～7%,聚合温度控制在80℃,反应7～8h。（3）通过引入两亲平衡值（P₀）、亲水平衡因子（k）、两亲匹配系数（λ）等概念,首次将两亲匹配理论应用于聚羧酸减水剂分子结构设计中。对于特定条件下的共聚物,可以通过计算两亲匹配系数,从而在聚合反应前预测其共聚物分散能力的大小,对聚羧酸减水剂的单体选择、配比优化设计有很强的指导作用。2.研究了二元共聚体系分子结构对C₃A、C₃S、普通硅酸盐水泥水化历程的影响规律,提出了功能可控制设计方法:（1）减水剂促进了2CaO·Al₂O₃·8H₂O结构向Al（OH）₃凝胶、3CaO·Al₂O₃·6H₂O结构的转化,但整体上抑制了C₃A的水化;从分子结构上来看,长侧链接枝密度越大,长侧链分子量越小,水化抑制作用越强;而大分子量长侧链有利于六方片状的C₂AH₈向立方状的C₃AH₆转化,小分子量长侧链的共聚物使水化产物中立方状C₃AH₆结晶更规则。（2）聚羧酸减水剂抑制了C₃S 1d的水化及CH的生成,随长侧链分子量的增加,水化抑制作用减弱;而随长侧链质量比的增加,水化抑制作用增强。聚羧酸减水剂对C₃S 7 d的水化抑制作用逐渐消失,促进CH晶体的生长。小分子量长侧链有利于CH的生长,使7 d水化产物中CH结晶更规则。从分子结构上来看,无论调整长侧链分子量还是长侧链的接枝密度,减水剂分子结构对于C₃S的水化7d影响不大,CH的生成量没有明显的区别,但都高于空白样,而主要影响CSH凝胶的形成。聚羧酸减水剂对C₃S 28 d的水化抑制能力逐渐消失。长侧链分子量越大,减水剂分子对C₃S 28d水化的抑制作用越弱。小分子量的长侧链有利于28 d CH的生长,而接枝高密度的羧基抑制了28d龄期CSH的生成。（3）功能可控制设计方法:羧基（COO-）和聚氧化乙烯基（-OCH₂CH₂-）是聚羧酸减水剂的主导官能团,对减水剂性能起决定作用,调整聚羧酸减水剂侧链接枝密度及长侧链分子量可实现减水剂分散性及分散保持性、凝结时间、引气量、早期强度、水化热、电阻率、化学收缩的可控制性。3.优先吸附与低成本聚羧酸减水剂的制备（1）提出优先吸附设计方法,利用低成本有机物,优先吸附于颗粒表面,有效屏蔽水化活点水化,从而提高减水剂分散性及分散保持性;配制的混凝土具有良好的流动性和流动保持性及力学性能,性价比明显高于萘系减水剂。（2）随羟基羧酸盐掺量的增加,聚羧酸减水剂的初始分散性提高。从作用机理上来看,羟基羧酸盐抑制初期C₃S的水化而加速C₃A初期的溶解和AFt的形成,作用效果随掺量的增加而增强。磺化多元醇与聚羧酸减水剂共同作用可提高分散保持性。随掺量的增加,分散保持性提高;从作用机理上来看,磺化多元醇抑制了早期C₃S、C₃A的水化及AFt的形成。（3）对于羟基羧酸盐、磺化多元醇、聚羧酸减水剂三元组分,随羟基羧酸盐掺量的增加,初始分散能力提高,而分散保持性缓慢下降,3d、7d、28d强度均下降;随磺化多元醇掺量的增加,初始分散性增加不明显,而流动保持性提高,当掺量达到0.3%时,1h无损失;当掺量小于0.3%时,3d、7d强度随掺量的增加逐渐下降,而对28d强度的影响较小。当羟基羧酸掺量为0.04～0.1%,磺化多元醇掺量为0.1～0.3%时,可有效提高聚羧酸减水剂的分散性和分散保持性而不影响后期力学性能。4.减水剂对水泥水化历程的调控作用机理:（1）随木钙掺量的增加1 d化学收缩变化不明显。而对于FDN、KH高效减水剂,1 d的化学收缩随掺量的增加而降低。与萘系、木钙减水剂相比,聚羧酸减水剂较大程度上减小早期化学收缩,降低开裂敏感性,抑制早期开裂。（2）对于木钙,由于对C₃A的促溶作用,结构形成期及结构稳定期电阻率随木钙掺量的增加变化不明显,但水化放热峰明显延迟并且放热峰削弱。对于FDN、聚羧酸减水剂,随掺量的增加,对浆体早期的水化的抑制作用增强,水化放热峰明显推后并且放热峰削弱,溶解平衡期延长。（3）微观结构分析表明,减水剂进入水泥体系后,抑制了C₃S的水化及CH的形成,掺量适中时,对后期水化的抑制作用渐渐消失。对于木钙,抑制了C₃S早期的水化及CH结晶,同时促进了C₃A的溶解和AFt形成。FDN抑制了C₃S 1 d的水化,促进了7d、28dC₃S的水化及CH的形成;聚羧酸减水剂抑制了1d、7d C₃S的水化,而不影响28d的水化。更多还原

【Abstract】 Polycarboxylate superplasticizer is the third generation water-reduce after naphthalene superplasticizer and lignin.With the high dispersibility and holding dispersibility,the polycarboxylate superplasticizer,which is widely used in construction of highway,railroad,water conservancy and building,is the direction of development of water-reducer.In the paper,financial supported by China "863" Program "2005AA332010" and "973" Program"2001CB610704-3" from the Ministry of Science and Technology and the "2007-k4-3" from Ministry of Construction of the P.R.China,the synthesis and application of polycarboxylate superplasticizer have been researched.Optimum conditions of synthesis middle-monomer and water-reducer has been confirmed;Effect of molecular structure on hydratation of cement clinker mineral phase and Portland cement have been researched to realize the controllability function;The assume of preferential adsorption has been put forward to prepare the low-cost water-reducer and use in the ready-mixed concrete;Mechanism of three generations water-reducer has been compared.The main work and results are listed as follow:1.Researching the synthesis technology of middle-monomer and polycarboxylate superplasticizer to make sure the optimum conditions and also constructing the production line:（1） The inhibitor for methacrylic acid is beforehand prepared by organic-inorganic composite. The inhibitor has good performance of stability that conversion rate of esterification can reach 99%（2） The optimum conditions of synthesis of middle-monomer:when the addition of activator is 5-6%,proportion of acid and alcohol is（1.15-1.2）:1,toluene is 50%,and the temperature is 120℃.The optimum conditions of synthesis of water-reducer:when the addition of initiator is 5-7%,the temperature is 80℃,and it reacts for 7-8h,the copolymer has good dispersibility and holding dispersibility.（3） Introducing amphiphilic balance（P₀）,hydrophilic balance（k）,amphiphilic matching coefficient（λ）,the amphiphilic balance and comb-shaped copolymers of the polycarboxylate superplasticizer have been researched.In some condition,the matching coefficient can confer the dispersing ability and monomer matching before we synthesize the copolymer.2.Research the effect of molecular structure on hydration of cement clinker mineral phase and Portland cement and establish the method of controllability function（1） Polycarboxylate superplasticizer accelerates the transformation from 2CaO·Al₂O₃·8H₂O to Al（OH）₃ and 3CaO·Al₂O₃·6H₂O.It restrains hydration of C₃A the as a whole.The ability to delay hydration of C₃A becomes strong with little molecular weight and less grafting density of long-side chain.The big molecular weight of long-side chain is advantaged to transformation of C₂AH₈ to C₃AH₆.The little molecular weight of long-side chain is advantaged to better crystallization of C₃AH₆.（2） Polycarboxylate superplasticizer restrains hydration of C₃S and formation of CH at 1d.With increase addition of molecular weight of long-side chain,ability to restrain hydration becomes weaker.With grafting density increasing of long-side chain,ability to restrain hydration becomes strong.It accelerates formation of CH,and has little ability to restrain hydration of C₃S at 7d.Water-reducer with little molecular weight of long-side chain is advantage to crystallization of CH.No matter how to adjust molecular weight and grafting density of long-side chain,weight of CH in hydration products is little change,but more than control.It mainly effects the formation of CSH at 7d.The ability to restrain hydration nearly disappears at 28d.The bigger molecular weight of long-side chain is,the weaker ability to hydration at 28 d is.The little molecular weight of long-side is advantage to form the CH, but the more grafting density of carboxyl accelerates formation of CSH at 28d.（3） Method of Controllability function of KH:carboxyl and gather oxygen ethylene,which are the main groups of polycarboxylate superplasticizer,has primary effect on the performance. To adjust grafting density and molecular weight of long-side chain can achieve to control dispersibility and holding dispersibility,setting time,air-entrained performance,early strength,hydration heat,electrical resistivity,chemical shrinkage of KH3.Preferential adsorption and low-cost polycarboxylate superplasticizer:（1） Low-cost organic compounds preferentially adsorb on the surface of cement particles to shield active hydrating points.In this way,dispersibility and holding dispersibility have been enhanced.The cement with KH-d has good fluidity and holding fluidity and mechanical properties,but the cost is lower than naphthalene superplasticizer.（2） With increasing addition of hydroxy carboxylate,initial dispersibility increase.Hydroxy carboxylate restrain the hydration of C₃S,but accelerate the hydration C₃A and formation of AFt.With sulfonation-polyol,holding dispersibility of polycarboxylate superplasticizer increases.Sulfonation-polyol restrains hydration of C₃S,C₃A and formation of AFt. （3） In system of hydroxy carboxylate,sulfonation-polyol and polycarboxylate superplasticizer, initial dispersibility increases and holding dispersibility reduces with addition of hydroxy carboxylate.And compressive strength also reduces at 3d,7d and 28d.Initial dispersibility has little change and holding dispersibility increases with addition of sulfonation-polyol. There is little loss of fluidity for 1h with addition of 0.3%,but compressive strength of 3d and 7d reduces and strength of 28d doesn’t drop.When addition of hydroxy carboxylate is 0.04-0.1%and addition of sulfonation-polyol is 0.1-0.3%,polycarboxylate superplasticizer has good dispersibility,holding dispersibility and mechanical properties.4.Mechanism of water-reducer in cement hydrating process:（1） Restrains hydration of C₃S and accelerates hydration C₃A at 1d.The chemical shrinkage with Calcium lignosulfonate for 1d has little change with addition.For FDN and KH,the chemical shrinkage for 1d reduces with addition.Compared with calcium lignosulfonate and FDN,KH is advantage to reduce cracking sensitivity and prevent early-age cracking behavior.（2） Because of acceleration of Calcium lignosulfonate for C₃A,electrical resistivity change little with increase addition,but peak of hydration heat has been cut and delayed.For FDN and KH,ability to prevent hydration becomes strong in early age with increase addition.So peak of hydration heat has been cut and delayed.（3） Microanalysis shows:water-reducer restrains hydration of C₃S and formation of CH in early age.If there is a proper addition,restraint becomes weaker and weaker with time going. Calcium lignosulfonate restrains hydration of C₃S and formation of AFt.FDN restrain hydration of C₃S at 1d age,but accelerates hydration of C₃S of 7d and 28d and formation of CH.KH restrain hydration of C₃S of 1d and 7d,but it has little effect on later hydration.更多还原