两性型聚羧酸减水剂与粉煤灰的相容性研究

采用不同粉煤灰掺量混凝土,分别掺入两种减水剂—阴离子型聚羧酸减水剂(PCan)和两性型聚羧酸减水剂(PCam),粉煤灰取代水泥总量为10％ ～ 50％,设计塌落度在(200±20) mm,测试混凝土塑性阶段和硬化阶段性能,以及通过总有机碳(TOC)实验,探讨两性型聚羧酸减水剂PCam与粉煤灰的相容性.结果表明:掺入减水剂,能有效降低混凝土用水量,PCam作用效果甚与PCan,减水率超过30％,能有效改善因粉煤灰掺入而导致早期强度的不足,提高20％以上强度.TOC吸附量表明硅酸盐水泥颗粒表面的吸附规律不同于水泥颗粒,由于粉煤灰颗粒较为光滑并且表面动电位为负值,因此对高效减水剂的吸附能力较弱.PCam阳离子基团的引入,使得其饱和吸附量大于普通阴离子型聚羧酸减水剂(PCan),相同掺量下具有更高塌落度及较低塌落度损失.因此,PCam阳离子基团的引入,增大了减水剂对粉煤灰颗粒的吸附量,与粉煤灰具有更好的相容性.     

蒸养条件下不同种类外加剂对水泥水化进程的影响

用直接测温法、X射线半定量分析方法,系统研究了蒸养条件下高效减水剂(聚羧酸高效减水剂、萘系高效减水剂)、早强剂(硫酸钠)和引气剂(十二烷基硫酸钠)对硅酸盐水泥的放热量和蒸养强度的影响.研究结果表明,聚羧酸高效减水剂延缓了水化放热温峰出现的时间,水化热和Ca(OH)2生成量明显减少;萘系高效减水剂和硫酸钠使水化热温峰出现的时间提前并随水化热量的增多蒸养强度提高,Ca(OH):生成量增加;十二烷基硫酸钠对水泥水化热几乎没有影响,蒸养强度随十二烷基硫酸钠掺量的增加而降低,Ca(OH)2生成量没有明显变化.     

减水剂的种类和掺量对水泥胶砂性能的影响

本文研究了减水剂的种类和掺量对水泥胶砂扩展度、凝结时间以及强度的影响。结果表明,随着聚羧酸系和奈系减水剂掺量的增加,水泥胶砂的扩展度逐渐增大。聚羧酸系和奈系减水剂均对水泥有缓凝作用。适量聚羧酸系和奈系减水剂的加入均可提高水泥胶砂的抗折和抗压强度。综合考虑,掺入适量聚羧酸系系减水剂的水泥胶砂比掺入奈系减水剂的水泥胶砂性能更好。     

蒸养条件下镍渣水泥胶砂的水化产物与力学性能

研究了掺20%镍渣粉的水泥胶砂在80℃蒸养7 h、7 d和标准养护28 d条件下的水化产物与力学性能。结果表明:镍渣中MgO主要存在晶体相(镁橄榄石与顽辉石)与玻璃体相两种形态。掺镍渣改变了蒸养7 d和标养28 d水泥水化产物的形貌和组成:蒸养7 d条件下,纯水泥胶砂的水化产物主要为纤维状C-S-H、片状CH和石榴粒状水化石榴石,而镍渣水泥胶砂,除以上水化产物外还有水滑石生成,说明蒸养促进了镍渣中MgO的反应;标准养护28 d纯水泥胶砂的C-S-H主要为网状,而镍渣水泥胶砂中的C-S-H主要有纤维状和球形等大粒子状2种形貌。蒸养7 h条件下镍渣水泥胶砂与纯水泥胶砂的化学结合水量基本相同,而蒸养7 d条件下水泥胶砂的化学结合水量高于标养28 d。蒸汽养护提高了镍渣的火山灰活性,从而显著提高了胶砂的强度活性指数。     

磺酸基对聚羧酸减水剂性能的影响

研究了磺酸基对聚羧酸减水剂性能的影响,研究表明:聚羧酸减水剂在合成过程中掺入磺酸基:(1)可以一定程度上改善水泥净浆初始流动度和水泥净浆1h经时流动度,但是磺酸基掺量过高则会降低水泥净浆流动度,当磺酸基与TPEG摩尔比为0.4的时候效果最好;(2)在剪切速率一定的情况下,剪切应力随着磺酸基掺量的增加而增加,水泥浆体粘度随着磺酸基掺量的增加而降低;(3)对水泥胶砂1d强度影响不大,但是水泥胶砂3d、28d强度均有所提高,摩尔比为0.4的时候效果相对较好;(4)对水泥水化产物并没有太大影响,但是磺酸基的加入会促进C3S的水化,同时也说明了掺入磺酸基的水泥胶砂28d强度有所提高。     

一种两性聚羧酸减水剂对水泥净浆及混凝土早期性能的影响

通过引入2-丙烯酰胺-2-甲基丙磺酸(AMPS)和甲基丙烯酰氧乙基三甲基氯化铵(DMC)两种小单体,并采用相对分子量较大的甲基烯丙基聚氧乙烯醚(HPEG)大单体,合成了一种两性聚羧酸减水剂ZQ-3,使用红外光谱对其结构进行了确证.将该减水剂与另外三种聚羧酸减水剂进行了性能对比研究.水泥净浆实验结果表明:减水剂ZQ-3具有良好的分散性及分散性经时保持性能,对净浆的凝结时间影响不大;混凝土实验及XRD分析表明:减水剂ZQ-3能够促进水泥的早期水化,明显提高混凝土蒸养脱模强度和早期强度.     

硫氰酸钠与聚羧酸减水剂复配对水泥水化的影响研究

采用硫氰酸钠(SN)对普通聚羧酸减水剂(PC)进行复配改性,旨在开发一种低温、早强型聚羧酸减水剂.对比测试了PC与PC +SN对水泥胶砂与混凝土在低温(5℃)和常温(20℃)两种养护温度下强度发展的影响,通过对水泥水化热与水泥浆体化学结合水、水化产物、微结构与孔结构的测试,分析了SN早强剂对水泥浆体早期水化性能的影响.结果表明:在养护温度5℃时,掺入PC +SN的水泥胶砂1d、3d、7d、28 d强度较掺PC比,分别提高了138.5％、48.3％、51.2％、17.2％,掺入PC +SN的混凝土1d、3d、7d、28 d强度分别增长了182.1％、35.2％、34.9％、31％,而20 ℃条件养护时PC +SN的早强效果并不显著;PC复配SN早强剂后,增加了水泥早期水化放热速率与放热量,提高了水泥的水化程度,且浆体的水化产物数量增多,孔隙率降低,孔径减小,从而有利于混凝土早期强度的提高.     

水泥与聚羧酸型混凝土减水剂适应性实验研究

针对聚羧酸型混凝土减水剂的生产工艺和原料配比,进行了不同配比生产的水泥与聚羧酸型混凝土减水剂的适应性试验。结果表明:熟料C_3A含量低于8.0%以下时,其进一步降低对聚羧酸型混凝土减水剂适应性影响较小;在生产1.0‰掺量的水泥助磨剂时,醇胺类有机物制得的水泥助磨剂,均具有明显的提高水泥早期强度和后期强度的作用;工业盐加入助磨剂后对水泥与聚羧酸型混凝土减水剂的适应性影响不明显;水泥中立磨粉磨的矿粉掺加量为70.0%时水泥与聚羧酸型混凝土减水剂的适应性急剧变差;掺加石灰石、炉渣、粉煤灰后水泥与聚羧酸型混凝土减水剂的适应性会随着掺加量的增加逐渐变差。     

蒸汽养护条件下复合水泥胶凝材料的优化匹配

利用XRD、SEM、TG/DSC、MIP等测试方法,对常压高温蒸汽养护下矿渣和粉煤灰等不同组成的复合胶凝材料物理性能及水化特性差异进行研究.结果表明,85℃常压蒸养条件下水泥水化产物与标准养护下基本相同,但水化产物数量有大幅提高,且有少量C9S6H18和钙矾石(AFt)稳定存在.辅助胶凝材料的适宜匹配,使水泥石结构较致密,蒸养强度较高.少量硅灰的掺加,有利于优化水泥石结构,促进蒸养条件下水泥石强度发展.     

自燃煤矸石掺合料与高效减水剂相容性研究

自燃煤矸石易粉磨,比表面积较大、吸附水较多、表面能较高,若不与具有表面活性的高效减水剂复掺,很容易形成絮凝结构,降低水泥浆的流动性,不仅不能满足预拌混凝土的泵送要求,也影响硬化混凝土强度.本文首先采用胶砂对比试验,分别将不同粉磨时间的自燃煤矸石粉30％取代水泥,以自燃煤矸石-水泥胶砂强度较高者确定粉磨时间;在此基础上,选择自燃煤矸石粉掺量、减水剂品种和掺量为影响因素,通过正交试验研究自燃煤矸石粉与两类不同减水剂的相容性.结果表明,自燃煤矸石作混凝土掺合料经济粉磨时间为4～6 min,与两类减水剂相容性程度为:聚羧酸系＞奈系.自燃煤矸石粉无论与哪类减水剂双掺,建议自燃煤矸石粉掺量≤15％,而聚羧酸系减水剂掺量≤0.43％,奈系减水剂掺量≤0.8％.     

Preparation of amphoteric polycarboxylate superplasticizers and their performances in cementitious system

A series of amphoteric polycarboxylate (PC) polymers were synthesized by radical copolymerization of acrylic acid (AA), [3‐(methacryloylamino) propyl] trimethylammonium chloride (MAPTAC) and ω‐methoxypolyoxyethylene methacrylate ester (MPEGMA). Cationic groups were introduced in to PC molecules with expectation of less retardation effect on cement hydration compared to the traditional anionic PC superplasticizers. The content of cationic groups in polymer was varied by changing the monomer ratio of MAPTAC to AA in the synthesis recipes. The structure of the synthesized amphoteric PCs was verified by gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). The performances of the amphoteric PCs were evaluated by measurement of flowability and zeta‐potential of cement pastes and adsorption amount of PC in cement pastes. Impacts of the PCs on cement hydration were studied by isothermal calorimetry. It is concluded that both anionic and cationic PC polymers can be effectively adsorbed onto the surface of cement particles and thus change the zeta potential of cement pastes. The adsorption amounts of the amphoteric PCs decrease with increasing content of cationic units. A proper incorporation of cationic units into PC polymers may lead to a higher fluidizing performance in fresh cement pastes. The amphoteric PC polymers with higher content of cationic units show less retardation effect on cement hydration and hence higher early strength of cementitious materials may be achieved by using amphoteric PCs with appropriated content of cationic units without losing their plasticizing efficiency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41348.     

蒸养制度对预制桥面板混凝土强度与抗渗性的影响

为了获得预制桥面板的最佳蒸养制度,研究了蒸养温度、蒸养时间及蒸养后补充养护方式对复掺粉煤灰和矿粉配制的C55混凝土的强度和氯离子扩散系数的影响,并采用X-射线衍射仪(XRD)和扫描电子显微镜(SEM)分析了不同蒸养制度下胶凝材料浆体的物相组成和微结构。结果表明,蒸养温度的提高和蒸养时间的延长,对水泥的水化和浆体微结构形成有促进作用,提高了混凝土的脱模强度,但降低了混凝土的后期强度和抗氯离子渗透性能。混凝土蒸养后的补充湿润养护为未水化水泥和矿物掺合料的持续水化提供水化用水,有利于混凝土的后期强度增进和抗渗性提高。预制桥面板在55 ℃温度下蒸养6 h,蒸养后补充覆盖洒水养护7 d具有较好的综合性能。     

有机助磨剂对水泥性能的影响及其有机水泥化学分析(英文)

现代水泥、混凝土中大量使用化学外加剂,特别是有机化合物和高分子聚合物化学外加剂,例如：水泥助磨剂、混凝土超塑化剂、引气剂、增稠剂等,大量有机物的加入改变了水泥水化过程、水化动力学、微观结构的发展,传统的水泥混凝土化学不再能很好地解释其微观结构与宏观性能的关系。为此,提出一个新兴的水泥混凝土化学的补充分支—有机水泥化学,在未来的水泥混凝土研究中该给予更多的重视。以有机化学外加剂—助磨剂为例,说明其对水泥水化动力学、水化产物形态以及水泥浆体的超塑化剂需求量、流变特性、强度发展等宏观性能的影响。水泥中加入微量的助磨剂,不仅改变了水泥颗粒分布,还改变了水化动力学,促进起始离子的溶解和铝酸钙（C3A）和铁铝酸钙（C4AF）的早期水化,明显地提高早期强度和28 d强度。助磨剂吸附在水泥表面改变了水泥的表面性质,其中助磨剂和Ca2＋、Fe2＋螯合起关键作用。     

Effect of crosslinked polycarboxylate superplasticizers with varied structures on cement dispersion performance

In order to investigate the effect of double bond content in the crosslinkers on the performance of superplasticizers, three different crosslinked polycarboxylate superplasticizers were synthesized herein with various respective crosslinkers. Their impacts on the fluidity, absorption, and hydration behavior of cement systems were studied. The results showed that the polymer, which was synthesized using a crosslinker with four double bonds and five/six double bonds, had higher fluidity and the highest fluidity reached up to 395 mm at W/C of 0.35. Additionally, thermogravimetric analysis and hydration heat tests showed that the crosslinked polycarboxylate superplasticizers could prolong the hydration process of cement slurries. Among these three kinds of crosslinked polycarboxylate superplasticizers, the induction period of cement slurry containing the polymer with crosslinker of four double bonds was significantly extended to facilitate the processing of the concrete. The purpose of this study is to provide strategies for studying high-performance polycarboxylate superplasticizers with novel topological structure.     

Influence of superplasticizers on the hydration of cement and the pore structure of hardened cement

This paper describes the influence of various types of superplasticizers such as naphthalene type (β-NS), refined lignin sulfonate type (LS) and polycarboxylate types (P34, S34) on the hydration of cement and the pore structure of hardened cement. Other superplasticizers except β-NS delayed the initial hydration of cement. In any case, it hardly influences the hydration reaction at late stage of cement. The retardation by the addition of superplasticizers is not observed after 28 days of curing. Large pores of 0.1 μm or more for hardened cement with LS or β-NS are larger than those of hardened samples with P34 or S34 cured for 28, 56 and 91 days. This is related to the coagulated structures of fresh cement pastes with various types of superplasticizers. It was presumed that the size of the cluster of aggregated particles became small when S34 or P34 that has a high dispersing ability was added compared to LS or β-NS that has a lower dispersing ability.     

The effect of excessive steam curing on Portland composite cement concrete

Steam curing at atmospheric pressure is an important technique for obtaining high early strength values in precast concrete production. Cement type, as well as curing period and temperature, is an important parameter in the steam-curing process. PC42.5 is the type of cement that is most commonly used in Turkish precast concrete plants. Its behavior is well known. Nowadays, the production of composite cements is becoming more popular every other day due to its advantages. The object of this study was to determine the properties of this relatively new binder comparatively with conventional PC42.5 under steam curing. For this purpose, 15-cm concrete cubes were prepared with a water/cement ratio (W/C) of 0.44 and were subjected to steam curing for five different curing periods of 4, 8, 16, 24 and 36 h under curing temperatures of 65 and 85 °C. Cement dosage was kept constant (400 kg/m³) for all specimens. The variation of compressive strength values and maturity for each condition has been presented comparatively within this study. Test results indicated that Portland composite cement (PKC/A42.5) can be used in place of PC42.5 for steam curing at atmospheric pressure in precast concrete production. However, in case of early high strength demand for early demolding purposes, curing temperature should be increased to 85 °C for PKC/A42.5 cement concretes.     

减水剂对硫铝酸盐水泥早期水化影响

研究了聚羧酸系高效减水剂(PCE)和萘系减水剂(FDN)对硫铝酸盐水泥净浆工作性能及力学性能影响,通过XRD和SEM检测手段对水化产物进行表征.结果表明:两种减水剂对硫铝酸盐水泥净浆流动度的影响存在饱和点;相比于FDN型减水剂,PCE型减水剂对硫铝酸盐水泥净浆具有更好的减水效率及分散能力.PCE型减水剂阻碍硫铝酸盐水泥净浆早期水化,并降低硫铝酸盐水泥净浆1 d抗压强度;FDN型减水剂能够加速硫铝酸盐水泥净浆早期水化,缩短初凝和终凝时间,提高硫铝酸盐水泥净浆1d抗压强度.两种减水剂对硫铝酸盐水泥净浆3d后抗压强度及水化产物种类均没有影响.     

Research on the performances of VPEG macromonomer grafted different functional groups to prepare polycarboxylate superplasticizers

The advent of novel polyether macromonomer has garnered significant attention within the industrial domain. In this study, a range of polycarboxylate superplasticizers (PCEs) was produced via free radical polymerization, employing a new polyether monomer, 4-hydroxybutyl vinyl polyethylene glycol ether (VPEG). This monomer served as the predominant component and was grafted with various functional monomers on its main chain. The molecular configuration of the resultant PCEs was discerned through Fourier infrared spectroscopy and gel permeation chromatography, while the surface tension underwent assessment via a surface tension meter. Both the initial and subsequent fluidity of cement paste and mortar were leveraged to ascertain the dispersion and retention efficacy of the synthetic PCEs. The ramifications of diverse functional group grafts of the new polyether monomer on the cement hydration procedure and strength attributes were elucidated via setting time, hydration heat assays of cement paste, SEM analysis, and compressive strength evaluations of mortar. Observations reveal that the carboxylic acid group significantly reduces surface tension, whereas the sulfonic acid group's effect remains minimal. The incorporation of both the amide and sulfonic acid groups marginally impacts the preliminary dispersion efficacy of PCEs but notably affects dispersion retention. Furthermore, these functional groups facilitate cement hydration, expedite the primary setting time of the cement paste, and bolster the initial compressive strength of the mortar. Specifically, the grafted of sodium methacrylsulfonate (SMAS) yields the most noticeable results. Finally, the working mechanism of PCEs with varying molecular structures has been explained in light both theoretical and experimental results. This research offers valuable insights for subsequent investigations into the fabrication of polycarboxylate superplasticizers using the VPEG macromonomer.