水泥沥青复合砂浆拌合物乳化沥青破乳过程研究

针对水泥沥青复合砂浆(CA砂浆)中乳化沥青的破乳过程,从CA砂浆固化过程中体系的粘度、颗粒粒径变化、水泥掺量对乳化沥青破乳的影响及乳化沥青的聚集过程的角度,分析了乳化沥青的破乳过程及其影响因素。研究表明:减水剂对乳化沥青粘度变化有较大影响,减水剂的用量越多,CA胶浆在低粘度状态下的保持时间越长,减水剂可调节乳化沥青的破乳速度。CA砂浆中乳化沥青的破乳过程分为3个阶段:水泥与乳化沥青的接触阶段、动态平衡阶段及加速破乳阶段。当水泥含量较多时,水泥颗粒被沥青包裹程度较小,水化速率较快,促进了乳化沥青的破乳和聚集。通过光学显微镜分析表明,CA砂浆中乳化沥青的破乳过程即是沥青颗粒的聚集结合过程。     

阳离子乳化沥青对硅酸盐水泥砂浆力学性能影响分析

针对乳化沥青掺量对水泥砂浆力学性能的影响,采用不同质量百分比的乳化沥青与水泥(AE/C)制备乳化沥青改性水泥砂浆,测试其抗压强度和抗折强度等力学性能,并采用扫描电镜(SEM)分析微观结构,解析乳化沥青对水泥砂浆力学性能影响机理.结果表明:乳化沥青含量大于5%时,砂浆的抗压强度显著下降,抗折强度提高;当含量达10%时,砂浆的韧性最佳.乳化沥青对水泥砂浆力学性能的改善机理为沥青胶浆填充在水化产物的空隙中,起到吸收荷载、为水化产物失稳破坏提供缓冲的作用.当沥青用量过大时,沥青膜厚度大于水化硅酸钙(C-S-H)长度,水化产物未穿过沥青膜生长,无法形成连续的网络结构,导致砂浆韧性降低.     

减水剂对CRTSⅡ型CA砂浆强度影响规律研究

高速铁路板式无碴轨道中CA砂浆主要由水泥、沥青乳液和多种外加剂组成,其中减水剂是最重要组分之一.为了探讨不同种类和掺量的减水剂对CRTSⅡ型CA砂浆强度和微观结构的影响,采用聚羧酸系、木质系磺酸钠和萘系3种减水剂,研究了其品种和掺量的变化对CA砂浆抗压强度的影响,并通过SEM观察了其微观型貌特征.结果表明,聚羧酸减水剂对CA砂浆抗压强度降低作用的影响最小;相同品种的减水剂掺量越大,CA砂浆抗压强度降低越明显,流动性越高.SEM微观分析表明,强度性能变化的原因是由于减水剂造成了CA砂浆的孔洞数量、孔径、孔洞连通情况不同.     

萘系减水剂不同掺加方法的作用机理的研究

本文通过水泥和水泥熟料矿物对减水剂的吸附及电化学测定,认为萘系减水剂不同掺法的作用机理主要与减水剂的吸附平恒浓度及水泥颗粒的ζ-电位有关,而这两者又取决于水泥中各熟料矿物的水化程度和电性质。本文还通过化学结合水和水化热以及流变参数等的测定,探讨了减水剂不同掺法对水泥浆体水化动力学过程和流变性能的影响,并提出了减水剂后掺—分两次加水的新方法。     

不同黏土对掺减水剂水泥净浆流动度影响

目的 研究4种不同黏土对掺聚羧酸减水剂及萘系减水剂水泥净浆流动度的影响规律并从黏土的吸附性能角度探究其影响机理.方法 采用水泥净浆流动度试验方法比较了4种黏土对掺聚羧酸减水剂水泥净浆流动度的影响,通过TOC总有机碳测试仪测定了4种黏土对聚羧酸减水剂的吸附量.结果 4种黏土对水泥净浆流动度的影响差异较大,其中钙基蒙脱土和钠基蒙脱土的掺量为2％时,掺聚羧酸减水剂水泥净浆已基本没有流动度,掺萘系减水剂的水泥净浆流动度也有所下降,但降幅稍小,而伊利土和高岭土对掺减水剂水泥净浆流动度无明显负面影响;钙基蒙脱土和钠基蒙脱土对聚羧酸减水剂的吸附量较大,伊利土、高岭土对聚羧酸减水剂的吸附能力和水泥相当.结论蒙脱土对掺聚羧酸减水剂水泥净浆流动度负面影响极为严重,而伊利土和高岭土对掺减水剂水泥净浆基本没有负面影响.     

基于氮吸附的水泥-沥青复合硬化体孔结构分析

水泥沥青砂浆是一种多相多孔的复合材料,其组分为水泥-沥青共同形成的复合胶凝体。为了解水泥沥青砂浆中的孔隙结构,应用低温氮吸附法分析了不同水泥-沥青质量比的水泥-沥青复合硬化体中BET比表面积、2～200nm孔分布随龄期的变化。测试结果显示:水泥-沥青复合硬化体的BET比表面积显著低于硅酸盐水泥石,随龄期增长而增大;在氮吸附法有效的孔径分析范围内(2～200nm),随龄期的增长,孔径50nm以下的孔数量增长显著,28d龄期CAB浆体的微分孔径分布曲线在5～7nm及20～50nm出现的分布峰,可分别归结于水化产物数量的增长及水化产物的填充作用;沥青含量对孔分布及孔结构形成有显著影响,随沥青含量的增大,复合硬化体的BET比表面积降低,小于50nm的孔数量减少。     

水泥对乳化沥青混合料微观结构的改善机理

采用扫描电镜(SEM)、红外光谱(IR)以及Zeta电位仪等微观试验手段,研究分析了水泥对乳化沥青混合料微观结构的改善机理.结果表明,掺加3.0%水泥后,乳化沥青胶浆中光滑区域减小,凝胶体数量增加,胶浆结构致密性加强.水化产物与沥青以物理结合方式构成网状结构;混合料胶浆与集料界面距离缩小,界面区出现分层现象,存在致密结构区域,界面区微观结构得到改善;提出了水泥在乳化沥青混合料微观结构改善中的4个作用,即促进乳化沥青破乳、构成水化产物/沥青膜网状结构、弥补混合料内部缺陷以及提高沥青与集料粘附性.     

一种聚醚型聚羧酸减水剂的制备

采用水溶液自由基共聚方法合成了一种聚醚型聚羧酸减水剂(RHW-1),考察了聚合工艺及单位配比对RHW-1分散性能的影响,获得了最佳工艺条件.针对该产品分子量经时变化、总有机碳(TOC)、水泥净浆流动度等指标与国内外同类产品进行了对比,并合理的解释了聚羧酸减水剂在水泥水化过程中的吸附行为.试验结果表明,该减水剂对水泥具有高度的分散作用和分散保持能力,具有掺量低,减水率高,塌落度保持性好等优点.     

基于后掺法的混凝土坍落度恢复技术研究

通过水泥对减水剂的吸附、水泥浆溶液Zeta电位、净浆流动度和混凝土坍落度等试验,分析了后掺聚羧酸减水剂量和添加时间对水泥净浆流动性、混凝土工作性能的影响及其相互关系,在此基础上提出了恢复混凝土坍落度的技术方法。结果表明:后掺法通过降低水泥颗粒对减水剂的吸附和减小颗粒的Zeta电位,能够有效避免早期水化产物对减水剂的吸附包裹,提高减水剂的有效分散能力;减水剂后掺的量与时间的合理匹配,可在一定时间内恢复混凝土坍落度,当先掺80%、后掺20%的减水剂时,在2h内可以显著地改善坍落度损失。     

多因素作用下水泥乳化沥青胶浆性能特征及机理

为揭示多因素作用下水泥乳化沥青胶浆(cement emulsified asphalt mortar, CEA)的水化特征及强度形成机理,选取乳化沥青与水泥质量比m(A)/m(c)、水灰比和养护方式等因素,研究新拌CEA的流动性以及在凝结硬化过程中水泥水化进程、力学性能、水分蒸发速率以及内部孔隙结构的发展规律。结果表明,随着m(A)/m(c)的增加,水泥水化诱导期不断延长,CEA的流动性与内部结构致密性遭到劣化,抗压强度受到不利影响;水灰比的增加虽可以减弱乳化沥青对水泥水化的延缓作用,但高水灰比CEA的内部水分蒸发速率较高,基体内部结构疏松多孔,抗压强度大幅降低;对于低m(A)/m(c)和高水灰比的CEA,可通过裹覆养护降低CEA基体内部水分蒸发速率,进而提升CEA的抗压强度。本研究揭示了多因素作用下水泥乳化沥青胶浆的性能特征及机理,为高性能水泥乳化沥青胶浆的设计提供理论依据。     

乳化沥青冷再生混合料中的复合胶浆性质

对乳化沥青冷再生混合料中的三种胶浆系统进行了研究,包括沥青+矿粉、乳化沥青残留物+矿粉和乳化沥青残留物+水泥。结果表明,因为水泥水化作用的存在,水泥⁃乳化沥青残留物胶浆表现出更高的模量增率效果;模量和相位角变化呈现与普通矿粉⁃沥青胶浆和矿粉⁃乳化沥青胶浆不同的特点,且不随粉胶比呈现线性单调的变化;胶浆界面黏结力与矿粉⁃沥青胶浆相当,并在低粉胶比范围内远高于单独利用矿粉的乳化沥青残留物胶浆。     

The Competitive Adsorption Characteristics of Welan Gum and Superplasticizer in Cement Mortar

Welan gum has been widely used in oil cement and grouting materials for its excellent rheological properties and anti-bleeding,and most of all,being friendly to the environment.However,when welan gum was added,the fluidity of mortar decreased sharply,so it should be used together with a superplasticizer to enable good workability.With its powerful charge density in the molecular structure,the competitive adsorption between welan gum and other admixtures happened remarkably during the addition process.Consequently,we experimentally studied on the bleeding rate and rheological properties of cement slurry,fluidity and mechanical properties of mortar with welan gum mixed with superplasticizer,aiming at understanding the competitive adsorption phenomenon by application of welan gum mixed with superplasticizer.By measuring the hydration heat and zeta potential,the mechanism of interaction of welan gum with superplasticizer was deduced and explained.The results showed that it could ensure a good dispersion effect when welan gum is mixed with the two kinds of superplasticizer.Welan gum had little impact on the naphthalene superplasticizer,but did have a substantial influence on polycarboxylate.In practice,adding welan gum after PCE acted with cement for 2 min could effectively avoid the competitive adsorption and then achieve better performance.On this viewpoint for mortar with PCE,new delay release welan gum needs further research and development.     

干燥环境下乳化沥青改性水泥砂浆的试验研究

研究了干燥环境下乳化沥青对水泥砂浆流动性和力学性能的影响，试验结果表明乳化沥青能提高水泥砂浆的抗压强度、抗折强度，降低脆性。并简迷了乳化沥青对水泥砂浆的改性作用机理。     

Adsorption of superplasticizers in fly ash blended cement pastes and its rheological effects

The adsorption of superplasticizers in fly ash blended cement paste and its rheological effects were investigated.It is shown that the absorption of superplasticizer on portland cement particles is very different from that on fly ash particles.The fly ash particles have smooth surfaces and are negatively charged,so its adsorption capacity is weaker than the portland cement particles.The amount of adsorbed SP in the fly ash blended cement paste depends highly on the replacement proportion of portland cement with fly ash,and to a much less extent on the nature of the fly ash.However,the amount of adsorbed superplasticizer does not correspond well the ζ-potential of the solid particles,due the strong adsorbing capacities of the Portland cement particles.When fly ash replaces portland cement in the paste,the rheological behavior is radically changed,which is closely related to the fineness and density of the ash.The packing and agglomeration of the solid particles are the controlling factors on the rheological parameters of the fresh paste,instead of the amount and type of adsorbed superplasticizer.     

ACS新型高效减水剂的研究(1)-减水剂的合成和其在水泥颗粒表面的吸附

根据聚合物分子设计原理,通过乙烯类单体的自由基溶液共聚合制备了分子链中含阴离子基团和支链的共聚物,制备了对水泥颗粒具有良好分散作用和分散稳定作用的混凝土用丙烯酸接枝共聚型高效减水剂（ACS）。用红外光谱表征了基结构。对照商品萘系高效减水剂FDN,研究了ACS在水泥颗粒表面的吸附。吸附量和ζ－电位的测定表明,ACS分子可吸附到水泥颗粒表面,其极限吸附量为1．97mg/g吸附后,水泥颗粒表面ζ－电位由＋10mV变成－15mV。     

Effect of competitive adsorption between sodium tripolyphosphate and naphthalene superplasticizer on fluidity of cement paste

The adsorption amount, ζ-potential of cement particles and fluidity of cement paste were tested to research the competitive adsorption between naphthalene superplasticizer(FDN) and STPP. The experimental results showed that the presence of STPP could significantly improve the fluidity of cement paste and reduce the fluidity loss with FDN. There existed a competitive adsorption between STPP and FDN. STPP and calcium ions formed complexes; they preferentially adsorbed onto surface of cement particles and preempt adsorption points of FDN; and it reduced adsorption amount of FDN. In the absence of STPP, saturation adsorption amount of FDN was 5.93 mg/g; but when the dosage of STPP was 0.1%, it reduced to 4.3 mg/g(about 72.5%). The adsorption amount of FDN was reduced by STPP, but ζ-potential of cement particles enhanced and fluidity of cement paste increased because of strong negative charge effect of the complexes. Adsorption of the complexes would delay Ca2+ into liquid and inhibit formation of active adsorption points. Then, content of FDN in liquid increased with the addition of STPP and ζ-potential of cement particles became stable. In this way, fluidity loss of cement paste reduced.     

磺化淀粉-聚羧酸复合减水剂的制备与表征

由于保护环境的原因,以天然高分子为原料来合成高效减水剂已经成为混凝土外加剂研究领域的新热点.本文研究了采用磺化糊精取代部分功能大单体来合成复合聚羧酸减水剂的方法.结果显示:当磺化糊精取代功能单体40%、复合聚羧酸减水剂掺量为0.5%时,水泥净浆的初始流动度达255,mm,1,h 后其流动度仍为250,mm.淀粉酸解后,增加亲水的羟基基团导致初期水化缓慢,而增加 Zeta 电位使水泥颗粒更易于分散.在复合减水剂中,长链 Starch 与短链的聚羧酸减水剂主链将被吸附于水泥颗粒表面上,交替发生静电与空间位阻作用,起到了增加减水率和降低缓凝的效果.     

The influence of steel slag with high Al2O3 content on the initial hydration of cement

The initial hydration of steel slag with high Al₂O₃ content and its influence on the initial hydration of cement were investigated in this study. Steel slag with high Al₂O₃ content may contain much calcium aluminate mineral but very little gypsum. The steel slag hydrates much more quickly than cement in the initial hydration period, producing many flake products which have a great influence on the fluidity, initial setting time, and adsorption level of superplasticizer of paste. Replacing part of cement by steel slag with high Al₂O₃ content can change the hydration condition of calcium aluminate mineral of the cement by decreasing the gypsum to calcium aluminate mineral ratio, resulting in accelerating the hydration rate of calcium aluminate mineral in the initial hydration period. Paste containing steel slag with high Al₂O₃ content has a shorter initial setting time, higher adsorption level of superplasticizer, and greater loss in fluidity than the pure cement paste.     

Adsorption mechanism of polycarboxylate-based superplasticizer in CFBC ash-Portland cement paste

Circulating fluidized bed combustion （CFBC） ash exhibits the desirable pozzolanic activity which makes it a potential supplementary cementitious material to replace cement for concrete production. However, the high unburnt carbon content and porous surface structure of CFBC ash may adsorb water reducer and thereby significantly reduce the efficiency of water-reducing agents. The adsorption mechanism of polycarboxylate superplasticizer in CFBC ash-Portland cement paste was investigated by ultraviolet-visible spectrophotometer, and the conception of ＂invalid adsorption site＂ of CFBC ash was presented. The results show that the adsorption behavior of polycarboxylate superplasticizer in coal ash-Portland cement paste can be described by Langmuir isothermal adsorption equation. The adsorption capacity of CFBC ash-Portland cement paste is higher than that of pulverized coal combustion （PCC） fly ash-Portland cement paste. Moreover, the adsorption amount of polycarboxylate superplasticizer increases with the ratio of ash-to-cement in the paste. At last, the fluidity of CFBC ash-Portland cement paste is lower than that of the PCC fly ash paste. This work suggests that when CFBC ash is used as concrete admixture, the poor flowability of the cementitious system due to the high adsorption of water and water-reducing agent should be taken into consideration.     

Effect of superplasticizers on the early age hydration of sulfoaluminate cement

The effects of two types of superplasticizers on the properties of CSA cement pastes during early hydration were studied. The influences of two types of superplasticizers on the properties of cement pastes, including the normal consistency, setting time, fl uidity, and compressive strength, were investigated by using various methods. The hydration products of the cement pastes cured for 1 day and 3 days were studied by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. The results show that the PCE type superplasticizer retards the early age hydration while the FDN type superplasticizer accelerates the early age hydration of the CSA cement. Both types of superplasticizers have no infl uence on the further hydration of CSA cement, confi rmed by the calorimeter tests as well. The ultrasonic pulse velocity measurements were used to probe the influence of two types of superplasticizers on the hydration of CSA cement pastes at a high water-cement ratio（0.45）. The results show that the PCE type superplasticizer retards the early age hydration of the CSA cement while the FDN type superplasticizer has little infl uence on the early age hydration of the CSA cement.