适用于聚羧酸减水剂的混凝土激发剂研究

提出一种适用于聚羧酸减水剂的复合矿物混凝土激发剂,研究了在不同养护条件、不同掺量下,激发剂对混凝土工作性能及各龄期强度的影响,结合XRD,SEM物相检测探讨了激发剂作用机理,并在连江可门港口泊位工程中试用,测试了掺激发剂混凝土的耐久性能.宏观测试结果表明所研激发剂I型对混凝土工作性能影响不大,能够提高混凝土早期强度,且对后期强度及长期耐久性能无不良影响;微观分析表明激发剂I型的掺入加速了C2S,C3S等矿物的水化,并激发了粉煤灰、矿粉的二次水化反应,混凝土强度发展拐点提前出现.     

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.     

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.     

水泥沥青浆体中减水剂与乳化沥青的竞争吸附行为

为揭示水泥沥青砂浆(CA砂浆)中水泥对乳化沥青和减水剂的吸附规律,采用微量热仪分析了减水剂、乳化沥青(单掺及同掺)对水泥水化诱导期的延迟作用.采用"固含法"研究了减水剂种类对水泥-乳化沥青经时吸附规律的影响,以及减水剂在不同添加顺序时对水泥-乳化沥青经时吸附规律的影响.采用偏光显微镜对减水剂作用下水泥-乳化沥青的吸附行为进行了原位观测.结果表明:CA砂浆中的乳化沥青和减水剂均能显著延迟水泥的水化诱导期,两者同掺使延迟作用产生了明显的协同效应;聚羧酸减水剂与乳化沥青对水泥的吸附作用存在明显的竞争关系,两者同掺时水泥优先吸附减水剂分子,减水剂耗尽后,水泥再吸附乳化沥青.减水剂后掺时可使部分吸附的乳化沥青发生解吸附.     

聚羧酸减水剂在水泥和泥土表面的吸附行为

采用有机碳测定仪研究了水泥、泥土和水体系中聚羧酸减水剂吸附量与吸附时间、减水剂浓度、体系温度的关系。同时,对减水剂吸附模型和吸附热进行了分析,探讨了聚羧酸减水剂在水泥、泥土颗粒表面的吸附特性。结果表明:水泥和泥土对聚羧酸减水剂的吸附量随时间延长不断增加,最后达到平衡,同时,泥土比水泥对减水剂的吸附量要大,泥土的掺入量为0.5%就会大大降低水泥净浆的流动度;聚羧酸减水剂的吸附基本符合Langmuir等温吸附模型,水泥和泥土对减水剂的饱和吸附量分别为3.7mg/g和10.1mg/g;水泥和泥土对聚羧酸减水剂的吸附量随温度的增大而减小,其吸附是一个放热过程。     

Properties and mechanism of CFBC fly ash-cement based stabilizers for lake sludge

Circulating fluidized bed combustion(CFBC) fly ash was mixed with cement or lime at a different ratio as a stabilizer to stabilize lake sludge.In order to understand the influences of stabilizers on the lake sludge properties,tests unconfined compressive strength,water stability and SEM observation were performed.The experimental results show that with the increase of the curing time,the strength of all the stabilized specimens increase,especially the samples containing cement.The strength of the specimens is decreased with the increasing of the CFBC fly ash/cement ratio,the optimum ratio between CFBC fly ash and cement is 2:3.The water stability of CFBC fly ash-cement based stabilizers is higher than those of cement and lime.Moreover,the lake sludge stabilization mechanism of CFBC fly ash-cement based stabilizers includes gelation and filling of the hydration products,i e,C-S-H gel and the AFt crystal,which act as benders to solidify those particles together and fill in the packing void of the aggregates.     

无机盐对硫酸盐与聚羧酸减水剂相互作用的影响

目的 探讨硫酸盐对聚羧酸减水剂分散效果的影响机理,改善硫酸盐对聚羧酸减水剂吸附性能的影响.方法 在粉煤灰中掺入硫酸钠以改变其体系中硫酸盐的含量,然后在硫酸盐-聚羧酸体系中加入无机盐,采用总有机碳质量浓度(TOC)、ζ电位以及红外光谱等试验.结果 当粉煤灰中硫酸钠质量分数为3％时,加入3％的硝酸钡以后,吸附完成时外加剂溶液中有机碳的质量浓度从898 mg/L增加到914 mg/L,ζ电位的绝对值由11.11 mV提高到14.6 mV;加入3％的氯化钙,吸附完成时外加剂溶液中有机碳的质量浓度从898 mg/L增加到1 141 mg/L,ζ电位的绝对值由11.11 mV提高到15.91 mV;同时当粉煤灰中硫酸钠质量分数为3％时,红外谱中透射率明显下降,但向体系中加入无机盐(3％硝酸钡或3％氯化钙)以后,红外谱中百分比透射率有很大提高.结论 硫酸钠与聚羧酸减水剂本身存在相互作用,粉煤灰中硫酸钠的含量越多对聚羧酸减水剂的吸附量增大,在硫酸盐-聚羧酸体系中加入无机盐,可以减弱硫酸盐对聚羧酸减水剂分散效果的影响.     

Determination of residual monomers in polycarboxylate superplasticizer using high performance liquid chromatography

A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer (PCs) by reversed-phase high performance liquid chromatography (RP-HPLC).Four kinds of residual monomers were well separated and determined on a SinoChrom ODS-BP (C18) column with mobile phases composed of acetonitrile and phosphate buffer solution.The monomers were detected by UV detector at 205 nm and quantitatively analyzed with an external standard method.For those residual monomers,the linear response ranged from 4.0×10-6 mol·L-1 to 2.0×10-3 mol·L-1.The determination limit of acrylic acid,sodium methylallyl sulfonate and 2-Acrylamido-2-methylpropane sulfonic acid was 0.02×10-5 mol·L-1,while that of methoxy-polyethylene glycol monoacrylate was 0.1×10-5 mol·L-1.The relative standard deviation (RSD) of high concentration samples was less than 1%,while that of the low concentration samples was between 1%-4%.The standard (additional) recovery ratio was 97.4% -104.2%.     

萘系减水剂/氧化石墨烯复合材料对水泥石微观结构和性能的影响

采用Hummers法和超声剥离制备了氧化石墨烯(GO)纳米片层分散液,再与萘系减水剂(NS)复合得到NS/GO复合材料.研究了NS/GO复合材料对水泥净浆流动性和水泥石抗压耐折强度的影响.研究结果表明,当NS/GO的掺量为4.8g/0.06g(每100g水泥)时,净浆流动度可以达到204mm,所得水泥石的抗压强度为65.4MPa,且耐折强度达到10.6MPa,分别比对照样品提高了29.3%和41.4%.SEM形貌结果表明,GO能够促使水泥水化反应形成致密的片层状结构.这些结果对于提高混凝土的抗压耐折强度,以及抗裂性和耐久性等具有重要的意义.     

早强型聚羧酸减水剂的合成及性能研究

以丙烯酸(AA)、异丁烯醇聚氧乙烯醚(HPEG)、甲基丙烯磺酸钠(SMAS)等为单体,分别采用丙烯酰胺(AM)、羟甲基丙烯酰胺(HAM)取代部分丙烯酸,通过水溶液聚合法制备出具有早强功能的聚羧酸系减水剂,并探讨了合成条件对水泥净浆流动度的影响.研究结果表明:在单体摩尔比n(AA)∶n(HPEG)∶n(SMAS)=4∶1∶0.36、反应温度为80℃、过硫酸铵(APS)用量为单体总质量的3%时,制备出的聚羧酸减水剂的分散性能较优.当AM取代为18%时,对提高混凝土的早期强度效果较佳,AM比HAM具有更好的早强效果.     

新型蔗糖基聚羧酸高效减水剂的合成与性能

以自制甲基丙烯酸蔗糖酯（MASE）、丙烯酸（AA）、甲基丙烯酸（MAA）、烯丙基磺酸钠和烯丙基聚乙二醇（A PEG ）为原料,以过硫酸钾为引发剂,自由基共聚法合成蔗糖基聚羧酸高效减水剂。研究了反应时间、蔗糖酯含量及引发剂用量对蔗糖基聚羧酸高效减水剂性能的影响。并通过流动度测试、红外光谱表征及黏度对减水剂的结构与性能进行了分析与比较。各组分物质的量nAA ：nMAA ：nSAS ：nAPEG ：nMASE ＝3∶1∶2∶1∶0．2,MASE含量为4．9wt．％,引发剂为单体用量1．9wt．％,反应时间为5h时合成的减水剂性能最好。在水灰比为0．29,折固掺量为0．3w t ．％,水泥净浆流动度达到340mm。     

Self-cementing mechanism of CFBC coal ashes at early ages

The self-cementing mechanism at early ages of circulating fluidized bed combustion （CFBC） coal ashes was studied by X-ray diffraction （XRD）, infrared （IR） spectroscopy and chemical method. The results indicate that the amorphous phase is predominant in CFBC coal ashes. The polymerization degree of [SiO4] and [AlO6] of CFBC desulphurization coal ashes is lower than that of those without desulphurization. The contents of the components with fast hydration rate of CFBC desulphurization coal ashes are significantly greater than those of the ashes without desulphurization. This work confirms that the amorphous minerals with high chemical activity are the main causes of the self-cementing property of CFBC desulphurization coal ashes at early ages.     

Effects of molecular structure of polycarboxylate-type superplasticizer on the hydration properties of C3S

Effects of polycarboxylate-type superplasticizer(PC) molecular structure on the hydration heat of tricalcium silicate(C3S) paste and polymerization degree of hydration products(C-S-H gel) were researched by using TAM AIR isothermal microcalorimetry(TA) and 29Si nuclear magnetic resonance(NMR).Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed.PC molecules with shorter main chain or longer side chains caused stronger retardation of C3S early hydration and lesser increase of C3S 3 d hydration degree.NMR measurement indicated that the incorporation of PC increased the hydration degree of C3S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel.The tendency for C3S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added.Whereas,PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.     

减缩剂与减水剂的相容性研究

研究了两种减缩剂与四种减水剂复合后对溶液表面张力、混凝土坍落度、混凝土强度、混凝土自由收缩和砂浆收缩的相容性问题.试验结果表明,两种自身表面张力相近的减缩剂对蒸馏水和减水剂溶液表面张力的作用差异较大,但对砂浆和混凝土的减缩率几乎相同,收缩规律的影响相似,说明表面张力并不是减缩率的惟一决定因素.就减缩率而言,减缩剂与减水剂的相容性是较好的,而对强度的相容性相对较差,其作用机理与减水剂分子的支链数及负离子基团数有关.     

粘土对聚羧酸减水剂性能的影响及机理研究

粘土作为杂质存在于混凝土的组分如砂石中,粘土对聚羧酸减水剂有较强的吸附性,从而影响混凝土的工作性。研究了不同粘土对掺聚羧酸减水剂的水泥浆体及砂浆流动性的影响规律,探讨了聚羧酸减水剂与粘土的相互作用机理。研究结果表明,不同粘土对水泥浆体的流动性有不同程度的影响,蒙脱土和膨润土相对于高岭土及筛分土对砂浆的流动性影响更为显著;同时,相对于不掺聚羧酸的砂浆,粘土对掺聚羧酸减水剂砂浆的流动性影响更为显著。粘土自身的吸附性与疏水基的定向吸附共同作用及粘土中的金属离子与聚羧酸的螯合作用可能是粘土吸附聚羧酸减水剂的机理。     

Effect of curing conditions on the hydration and performance of CFBC ash cementitious system

Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system （30： 70, by mass） including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages （the increase rate lowers down in the following ages） and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.     

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.     

Synthesis, properties and dispersion mechanism of sulphonated acetone-formaldehyde superplasticizer in cementitious system

The synthesis, properties and dispersion mechanism of sulphonated acetone-formaldehyde superplasticizer （SAF） were presented. This superplasticizer was synthesized by the reaction among acetone, formaldehyde, sodium sulfite and pyrosulfite. The structure and property were respectively characterized by IR and surface tension measurement. Performance of SAF in cement was evaluated by paste flow as well as heat calorimetry. The dispersion mechanism was identified via adsorption and zeta potential measurement. The results show that cement paste mixed with SAF shows good fluidity. SAF exerts little retarding effect on cement paste and it behaves like a typical polycondensate superplasticizer. The main dispersion mechanism of SAF is attributed to electrostatic repulsion.     

Effect of polycarboxylate-type superplasticizer on the paste fluidity based on the water film thickness of flocs

The excess water film theory and the properties of flocs are integrated to examine the effect of the polycarboxylate-type superplasticizer on the paste fluidity.The theory states that excess water can surround the flocs rather than the particles and that the cell consists of a floc and a superficial water film.Experiments on limestone powder pastes were conducted to verify the theory.The superplasticizer dosage(sp%)and the water–powder ratio by volume(Vw/Vp)were systematically varied.A sedimentation balance method was used to measure the size distribution of the flocs in the limestone powder pastes.The water film thickness(WFT)of flocs was then calculated and shown to determine the paste fluidity.Based on this WFT of flocs,the effect of the sp on the paste fluidity was determined and then compared with the effect of water.     

葡萄糖酸钠与高效减水剂复合使用对水泥水化历程的影响

用直接测温法及X射线衍射技术,系统研究了葡萄糖酸钠与萘系、氨基磺酸盐系及聚羧酸盐系3种高效减水剂复合使用对水泥水化热、水化温峰、温峰出现时间及不同水化龄期Ca(OH)2和钙矾石(AFt)生成量等方面的影响.结果表明:与糖钙和三聚磷酸钠相比,葡萄糖酸钠及其与高效减水剂复合对水泥水化历程的影响规律明显不同.单掺葡萄糖酸钠使水泥水化第2放热峰出现时间延迟,但温峰值及水化热与空白样基本持平,温峰时的Ca(OH)2生成量增大.复合使用葡萄糖酸钠与高效减水剂时,与不同品种高效减水剂复合使用对水泥水化历程的影响不同.