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.     

聚丙烯纤维改善混凝土抗冲磨性能的试验研究

对聚丙稀纤维和聚羧酸超塑化剂等新型材料合掺条件下混凝土的抗冲击性能、抗冲耐磨性能和抗裂性能进行了试验研究。研究表明,由于聚羧酸超塑化剂和粉煤灰的高效减水作用,使得该混凝土与硅粉混凝土相比具有胶材用量少,裂缝显著减少等特点。在聚丙稀纤维的作用下,混凝土抗冲击、耐磨损和抗裂等性能得到显著提高。     

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.     

外掺材料对多孔水泥混凝土胶浆强度的影响研究

文章采用超细粉煤灰与硅灰的复合技术配制多孔水泥混凝土水泥浆体试件.通过与双掺硅灰和减水剂、双掺粉煤灰和减水剂以及复合掺粉煤灰、硅灰和减水剂的情况对比,系统研究了硅灰粉煤灰作为外掺挤对多孔水泥混凝土水泥浆体的强度的影响.实验结果表明,由于硅灰与超细粉煤灰的复合,在水泥浆体形成过程中,这2种材料充分发挥了各自的功能效应,使得多孔水泥混凝土水泥浆体的强度性能显著提高.文章通过扫描电镜试验,剖析了超细粉煤灰与硅灰复合效应的机理,论证了用超细粉煤灰和硅灰以及减水剂复合配制多孔水泥混凝土水泥浆体的可行性.     

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.     

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.     

减水剂对高掺量粉煤灰砂浆性能的影响

研究了萘系高效减水剂（FDN）和木质素磺酸钙（LS）对高掺量粉煤灰砂浆性能的影响,测定了减水剂在胶凝颗粒表面的吸附、对水泥颗粒表面zeta电位等方面的影响。结果表明,和FDN相比,LS对砂浆的减水率较低,而对砂浆流动度保持能力较优;当掺量为0.4 wt%时,两者对砂浆稳定性的影响几乎一样。当掺量低于0.4 %时,LS的减水率和FDN接近是因为其具有较强的引气作用和FDN在胶凝颗粒表面吸附不完全;LS保持砂浆流动性能力较好是由于它的缓凝作用以及吸附LS的水泥颗粒表面zeta电位较稳定导致的。为了更好地将LS应用在高掺量粉煤灰砂浆中,可以从提高其减水率方面对其进行改性。     

Influence of ultra-fine fly ash on hydration shrinkage of cement paste

1INTRODUCTION Hydrationshrinkageisalsoknownaschemicalshrinkage[1].Thesolidvolumeincreasesafterce menthydrating,buttheabsolutevolumeofcementwatersystemreduces.Usuallythetotalamountofvolumeshrinkageofcementwatersystemis7%9%[1,2].Withthedevelopmentofthetechno logyofcementandconcrete,concretewithhighstrengthandhighperformanceisthedevelopingtendencynow.However,nowadays,comparedwithordinaryconcrete,thehydrationshrinkageofhighperformancecementconcreteincreasesobvi ouslybecauseoftheaccelerationof…     

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。     

自燃煤矸石粉与粉煤灰复合对胶凝材料体系需水性的影响

主要研究自燃煤矸石粉对胶凝材料体系需水性的影响,并通过与粉煤灰的对比与复合,进一步确定自燃煤矸石粉的需水性.试验结果表明,随着自燃煤矸石粉取代水泥量的增加,胶凝材料体系需水量逐渐增大.自燃煤矸石粉与粉煤灰复合后,胶凝材料体系的需水性比单掺自燃煤矸石粉减小,其需水性趋势随自燃煤矸石在粉体中所占比例的增加而逐渐增大.在高效减水剂存在的情况下,掺复合粉的胶凝材料浆体匀质性优于空白水泥与单掺粉煤灰.     

氨基磺酸盐系高效减水剂的改性研究

氨基磺酸盐系减水剂具有高减水率、抑制混凝土塌落度经时损失等优点,但泌水严重,限制了其在混凝土中的应用。本文根据“分子设计”原则,通过单体A和单体U引入适当的官能团,对传统氨基磺酸盐系高效减水剂进行改性,测试了产品对水泥净浆流动度、流动度经时损失和泌水率的影响。试验表明,单体A的改性效果优于单体U,以9%的单体A改性后,减水剂的分散性和分散保持性能好,泌水率显著降低。     

Influence of fly ash fineness and shape on the porosity and permeability of blended cement pastes

The effects of the fineness and shape of fly ash on the porosity and air permeability of cement pastes were investigated. Pulverized coal combustion (PCC) fly ash and fluidized bed coal combustion (FBC) fly ash classified into three different finenesses were used. River sand with particle size distribution similar to that of fly ash was also used for comparison. Portland cement was replaced with fly ash and ground sand at the dosages of 0, 20wt%, and 40wt%. A water-to-binder ratio (w/b) of 0.35 was used thr...     

聚羧酸系高效减水剂PC的合成及性能研究

以甲基丙烯酸、聚乙二醇1000、对甲苯磺酸、对苯二酚、过硫酸铵和甲基丙烯磺酸钠为原料,采用两步法合成出新型聚羧酸系高效减水剂(简称PC)。将合成的PC与目前广泛使用的萘系高效减水剂(简称FDN)相比,具有更加优异的性能,具体表现为:在掺量很少情况下,水泥净浆就具有较高的流动度;当掺量相同时,其对水泥净浆流动度远超FDN。此外,它与水泥的相容性好,具有缓凝及明显抑制水泥净浆流动度经时损失性能,对混凝土也能表现出显著的减水增强性,是一种性能优良,适合于配制高强、超高强混凝土的高效减水剂。     

INITIAL BINDING CAPACTIES OF CHLORIDE ION OF COMPONENTS IN HIGH-PERFORMANCE CONCRETE

An investigation is reported on the influence of different components of high performance concrete (HPC) on the initial binding capacities (IBC) of chloride ion. The testing results demonstrate that cement has the largest IBC, and the relative binding ratio is as high as 30% of total ion amount. Among the mineral admixtures, fly ash has the largest IBC of chloride ion. The IBC of silica fume is about 14.4% ,which is smaller than that of fly ash. The IBC of refined ground blast-furnace slag (microslag) is abnormal due to the influence of sulfate ion contained. The addition of superplasticizer and corrosion inhibitor containing calcium nitrite weakens the IBC of mixtures. The fluidity and pore-filling effect of mineral admixtures are studied with paste samples with W/C ratio of 0.3. The influence mechanism of various components in high-performance concrete in IBC is studied further through SEM and Mercury Instrusion Porosimetry tests with paste samples at the age of 3 days.     

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.     

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.     

矿物掺合料对自密实混凝土抗氯离子渗透性的影响

耐久性是自密实混凝土（SCC）的重要性质。本文应用电通量法研究了掺粉煤灰、矿渣的SCC抗氯离子渗透性能,通过对单掺和复掺时SCC电通大小的分析发现：粉煤灰和矿渣都能改善SCC的抗氯离子渗透性能,矿渣提高SCC的抗氯离子渗透性能要优于粉煤灰,二者复掺对SCC抗氯离子渗透的复合叠加效应并不明显。其机理是粉煤灰和矿渣提高水泥石密实性,强化混凝土界面过渡区,粉煤灰、矿渣物理化学吸附作用能固结Cl-,降低Cl-渗透性。SCC中掺入掺合料能减少离析、避免泌水,达到自密实效果,粉煤灰对混凝土流动增大的作用效果要优于磨细矿渣的效果。掺合料复掺对自密实混凝土强度具有复合叠加效应,混凝土28 d强度等级可提高1～2级。     

粉煤灰对酸性染料的脱色研究

以燃煤废弃物粉煤灰作为吸附剂,对酸性蓝197与酸性黑1进行吸附脱色,研究影响脱色的因素。实验结果表明：粉煤灰浓度为10 g/L时,对两支酸性染料的吸附在初始30 min内基本达到平衡,高温改性粉煤灰的吸附脱色性能明显提高;两支染料溶液初始pH值小于5.5时,脱色效率最佳;随染液初始浓度增大,染液的脱色率不断降低,但粉煤灰吸附量却不断增大;粉煤灰及改性粉煤灰对两支染料的恒温吸附脱色数据符合Lang-muir和Freundlich两种恒温吸附方程;吸附参数表明粉煤灰对水溶性酸性染料的吸附过程容易进行;粉煤灰及改性粉煤灰对两支染料的吸附动力学过程为准二级吸附。     

Quantitative determination of composition of quaternary cementitious materials

Based on the principle of ENV 196-4 ＂Methods of testing cement - Part 4 Quantitative determination of constituents or Chinese Standard GB/12960-2007 Quantitative measurement of mineral admixtures in cement, methods were developed for quantitative determination of fly ash, slag and limestone powder in fresh cement pastes, mortars and concretes. Limestone powder was determined using thermal analysis method. The residue content of fly ash on an 80um sieve, and silt contents of aggregate were also considered during the quantitative determination of mineral composition of quaternary cementitious system. With the developed methods, the deviations between the measured and the actual mineral contents of the constituent in the eemantitious material in fresh cement paste, mortar and concrete, were within 3%.     

高效减水剂分散、助磨与减水复合效应实验研究

研究了高效减水剂与胶凝材料共粉磨时间高效减水剂对物料分散性和物料物磨效率的影响,以及共粉磨法与同掺法对高效减水剂减水效果的影响,结果表明,高效减水剂的存在有助于改善粉磨物料分散性,并可提高粉磨效率。与同掺法相比,采用共粉磨法可提高高效减水剂的减水效果,且水泥净浆稠度经过变化小,从而表明,用共粉磨改性超细水泥配制高性能砼时,用水量相同情况下,其初始坍 落度较同掺法时大,而坍 落度损失较小。