固硫渣混合水泥的研究及钙矾石相的定理分析

通过试验系统地研究了固硫渣混合水泥的配制方法及其性能的测试结果，论述了硬化水泥浆体中钙矾石相的定量分析方法，通过对不同龄期固硫渣水泥硬化浆体中钙石相的定量分析，总结了钙矾石相成量随龄期变化的趋势，为推广使用固硫渣混合水泥和制订出相应的规范提供了理论依据。     

膨胀型水泥硬化浆体变形的分形与粘弹性分析——含钙矾石和水镁石膨？…

应用分形学与粘弹性力学对含钙矾石和水镁石膨胀源的水泥硬化浆体的膨胀机理进行了研究与分析。得到在这种膨胀型水泥硬化浆体中的钙矾石和水镁石膨胀随ＳＯ３与ＭｇＯ质量分数和时间的变化规律;揭示了膨胀型水泥硬化浆体的分形行为,其膨胀曲线的分形元服从指数规律;解释了在钙矾石膨胀的基础上水镁石膨胀的非线性叠加现象;解释了来自钙矾石和水镁石的结晶膨胀能不可能全部用作膨胀功,而是部分消耗在变形过程中,部分贮存在硬化     

利用固硫灰制备混凝土膨胀剂试验

探讨了利用固硫灰、锂渣、硬石膏为原料制备混凝土膨胀剂。通过正交试验研究了原料掺量和细度对其膨胀性能的影响。结果表明：固硫灰、锂渣和硬石膏按照质量比25：15：60能制备出满足GB23439—2009的I型膨胀剂;各原料掺量和细度对混凝土膨胀剂的7d和28d膨胀性能的影响不尽相同。运用SEM电镜扫描、x—ray衍射分析研究了混凝土膨胀剂掺入水泥的水化反应,表明随着水化龄期延长钙矾石含量增多。制备的膨胀剂是以钙矾石为主要膨胀源的混凝土膨胀剂。     

应用量子化学方法研究钙矾石的强度特性

钙矾石相是许多水泥品种的主要水化相之一，对水泥石的强度起着重要作用。本文用量子化学ＳＣＣ－ＤＶ－Ｘａ方法对钙矾石和含锶钙矾石相进行了研究。研究结果表明：两者结构中Ａｌ的键级和Ａｌ—Ｏ键共价键级大致相同。含锶钙矾石中Ｓｒ的键级和Ｓｒ—Ｏ共价键级大于钙矾石中的Ｃａ和Ｃａ—Ｏ键．由此可以认为这是含锶硫铝酸钙水化强度高于硫铝酸酸钙的主要原因之一。     

固硫灰的膨胀及其控制

研究了纯固硫灰的膨胀,固硫灰掺量、固硫灰细度、不同养护条件对固硫灰水泥净浆膨胀的影响,并对各龄期的水化产物进行XRD、SEM分析,得出了固硫灰的膨胀机理,在此基础上探讨了各种控制固硫灰膨胀的方法。结果表明:固硫灰硫、钙含量高,加水后7 d内钙矾石大量生成引起膨胀。而相对湿度对固硫灰的膨胀有很大影响,通过磨细可以提高固硫灰的活性和在早期释放固硫灰的膨胀,并且通过添加骨料和在早期使体系强度快速增加能有效的控制体系的膨胀。     

钙矾石吸水膨胀的试验研究

用无C_3A水泥(或纯阿利特)与钙矾石按不同比例混合压成密实体的吸水试验表明,钙矾石能吸水而产生膨胀。其膨胀量随钙矾石加入量和密实压力的增大而增大。当钙矾石(27.5个结晶水)的含量为50％时,取决于钙矾石的制备方法的不同,密安体的胀胀量约在2～3％。用C_3A加石膏通过浆体水化制备的含有27.5、29.0、32.1个结晶水的钙矾石的密实体(钙矾石含量50％)的膨胀量分别为3.1％、2.97％和2.5％。     

蒸压养护对固硫灰渣膨胀性能的影响研究

循环流化床燃煤固硫灰渣含有较高的SO3和f-CaO,常温下水化时易产生较大的体积膨胀。研究了蒸压养护和自然养护下,2种固硫灰和1种固硫渣的线性膨胀率和强度发展,并用X射线衍射和SEM分析了其水化产物,结果表明：蒸压养护对固硫灰渣的膨胀有显著的抑制作用;蒸压养护后固硫灰渣中无二水石膏、钙矾石生成,在钙组分充足时生成了托贝莫来石;蒸压养护后固硫灰渣的水化产物更加丰富、结晶更完善,从而强度更高。     

固硫灰对水泥性能的影响

利用XRD、SEM、差热分析和水化热分析等方法研究不同细度和不同掺量固硫灰对水泥物理性能和水泥水化的影响。结果表明,当固硫灰掺量为10%～30%时,水泥安定性、凝结时间均符合国家标准;水泥强度随固硫灰细度的增加而增加,随固硫灰掺量的增加先增加后降低,其最佳掺量为20%;适量的固硫灰,能促进早期C2S、C3S水化,固硫灰细度越细,水泥早期水化速率越快,并影响其早期水化产物的形成;固硫灰掺入后,水泥的水化产物主要为钙矾石、C-S-H、氢氧化钙,并改善了水化产物的热稳定性,同时固硫灰掺量的变化会导致水泥中硫含量的变化,使得C3A水化的最终产物有所不同。     

水泥不同掺量对石膏胶凝材料性能影响的研究

石膏硬化体的缺点是强度低、耐水性差。掺入普通硅酸盐水泥后形成的低溶解度、高结合力水硬性物质——钙矾石和水化硅酸钙可以穿插生成于石膏的多孔结构中,发挥其针状结构及与其他物质交叉、共生而产生增强作用的优势,从而改善硬化体性能。     

超细CaCO3增强硫铝酸盐水泥强度的研究

在硫铝酸盐水泥硬化体中,钙矾石主要以柱状、棒状而存在,这对水泥的性能产生了不利影响。探讨了超细CaCO3对硫铝酸盐水泥进行改性的研究。试验结果表明,超细CaCO3掺量为3%时,明显改善了硫铝酸盐水泥的强度,其28 d净浆与砂浆抗压强度分别达到100.6 MPa和94.1 MPa,且水泥的28 d砂浆抗折强度高达12.5 MPa。SEM显示掺超细CaCO3硫铝酸盐水泥硬化体中难以发现大颗粒状的水化硫铝酸钙晶体,结构较致密、均匀。     

粉煤灰-脱硫石膏水泥基材料水化活性及微结构

采用DTA—TG、XRD、SEM以及宏观水化收缩和强度试验等手段研究了粉煤灰一脱硫石膏一水泥三元复合胶凝体系的水化过程、活性效应及微观结构等,根据试验结果总结了复合胶凝材料的水化动力学过程。结果表明,粉煤灰一脱硫石膏水泥石的钙矾石吸热峰强于基准样;在各组分相互活性激发和外掺激发剂作用下,粉煤灰一脱硫石膏水泥石中2次水化效应明显;SEM、XRD表明水泥石早期有明显的钙矾石生成,同时粉煤灰颗粒的表面侵蚀现象明显,进一步说明复合胶凝体系的早期活性得到有效激发,硬化后综合性能得到有效保证。且宏观收缩及强度试验也从侧面印证了微观试验结果。粉煤灰一脱硫石膏水泥基复合胶凝材料体系的研发可大量消耗燃煤电厂的工业废渣,具有显著的“绿色”效应。     

粉煤灰-水泥熟料-水系统反应动力学的研究

本文用x-射线衍射法测定了不同品质粉煤灰与水泥熟料在不同养护龄期时的反应程度。结果发现,以该法测得的值与粉煤灰水泥石的强度劣化值有很好的关系。     

UFA水泥基材料早期自干燥及自收缩研究

基于水泥石孔隙理论对超细粉煤灰（Ultra-fine fly ash，简称UFA）水泥基材料的早期自干燥效应进行了理论分析及试验研究。在此基础上，采用改进的混凝土自收缩试验装置对UFA混凝土的早期自收缩变形进行了测试。结果表明，相比于基准水泥石，UFA水泥石内部自干燥程度大大降低；且随着UFA的掺入，混凝土早期水化反应的有效水灰比增大，自收缩变形随之减小，进一步证明水泥基材料早期内部孔隙的自干燥效应与混凝土的早期自收缩变形具有较好的相关性。     

UNIFORMITY ASSESSMENT OF CARBON FIBRES DISPERSION IN CEMENT PASTE BY IMPEDANCE MEASUREMENTS

An alternating current was applied to measure the impedance of a hardened cement paste with various contents of carbon fibres. When the free water content in the hardened cement paste is 90%-98%, and the measuring frequency 500Hz, an approximate linear relationship was found between fibre content and impedance of the composite. Based on this relationship , a new attempt was made to evaluate the dispersion uniformity of carbon fibres in cement paste by impedance measurement. The standard deviation S and the coefficient of vriation S/Xi     

Effect of MSWI Fly Ash and Incineration Residues on Cement Performances

The activities of municipal solid waste incineration (MSWI) fly ash and incineration residues were studied contrastively, through the component analysis and the activity ratio tests. The mechanical properties, hydration mechanism and leaching toxicity of the hardened cement paste mixing with MSWI fly ash and incineration residues were investigated. The experimental results indicated that the active constituents (CaO+Al2O3+Fe2O3) in MSWI fly ash were higher than those in incineration residues. Therefore the ...     

The Hydration Characteristics and Expansion Machanism of Expansive Cement at Low W/B Ratio

1　IntroductionAnexpansiveagentcannotonlymakethestructurehasself waterproofperformance ,butalsoreducetheshrinkageandthecrackingofconcreteeffectively .Soitisextensivelyusedincommonconcrete .However,theappli cationofexpansiveagentinhigh strengthconcreteisnotattractedmuchattention .Itisnotonlybecauseofthebondageoftraditionalviewpointthatitsshrinkagevalueofhigh strengthconcreteismuchgreaterthanthatofcom monconcrete ,butalsothedeficiencyofadequatestudyonthehydrationcharacteristicsandexpansivemechan…     

流化床燃煤固硫渣火山灰活性评定的探讨

流化床燃煤固硫渣是一种特殊的、具有火山灰活性的燃煤副产品,由于其f-CaO和SO3含量较普通煤粉锅炉灰渣高,具有一定的自硬性和膨胀性,目前尚无统一的方法或标准准确评定其火山灰活性,影响了该燃煤副产品的建材资源化利用。根据流化床燃煤固硫渣火山灰活性来源及其特点,参照《用于水泥中的火山灰质混合材料》GB2847和《用于水泥混合材料的工业废渣活性试验方法》GB12957-91,提出采用“水泥熟料胶砂28天抗压强度比”来评定流化床燃煤固流渣的火山灰活性。试验研究表明该方法测定的火山灰活性与其自硬性强度和活性率具有较好的一致性。     

The hydration characteristics and expansion machanism of expansive cement at low<Emphasis Type="Italic">W/B</Emphasis> ratio

The hydration characteristics and expansion impetus of three kinds of cement paste under free-and confined-curing conditions were investigated, which were respectively mixed with three different kinds of expansive agent at low W/B ratio. The results show that the hydration products of pure cement paste and paste mixed with expansive agent are same, but the amount of hydration products, un-hydrated C₃S and C₂S are obviously different at the same hydration age. At 3 d age, the amount of CH in pure cement paste is less than that of paste mixed with expansive agent, but it is reverse when at 28 d age. The amount of AFt at 3d and 28d age in pure cement paste is less than those of paste mixed with expansive agent. Regardless of under free- or confined-curing condition, the amount of ettringite produced varies little since 3d age. The joint effect of the tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore caused by the crystalloid ettringite is the cause of the volume expansion of cement paste, and the former effect is much greater than the latter. LU Lin-nu : Born in 1972 Funded by 973 High-tech Project of China (No. 2001CB610704-2) and the Natural Science Foundation of Hubei Province(No. 2002AB075)     

Hydration mechanism of sulphoaluminate cement

The feasibility of sulphoaluminate cement (SAC) utilization in support mortar was studied. Setting time and strength of as-received sulphoaluminate cement (SAC) paste were examined, hydration kinetics behavior was determined through Isothermal Calorimeter, and hydration mechanism was investigated by X-Ray diffraction analysis (XRD) and field emission scanning electron microscopy analysis(FSEM). Results showed that as-received SAC contained 61% of anhydrous calcium sulfate (3CA·CaSO4) and dicalcium silicate (C2S). The strength after 1 day or 3 days grew to 68.6% or 85.7% of that after 28 days respectively, while most of hydration heat was released within 1 day. The emergency of three exothermic peaks at acceleration stage was found and hydration kinetics model was established choosing the terminal time of the first exothermic peak at accelerating stage as the beginning of accelerating stage. XRD analysis suggested that large amount of ettringite (AFt) was produced at early age and FSEM observation revealed that ettringite (AFt) formed in sulphoaluminate cement (SAC) paste was characterized of different morphology which was proved to be caused by different ion concentrations.     

Properties and Acceleration Mechanism of Cement Mortar Added with Low Alkaline Liquid State Setting Accelerator

Low alkaline liquid state setting accelerator(LSA) for Portland cement was prepared in laboratory from aqueous solution of several inorganic sulfate salts and some organic chemical substances. Properties of cement with addition of LSA relating to its setting time and strength development as well as its resistance to sulfate attack for short and long term exposure were experimentally examined. The experimental results showed that 5%-7% addition of LSA significantly accelerated the initial and final setting of Portland cement in the presence or absence of the blending of mineral admixtures, the initial and final setting time being less than 3 min and 6 min respectively. Meanwhile, the early 1 day curing age compressive strength increased remarkably by 20%, while the late 28 th day curing age compressive strength remained almost unchanged as compared with that of the reference accelerator free cement mortar specimen. Furthermore, mortar specimens of cement added with LSA and exposed to 5% Na2SO4 solution showed their excellent resistance to sulfate attack, with their short and long term curing age resistance coefficient to sulfate attack being around 1.04 to 1.17, all larger than 1.0. XRD analysis on hardened cement paste specimens at very early curing ages of several minutes disclosed the existence of more ettringite in specimens added with LSA than that of the reference specimens, meanwhile SEM observation also revealed the existence of well crystallized ettringite at very early hydration stage, suggesting that the accelerated setting of Portland cement can be attributed to the early and rapid formation of ettringite over the whole cement paste matrix due to the introduction of LSA. MIP measurement revealed that hardened cement paste specimens with the addition of LSA presented less medium diameter pores, more proportion of small pores and less proportion of large capillary pores, which is in a very good coincidence with the improvement of strength development of cement mortars added with LSA.