固硫灰渣水化浆体中钙矾石稳定性

流化床燃煤固硫灰渣(简称固硫灰渣)含有大量烧粘土质矿物,还含有较多f-CaO和无水石膏,因此固硫灰渣水化浆体中含有一定量的钙矾石.用X射线衍射和化学分析方法研究钙矾石含量随水化龄期的变化规律,并以此反映其稳定性.结果显示:在标准养护条件下,钙矾石含量从1 d至28 d水化龄期呈逐渐增长趋势,但在28 d龄期后则显著减少.研究表明固硫灰渣水化浆体中的钙矾石是不稳定的,在一定龄期后会出现明显分解现象.     

Fe_2O_3－Al_2O_3钙矾石型固溶体系列

钙矾石是水泥的一种重要水化产物。经过反复摸索，本研究找出了合成Ｆｅ２Ｏ３的克分子百分含量从０至１００的钙矾石型固溶体的条件。精确测定了含Ｆｅ２Ｏ３量不同的钙矾石的晶胞参数，并做了失重和差热分析。结果表明：①晶胞参数和热性能随钙矾石中的Ｆｅ２Ｏ３含量增加而连续变化；②随铁含量的增加，钙矾石晶胞变大；③钙矾石中溶入Ｆｅ２Ｏ３之后，热稳定性稍有下降，全铁端员差热曲线主吸热谷较全铝端员降低约６℃。     

熟料-无水石膏系统与粉煤灰-石灰-无水石膏系统的水化产物

本文用XRD和SEM对CA和FLA不同龄期的水化产物数量和形貌进行了分析.随龄期增加,CA中CaSO4数量慢慢减少,而FLA中CaSO4数量则快速减少.3 d龄期时CA中有一些钙矾石晶体,此后随龄期增加钙矾石数量无明显增加;3 d龄期时FLA中只有很少的钙矾石晶体,此后随龄期增加,钙矾石数量显著增加.3 d后CA中CaSO4·2H2O的数量都很少;随龄期增加,FLA中CaSO4·2H2O的数量先增加后减少.3 d后CA中Ca(OH)2数量随龄期增加基本保持不变,而FLA中Ca(OH)2数量随龄期增加逐渐减少.CA中水化硅酸钙凝胶为典型的成簇生长的呈放射状分布的纤维状形貌,而FLA中水化硅酸钙凝胶则为无定形物质.3 d时CA中钙矾石晶体为短柱状,而FLA中钙矾石为短针状;70 d后CA和FLA中都能见到长针状钙矾石.     

0～20℃养护下硅酸盐水泥水化时钙矾石的生成及转变

采用X射线衍射仪及核磁共振仪研究了0、5、10、20℃硅酸盐水泥水化产物钙矾石的生成及转变。结果表明：硅酸盐水泥水化1d至180d,4种养护温度下钙矾石生成量皆先增大后减小,但该规律随养护温度不同而不同：在10℃和20℃养护时,钙钒石生成量在水化3 d时达到最大,0℃和5℃养护时,水化28d时才达到最大;而从水化龄期来看,钙矾石生成量在水化1d时20℃养护时最高（10.2%）,水化3d时10℃养护时最高（12.1%）,3～180 d时0℃时最高;此外,低温养护显著延迟了钙矾石向单硫型水化硫铝酸钙转变。     

粉煤灰-石灰-二水石膏胶凝材料的体积稳定性及水化产物的性能

用雷氏夹法对粉煤灰-石灰-二水石膏胶凝材料(FLD)的体积稳定性进行了研究,用SEM和XRD对FLD的水化产物形貌和数量变化规律进行了研究。FLD中SO3含量为2.33%时体积稳定性良好,而SO3含量大于4.65%时体积稳定性差。在FLD中,随龄期增加,钙矾石数量不断增加,CaSO4.2H2O和Ca(OH)2数量不断减少。配比为粉煤灰:石灰:二水石膏=65:25:10的FLD到420d龄期时仍在进行着粉煤灰的水化反应,还有钙矾石生成。FLD中钙矾石为典型的针状晶体,水化硅酸钙凝胶为无定形物质。FLD体积稳定性差的原因是石膏含量过多,硬化后在很长龄期内针状钙矾石晶体不断产生。     

添加不同温度煅烧煤矸石水泥的早期水化及浆体的显微结构

用X射线衍射仪,热重-差热仪,扫锚电镜。压汞法测定孔隙率和Ca(OH)2生成量分析等。研究分别掺加500～1100℃7个温度点煅烧煤矸石水泥的早期水化过程及其浆体的显微结构。结果表明：在7种试样中,掺700℃煅烧煤矸石水泥的早期水化最快。力学强度高,凝胶孔多,总孔隙率低,其早期水化产物为C-S-H凝胶、Ca(OH)2和钙矾石,在1～28d的水化试样中均存在钙矾石。研究表明：煅烧煤矸石能促进水泥熟料的水化。该促进作用随煤矸石的煅烧温度而异,以700℃煅烧煤矸石的促进作用为最好。     

石膏对水泥熟料的缓凝促强作用

从理论上说，石膏对硅酸盐水泥熟料的缓凝促强作用是由于熟料与石膏一起磨细加水后，熟料中各矿物与石膏一起迅速溶解于水，并开始水化，形成石膏、石灰饱和溶液。而在熟料各矿物中，Ｃ３Ａ的水化速度最快，Ｃ３Ａ在石膏、石灰的饱和溶液中生成钙矾石，在熟料颗粒表面形成钙矾石保护膜，封闭熟料组分的表面，阻滞水分子以及离子的扩散，从而延缓了熟料颗粒特别是Ｃ３Ａ的继续水化，也就是延长了熟料的凝结时间。随着扩散作用的进展，生成钙矾石的量不断增加，在尚未硬化的浆体中生成钙矾石，有助于强度、尤其是早期强度的发挥，从而提高了熟…     

硫铝酸盐基促强减缩剂对水泥性能的影响

分别研究了随硫铝酸盐基促强减缩剂(SP-SRA)掺量变化,P·Ⅰ和P·O两种水泥的标准稠度用水量、凝结时间、28 d干空收缩以及胶砂强度的变化规律,分析了不同掺量的SP-SRA对P·Ⅰ水泥水化热、水化产物物相和微观形貌的影响。结果表明:随SP-SRA掺量的增加,两种水泥的初凝、终凝时间明显缩短,28 d干空收缩减少,各龄期抗折、抗压强度增大;早期水化放热速率随SP-SRA掺量的增加而增大,XRD和DSC分析表明SP-SRA使钙矾石含量明显增多,MIP分析结果显示随水化的进行,掺SP-SRA的水泥浆体小孔数量逐渐增多,说明钙矾石等水化产物填充了水泥石毛细孔,使得大孔数量减少,小孔数量增加,水泥石更加密实,强度增大,并且钙矾石的膨胀性抵消了部分收缩,使得掺SP-SRA的水泥干空收缩减小。     

钙矾石对Cr6+和Cr2+的固化及稳定性

通过溶液法人工合成钙矾石,分析比较了水化形成过程中钙矾石对Cr6+和Cr2+固化机制及其稳定性.结果表明,Cr6+和Cr2+均可对钙矾石晶格结构产生一定影响,但两者在钙矾石中固化机制并不完全相同.Cr6+挤入钙矾石晶格层间结构,改变了分子对称性,对钙矾石晶体结构有较大影响;而Cr2+对钙矾石晶体结影响较小.在水化液相中重金属离子含量较低时,钙矾石对Cr2+、Cr6+俘获能力较高,且少量Cr2+对钙矾石晶体生长发育促进作用;而重金属离子含量较高时,钙矾石对Cr6+俘获能力明显下降,但对Cr2+的固化能力仍较高.钙矾石对Cr2+固化受环境条件影响较小,同时少量Cr2+在一定程度上有利于稳定碳化条件下钙矾石晶形结构;而钙矾石对Cr6+的固化受外界环境因素影响较大,且碳化、冻融、氯盐侵蚀多因素复合对其固化稳定性有极大影响.     

低水灰比水泥石中钙矾石性状研究

研究了含超细水泥（掺量０～２０％）的水泥在低水灰比（Ｗ／Ｃ＝０．２１）水化１～７ｄ钙矾石相对形成量的变化情况，并观察了ｌｄ龄期水泥石结构。结果表明，低水灰比条件下含与不含超细水泥的硬化浆体中钙矾石相对形成量均比高水灰比（Ｗ／Ｃ＝０．３５）的低；在低水灰比系列中，含超细水泥体系的钙矾石形成量均高于不含超细水泥体系的钙矾石形成量；随着超细水泥掺入量增加，钙矾石相对形成量先增后降，这是水化速度与产物生长空间共同作用的结果。低水灰比水泥石体系中可以观察到的钙矾石晶体不多，且呈细小状，与其他水化产物紧密联系。     

卤水侵蚀对水泥粉煤灰浆体微结构影响

采用XRD、29Si和27Al MAS NMR测试技术,研究了粉煤灰掺量和侵蚀龄期对卤水侵蚀下水泥-粉煤灰浆体水化产物相组成、含铝相产物迁移与转变、C-S-H凝胶微结构变化的影响规律.研究结果表明:卤水侵蚀导致浆体Ca (OH)2含量降低,AFm和TAH向AFt转变,同时生成大量Friedel盐,C-S-H凝胶中Al[4]脱出;随粉煤灰掺量增加,浆体中AFt、AFm和TAH生成量降低,C-S-H的MCL和Al[4]/Si增大,Friedel盐生成量先增后减;侵蚀早期,水泥-粉煤灰浆体结构疏松,AFt生成量较纯水泥高,后期浆体致密性提高,抑制卤水侵蚀,AFt生成量较少,C-A-S-H脱铝作用减弱.     

钢渣对硬化水泥浆体结构形成的影响研究

研究了钢渣对水泥强度及体积膨胀率的影响,采用SEM和EDXA分析了水化产物的形貌和微区化学成分,并用XRD对水化产物的矿物组成进行了分析研究。研究结果表明,钢渣的掺入会降低水泥净浆的早期抗压强度,但随钢渣水化的进行,掺钢渣的水泥浆体7d以后的强度增长较快,至120d时净浆抗压强度已与纯硅酸盐水泥相近。掺钢渣的水泥的体积膨胀率比纯硅酸盐水泥的体积膨胀率大,钢渣水泥的体积膨胀率主要取决于钢渣中的fCaO含量。掺钢渣水泥的主要水化产物组成和形貌与纯硅酸盐水泥无明显差别,所不同的是C-S-H凝胶中有较多的铁相。掺钢渣水泥的水化产物主要有C2SH(C)、AFt和Ca(OH)2。     

新型磷渣硅酸盐水泥的水化特性

新型磷渣硅酸盐水泥作为一种新型结构材料,巳投入批量生产和应用。考虑到达种水泥系采用含有Na_2SO_4的矿物CNS代替石膏作水泥调凝剂,并且磷渣带入的少量P_2O_5将对水泥的水化过程产生一定影响,作者采用XRD,SEM及反应过程分析等手段对新型磷渣水泥的水化恃性进行了研究,发现其水化过程与普通矿渣水泥有些不同,主要表现在:(1)CNS加速了AFt的形成及水泥矿物的水化;(2)CNS促进了AFt的分散及磷渣的溶解反应;(3)磷渣玻璃体的结构特征决定了新型磷渣水泥中的AFt能够长期稳定存在。因此使其具有正常的初凝时间和较高的早期强度。     

三异丙醇胺对石灰石硅酸盐水泥的水化机理及微观结构的影响

通过水泥净浆和砂浆强度试验、测量水化热、硬化水泥浆体的热分析、微观结构的扫描电镜观察和孔结构的测量,研究了三异丙醇胺（triisopropanolamine,TIPA）对石灰石硅酸盐水泥强度、水化过程和硬化水泥浆体的微观结构的影响。结果表明：掺加TIPA能够显著提高石灰石硅酸盐水泥净浆和砂浆的后期强度;TIPA对C4A...     

大掺量矿渣石膏水泥基复合材料的水化特性

通过测试宏观抗压强度,同时采用XRD和TG-DTA技术对大掺量矿渣石膏水泥基复合材料的水化特性进行了研究,研究表明:大掺量矿渣石膏水泥基材料早期强度远低于纯水泥,但其强度发展较快,尤其是7～28 d阶段,28 d强度基本达到42.5 MPa水平,90 d龄期强度除SG-4试件均超过纯水泥水平.试件早期强度随着熟料含量的增加而增长,而后期强度并不遵循这一规律,水化后期主要是矿渣粉中活性Al2O3与活性SiO2参与水化反应,提高了体系抗压强度.SG系列水化产物主要为C-S-H凝胶和AFt,而纯水泥试样有大量Ca(OH)2而几乎无AFt存在.熟料含量对早期水化产物数量影响较大,而对水化产物种类及水化后期产物数量影响不大.     

Analytical Electron Microscopy of Cement Pastes: II, Pastes of Portland Cements and Clinkers

Three hundred sixty-five particles of C-S-H, Ca(OH)₂, AFm phase, and AFt phase from pastes of normally ground portland cements and of finely ground cements and clinkers were analyzed. All the phases, except the Ca(OH)₂, showed significant variation in composition among paste specimens and among particles within each specimen. The C-S-H contains significant amounts of Al, Fe, and S; for that of a normally ground portland cement paste, cured for 28 days, the median Si:AI, Si:Fe, and Si:S ratios were 11, 43, and 15, respectively, whereas the mean Ca:Si ratio for all the particles analyzed was 2.0. The AFm phase in cement pastes is not pure monosulfate but has a mixture of sulfate, hydroxide, and Al- and Si-bearing ions in its interlayer sites; the AFt phase is not pure ettringite but contains Si and its sulfate is probably partly replaced by hydroxide. The Al and Fe contents in the C-S-H and the Si contents in the AFm and AFt phases are greater when finely ground starting materials are used. This fact, together with the marked variation among particles, emphasizes the difficulty of ionic transport in cement pastes.     

Hydration products of alkali-activated slag-red mud cementitious material

A new kind of alkali-slag-red mud cementitious material, abbreviated as ASRC, with both high early and ultimate strength and excellent resistance against chemical attacks has been developed by the application of composite solid alkali activator into slag-red mud mixture system. The hydration products of this cement at ambient temperature have been investigated by means of XRD, IR, TG-DTA, TEM, EDXA, etc. The results showed that the hardened cement paste was mostly consisted of C-S-H gel, being very low in Ca/Si ratio, very fine in size and extremely irregular in its shape. Neither Ca(OH)₂ and AFt, which are usually present in the hardened Portland cement paste, nor zeolite-like products have been detected. These characteristics are considered to be the chemical reasons for the high early and ultimate strength and good resistance against chemical attacks of the hardened ASRC cement paste.     

Early performances of cement paste in the presence of triethanolamine: Rheology,setting and microstructural development

The effect of triethanolamine (TEA) at various dosages on the early performance of cement paste was systematically evaluated through the techniques of rheological measurements, penetration tests, and ultrasonic pulse velocity. The correlation of early performance to the chemical hydration process was analyzed by calorimetry, zeta potential, in situ XRD, and pore solution analysis. It is found that the effect of TEA on the early performance of cement paste is strongly dependent on its dosage. With the TEA dosage below 0.1 wt%, the setting and microstructural development of cement paste are retarded. Meanwhile, the yield stress of fresh paste is decreased due to the increasing zeta potential of cement grains. The promoted formation of ettringite (AFt) and monosulfate (AFm) caused by TEA decreases the rheological retention ability. At dosages ≥0.2 wt%, the reaction of aluminate-containing phases is greatly accelerated and a flash setting is observed. Besides, the importance of ferric phase on the reaction of cement with TEA is highlighted. At a low dosage, TEA prefers to accelerate the dissolution of tetracalcium aluminoferrite (C₄AF) first and increases the [Fe] in the pore solution of cement paste. In cement without C₄AF, the retardation of TEA on silicate phase hydration is significantly alleviated.     

石膏对贝利特-硫铝酸钡钙水泥强度和硬化浆体结构的影响

研究了石膏对贝利特-硫铝酸钡钙水泥强度和硬化浆体结构的影响.结果表明:贝利特-硫铝酸钡钙水泥熟料的矿物组成主要有C3S、C2S、C,A、C4AF和C2.7B1.25A3S;当水泥中石膏掺量为10%时,贝利特-硫铝酸钡钙水泥的3d、7 d、28 d和90 d抗压强度分别达到了45.0、61.9、82.1和85.6 MPa;贝利特.硫铝酸钡钙水泥的水化产物主要有AFt、Ca(OH)2、C-S-H凝胶等,随石膏掺量的增加,AFt的数量逐渐增加,水化后期的Ca(OH)2数量逐渐减少.用XRD和SEM来分析硬化水泥浆体组成和结构.     

The role of calcium carbonate in cement hydration

Limestone, mainly consisting of calcite, is a permitted additive to Portland cements often up to a 5 wt.% limit. It is shown by experiment and calculation that much, if not all, of this calcite is reactive and affects the distribution of lime, alumina and sulfate and thereby alters the mineralogy of hydrated cement pastes. Calcite affects the mineralogical variant of the AFm phase(s). Calcite additions affect the amount of free calcium hydroxide as well as the balance between AFm and AFt phases, although C-S-H is unaffected in much of the range of compositions. Generic data are shown in graphical form to quantify these mineralogical changes as functions of cement composition and amount of added calcite. Calculations of the specific volume of solids as a function of calcite addition suggest that the space-filling ability of the paste is optimised when the calcite content is adjusted to maximise the AFt content. However, before the calculated data can be used uncritically, certain kinetic constraints on reactivity also need to be assessed. Progress towards the quantification of paste mineralogy suggests that (i) elucidation of the mineralogy of pastes, particularly blended cement pastes, is facilitated by using both theoretical and experimental approaches and (ii) that the ultimate goal, of calculating paste mineralogy from the bulk chemistry, is attainable.