Preparation and hydration study of rich C2S cements

Three laboratory clinkers were made with variable C₂S content (28–57%), using industrial raw materials. These clinkers were cooled by air and studied by X-Ray Diffraction (XRD). It is concluded that by fast cooling, the active crystal forms of - and ′-C₂S were stabilized in the rich C₂S clinker.

The hydration phenomena were also studied in cements prepared from these clinkers by DTA-TG and XRD, at 2, 7, 28 and 90 days. The combined water and the liberated Ca(OH)₂ were quantitatively determined by means of thermogravimetry and the hydration rate was studied.

It is concluded that the hydration rate differs at the early ages, but it progresses with the same rate after 28 days. No significant differences in the formed hydration products of these cements were observed by XRD.     

On the hydration of MgO in cement pastes hydrated up to eight years

The present work extends the knowledge on the behaviour of high magnesia cements, pure or with pozzolanic additives cured for 8 years in potable water at 18+2°C. For this purpose, clinker containing 10% MgO was prepared in an appropriate furnace. The raw materials used were all of industrial origin. Four cements were prepared by cogrinding clinker with gypsum and the following pozzolanic materials: Santorin Earth (S.E.), Fly Ash I (F.A.I.), Fly Ash II (F.A.II) and Fly Ash III (F.A.III), in a proportion of 30%.The Mg(OH)₂ produced during the hydration of the above cements was determined quantitatively by thermogravimetric method, while the hydration phenomena were studied by X.R.D. It is concluded that when clinker containing ca. 10% MgO is coground with a good pozzolan, the hydration of MgO reaches a limited value at the age of ca. 6 years. The percentage of hydrated MgO permits the safe use of these cements, as for the long term unsoundness due to MgO hydration.     

利用城市垃圾焚烧飞灰研制阿利尼特水泥熟料

以城市垃圾焚烧飞灰(以下简称焚烧飞灰)为主要原料,在实验室电炉里成功烧成了阿利尼特水泥熟料,分析了熟料烧成所需适宜的生料组成和最佳煅烧温度,并研究了石膏掺量对阿利尼特水泥强度影响,以及阿利尼特水泥的标准稠度用水量和凝结时间.结果表明:以焚烧飞灰为主要原料合成阿利尼特水泥熟料无需外掺MgO;较适宜的生料化学组成为CaO 55%～59%,SiO2 17%～20%,Al2O3 3%～5%-MgO 0.5%～3%,Cl 8%～10%最佳煅烧温度为1200℃;添加适量石膏有助于提高阿利尼特水泥早期抗压强度;阿利尼特水泥较硅酸盐水泥有较低的标准稠度用水量和较短的凝结时间.     

Synthesis and Hydration Characteristics of Alinite Cement

A chlorine-bearing alinite cement was synthesized using reagent-grade chemicals, and the phase evolution and hydration behavior of the alinite clinker were examined. The effects of the MgO content on alinite formation and hydration also were investigated. Alinite began to appear at 1000°C from β-C₂S, C₁₁A₇CaCl₂, and unreacted raw materials, and an almost single-phase alinite was obtained at 1300°C. The alinite phase also was produced without MgO addition. However, CaO, β-C₂S, and C₁₁A₇CaCl₂ phases were present. Alinite cements hydrated rapidly after a short incubation period, and the hydration products were C-S-H gels, Ca(OH)₂, and a Fridel's saltlike phase. The local environmental changes of silicon and aluminum during the formation and hydration of alinite were determined using magic-angle-spinning nuclear magnetic resonance spectroscopy. The Cl⁻-ion exsolution from the alinite paste during hydration was measured using ion chromatography.     

A study of the effect of some factors influencing Alinite clinker formation

Research interest in chloride salts has been revived due to the new technological trends in cements following the development of Alinite Technology. Thus, the present work, which is a part of an extensive program, deals with the searching of the effect of LSF, MgO, alkalies and chlorides on the formation of Alinite clinker. In this context, seven raw mixes were prepared by varying the factors mentioned. The clinkers formed were studied by means of both XRD and chemical analysis. Useful information is derived concerning the influence of these factors on Alinite clinker formation.     

高镁水泥制备及其膨胀性能

制备MgO质量分数分别为6%、9%、12%和15%的高镁水泥,通过扫描电镜（SEM）、扫描电镜/能谱联合仪（SEM/EDS）、X射线衍射（XRD）等检测方法和膨胀性试验分析MgO质量分数对熟料煅烧和净浆膨胀性能的影响.结果表明：随着MgO质量分数增加,熟料煅烧时液相量增加,熟料密实度提高.当熟料中MgO质量分数为12%时,养护温度由20℃增加到38℃,试件90d龄期膨胀率由0.120%增加到0.244%;38℃养护时,掺入35%粉煤灰的试件90d龄期膨胀率由0.244%降至0.070%.当MgO质量分数高于12%时,尽管存在粉煤灰的抑制作用,但高镁水泥依然能产生一定膨胀,可以有效地补偿混凝土的温降收缩.     

垃圾焚烧飞灰煅烧阿利尼特水泥熟料的形成过程及其水化性能研究

以城市垃圾焚烧飞灰(以下简称焚烧飞灰)为主要原料,在实验室电炉里成功研制了阿利尼特水泥熟料。本文主要研究水泥熟料煅烧形成过程及其水化性能,分析了阿利尼特水泥的适宜石膏掺量、水化放热特征、水化产物及其显微结构。研究结果表明:利用垃圾焚烧飞灰为主要原料可以成功烧制阿利尼特水泥熟料,煅烧过程中首先出现C2S、C12A7和C2S·CaCl2,随后与MgO和CaCl2反应生成阿利尼特;掺加5%二水石膏可以促进阿利尼特水泥水化,较普通硅酸盐水泥更快,阿利尼特水泥可以作为一种早强快硬型水泥使用;阿利尼特水泥主要水化产物除含有硅酸盐水泥中常见的CSH凝胶、棒状AFt和Ca(OH)2晶体外,还含有C3A·CaCl·210H2O晶体。     

Mechanical behaviour of various mortars made by combined fly ash and limestone in Moroccan Portland cement

Physico-chemical properties and mechanical behaviour of ternary cements made by Portland cement, fly ash and limestone are studied. The mixtures at various compositions of clinker, gypsum fly ash and limestone are intimately ground and compared to other compositions without fly ash. Blended fly ash cements are also studied. The results show that fly ash acts as grinding agent by reducing the required time to obtain the same percentage of particles retained on a 80-μm sieve as the standard cement. Fly ash cements lead to an important extension of setting time than limestone cements. The replacement of clinker by limestone gives better mechanical strengths than the mixtures containing fly ash at early days; after 28 days, the cements prepared by incorporation of fly ash gain an important strength. From mechanical point of view, an optima dosage was obtained at 77% clinker, 2% gypsum, 7.5% fly ash and 13% limestone composition.     

利用低品位重晶石烧制含钡硫铝酸盐水泥熟料及其性能研究

采用低品位的重晶石为原料,烧制新型含钡硫铝酸盐水泥熟料,并对该水泥熟料的烧成制度进行了研究。借助于ＸＲＤ（Ｘ射线衍射）、ＳＥＭ（扫描电镜）、ＩＲ（红外光谱）等测试手段研究了该水泥熟料的组成和性能的关系,讨论了其水化机理。     

污泥灰替代粘土制备水泥熟料的试验研究

在率值不变(IM ＝1.31,SM＝2.62,KH＝0.89)的前提下,用污泥灰替代(替代量0wt%、25wt%、50wt%、75wt%和100wt%)粘土煅烧水泥熟料.研究了水泥生料易烧性的变化;通过分析水泥熟料XRD图谱和NMR图谱;研究了水泥熟料矿相组成和含量变化;借助SEM,研究了污泥灰对水泥熟料微观结构的影响.研究表明,污泥灰的掺加不仅不会改变生料的率值,而且会降低水泥生料的易烧性,增大水泥熟料中C2S的含量,降低了C3S含量,说明污泥灰可以替代粘土用作水泥原料.     

Examination of the jarosite-alunite precipitate addition in the raw meal for the production of portland cement clinker

The aim of the present research work was to investigate the possibility of adding a jarosite-alunite chemical precipitate, a waste product of a new hydrometallurgical process developed to treat economically low grade nickel oxides ores, in the raw meal for the production of Portland cement clinker. For that reason, two samples of raw meals were prepared, one with ordinary raw materials, as a reference sample ((PC)_Ref) and another with 1% jarosite-alunite precipitate ((PC)_J/A). Both raw meals were sintered at 1450 °C. The results of chemical and mineralogical analyses as well as the microscopic examination showed that the use of the jarosite-alunite precipitate did not affect the mineralogical characteristics of the so produced Portland cement clinker. Furthermore, both clinkers were tested by determining the grindability, setting time, compressive strength and expansibility. The hydration products were examined by XRD analysis at 2, 7, 28 and 90 days. The results of the physico-mechanical tests showed that the addition of jarosite-alunite precipitate did not negatively affect the quality of the produced cement.     

Isomorphic substitution and the hydration behavior of alinite cement

Zn and/or Fe substituted alinite cement was synthesized using reagent grade chemicals, and its formation and hydration behavior were investigated. Mg, which is known to be essential for alinite formation, was completely replaced by Zn. XRD, FT-IR, and ²⁹Si MAS NMR results indicated that a Zn substituted alinite was a nearly single phase and was easy to grind compared to Mg-alinite. In addition, partially or fully Zn substituted alinite had superior hydration characteristics, and NMR results showed that most of the alinite was hydrated after 100 days. Fe substitution of Al was not effective for alinite formation and its hydration properties were similar to Mg-alinite. Cl⁻ ions leached out during alinite hydration, but the exsolution of Zn and Fe was below the detection limit.     

掺加拆除建筑垃圾水泥熟料的性能

利用拆除建筑垃圾来烧制水泥熟料,可以减少城市建筑垃圾的污染.用XRD、荧光分析术研究了建筑垃圾的主要成分,并将其按0％、5％、10％、15％和20％比例掺入到生料中,对生料的易烧性、熟料矿物组成和水泥胶砂抗压强度进行了测试,结果表明,利用建筑垃圾配料煅烧水泥熟料能改善生料易烧性,烧制的熟料矿物组成和性能均满足国家相关标准.     

New waste based clinkers: Belite and lime formulations

This work describes the formulation of new belite-based (CR2) and lime-based (CR3) cementitious materials derived from industrial wastes, such as sludges (generated in the Al-anodising and surface coating industrial processes, potable water filtration/cleaning operations and in marble sawing processes) and foundry sand.Powder mixtures were prepared and fired at different temperatures. For comparison, similar formulations were prepared with pre-treated and commercially available natural raw materials and processed in similar conditions. The thermal process was followed by differential scanning calorimetry (DSC) and high-temperature powder X-ray diffraction (HT-XRD) studies.The CR2 clinker was found to contain belite as the main cementitious phase, the main polymorph being identified by NMR. The CR3 clinker contained common cementitious phases, such as C₃A and C₃S, but free lime and calcium aluminium oxide sulphates were also identified by high temperature XRD and NMR.Then the corresponding cement was prepared and the evolution of the mechanical strength with time was evaluated. The lime-based cement obtained from wastes shows a stronger hardening character than the standard material, which tends to show dusting phenomena due to the presence of a reasonable amount of free lime (as the result of its expansive reaction with ambient moisture). Some fluxing impurities (e.g. alkalis) present in the waste materials improve the overall reactivity of the mixture and induces the combination of the lime in CR3. Raman, XPS and FIB techniques were used to fully characterise the aged cements.     

电解锰渣-镁渣制备复合矿渣硫铝酸盐水泥熟料的研究

利用化学分析法、X射线衍射分析(XRD)、扫描电子显微镜(SEM)、热重分析(TG-DSC)等检测手段对电解锰渣、镁渣的化学组分、矿物组成、物化性能进行分析.根据分析结果,合理设计以锰渣、镁渣为原料制备硫铝酸盐水泥熟料的配比方案,并考察烧结温度对熟料性质的影响.在制备的水泥熟料中掺入一定量的石膏可制备出早强、快硬的硫铝酸盐水泥.在此过程中测定水化放热过程,并分析石膏掺量与水泥抗折和抗压强度的关系,确定最佳的石膏掺量.实验结果表明,电解锰渣、镁渣可以作为有价值的原料制备硫铝酸盐水泥熟料,两种废渣的掺比可分别达到21%,烧结过程的最佳温度为1260 ℃,保温时间为30 min,此时烧结出的试样的矿物相主要为C2S、C4A3S-.当石膏掺量为15%时,放出的水化总热最多,制备出的水泥力学性能最好,28 d的抗折强度为5.1 MPa,抗压强度为31.2 MPa,抗渗等级达到P6,烧制熟料和水化产物将锰渣和镁渣中的重金属有效的固化稳定,不易被浸出.     

珠江水泥厂配料方案及其水泥特性的研究

分析了广东省内几家新型干法水泥厂的熟料成分及水泥性能,并着重研究了“粤秀”牌水泥配制混凝土时具有优良性能的原因。研究表明:即使同是新型干法窑生产的熟料,其矿物组成、物理性能及其与减水剂相容性仍存在着较大的差异;磨制成水泥后,由于受熟料矿物组成及水泥颗粒组成的影响,在配制混凝土时性能差异更大。故若要提高新型干法窑水泥在配制混凝土时的性能,应重视熟料的矿物组成,优化水泥的颗粒级配,改善水泥与减水剂的相容性,而不应单一重视熟料的物理性能。     

A study on the hydration products of a non-expansive sulfoaluminate cement

In the context of a project aiming at the preparation of an energy-saving cement within the CaO---SiO₂---AlO₃---SO₃ system having non-expansive properties, clinker was prepared by sintering a mix of industrial raw materials at 1280 °C in a laboratory oven.

The hydration products of the cement cured to 90 days were studied by Scanning Electron Microscopy, X-Ray Diffraction and Thermogravimetric Analysis, and found similar to these of a typical sulfoaluminate cement. The low rate of hydration of the belite phase was attributed to its microcrystalline form.     

Mineralogical Composition of Clinker as an Indicator of Sulfate Resistance: A Rietveld XRD/Takashima Approach

This study aims to optimize quantitative X‐ray diffraction (XRD) mineralogical analysis of the minority phases in clinker. The proposed method consists of applying Rietveld quantitative refinement to the XRD patterns for both clinker and the insoluble residue remaining after it is attacked with methanol and salicylic acid (Takashima method). The method was tested with industrial clinker and the same material after modifying its mineralogy by refiring at 1500°C followed by slow cooling. The findings showed that the C₄AF/C₃A ratios for quickly and gradually cooled clinker were much higher when the clinker diffractograms were refined with the Rietveld procedure than when the proposed method was used. The proportion of C₃A found with the proposed method was ≈2.8‐fold higher than when Rietveld only was applied to the diffractograms for clinkers. Taken together, the refinement data for the two materials (clinker and Takashima residua) revealed that Rietveld quantitative XRD applied to clinker underestimates the low C₃A content. These findings are supported by postsulfate attack durability studies conducted on cements prepared with the two clinkers.     

海工水泥原料组成的优化试验研究*

根据国家标准对海工水泥原材料组成的要求,本文以粉煤灰、矿粉、硅灰为混合材与硅酸盐水泥熟料、石膏复合,通过水泥砂浆物理性能试验、抗渗性能试验、抗硫酸盐侵蚀试验和混凝土氯离子扩散系数试验,优化、确定了海工水泥合理的原材料组成范围。试验结果表明,当熟料掺量≥33%,硅灰掺量≤3%时,所制备的海工水泥的力学性能满足国家标准42.5级海工水泥的要求;以33%的熟料、7%的石膏、17%的粉煤灰、40%的矿粉和3%的硅灰制备的海工水泥具有较好的早期、后期强度和良好的耐久性能。XRD和SEM分析结果表明,与普通硅酸盐水泥相比,海工水泥水化体系中AFt含量多,可提高水泥石的致密度,减小孔隙率,使水泥硬化体具有优异的力学性能和耐久性能。     

磷矿石、磷渣、磷尾矿在烧成高强度水泥熟料中的作用

利用磷渣、磷矿和磷尾渣并复合适宜的废渣或无机非金属矿配制了水泥熟料烧成助剂,利用这些助剂并适当调整配料方案在正常条件下烧成了高强熟料2对熟料进行了XRD,SEM和反光显微镜形貌分析及物理性能检验2结果表明:配制的烧成助剂利用磷废渣以及磷矿中某些元素的助熔作用和一些工业废渣的助熔作用,改善了水泥熟料易烧性2实验烧成的熟料中含有较多的C3S,同时使液相条件下形成的C3S亚微结构得到了改善,因而熟料具有较高强度2本研究配制的烧成助剂中挥发性组分很少,不会对环境污染和设备腐蚀带来明显影响,适宜于新型干法生产使用.