利用工业废渣烧制贝利特硫铝酸盐水泥

贝利特硫铝酸盐水泥是一种主要含β-C2S(贝利特)和(硫铝酸钙)矿物的水泥，具有凝结硬化快、早期强度高的特点．由于其熟料矿物组成中不含C2S(阿里特），因此熟料烧成温度低，消耗的石灰质原料少．可减轻对环境的负荷．又是一种节能环保型水泥。如采用工业废渣为主要原料开发研制贝利特硫铝酸盐水泥，将进一步有利于水泥工业的可持续发展。     

利用低品位铝矾土和铸造废砂制备高贝利特硫铝酸盐水泥的研究

采用正交试验研究利用低品位铝矾土、铸造废砂、石灰石、石膏等原料制备高贝利特硫铝酸盐水泥的煅烧条件.对生料热稳定性、水泥熟料组成及其水化产物形貌等进行测试表征.可初步确定熟料的煅烧温度范围在1250～1360℃,该水泥熟料的主要矿物组成为贝利特和无水硫铝酸钙,用X-射线K值法定量分析熟料物相组成与理论计算值基本接近.该水泥的主要水化产物有钙矾石、水化硅酸钙凝胶、单硫型水化硫铝酸钙等.实验研究表明:煅烧温度1300℃,保温时间90 min,急冷,制得的高贝利特硫铝酸盐水泥凝结时间短,初凝时间30 min,终凝仅40 min,28 d水泥净浆强度可达65.4 MPa,胶砂强度与市售42.5硫铝酸盐水泥相比,早期强度比较接近,后期强度高出10％.     

低钙水泥熟料矿物水化活性、性能及其制备熟料的发展

与硅酸三钙相比,硫铝酸钙、硅酸二钙和硫硅酸钙等具有钙含量低、烧成温度低和CO₂排放量少的特点,属于低钙水泥熟料矿物。发展以低钙矿物为主要组成的水泥熟料是水泥低碳发展的重要方向。本文在分析硫铝酸钙、硅酸二钙和硫硅酸钙3种低钙矿物的活性、水化和性能发展的基础上,分别对以低钙矿物为主要矿物的硫铝酸盐水泥熟料、高贝利特硫铝酸盐水泥熟料的水化和性能发展,硅酸二钙–硫铝酸钙–硫硅酸钙水泥熟料的制备、水化和性能优化进行了综合评述。同时,鉴于石膏在低钙水泥熟料水化方面具有重要影响,综述了石膏在几种低钙水泥中的作用。文章以期为运用硫铝酸钙、硅酸二钙和硫硅酸钙等矿物制备低钙水泥熟料提供参考。     

高贝利特-硫铝酸盐水泥熟料的煅烧试验

高贝利特水泥配制的混凝土具有良好的工作性能和耐久性,但早期强度较低,为此,尝试在其中引入早强矿物硫铝酸钙。同时在煅烧水泥熟料时能明显降低生产成本。我公司在成功利用煤矸石、工业石膏(青海铝电公司脱硫渣)和石灰石煅烧阿利特-硫铝酸盐水泥熟料的基础上,为进一步降低水泥     

硫硅酸钙-硫铝酸盐水泥研究进展

硫铝酸盐水泥具有煅烧温度低、CO₂排放少、快硬早强以及抗冻抗渗等优良特性,在建材、固废领域具有广阔的应用前景,并衍生出贝利特-硫铝酸钙、贝利特-硫铝酸钡钙等一系列硫铝酸盐水泥。然而,硫铝酸盐水泥主要矿物成分贝利特(β-C₂S)具有水化活性低、水化速度慢的缺点,易导致水泥后期强度增长缓慢。硫硅酸钙(C₅S₂$\bar{\text{S}}$)曾被认为是一种“惰性”矿物,但在硫铝酸盐体系下可表现出比β-C₂S更强的水化活性,因此硫硅酸钙-硫铝酸盐水泥(TSAC)的研究具有重要意义。本文从C₅S₂$\bar{\text{S}}$矿物的形成和水化、TSAC的制备和性能等方面,综述了C₅S₂$\bar{\text{S}}$和TSAC的研究现状,并提出了TSAC需进一步研究和解决的问题,如固废原料探寻、TSAC性能调控以及TSAC熟料矿物组成优化等,以期为新型低碳水泥的研究和应用提供积极有利的参考和支持。     

颗粒细度及形貌对高贝利特-硫铝酸盐水泥性能的影响

利用循环流化床固硫灰替代部分原材料,制备以硫铝酸钙、硅酸二钙为主要矿物的高贝利特-硫铝酸盐水泥熟料,然后通过激光粒度分析仪和扫描电镜研究熟料的颗粒细度及形貌对其性能的影响。结果显示:利用振动磨粉磨的高贝利特-硫铝酸盐水泥颗粒组成中<3μm细粉颗粒含量增多,凝结时间变短,需水量增加,相应地早期胶砂干缩率随之减小;其早期线性膨胀率与3～10μm范围内的颗粒含量呈正相关关系,后期的线性膨胀率随着30～60μm内的颗粒含量增加而增大;3d强度随着10～30μm范围内的颗粒含量增加而增大,而10～30μm范围内的颗粒含量对28d强度的发展起主要作用;利用球磨机粉磨的以多角形颗粒为主的高贝利特-硫铝酸盐水泥表现出标准稠度用水量高、凝结时间短、线性膨胀率和胶砂干缩率大的特点。     

硫硅酸钙-硫铝酸钙水泥熟料矿物组成的优化研究

硫硅酸钙-硫铝酸钙水泥是一种新型低碳水泥,硫硅酸钙矿物的水化活性对水泥性能具有积极作用。本文利用离子掺杂制备了硫硅酸钙-硫铝酸钙水泥,研究了硫硅酸钙、硫铝酸钙矿物以及后掺石膏的配比优化。结果表明,硫硅酸钙-硫铝酸钙水泥熟料的实际矿物组成与设计含量较为一致。硫铝酸钙含量的增加有利于提高水泥的早期强度,其适宜含量范围为30%~40%(质量分数);水泥的强度随着硫硅酸钙含量的增加而提高,当其设计含量增加至48%(质量分数)时,水泥强度降低,该矿物的适宜含量范围为40%~55%(质量分数),其优化含量根据硫铝酸钙的含量而有所不同。石膏的添加有利于硫硅酸钙-硫铝酸钙水泥强度的增长,与天然石膏相比,硬石膏更能促进水泥强度的发展;水泥的后掺石膏优选硬石膏,其优化掺量为8%(质量分数),28 d强度达到76 MPa。硬石膏掺量的增加促进了钙矾石的形成,但过高掺量的硬石膏会抑制硫硅酸钙的水化。     

高贝利特硫铝酸盐熟料矿物组成优化

采用石灰石、矾土、黏土和石膏4种原料,制备了以贝利特、无水硫铝酸钙和铁相为主的高贝利特无水硫铝酸盐水泥(BCSA)熟料矿物体系,研究了其生料易烧性、熟料煅烧制度和熟料矿物优化配比等。结果表明:当BCSA熟料煅烧温度为1280～1320℃时,可获得结晶度良好、形成数量较多的贝利特和无水硫铝酸钙矿物。在BCSA熟料矿物组成为32%～42%C4A3—S、5%～9%C4AF、46%～56%C2S,石膏掺量为12.5%时,水泥28 d抗压强度达最佳,为55MPa。此外,由于熟料烧成温度及氧化钙总含量(约50%)均较低,BCSA水泥在能耗和排放方面均比普通硅酸盐水泥低。     

游离石膏对高贝利特硫铝酸盐水泥熟料烧成的影响

设计了五种不同f-CaSO4/C4 A3 S的生料配比,研究了f-CaSO4含量变化对高贝利特硫铝酸盐水泥熟料烧成的影响.通过TG-DSC分析了高贝利特硫铝酸盐水泥熟料的形成过程,利用XRD、f-CaO含量分析得到了熟料的适宜煅烧制度,进一步用SEM观察了不同含量f-CaSO4对熟料矿物微观形貌影响,最后研究了f-CaSO4对高贝利特硫铝酸盐水泥熟料力学性能的影响.结果表明:高贝利特硫铝酸盐水泥熟料的适宜煅烧温度范围为1300～1400℃,保温时间为40 min;熟料中C2 S、C4 AF含量与设计值相一致,随着f-CaSO4/C4 A3 S增加,非晶固溶体有逐渐增多的趋势;随着f-CaSO4/C4 A3 S增加,熟料早期强度先增大后降低,后期强度逐渐增大,当f-CaSO4/C4 A3 S为0.4时有最高早期强度.     

利用铝尾矿制备高铁相贝利特硫铝酸盐水泥的研究

本研究采用低品位的工业原材料铝尾矿进行配料,制备高铁相矿物含量(铁相矿物>15%)的高铁相贝利特硫铝酸盐水泥(BBSC),借助DTA-TG、岩相、QXRD等检测手段研究高铁相矿物对高贝利特硫铝酸盐水泥生料易烧性、熟料矿物形貌、矿物组成及物理性能等方面进行研究。研究表明：铁相含量对高贝利特硫铝酸盐水泥的烧成影响较为复杂,高铁相可以促进■的形成,改变C₂S矿物的晶型及形貌,其自身存在的形态及形貌也发生了明显的变化;在铁相含量小于25%时,随着铁含量的增加,后期强度(21 d、28 d)增进率较大,会降低抗折强度的倒缩。     

Examination of ye’elimite formation mechanisms

Ye’elimite is the main constituent of calcium sulfoaluminate (CSA) cement and one of the major constituents of belite sulfoaluminate or belite sulfoaluminate ferrite cements. The main objective of this work is to describe precisely the formation mechanisms of ye’elimite by solid-state reaction. Mineralogical composition development was monitored using XRD analysis, while microstructural monitoring was conducted using BSE-SEM coupled to EDS analysis. The results show that CaAl₂O₄ and CaAl₂O₇ are the main intermediate products during ye’elimite formation. At the microstructural scale, ye’elimite forms on calcium aluminate phases. Finally, Avrami’s model was suggested to discuss the ye’elimite formation rate according to sintering temperature and duration.     

硫铝酸盐与硅酸盐矿物合成高性能水泥

主要阐述以硅酸盐矿物阿利特(C3S)或贝利特(C2S)与硫铝酸盐矿物硫铝酸钙(C4A3S↑-)或硫铝酸钡钙[C(B)1A3S↑-]为主导矿物的复合型水泥的组成设计、低温合成技术及其性能与应用,同时还阐述了具有突出快硬旱强特点的硫铝酸钡钙矿物的性能以及由该矿物复合成的新型水泥的研究进展,对以阿利特-硫铝酸钡钙为主导矿物的新型高胶凝性水泥的发展前景进行了展望。     

Crystallographic Analysis of Sr-Bearing Ye’elimite

Ye’elimite (C₄A₃$) is the main phase in calcium sulfoaluminate (CSA) cement. To improve the performance of CSA cement, substitutions of Ca²⁺ by Sr²⁺ cations in C₄A₃$ can be done to synthesize Sr-bearing ye’elimite. In this study we performed crystallographic analysis of Sr-bearing ye’elimite (C_4?x?_xA₃$) synthesized with 0.25–3.00 mol Sr²⁺ ions. The effect of strontic substitutions on the crystal structure of ye’elimite was investigated. Compositions of clinkers and the lattice parameters of Sr-bearing ye’elimite were determined by the Rietveld method. Results showed that strontic substitutions promoted the transformation of the crystal system from orthorhombic to cubic for ye’elimite. Sr-bearing ye’elimite almost purely exists in a cubic structure when amounts of strontic substitutions exceed 1.25 mol. The amount of Sr-bearing ye’elimite in crystalline phases is over 95 wt% while impurities in the clinkers of Sr-bearing ye’elimite contain minor amounts of calcium aluminate phases. Lattice parameters of Sr-bearing ye’elimite exhibit linear growth with strontic substitutions increasing for both cubic and orthorhombic systems. Both calcium and strontium evenly distribute in the particles of Sr-bearing ye’elimite.     

高贝利特硫铝酸盐水泥改性白水泥的物理力学性能与水化作用

白色硅酸盐水泥(白水泥)具有较好的白度,是一种具有装饰效果的胶凝材料。针对该种水泥凝结时间长、早期强度发展慢及收缩变形较大等问题,采用高贝利特硫铝酸盐水泥对白水泥进行改性,系统研究了掺入10%~30%(质量分数)的高贝利特硫铝酸盐水泥对白水泥凝结时间、胶砂强度和自由膨胀率的影响。使用水化微量热仪、XRD、TGA、SEM等方法对复合胶凝体系水化过程、水化产物和微观形貌进行分析。结果表明:高贝利特硫铝酸盐水泥增大了白水泥水化放热率,显著缩短了白水泥的凝结时间;改性后的白水泥水化产物生成了大量的AFt,穿插生长在C-S-H凝胶中,消耗掉了部分Ca(OH)₂,使结构更加致密,强度更高,膨胀性能更好。     

Solid-state synthesis of pure ye’elimite

Ye’elimite is formed during the production of sulfoaluminate cement. In this article, the orthorhombic ye’elimite formation, the optimal synthesis conditions and the microstructural evolution during synthesis, by solid-state reaction from pure oxide raw materials, is investigated. The phase assemblage was substantially affected by temperature and duration of sintering. Making reference to Rietveld quantitative analysis results, optimal solid-state synthesis conditions of ye’elimite was 1300?°C for 3?h. During ye’elimite synthesis, significant gas releases were observed at different stages of firing using TGA coupled with mass-spectrometer. The gases are the product of carbonate decomposition, gypsum dehydration and sulfate decomposition from the unreacted anhydrite and the formed ye’elimite. Based on the present work, it emerges that a key strategy for forming ye’elimite with a high purity is to compensate sulfate decomposition by the addition of a slight excess of CaSO₄ before repeating the firing cycle at optimal conditions. Finally, the porosity was investigated using Archimedes principle measurements compared to BSE-image analysis. It shows the difficulty to achieve dense sintered ye’elimite because of the high decomposition gas releases during the firing process.     

贝利特-硫铝酸钡钙水泥的微观结构和力学性能

贝利特-硫铝酸钡钙水泥是一种新型的水泥材料,通过在贝利特熟料矿物体系中引入硫铝酸钡钙矿物,达到提高贝利特水泥早期强度的目的.研究了过量掺加SO3和BaO对贝利特-硫铝酸钡钙水泥性能的影响.研究结果表明:熟料中SO3和BaO最佳过掺量(质量分数)分别为50%和80%,制得的贝利特-硫铝酸钡钙水泥的3 d和28 d抗压强度分别达到27.0MPa和85.6MPa,展现了良好的力学性能.SO3和BaO的掺入促进了硫铝酸钡钙矿物的形成,同时对阿利特在低温下形成及对贝利特矿物的活化起到了重要作用.     

Synthesis of belite cement from lignite fly ash

Synthesis of belite cement from lignite fly ash is studied as it can be produced using low temperature between 750 and 1200 °C leading to energy saving and low carbon dioxide emission. Two synthesis methods viz., clinkerization and hydrothermal processes assisted by calcinations are studied. Lignite fly ash is used as a main starting material. For the clinkerization process, the firing temperatures, types of additives and calcium oxide/silicon dioxide ratios (Ca/Si) are studied. In this process, the reaction between fly ash and calcium carbonate produces gehlenite (2CaO·Al₂O₃·SiO₂) which is undesirable due to its poor hydraulic property. A slightly higher belite (2CaO·SiO₂) phase is obtained using sulfate ion as a dopant and using high Ca/Si ratio. The strength of gehlenite bearing belite cement is, however, rather poor. For the hydrothermal–calcination process, the alkaline concentrations and calcining temperatures are studied. The final products are belite phase and mayenite (12CaO·7Al₂O₃) which are desirable as they possess hydraulic properties. The reasonable 28-day compressive strength of the belite cement mortar of 9.5 MPa is obtained. The hydrothermal process assisted by calcination is, therefore, suitable for use in the synthesis of belite cement from lignite fly ash.