Incorporation of V, Zn and Pb into the crystalline phases of Portland clinker

Burning of industrial wastes in cement kilns has an increasing environmental importance, brought about by the incorporation of potentially hazardous elements into clinker crystalline phases and partial substitution of primary fuel and raw materials. In this study, experimental clinkers were synthesized, with the addition of V, Zn and Pb to a standard raw meal, from which a control clinker was obtained for comparison. The three metals were chosen as they are present in the alternative fuel petcoke (V) and in industrial wastes (Zn, Pb) commonly burned in cement kilns. Electron microprobe and scanning electron microscope analysis revealed the preferential partition of these metals among the clinker crystalline phases. It was observed that V has shown a preferential partition towards C₂S. Zn appears in higher amounts in periclase, and C₃S has higher Zn contents than C₂S. Pb concentrates in minute spherules and partitions toward C₃S in small amounts.     

Active low-energy belite cement

The term ‘low-energy cement’ is used for cements that can be in some applications used instead of OPC, and which are produced with less energy. A more extensive utilization of these cements would lead to the lowering of expenses on production of binders as well as a reduction of undesirable emissions. The belite-rich cement belongs to this group. Pure belite clinkers with interstitial matter consisting of C₃A and C₄AF have not been produced, as they have insufficient strength. This work describes the results of hydraulic activation of belite-rich clinkers with sulfate anions. The principle of activation is used for the preparation of belite-rich clinkers with an increased Ca:Si ratio in the structure of dicalcium silicate and partial substitution of SiO₄⁴⁻  by SO₄²⁻. Cements, prepared from these belite-rich clinkers, containing up to 20% of alite, which are burned at 1350 °C, have the same technological properties, including early strengths, as OPC.     

Expansive sulphate aluminate cements

The possibility to prepare expensive sulphate aluminate masses from certain wastes (phosphogypsum and belitic waste) and usual raw materials (limestone, bauxite) has been investigated. The chemical and minerological composition of these synthetic clinkers as well as the nature of their hydration products has been determined by current methods. The mechanism of cement expansion and the factors affecting the correlation between mechanical strength and expansion have been also studied.     

资源和环境与生态化水泥技术

生态化水泥技术是当今世界水泥工业发展的方向。生态化水泥是指水泥在生产过程中,一方面消纳大量的工业废弃物,另一方面最大限度减少污染物的排放,从而达到保护环境和保护自然资源的目的。本文较为详细地介绍了水泥生产有害物的排放、利用工业废弃物作水泥生产的原燃料和混合材的状况、生态化水泥的技术难点,进而提出发展生态化水泥技术的建议。     

ZnO对硅酸盐水泥熟料矿物组成影响的研究

以空白生料为基准,掺入0.1%、0.3%、0.5%、1.0%、1.5%的ZnO,分别在1300 ℃,1350 ℃,1400 ℃,1450 ℃煅烧成熟料,用甘油-乙醇法、XRD结合Rietveld方法、岩相分析对熟料进行分析.结果表明:ZnO可以改善生料的易烧性,在较低温下明显促进f-CaO的吸收.不同煅烧温度下,随着ZnO掺量的增加,熟料中铝相减少,铁相增加,C3S矿物含量增多;在1450 ℃,当掺入1.5%的ZnO时,C3S存在晶型转变,由M3型转化为M1型.从1450 ℃煅烧条件下的样品熟料岩相图中可以看出,随着ZnO的掺入,改善了C3S晶型晶貌,使熟料具有良好的微观结构.     

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.     

Reuse of heavy metal-containing sludges in cement production

The feasibility of the replacement of raw material for cement production by heavy metal-containing sludge from surface finishing and electroplating industries was investigated. The effect of heavy metal content in the cement raw mix on the crystalline formation in cement production was also examined by XRD analyses. It was found that both sludges were applicable for the replacement of raw mix for cement production by moderate conditioning of the sludge compositions with several compositional parameters. As the replacement of raw mix by sludge was within 15%, the formation of tricalcium silicate (C₃S) phase in cement would be enhanced by the introduced heavy metals. While owing to a high level of heavy metals concentration (> 1.5%) in cement raw mix, C₃S crystalline in cement would be inhibited by a large sludge replacement (> 15%). During the sintering process, over 90% of the high volatile elements such as Pb would evaporate in high temperature, yet 90% of the less volatile elements such as Cu, Cr and Ni would be trapped in clinkers. Most of all, the results of leaching test shows that the trapped elements in hydrated samples would not leach out under acidic conditions. The reuse of heavy metal-containing sludges as cement raw material would not cause leaching hazard from sintered clinkers. Heavy metal-containing sludges thus should have the potential to be utilized as alternative raw materials in cement production.     

Fabrication of sustainable magnesium phosphate cement micromortar using design of experiments statistical modelling: Valorization of ceramic-stone-porcelain containing waste as filler

Magnesium phosphate cement (MPC) is a potential sustainable alternative to Portland cement. It is possible to lower the total CO₂ emissions related to MPC manufacturing by using by-products and wastes as raw materials. When by-products are used to develop MPC, the resultant binder can be referred to as sustainable magnesium phosphate cement (sust-MPC). This research incorporates ceramic, stone, and porcelain waste (CSP) as a filler in sust-MPC to obtain a micromortar. Sust-MPC is formulated with KH₂PO₄ and low-grade MgO (LG-MgO), a by-product composed of 40–60 wt% MgO. CSP is the non-recyclable glass fraction generated by the glass recycling industry. The effect of water and CSP addition on the mechanical properties of sust-MPC was analyzed using design of experiments (DoE). A statistical model was obtained and validated by testing ideally formulated samples achieved through optimization of the DoE. The optimal formulation (15 wt% of CSP and a water to cement ratio of 0.34) was realized by maximizing the compressive strength at 7 and 28 days of curing, resulting in values of 18 and 25 MPa respectively. After one year of curing, the micromortar was physico-chemically characterized in-depth using backscattered scanning electron microscopy (BSEM-EDS) and Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR). The optimal formulation showed good integration of CSP particles in the ceramic matrix. Thus, a potential reaction between silica and the K-struvite matrix may have occurred after one year of curing.     

氧化锌对高胶凝性水泥熟料矿物形成及强度的影响

采用工业原料配料，对以硅酸三钙（C3S，C=CaO，S=SiO2）、硫铝酸钙（C4A3 S^-，C=CaO，A=Al2O3，S^-=SO4^2-）为主导矿物的含C4A3 S^-矿物硅酸盐水泥熟料的矿物形成及其强度进行了研究。借助X射线衍射和热重一差热分析研究了矿物形成过程；探讨了微量元素ZnO对熟料性能的影响及在熟料体系中的固溶情况。研究结果表明：生料中掺入ZnO可使C4A3 S^-和CaS等矿物通过低温反应形成，共存于同一熟料体系中，并可提高熟料的强度；过高的ZnO含量亦会降低C4A3 S^-矿物的分解温度。     

石煤提钒尾矿制备硅酸盐水泥熟料的研究

以石煤提钒尾矿细粉、碳酸钙、粘土和铁粉为原料,在不同煅烧条件下制备了不同配比的产物,并研究了其性能.结果表明:(1)产物的主要成分为硅酸三钙、硅酸二钙、铁铝酸四钙和铝酸三钙,符合水泥熟料的化学组成;(2)熟料煅烧温度为1400℃,粘土掺加量为8％时的方案最优.     

工业废渣-阴离子团多元复合掺杂对高C3S水泥熟料烧成及性能的影响

利用某些工业废渣并复合一些阴离子(团),以一定比例配入生料中,采用高饱和比、高硅率、高铝率配料,在实验室于正常烧成温度下烧成了3d和28d抗压强度分别达42MPa和84MPa、其它性能正常的高C3S水泥熟料(ARPC),实现了熟料的高胶凝性。废渣-阴离子多元复合掺杂通过改善C3S形成的动力学过程改善了生料的易烧性。熟料的高胶凝性一方面是由于熟料中C3S的含量高,另一方面是由于不同的离子以一定量固溶到C3S晶格,会稳定不同的晶型,杂质离子还会改变液相性质,调整CS晶貌,使得水泥熟料具有良好的微观结构。     

氧化铜对硅酸三钙和硫铝酸钙矿物形成及共存的影响

研究了CuO对含硫铝酸钙矿物硅酸盐水泥中硅酸三钙（C3S）和硫铝酸钙（C4A3S）矿物形成及共存的影响。借助化学分析和X射线衍射内标法分别测定了水泥熟料中C3S及C4A3S矿物的含量。用X射线衍射仪分析了熟料矿物组成,并采用差热分析和透射电镜分别研究了CuO对熟料形成特性和C3S晶体结构的影响。研究结果表明：生料中掺入生料质量0．1％的CuO,能降低水泥熟料的烧成温度。促进C3S和C4A3S两种矿物相互共存．提高熟料的强度。过量的CuO亦会降低C4A3S矿物的分解温度。     

Synthesis and characterization of calcium silicate insulating material using avian eggshell waste

This work focuses on the synthesis of calcium silicate insulating material via solid state reaction using avian eggshell waste as alternative calcium source. The calcium silicate formulations were mixed in a molar ratio SiO₂:CaO (1:1) and fired at 1100 °C for 24 h. The calcium silicate formulations were characterized by XRD, TG-DTA, dilatometry, SEM/EDS, and thermophysical properties (thermal diffusivity, heat capacity per unit volume, and thermal conductivity). The synthesized calcium silicate materials are composed mainly of wollastonite with minor amounts of larnite and rankinite. It was found that a processing of the avian eggshell waste (raw eggshell waste and calcined eggshell waste) had an influence on the thermophysical properties. Calcium silicate pieces were prepared by uniaxial pressing at 82 MPa, curing, and then testing to determine their use as thermal insulating material. The microstructure was evaluated by SEM. The results showed that both raw and calcined avian eggshell wastes could be used as an alternative calcium source in the calcium silicate formulation. It was found that the calcium silicate pieces reached low thermal conductivity values (0.252–0.293 W/mK). Thus, the developed calcium silicate materials using avian eggshell waste act as a good thermal insulation ceramic material.     

论与资源、环境相协调的水泥工业

水泥工业是资源与环境的影响大户.目前,制约我国水泥工业与资源、环境协调发展的主要问题是：天然原料和能源的消耗与利用,水泥质量以及水泥生产中的粉尘和有害气体的排放与污染等问题.在充分分析这些方面的现状和相关原因的基础上,着重探讨了实现水泥工业与资源、环境协调发展的技术途径.包括：促进结构调整、积极发展新型干法窑;进行可燃废弃物（二次燃料）的利用;提高水泥熟料质量;综合利用天然资源与工业废渣及提高水泥生产环境治理水平等.     

Microwave promoted clinkering of sulfoaluminate cement

Sulfoaluminate clinkers were made by combination of electric heating and microwave processing. When raw sulfoaluminate materials were heated to 1000-1200 °C conventionally, microwaves were inputted for 1-2 min. The f-CaO of the obtained clinkers was zero. Comparatively, when the samples with the same composition were conventionally heated at 1300 °C for 1 h, the f-CaO of the obtained clinkers was as high as 1.03-4.78%, and when the samples with the same composition were heated only by microwave for 25 min, CaCO₃ in the raw materials was not decomposed completely. It is shown that combination of electric heating and microwave processing greatly accelerate clinkering reaction. The X-ray diffraction (XRD) of the clinkers indicates that their mineral composition and XRD patterns are the same as those of the clinkers prepared by conventional firing methods. It has also been proven that Fe₂O₃ contributed to sulfoaluminate cement clinkering.     

Circular economy in cementitious ceramics: Replacement of hydrated lime with a stoichiometric balanced combination of clay and marble waste

Cementitious ceramics, produced from the hydration of cement and hydrated lime, are responsible for a great deal of damage to the environment due to the high emission of CO₂ that occurs in the production of cement and lime. Therefore, the objective of this work was to substitute the hydrated lime with a combination of clay residue and marble waste extracted from ceramic and ornamental rock producing industries, respectively, which constitutes a circular economy for the ceramic industry related to masonry applications. Ceramics were produced in the proportion 1:1:6:1.5 (cement:lime:sand:water), through the molding procedure, and were studied by replacing hydrated lime with 100% clay residue and 100% marble residue, in addition to stoichiometric calculated parts of marble to clay. The molar ratios used were 1:1, 1:2, and 2:1 (marble:clay). Tests of consistency, incorporated air content, water retention, compression strength, density, water absorption by capillarity, adhesion, and electrical resistivity were performed. The results obtained demonstrate that the use of residue of marble and clay together, as long as they are correctly balanced, provides a high gain in technological properties, enabling the circular economy of cementitious ceramics, mainly for the composition 1 marble:1clay, which presented the best properties, both in the fresh and hardened state. The economic analysis carried out proved the financial gains for the industrial sectors involved (civil construction, ornamental rock, and ceramic).     

Waste fuels: their effect on Portland cement clinker

Nowadays, different kinds of industrial wastes are increasingly used in the clinkering process by the cement industry, with the aim of taking advantage of their energy content or confining unsuitable substances. This work evaluates the physicochemical characteristics of the clinkers obtained after incorporating three different wastes in different proportions: two of them with energetic capacity—trade marked waste fuel and waste carbon of petroleum—and the third that would be confined—pyrolitic carbon.The fusion temperature of the mixtures, the differential thermal analysis and the thermogravimetric analysis (DTA/TG) during clinkering and after hydration, the specific surface area at the same milling times, X-ray diffraction (XRD) and mechanical strength of the pastes elaborated with a water/cement 0.4 relation were analyzed. The results obtained were compared to those of the clinker obtained without additions.     

Cement Formulations in the Calcium Phosphate H2O–H3PO4–H4P2O7 System

Despite numerous reports of calcium phosphate cement materials, a calcium cement that sets to form a matrix consisting of a pyrophosphate phase has not been reported. The formulation of such a material from the mixture of α-tricalcium phosphate (TCP), β-TCP, or tetracalcium phosphate with a solution containing pyro- and orthophosphoric acid is reported in this study. The effects of liquid and solid compositions on the setting times, compressive strengths and phase compositions of the resultant cements were investigated. It was found that cements could be produced that set to form up to 28 wt% dicalcium pyrophosphate, which appeared by comparison with Rietveld refinement and chemical methods to be entirely amorphous in nature. The solubilities of the different solid components were shown to have a marked effect on the composition of the cements. The strongest cement formulations exhibited compressive strengths comparable with those previously reported in the literature for brushite cements and set within clinically relevant time scales. This class of cement would appear to demonstrate potential as a bone replacement material.     

Potential use of Kraft pulp mill and flat glass cutting wastes in red ceramic products

This study assessed the incorporation of green liquor dregs, an inorganic solid waste from Kraft pulp mill, and flat glass cutting waste (FGCW) into red ceramic formulations. Since in Brazil sanitary landfills are still the main destination of industrial wastes such as those used in this research, a survey was conducted to identify the number of landfills in the region of origin of each waste and the amount of waste that could have this destination avoided. The effects of firing temperature and simultaneous incorporation of both industrial wastes were analyzed to optimize heat treatment and waste content in the formulation to manufacture red ceramic products. The influence of green liquor dregs and FGCW incorporation into clayey mass was evaluated varying waste content between 0 and 50 wt%. The specimens were prepared by uniaxial pressing, fired at 850 and 950 °C, and had their physical-mechanical properties and mineralogical and microstructural characteristics analyzed. The best results were obtained for the formulation with 10 wt% green liquor dregs and 30 wt% FGCW fired at 950 °C. This result highlights the potential of using green liquor dregs, a waste difficult to be recycled due to its chemical composition, associated with FGCW, which acts as a fluxing agent in ceramic formulations.