矿渣粉煤灰制备胶凝材料的实验研究

阐述了一种利用矿渣和粉煤灰制备胶凝材料的方法(矿渣和粉煤灰的比表面积为500m2/kg).研究了二水石膏和激发荆的质量分数对该胶凝材料强度的影响,运用扫描电镜分析了该胶凝材料的微观结构和形貌特征.结果表明,当矿渣、粉煤灰、二水石膏和激发剂的质量比为80∶5∶10∶5时可制备出满足现行国家标准的胶凝材料,这对矿渣和粉煤灰的综合利用具有一定的参考价值.     

养护条件对碱-矿渣-偏高岭土复合胶凝材料强度的影响

研究了偏高岭土对碱矿渣水泥强度的影响规律和不同养护条件下碱-矿渣-偏高岭土复合胶凝材料(M-AAS)的强度发展情况.结果表明:80%湿度和40℃温度下,掺入适量偏高岭土能提高碱矿渣水泥的强度性能,最佳掺量为20%左右;对于掺20%偏高岭土的碱-矿渣-偏高岭土复合胶凝材料,在80%湿度下,养护温度的提高有利于抗压强度的发挥,但对抗折强度的发挥不利;在80%湿度和20℃温度下,复合材料的抗折强度出现倒缩,对80%湿度养护和水中养护两种养护条件进行适当的组合,强度倒缩现象没有发生.     

再生微粉对碱激发胶凝材料性能的影响

以水玻璃与氢氧化钠作为激发剂,利用建筑垃圾再生微粉制备碱激发胶凝材料。研究再生微粉掺量、激发剂掺量(以固含量计)以及激发剂模数对碱激发胶凝材料的工作性能、力学性能和干燥收缩的影响。研究表明：在再生微粉掺量≤40%,激发剂掺量16%,激发剂模数1.2时,碱激发胶凝材料具有较好的工作性和抗压强度,而再生微粉的“微集料”效应对碱激发胶凝材料的干燥收缩有较强的抑制作用。     

一类新型碱激发胶凝材料催化剂的研究进展

碱激发固体铝硅酸盐胶凝材料是先进无机非金属材料的前瞻性研究领域之一, 本文对碱激发铝硅酸盐胶凝材料的分类、制备工艺、形成机理以及潜在的应用前景进行了综述; 详尽地论述了碱激发胶凝材料基新型催化剂的最新研究进展, 综合分析了碱激发胶凝材料作为结构材料研究的局限性, 展望了该材料作为新型催化材料的发展动态。     

辅助胶凝材料玻璃体结构与胶凝活性的研究进展

大宗工业副产品或废弃物(如粒化高炉矿渣、粉煤灰等)作为辅助胶凝材料用于硅酸盐水泥及混凝土中已有不短的时间.利用辅助胶凝材料可有效缓解水泥生产所带来的制备能耗高、自然资源消耗大、二氧化碳排放等问题.在胶凝材料性能不大幅降低的前提下,要实现大比例取代(≥30％(质量分数))硅酸盐水泥,激发辅助胶凝材料的活性是关键.然而,从材料学观点出发,过往基于宏观性能的经验测试方法,对辅助胶凝材料活性的理解仍相当碎片化.除比表面积等物理性质外,多数辅助胶凝材料的水硬活性取决于其中玻璃相的溶解-沉淀反应.辅助胶凝材料中的玻璃体结构可简化为网络调整体(如Ca、Na等)和网络形成体(如Si、Al等)的物质的量比,如解聚度.近来对CaO-SiO2-Al2 O3体系玻璃体的研究,进一步增强了对玻璃体聚合度的理解.玻璃体的溶解与聚合程度及溶液组成(如溶液的饱和程度、阴阳离子类型及浓度、pH等)密切相关.同时,沉淀的生成也会显著改变玻璃体的溶解动力学.本文归纳了辅助胶凝材料玻璃体结构与水硬活性的研究进展,分别对表征辅助胶凝材料玻璃体结构的解聚度及玻璃体中Si(Qn(mAl))聚合程度进行了介绍,分析了玻璃体结构在不同激发条件下的反应活性,以期为制备性能稳定和耐久性优良的低碳建筑材料提供参考.     

热处理粉煤灰及其胶凝性

在适当煅烧温度下,分别运用Na2CO3、CaO和CaF2等材料对二级低钙粉煤灰进行了改性研究,从而促进了粉煤灰活性的发挥.运用XRD、TGA等测试方法,研究了热处理粉煤灰的晶相组成及其水化特性.研究表明,粉煤灰能够和这些组分发生化应,形成NaAlSiO4、CaO·Al2O3·SiO2、α-Ca2SiO4和Na,Ca)(SiAl4)4O8等晶相,玻璃态网络结构也发生了相应的变化.热处理粉煤灰表现出了良好的胶凝性能.上述3种组分对粉煤灰活性的影响不尽相同,其中CaF2对粉煤灰的活性有更加积极的影响.     

胶凝材料影响水泥基饰面砂浆泛碱的研究进展

介绍了胶凝材料影响水泥基饰面砂浆泛碱性能的研究进展。研究主要针对水泥基饰面砂浆的泛碱成因,从无机胶凝材料入手,探讨其对砂浆泛碱的影响和抑制泛碱的措施。涉及的无机胶凝材料主要集中在硅酸盐水泥、铝酸盐水泥及其分别或共同与石膏组成的二元和三元体系。水泥基饰面砂浆的抗泛碱主要通过两条途径,一是控制水化时Ca（OH）₂的产生,二是提高砂浆的密实度。     

胶凝材料影响水泥基饰面砂浆泛碱的研究进展

介绍了胶凝材料影响水泥基饰面砂浆泛碱性能的研究进展。研究主要针对水泥基饰面砂浆的泛碱成因，从无机胶凝材料入手，探讨其对砂浆泛碱的影响和抑制泛碱的措施。涉及的无机胶凝材料主要集中在硅酸盐水泥、铝酸盐水泥及其分别或共同与石膏组成的二元和三元体系。水泥基饰面砂浆的抗泛碱主要通过两条途径，一是控制水化时Ca（0H）2的产生，二...     

无熟料碱激发胶凝材料的研究进展

无熟料碱激发胶凝材料对于解决社会发展中资源与环境间的矛盾具有不可估量的重要意义。对无熟料胶凝材料的分类、反应机理、制备及其性能等研究成果进行了总结,并结合研究现状提出了现存问题以及努力方向。     

碱激发碳酸盐复合胶凝材料性能研究

以白云石粉为主要原料,矿渣、粉煤灰和偏高岭土为辅助原料,用改性水玻璃激发的方式,制备得到碱激发碳酸盐复合胶凝材料。通过正交试验,研究了水玻璃的模数(A)和固含量(B),水玻璃与固体粉料的比例(C,简称液固比),以及矿渣(D)、粉煤灰(E)和偏高岭土(F)在固体粉料中的质量分数,对碱激发碳酸盐复合胶凝材料的流动度、凝结时间和力学强度的影响。结果表明,B、C和F对流动度影响显著,B和C对凝结时间影响显著,6个因素对力学强度的影响比较复杂。制备得到的碱激发碳酸盐复合胶凝材料流动度较好,凝结时间适宜,早期强度可达到37.9MPa,绝热温升为31.8℃。和混合水泥相比,碱激发碳酸盐复合胶凝材料在某些领域更有优势得到应用。     

Electrically tunable dielectric materials and strategies to improve their performances

Electrically tunable dielectric materials have potential applications as various microwave devices, such as tunable oscillators, phase shifters and varactors. High dielectric tunability, low dielectric loss tangent and appropriate level of dielectric constant, are basic requirements for such applications. Ferroelectric materials are the most promising candidates. In general, strontium titanate (SrTiO₃ or ST) is used for devices operating at low temperatures, while the devices based on barium strontium titanate (Ba_1?xSr_xTiO₃ or BST) are operated at room temperatures. The modifications of parent ferroelectrics, such as Sr_1?xPb_xTiO₃, BaZr_xTi_1?xO₃ and BaTi_1?xSn_xO₃ etc., have also been widely investigated. In addition, there have been reports on electrically tunable dielectric materials, based on non-ferroelectric compounds, such as microwave dielectrics and carbon nanotube (CNT) composites. Specifically for ferroelectric materials, a critical issue is the reduction of the dielectric losses, because their dielectric loss tangents are relatively high for practical device applications. Recently, many efforts have been made in order to reduce the dielectric losses of BST based ferroelectrics. An efficient way is to dope oxides that have low dielectric losses, such as MgO, ZrO₂ and Al₂O₃, TiO₂, LaAlO₃, and Bi_1.5ZnNb_1.5O₇ etc., into the ferroelectric materials. In addition to the reduction in dielectric loss tangents, the introduction of oxides would also be able to modify the dielectric constant to be suitable for practical design of various devices. Meanwhile, dielectric and electrical properties of thin films can be improved by chemical doping, substrate adaptation, orientation and anisotropy optimization. This review provides an overall summary on the recent progress in developing electrically tunable dielectric materials, based on ferroelectrics and non-ferroelectrics, with a specific attention to the strategies employed to improve the performances of ferroelectric materials for microwave device applications.     

Effects of nano-TiO2 on strength,shrinkage and microstructure of alkali activated slag pastes

For alkali-activated slag (AAS), high drying shrinkage is an obstacle which impedes its application as a construction material. In this investigation, nano-TiO₂ was added to AAS, and its mechanical properties and shrinkage were tested to examine its effect on hardened alkali-activated slag paste (AASP). To understand the impact of nano-TiO₂ on AASP at micro scale, FTIR, MIP and SEM were carried out. Experimental results indicate that the addition of nano-TiO₂ to AAS enhances the mechanical strength, and decreases the shrinkage of AASP. FTIR and SEM results demonstrated that the addition of nano-TiO₂ into the AASP accelerates its hydration process, resulting in more hydration products and denser structure. MIP results showed that the addition of nano-TiO₂ reduces the total porosity of AASP and changes the pore structure. The porosity of 1.25–25 nm mesopores, which is believed to be responsible for the high shrinkage of AASP, is remarkably reduced due to the addition of nano-TiO₂.     

热处理温度对PAN基炭纤维结构的影响

利用SEM观察了3种PAN基炭纤维（TX－63、T300、T700）热处理前和经不同温度热处理后的表面形貌，并测试了其石墨化度、Lc和d002值，以研究热处理温度对炭纤维表面和内部微观结构的影响。结果表明：TX－3、T300炭纤维表面本身有不规则沟槽、凸起和缺陷等，T700炭纤维表面比较圆滑，随着热处理温度升高，PAN基炭纤维的表面形貌发生明显的变化，尤其是2700℃处理后炭纤维表面的褶皱相对较浅而小；石墨化度与Lc随热处理温度升高而增大，d002值则呈减小趋势，说明热处理温度对炭纤维的表面和内部结构有显著影响。     

Properties of controlled low-strength materials incorporating cement kiln dust and slag

This research evaluated the potential use of cement kiln dust (CKD) together with slag to replace the use of cement in the production of controlled low-strength material (CLSM). The low strength requirements of CLSM compared to conventional concrete enable the use of industrial by-products for the production of CLSM. In this study, the workability-related fresh properties of CLSM mixtures were observed through slump flow diameter, V-funnel flow time and filling capacity. Setting times, temperature rise, air content and unit weight of CLSM mixtures were also determined as part of fresh properties. The hardened properties that were monitored for 28 days included the unconfined compressive strength. The test results presented herein show that a combination of less than 50 kg/m³ slag and up to 300 kg/m³ CKD provides a good mix that satisfies the requirements of a CLSM with similar or better properties to that of CKD-based CLSM mix containing Portland cement. Suitable CLSM mixtures with reasonable fresh and hardened properties could also be developed by using CKD alone. However, reduced strength in such CLSM mixtures may limit their field application. The slag significantly assisted in increasing compressive strength of CKD-based CLSM mixtures. A CLSM mix containing a combination of slag and CKD was shown to have excellent characteristics for flowable backfill and excavatable base material. Therefore, producing CKD/slag based CLSM through the use of co-generated products from the cement and iron manufacturing processes can provide leadership for the construction industry in the transition for sustainable development.     

半固态处理对Ti基非晶复合材料的组织和力学性能影响

利用"形变诱导相变机制"对非晶基体同时增强增韧,采用悬浮熔炼-铜模吸铸法制备了Ti基非晶复合材料。在此基础上,通过半固态处理工艺对凝固过程动力学控制优化组织,研究了半固态处理对试样的组织和力学行为的影响。结果表明,铸态试样组织为过冷奥氏体相、热致马氏体相和非晶复合结构,应力加载形变过程中通过形状记忆晶相TRIP效应对非晶基体增韧,表现为加工硬化行为。铸态试样的心部组织为较粗大的树枝晶,且生长不均匀;经半固态处理后,先析出相按照尖角溶解平面析出长大形式近球化,形成等轴晶,并在磁悬浮搅拌作用下均匀化,获得奥氏体相晶粒细小、圆整度高、组织致密,复合材料组织得到有效优化,(Ti0.5Ni0.48Co0.02)80Cu20合金断裂强度和塑性变形量由2 582 MPa和15%分别提高至2 745MPa和21.5%。     

Development of alkali activated cement from mechanically activated silico-manganese (SiMn) slag

Silico-manganese (SiMn) slag has been used to develop alkali activated cement binder. The reactivity of SiMn slag was altered by mechanical activation using eccentric vibratory and attrition mill. The reaction kinetics during alkali activation of SiMn slag and structural reorganization were studied using isothermal conduction calorimetry and Fourier transform infrared spectroscopy. The particle size after milling was smaller in attrition milled samples but reaction started earlier in vibratory milled samples due to more reactivity. This observation was further supported by compressive strength which was highest in samples prepared from vibratory milled slag. The main reaction product was C–S–H (C = CaO, S = SiO₂, H = H₂O) of low crystallinity of different types with varying Si/Al and Ca/Si ratio. An attempt has been made to relate the microstructure with mechanical properties. The results obtained in this study establish technical suitability of SiMn slag as raw material for alkali activated cement.     

Effect of aggregates on the diffusion properties and microstructure of cement with slurried silica fume based materials

Diffusivity of cement-based materials is an important factor regarding durability and the service life prediction of concrete structures. The present research focuses on investigating the influence of aggregates on tritiated water diffusivity of cement-based materials containing slurried silica fume. Effective diffusion coefficients of mortars with several sand volume fractions varying from 0 to 65% were determined by through-out diffusion tests. Microstructure was examined by scanning electron microscopy associated to energy dispersive spectrometry analysis, thermogravimetric analysis, water and mercury porosimetry, and BET adsorption analysis. It was found that large agglomerated particles of silica fume observed in cement paste and mortar with a low sand content (here 10%), reduce pozzolanic reactivity and thus affect the effectiveness of silica fume on the materials sustainability parameters. The clusters present in these formulations are mainly due to the interaction of silica fume with calcium hydroxide of the mixing solution and not to the initial state of the slurry, which was well stirred and whose particles size were checked before use. However, the presence of high content of aggregates (more than 30% of sand volume fraction) during mortar's mixing improves the dispersion of slurried silica fume particles and helps to ‘shear’ and break up agglomerates of silica fume providing a better homogenization of the material and improving the microstructural and diffusivity parameters. The addition of superplastizer in mortars with more than 50% sand content may also participate in dispersing silica fume.     

Comparative performance of alkali activated slag/metakaolin cement pastes exposed to high temperatures

This paper presents a study on the effect of temperature exposure of binders of blast furnace slag (BFS) and metakaolin (MK) in BFS-MK weight ratios of 100-0, 50-50, and 0-100 activated with sodium silicate of modulus Ms = SiO₂/Na₂O = 1 and 5, 10 and 15% Na₂O. A blended ordinary CPC-30R Portland cement reference was used. Pastes were subjected to exposure up to 1200 °C and the performance was evaluated in terms of compressive strength, residual strength, volumetric shrinkage, physical appearance and microstructural changes at different temperatures. All the binders retained more than 30 MPa after exposure to 800 °C for 4 h; specimens of MK and CPC-30R experienced the highest strength losses of 42 and 56% respectively, while those of 100-0 and 50-50 showed minor losses of ∼20%. After heating at 1200 °C the samples showed microstructural damage and more than 65% of strength losses. XRD indicated that the 100-0 and 50/50 binders are prone to form crystalline phases as akermanite, nepheline and nosean at temperatures greater than 1000 °C, while 0-100 geopolymeric binders preserved mostly an amorphous structure even at 1200 °C with some traces of mullite. The dehydration of C-A-S-H and N-A-S-H altogether with the crystallization of the binder gel induced the formation of highly porous microstructures.     

Recycling of steel slag as an alkali activator for blast furnace slag: geopolymer preparation and its application in composite cement

Clean Technologies and Environmental Policy - The recycling–utilization rate of steel slag in China is less than 30%. Steel slag is rich in CaO and can produce the Ca(OH)2 after hydration,...     

A method for predicting the alkali concentrations in pore solution of hydrated slag cement paste

The alkalinity of the pore liquid in hardened cement paste or concrete is important for the long-term evaluation of alkali-silica reaction (ASR) expansion and corrosion prevention of steel bar in steel reinforced structures among others. It influences the reactivity of supplementary cementitious materials as well. This paper focuses on the alkali binding in hydrated slag cement paste and a method for predicting the alkali concentrations in the pore solution is developed. The hydration of slag cement is simulated with a computer-based model CEMHYD3D. The amount of alkalis released by the cement hydration, quantities of hydration products, and volume of the pore solution are calculated from the model outputs. A large set of experimental results reported in different literatures are used to derive the alkali-binding capacities of the hydration products and practical models are proposed based on the computation results. It was found that the hydrotalcite-like phase is a major binder of alkalis in hydrated slag cement paste, and the C?CS?CH has weaker alkali-binding capacity than the C?CS?CH in hydrated Portland cement paste. The method for predicting the alkali concentrations in the pore solution of hydrated slag cement paste is used to investigate the effects of different factors on the alkalinity of pore solution in hydrated slag cement paste.