水胶比和组成对补偿收缩胶凝材料的水化反应的影响

在不同水胶比条件下，利用等温量热法测量了不同组成的补偿收缩胶凝材料的水化放热速率和放热量曲线，以评价其水化特性及其对强度和膨胀性能的影响。随着水胶比逐渐降低，水化受到抑制。在水胶比为0．3时，补偿收缩胶凝材料的总放热量和水化放热速率有明显降低。由矿物掺和料、膨胀剂和硅酸盐水泥组成的复合胶凝材料的总放热量和水化放热速率较低，但后期水化放热增加量较大。水胶比大于0．4后，水胶比的变化对复合胶凝材料的水化过程影响很小。     

循环流化床固硫灰复合胶凝材料的早期水化特点

研究了大掺量循环流化床固硫灰复合胶凝材料的物理力学性能,以及其早期水化放热特点和水化产物。研究结果表明:利用掺量为30%～60%固硫灰制备的复合胶凝材料满足32.5、42.5强度等级水泥标准;固硫灰复合胶凝材料的标准稠度比水泥的标准稠度大,且随着固硫灰用量的增加标准稠度增加,同时凝结时间变长;与P.O42.5水泥相比,循环流化床固硫灰复合胶凝材料水化的诱导期较长,水化放热速率明显变小,水化热较低。     

Influence of the composition of cement kiln dust on its interaction with fly ash and slag

Cement kiln dust (CKD), a by-product of the cement industry, contains significant amounts of alkali, free lime, chloride and sulfate. Wide variation reported in the chemical composition of CKDs limits their potential application as a sustainable binder component in concrete. In the current study, the performance of two different CKDs as components in a novel binder is evaluated. Several binders are developed by blending CKDs with fly ash or slag. Binders with 70% CKD were prepared at a water-to-binder ratio of 0.4, and heat-cured at 75 °C to accelerate the strength development. The hydration progress was monitored using X-ray diffraction, and morphological examination was performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Ettringite and calcium aluminosilicate hydrate (C-A-S-H) were identified as the main hydration products in the hardened binder system. Strength development of CKD-based binder was found to be significantly influenced by its free lime and sulfate contents.     

E-modulus evolution and its relation to solids formation of pastes from commercial cements

Models for early age E-modulus evolution of cement pastes are available in the literature, but their validation is limited. This paper provides correlated measurements of early age evolution of E-modulus and hydration of pastes from five commercial cements differing in limestone content. A recently developed methodology allowed continuous monitoring of E-modulus from the time of casting. The methodology is a variant of classic resonant frequency methods, which are based on determination of the first resonant frequency of a composite beam containing the material. The hydration kinetics — and thus the rate of formation of solids — was determined using chemical shrinkage measurements. For the cements studied similar relationships between E-modulus and chemical shrinkage were observed for comparable water-to-binder ratio. For commercial cements it is suggested to model the E-modulus evolution based on the amount of binder reacted, instead of the degree of hydration.     

Effects of curing temperature and NaOH addition on hydration and strength development of clinker-free CKD-fly ash binders

Effects of curing temperature and NaOH addition on hydration and strength development of cement kiln dust (CKD)-fly ash (FA) binders were investigated. Pastes made with 50% CKD and 50% FA, having 0, 2, and 5% NaOH addition, and cured at temperatures of 24, 38, and 50 °C were evaluated. The hydration products of the binders were examined by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) tests. The results indicate that the major crystalline hydration product of the CKD-FA binders is ettringite, and the ettringite is stable in the CKD-FA system at age over 100 days. Curing at elevated temperature is more effective for CKD-FA binder strength improvement than NaOH addition, the later often depressing ettringite formation in a CKD-FA system. At a proper curing temperature (38 °C), addition of a small amount of NaOH (2%) may increase CKD-FA binder strength; while at a high curing temperature (50 °C), addition of NaOH (2%) may reduce the binder strength.     

含粉煤灰或石英粉复合胶凝材料的抗压强度发展规律

用细度基本相同的粉煤灰和石英粉作为活性和惰性矿物掺和料,研究了不同水胶比、不同养护温度条件下,矿物掺和料的种类和掺量对复合胶凝材料抗压强度发展特性的影响.在水化初期,颗粒形貌等物理因素比反应程度等化学因素更能影响含有矿物掺和料的复合胶凝材料的抗压强度发展特性,活性与惰性矿物掺和料的作用基本相同.热激发能明显促进粉煤灰的火山灰反应,有利于含粉煤灰的复合胶凝材料的抗压强度发展.含大掺量粉煤灰的复合胶凝材料特别适合用于内部能较长时间维持较高温度的大体积混凝土结构.     

Pore structure characteristics of MgO–SiO2 binder

This paper reports on an investigation into the pore structure characteristics of MgO–SiO₂ binders. Paste specimens were prepared using two MgO/SiO₂ ratios (1 and 1.5), two silica sources (Silica fume-SF and Metakaolin-MK), two water to binder ratios (0.5 and 0.6) and compared to a portland cement (PC) control mix. Mercury intrusion porosimetry was used to understand the evolution of pore structural features of the binder with hydration period. A continued reduction in porosity and refinement of pores was observed with the progress in hydration irrespective of the type of the silica source or the initial MgO/SiO₂ ratio. The MgO–MK mixes exhibited a finer and denser microstructure as compared to the equivalent MgO–SF mixes. The formation of hydrotalcite in addition to M-S-H in MgO–MK mixes was postulated to be the primary reason for the difference in microstructural characteristics, compared to MgO–SF mixes. The space-filling capacity of hydration products of MgO–MK binder was found to be better than PC.     

Heat of hydration of Portland Cement–Metakaolin–Fly ash (PC–MK–PFA) blends

In the present study two pozzolanic materials are used, Metakaolin (MK) and Fly Ash (PFA), as binary and ternary partial replacement binders with Portland cement (PC) to investigate their effect on the rate of heat evolution (dQ/dt in J/gh) during hydration, and the heat of hydration, (Q(t) in J/g). For binary PC–PFA blends PC hydration is enhanced in the very early stages of hydration, but at extended periods (up to 120 h) an increase in PFA replacement level causes a systematic reduction in heat output. For binary PC–MK blends the results suggest that the MK initially diminishes PC hydration but the subsequent pozzolanic reaction of MK increasingly contributes to the heat output causing some blends to exceed the heat output of the PC control. For both systems a principal controlling factor in the PC hydration rate (and the heat evolution rate) is the water requirement of the pozzolan, but for PC–MK blends the pozzolanic reaction of the MK makes a significant contribution to the heat output. However this reaction is controlled both by the availability of water and the supply of Ca²⁺ ions from the hydrating PC which introduces an increasing level of complexity to the heat output versus time profiles. When combining MK and PFA in ternary PC–MK–PFA blends the MK has a dominant influence on the heat output versus time profiles.     

含有活性或惰性掺合料的复合胶凝材料硬化浆体的微观结构特征

用压汞法测定了不同温度条件下养护的含有粉煤灰或石英粉的复合胶凝材料硬化浆体的孔隙率.用扫描电镜观察了硬化浆体的微观形貌,同时测定了各种组成的复合胶凝材料的净浆强度.常温水化初期,活性与惰性矿物掺合料都只具有物理填充的作用,硬化浆体的孔隙率和强度由矿物掺合料的掺量所决定.高温水化条件下粉煤灰的火山灰反应提前发生.随水化龄期延长,粉煤灰逐渐发生火山灰反应,使硬化浆体结构密实,其强度逐步提高.活性与惰性矿物掺合料对复合胶凝材料浆体结构与性能的影响的差异在水化后期逐渐显现.     

Characterization of acrylic copolymers applied in negative-type photoresist via a ternary composition diagram

Three-component acrylic copolymers used as a binder for negative-type photoresists were synthesized and characterized. First, free radical polymerization was employed to synthesize two-component binders, i.e., acrylic ester copolymers with different ratios of benzyl methacrylate (BZMA) and methacrylic acid (MAA). Thermal behavior, viscosity and molecular weight of the prepared two-component binders were studied. Then, a series of three-component binders were prepared through incorporation of another monomer, 2-hydroxyethyl methacrylate (2-HEMA). FTIR was used to examine the evolution of chemical bonds at various stages of the synthetic process. Thermal analyses, TGA and DSC, were used to evaluate the level of enhancement on thermal stabilities of the prepared three-component binders. Finally, an optimal region in the ternary composition diagram of BZMA, MAA, and 2-HEMA can be identified by comparing the results of acid value, viscosity, and molecular weight of the binder. A negative-type photoresist was prepared using an optimized composition, for which resolution of the circuit could reach the level of 6 μm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Sodium silicate activated slag‐fly ash binders: Part I – Processing,microstructure, and mechanical properties

Alkali silicate activated slag and class F fly ash‐based binders are ambient curing, structural materials that are feasible replacements for ordinary Portland cement (OPC). They exhibit advantageous mechanical properties and less environmental impact than OPC. In this work, five sodium silicate activated slag‐fly ash binder mixtures were developed and their compressive and flexural strengths were studied as a function of curing temperature and time. It was found that the strongest mixture sets at ambient temperature and had a Weibull average flexural strength of 5.7 ± 1.5 MPa and Weibull average compressive strength of 60 ± 8 MPa at 28 days. While increasing the slag/fly ash ratio accelerated the strength development, the cure time was decreased due to the formation of calcium silicate hydrate (C–S–H), calcium aluminum silicate hydrate (C–A–S–H), and (Ca,Na) based geopolymer. The density, microstructure, and phase evolution of ambient‐cured, heat‐cured, and heat‐treated binders were studied using pycnometry, scanning electron microscopy, energy dispersive X‐ray spectroscopy (SEM‐EDS), and X‐ray diffraction (XRD). Heat‐cured binders were more dense than ambient‐cured binder. No new crystalline phases evolved through 28 days in ambient‐ or heat‐cured binders.     

Fuel briquettes from brown coals of Yakutia

Experimental data on the development of technology for the manufacture of briquetted fuel from brown coals with the use of various petroleum binders are presented. The influence of the moisture content, the coal particle-size composition, the binder type and concentration, the compacting pressure, and heat treatment regimes on the mechanical properties of the materials was studied. The optimal compositions and optimal values of the engineering parameters for the production of graded briquetted fuel from brown coals of the Kangalassy deposit in the Republic of Sakha (Yakutia) were established.     

Chemical factors that influence the performance of mine sulphidic paste backfill

Sulphide-rich tailings from four Canadian mines were sampled (Mines A1, A2, B and C) to prepare several different paste backfill mixtures. The sulphur grade within these tailings samples range from 5 to 32 wt.%. The binders used were Portland-cement-based binders, fly-ash-based binders and slag-based binders with proportions ranging from 3 to 6 wt.%. The study was carried out in two stages. Stage I allowed us to understand the effects of binder type, binder proportion and tailings properties on compressive strength development of paste backfill during the course of curing time. It was pointed out that for high sulphide tailings, neither the slag-based binders nor the fly-ash-based binders were effective, whereas the sulphate-resistant-based binder (mix of Type I [TI] and Type V [TV] Portland cements) gave good long-term strength. However, the slag-based binders gave the best strength for low and medium sulphide-bearing tailings for which the Portland- and the fly-ash-based mixtures have a relatively low strength. Stage II allowed us to study the early stage strength acquisition of the various mixtures. It was found that the chemical composition of the mixing water plays a role on the mechanical behavior of certain cemented backfills.     

Alkali activation of a novel calcium‐silicate hydraulic binder with CaO/SiO2 = 1.1

A quasi‐amorphous low‐calcium‐silicate hydraulic binder, with an overall CaO/SiO₂ (C/S) molar ratio of 1.1, was produced. This cementitious material was then hydrated with aqueous solutions containing 3 wt% alkalis (either NaOH, Na₂CO₃ or Na₂SiO₃). The evolution of the hydration processes of the samples were monitored by compressive strength testing, XRD, FTIR, ²⁹Si and ²⁷Al MAS NMR, isothermal calorimetry and TGA. It was found that the nearly exclusive hydration product formed was a C‐S‐H phase with a semi‐crystalline structure. More importantly, the paste prepared with the Na₂SiO₃ solution developed compressive strength values similar to those of ordinary portland cements (OPC) with faster early age kinetics. In addition, the isothermal calorimetry results indicated that these new hydraulic binders present much lower heat of hydration values compared with a traditional OPC. The results presented here open the possibility of producing cement with a compressive strength comparable to that of OPC but with lower CO₂ emissions during the production process and with lower hydration heat related problems during the production of concrete structures.     

Some features of the production of thermal-shock-resistant cast corundum materials in ethyl silicate binders

Conclusions The use of ethyl silicate binders of an optimal composition makes it possible to produce cast corundum articles with a mullite-corundum binder with excellent characteristics.The best combination of properties is found in the articles when binders of optimal composition, close to stoichiometric, are used in the hydrolysis reaction of the ethyl silicate.The destruction and sintering processes in the corundum casts in an ethyl silicate binder during heat treatment are produced by the destruction kinetics of the hydrolysis products of the ethyl silicate and by the presence in them of active SiO₂. The sintering of articles of such a composition begins at 1100°C. The excellent thermal-shock resistance of the ceramic made from masses with ethyl silicate binders and the slower destruction of these ceramics result from the rational phase composition and structure of the material.Translated from Ogneupory, No. 2, pp. 35–39, February, 1982.     

Thermal Decomposition of RDX Composite Propellants

The thermal decomposition characteristics of RDX, binders, and RDX composite propellants were studied using thermal analytical techniques. Three kinds of binders were tested to elucidate the role of binder on the burning rate of the propellants. There were no apparent correlations between the thermal decomposition rates of binders and the burning rates of propellants, whereas there was a correlation between the decomposition temperature and the burning rate of the propellants. It is found that the major factor which controls the burning rate is the initial thermal-decomposition stage of the binders. Thus, the burning rate of nitramine composite propellants appeared to be largely dependent on the physical and chemical properties of binder.     

一种水性负极黏结剂的合成及性能

黏结剂对电极的性能有着重要的影响。本文设计并制备了一种新型水性聚(乙烯-乙烯醇)-磺酸锂（EVOH-SO₃Li,简称ES-Li）电极黏结剂,并对其键接结构及组成进行分析;对其溶解性、电解液稳定性、热稳定性进行测试;对所制电极柔性、微观形貌及电化学性能进行研究。经与聚(乙烯-乙烯醇)（EVOH）及商业的聚偏氟乙烯（PVDF）黏结剂进行对比。结果表明：ES-Li水性黏结剂具有不溶解于电解液,热稳定性良好等优点;ES-Li黏结剂制备负极柔性及微观形貌优良,采用ES-Li作为负极黏结剂的电池在电化学稳定窗口、界面阻抗、首次循环效率、循环及倍率等方面均表现优异,ES-Li负极的首次库仑效率为89.93%,在1C下循环100次的容量保持率为96.93%,且在2C、5C倍率下的循环性能均优于EVOH及PVDF制备的负极,具有应用潜力及商业化前景。     

Modeling of hydration reactions using neural networks to predict the average properties of cement paste

This paper presents a hydration model that describes the evolution of cement paste microstructure as a function of the changing composition of the hydration products. The hydration model extends an earlier version by considering the reduction in the hydration rate that occurs due to the reduction of free water and the reduction of the interfacial area of contact between the free water and the hydration products. The BP Neural Network method is used to determine the coefficients of the model. Using the proposed model, this paper predicts the following properties of hardening cement paste: the degree of hydration, the rate of heat evolution, the relative humidity and the total porosity. The agreement between simulation and experimental results proves that the new model is quite effective and potentially useful as a component within larger-scale models designed to predict the performance of concrete structures.     

固体推进剂用粘合剂研究进展

介绍了固体推进剂用粘合剂的研究进展,着重介绍了丁羟类、叠氮类、HTPE、NEPE以及硝基和硝酸酯类粘合剂的合成、工艺以及性能研究情况,并对未来固体推进剂用粘合剂的发展进行了展望。     

Mechanical and lamination properties of alumina green tapes obtained by aqueous tape-casting

Mechanical characterisation and lamination were carried out on alumina green tapes prepared by aqueous tape casting using two acrylic emulsions having different glass transition temperatures (T_g) as binders. The tensile strength and strain were strongly dependent on the binder nature and content. Namely, the mechanical properties of the green tapes reflected those of the binders at room temperature: the green tapes obtained with the higher T_g binder showed a brittle behaviour, whereas those obtained with the lower T_g binder showed an elastoplastic behaviour. The mechanical properties of the green tapes prepared by mixing the two acrylic binders lies in between, giving the possibility of tailoring the flexibility and strength in the range of the values obtained for pure binders. Lamination gave rise to an increase of both green and sintered densities, compared with monolayer specimens, whatever the composition of the binder system. Such improvements significantly depended on lamination pressure, but were insensitive to lamination temperature for the two temperatures tested higher than the T_g of the two binders. ©