Hydration and properties of novel blended cements based on cement kiln dust and blast furnace slag

The aim of the present paper is to address the key technical issues pertaining to the utilization of cement kiln dust (CKD) as an activator for ground granulated blast furnace slag (GGBFS) to create nonconventional cementitious binders for concrete. The relatively high alkaline content of CKD is the predominant factor preventing its recycling in cement manufacture. However, it was observed that depending on the water-soluble alkali and sulfate compounds, CKD could provide the environment necessary to activate latent hydraulic materials such as GGBFS. Binary blends containing slag and CKDs from different sources were characterized and compared in terms of the rates of heat evolution and strength development, hydration products, and time of initial setting. A study of the effects of the influencing factors in terms of soluble alkali content, particle size, and free lime content was undertaken. The results confirm the dependence of the dissolution rate of slag on the alkalinity of the reacting system, and the importance of the optimum lime content on the rate of strength gain.     

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.     

Characterization of cement minerals, cements and their reaction products at the atomic and nano scale

Recent advances and highlights in characterization methods are reviewed for cement minerals, cements and their reaction products. The emphasis is on X-ray and neutron diffraction, and on nuclear magnetic resonance methods, although X-ray absorption and Raman spectroscopies are discussed briefly.     

Quantitative study of Portland cement hydration by X-ray diffraction/Rietveld analysis and independent methods

X-ray diffraction (XRD) is a powerful technique for the study of crystalline materials. The technique of Rietveld refinement now enables the amounts of different phases in anhydrous cementitious materials to be determined to a good degree of precision. This paper describes the extension of this technique to a pilot study of the hydration of a typical Portland cement. To validate this XRD-Rietveld analysis technique, its results were compared with independent measures of the same materials by the analysis of backscattered electron images (BSE/IA) and thermogravimetric analysis (TGA). In addition, the internal consistency of the measurements was studied by comparing the XRD estimates of the amounts of hydrates formed with the amounts expected to form from the XRD estimates of the amounts of anhydrous materials reacted.     

Influence of superplasticizers on the hydration of cement and the pore structure of hardened cement

This paper describes the influence of various types of superplasticizers such as naphthalene type (β-NS), refined lignin sulfonate type (LS) and polycarboxylate types (P34, S34) on the hydration of cement and the pore structure of hardened cement. Other superplasticizers except β-NS delayed the initial hydration of cement. In any case, it hardly influences the hydration reaction at late stage of cement. The retardation by the addition of superplasticizers is not observed after 28 days of curing. Large pores of 0.1 μm or more for hardened cement with LS or β-NS are larger than those of hardened samples with P34 or S34 cured for 28, 56 and 91 days. This is related to the coagulated structures of fresh cement pastes with various types of superplasticizers. It was presumed that the size of the cluster of aggregated particles became small when S34 or P34 that has a high dispersing ability was added compared to LS or β-NS that has a lower dispersing ability.     

Thermal analysis of borogypsum and its effects on the physical properties of Portland cement

Borogypsum, which consists mainly of gypsum crystals, B₂O₃ and some impurities, is formed during the production of boric acid from colemanite, which is an important borate ore. In this study, the effect of borogypsum and calcined borogypsum on the physical properties of ordinary Portland cement (OPC) has been investigated. The calcination temperature and transformations in the structures of borogypsum and natural gypsum were determined by differential thermal analysis (DTA), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques. Thermal experiments were carried out between ambient temperature and 500 °C in an air atmosphere at a heating rate of 10 °C min⁻¹. After calculation of enthalpy and determination of conversion temperatures, borogypsum (5% and 7%), hemihydrate borogypsum (5%) and natural gypsum (5%) were added separately to Portland cement clinker and cements were ground in the laboratory. The final products were tested for chemical analysis, compressive strength, setting time, Le Chatelier expansion and fineness properties according to the European Standard (EN 196). The results show that increasing the borogypsum level in Portland cement from 5% to 7% caused an increase in setting time and a decrease in soundness expansion and compressive strength. The cement prepared with borogypsum (5%) was found to have similar strength properties to those obtained with natural gypsum, whereas a mixture containing 5% of hemihydrate borogypsum was found to develop 25% higher compressive strength than the OPC control mixtures at 28 days. For this reason, utilization of calcined borogypsum in cement applications is expected to give better results than untreated borogypsum. It is concluded that hemihydrate borogypsum could be used as a retarder for Portland cement as an industrial side. This would play an important role in reducing environmental pollution.     

Study of the influence of superplasticizers on the hydration of cement paste using nuclear magnetic resonance and X-ray diffraction techniques

Melamine and naphthalene-based superplasticizers have been used, over the past few decades, in order to improve the workability of concrete. Recently, more efficient copolymer formulations have been introduced for the same purpose. However, the influence of these chemical admixtures on the microstructure of the hardened concrete and, consequently, on its properties still needs to be extensively evaluated. Accordingly, the present work analyzes the hydration characteristics of cement pastes with naphthalene, melamine and copolymer-based superplasticizers, using the techniques of X-ray diffraction (XRD) and nuclear magnetic resonance (NMR), up to the age of 28 days. The results indicate a significant influence of the superplasticizer on the growth rates of the hydrates and on the state of polymerization of the silicates.     

Influence of water activity on belite (β-C2S) hydration

The hydration of the two most reactive phases of ordinary Portland cement (OPC), tricalcium silicate (C₃S), and tricalcium aluminate (C₃A) is successfully halted when the activity of water () falls below critical thresholds of 0.70 and 0.45, respectively. It has been established that the reduction in relative humidity (RH) and  suppresses the hydration of all anhydrous phases in OPC, including less explored phases like dicalcium silicate, that is, belite (β-C₂S). However, the degree of suppression, that is, the critical threshold, for β-C₂S, standalone has yet to be established. This study utilizes isothermal microcalorimetry and X-ray diffraction techniques to elucidate the influence of on the hydration of -C₂S suspensions via incremental replacements of water with isopropanol (IPA). Experimentally, this study shows that with increasing IPA replacements, hydration is increasingly suppressed until eventually brought to a halt at a critical threshold of approximately 27.7% IPA on a weight basis (wt.%_IPA). From thermodynamic estimations, the exact critical threshold and solubility product constant of -C₂S () are established as 0.913 and 10^−12.68, respectively. This study enables enhanced understanding of β-C₂S reactivity and provides thermodynamic parameters during the hydration of β-C₂S-containing cementitious systems such as OPC-based and calcium aluminate-based systems.     

基于灰色关联分析和层次分析法的水泥回转窑用煤质量指标综合评价

本文结合现行国家标准和行业规范,确定水泥回转窑用煤综合评价指标体系和评价指标划分方案,建立基于灰色关联分析和层次分析法（AHP）的水泥回转窑用煤质量等级评价模型,以集团内6家公司进厂煤炭进行综合评价研究。该方法不仅能够反映不同级别样本之间的差别,而且还能反映同一级别的样本质量优劣,可用于不同公司或不同供应商之间的煤炭质量综合评价对比,为回转窑用煤使用价值最大化,合理确定进厂验收指标提供决策依据。     

Langbeinite phosphosilicates K2-xCsxZr2P2SiO12 (x = 0, 0.5, 1.0, 1.5, 2.0) for cesium encapsulation; synthesis,chemical durability and thermal expansion study

The volatization of cesium at high temperatures makes its immobilization challenging to the nuclear scientists. Present work reports the feasibility of cesium incorporation into an orthorhombic langbeinite phosphosilicate. The structural flexibility, leachability and thermal expansion of K_2-xCs_xZr₂P₂SiO₁₂ (x = 0, 0.5, 1.0, 1.5, 2.0) have been investigated. Powder X-ray results authenticates the accommodation of cesium into a single phasic orthorhombic langbeinite structure up to 29.17 wt %. Morphological study reveals the particle agglomeration and poor crystallinity, and vibrational spectral analysis shows peak broadening and peak shift upon increasing the cesium concentration. The static leach test has been performed on the pellet sample and the normalized leaching of Cs is found to be in the order of 10¹ g/m². The average coefficient of thermal expansion for K_0.5Cs_1.5Zr₂P₂SiO₁₂ is registered as 7.45 × 10⁻⁶/K between 303 and 873 K. Cesium insertion into K₂Zr₂P₂SiO₁₂ displays a large deviation in thermal expansion due to the size effect as observed by several researchers for other phosphate and phosphosilicate members.     

Sol-gel processing and characterization of (RE-Y)-zirconia powders for thermal barrier coatings

The effect of doping on the structural, morphological and thermal properties of ZrO₂-XO_1.5 (X = Y, La, Sm, Er) solid solutions for thermal barrier (TBC) applications was investigated. Oxide powders of various compositions from 9.7 to 40 mol% XO_1.5 (X = Y, La, Sm, Er) were synthesised by the sol-gel route. The structural analysis of the powders was performed using X-ray diffraction analysis coupled with Rietveld refinements and the measurement of their specific surface area with the BET method. For each rare earth dopant, the morphology of the powders varies from monoliths to agglomerates of thinner particles when the doping amount increases. In order to determine the specific heat, the thermal diffusivity at room temperature and the thermal expansion coefficient of some selected compositions, DSC, laser thermal diffusivity and high-temperature dilatometry measurements were performed on samples densified by Spark Plasma Sintering. Working thermal characterisation indicated that zirconia doped with 30 mol% SmO_1.5 and ErO_1.5 have better insulation properties and a lower thermal expansion coefficient than our reference YSZ ceramic. These various compositions are very promising for the elaboration of multilayer TBCs by the sol-gel process.     

Influence of 2-hydroxypropyltrimethyl ammonium chloride chitosan on sedimentation and volume change behavior of cohesive soil sediments

The 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC), introducing the functional quaternary ammonium group to the structure of Chitosan, has greatly broadened the application prospect. The influence on natural cohesive soil has rarely been considered. The sedimentation tests for the natural soil in HACC solutions and the HACC-treated soils in distilled water are considered to analyze the change of sedimentation behaviors in this paper. Moreover, the potential change on the surface of soil particles, the change in particle size distribution, X-ray diffraction of Ca-montmorillonite/HACC, and scanning electron microscopy images are investigated to explain the reasons for the results. Results indicate that the surface potential of soil particles achieved reversal, and the particle size had significant agglomeration. The adsorption of HACC results in the rapid sedimentation of the treated soils in water. HACC has a significant influence on setting time and final volume. HACC cannot inhibit the interlayer swelling of Ca-montmorillonite. The dehydration process can promote the aggregation effect of the treated soils. The specific effects provided an essential train of thought to solve soil problems.     

In situ X-ray analysis under controlled potential conditions: An innovative setup and its application to the investigation of ultrathin films electrodeposited on Ag(1 1 1)

An innovative setup to combine electrochemical and in situ surface X-ray diffraction (SXRD) measurements is described. This electrochemical cell has a different design from the other ones commonly used for X-ray diffraction studies. It allows the sample surface to stay always completely immersed into the solution under controlled potential conditions even during the SXRD measurements. The X-ray beam crosses the liquid (about 1 cm) and the cell walls. Because of the high X-ray energy, the beam attenuation is negligible and by an appropriate positioning of the detector arm slits it is possible to minimize the diffuse scattering induced by the liquid and cell walls in order to still detect the minima of the crystal truncation rods (CTRs). The liquid solution in the cell is managed by a special device, which allows the controlled exchange of the electrolyte solutions necessary in the electrochemical atomic layer epitaxy (ECALE) growth. The whole setup can be remotely controlled from outside the experimental hutch by a dedicated computer. As an example we report measurements on S layers deposited at underpotential on the Ag(1 1 1) surface, and on CdS films of increasing thickness.     

Influence of barium borosilicate glass on microstructure and dielectric properties of (Ba,Ca)(Zr,Ti)O3 ceramics

Barium borosilicate (BBS) glass was added as a sintering aid to (Ba_0.7Ca_0.3)TiO₃-Ba(Ti_0.8Zr_0.2)O₃ (BCZT) ceramics at levels from 2 to 15?wt%, yielding enhanced densification. The addition of BBS also induced changes in phase composition, from predominantly tetragonal to orthorhombic at room temperature. It is shown that the changes in phase content are caused by a shift of the orthorhombic to tetragonal phase transformation from below room temperature to ≈50?°C. An additional high temperature transition around 120?°C was also identified. These observations are interpreted in terms of the development of chemical heterogeneity associated with the redistribution of dopant elements (particularly Zr and Ca) through the liquid phase during sintering. The relative permittivity and electric field-induced polarisation values were generally degraded by the presence of the glass phase, but a reduction in ferroelectric hysteresis and improved densification behaviour have potential benefits in dielectric energy storage applications.     

Influence of Se and Te substitutions at Tl-site of Tl(Ba,Sr)CaCu2O7 superconductor on the AC susceptibility and electrical properties

The Sr and Ba bearing Tl-1212 phase, Tl(Ba,Sr)CaCu₂O₇ is an interesting superconductor. The Sr only bearing TlSr₂CaCu₂O₇ is not easily prepared in the superconducting form. The Ba only bearing TlBa₂CaCu₂O₇ on the other hand does not show improvement in the transition temperature with elemental substitution. In this work the influence of multivalent Se (non-metal) and Te (metalloid) substitutions at the Tl-site of Tl_1-xM_x(Ba,Sr)CaCu₂O₇ (M = Se or Te) superconductors for x = 0–0.6 was studied. The samples were prepared via the conventional solid-state reaction method. XRD patterns showed a single Tl-1212 phase for x = 0 and 0.1 Se substituted samples. The critical current density at the peak temperature, T_p of the imaginary (χ”) part of the AC susceptibility (χ = χ’ +χ”), J_c-inter(T_p) for all samples was between 15 and 21 A cm⁻². The highest superconducting transition temperature was shown by the x = 0.3 Se-substituted sample (T_c-onset = 104 K, T_c-zero = 89 K, T_cχ’ = 104 K and T_p = 80 K). Te suppressed the superconductivity of Tl-1212 phase. The order of highest transition temperatures are as follows: Tl_1-xTe_x(Ba,Sr)CaCu₂O₇<Tl(Ba,Sr)CaCu₂O₇<Tl_1-xSe_x(Ba,Sr)CaCu₂O₇. This work showed that Se was better than Te in improving the transition temperature and flux pinning of the Tl-1212 phase. The roles of ionic radius of Se and Te on the superconductivity of Tl(Ba,Sr)CaCu₂O₇ are discussed in this paper.     

Unraveling the cause for the unusual processing behavior of commercial partially bio-based poly(butylene succinates) and their stabilization

The commercially available partially bio-based poly(butylene succinate) (PBS) and poly(butylene succinate-co-adipate) (PBSA) are subjected to prolonged and multiple extrusion cycles to investigate their thermal behavior. Empirically, both PBS and PBSA form branches at 190°C, with PBS possessing a higher tendency for branching than PBSA as studied by rheology and size exclusion chromatography (SEC). In each case, the branching is favored by fumaric acid moieties, making both PBS and PBSA susceptible to accelerated thermal oxidation. Indeed, the NMR signal attributed to fumaric acid disappears upon thermal processing of PBS and PBSA. Presumably, the bio-based succinic acid used contains minor quantities of fumaric acid, yet still sufficient to cause this surprising processing behavior. The branching of both polymers is suppressed by stabilizers such as phenolic antioxidants, as proven by rheology and SEC. This is complemented by nuclear magnetic resonance (NMR), revealing that the fumaric acid signal is still well-resolved in the stabilized processed samples.     

A flow cell for transient voltammetry and in situ grazing incidence X-ray diffraction characterization of electrocrystallized cadmium(II) tetracyanoquinodimethane

An easy to fabricate and versatile cell that can be used with a variety of electrochemical techniques, also meeting the stringent requirement for undertaking cyclic voltammetry under transient conditions in in situ electrocrystallization studies and total external reflection X-ray analysis, has been developed. Application is demonstrated through an in situ synchrotron radiation-grazing incidence X-ray diffraction (SR-GIXRD) characterization of electrocrystallized cadmium (II)-tetracyanoquinodimethane material, Cd(TCNQ)₂, from acetonitrile (0.1 mol dm⁻³ [NBu₄][PF₆]). Importantly, this versatile cell design makes SR-GIXRD suitable for almost any combination of total external reflection X-ray analysis (e.g., GIXRF and GIXRD) and electrochemical perturbation, also allowing its application in acidic, basic, aqueous, non-aqueous, low and high flow pressure conditions. Nevertheless, the cell design separates the functions of transient voltammetry and SR-GIXRD measurements, viz., voltammetry is performed at high flow rates with a substantially distended window to minimize the IR (Ohmic) drop of the electrolyte, while SR-GIXRD is undertaken using stop-flow conditions with a very thin layer of electrolyte to minimize X-ray absorption and scattering by the solution.     

Effect of a small amount of poly(3‐hydroxybutyrate) on the crystallization behavior of poly(l‐lactic acid) in their immiscible and miscible blends during physical aging

The miscibility and effect of physical aging on the crystallization behavior of poly(l ‐lactic acid) (PLLA)/poly(3‐hydroxybutyrate) (PHB) blends with a small amount of PHB (≤10 wt%) have been investigated using differential scanning calorimetry and Fourier transform infrared spectroscopy. It is found that the miscibility of PLLA/PHB blends with a very small percentage of PHB can be modulated by varying the molecular weight of the PHB. That is, a PLLA/PHB blend with low‐molecular‐weight PHB is miscible, whereas that with high‐molecular‐weight PHB is immiscible. It is found that physical aging at temperatures far below the glass transition temperature can promote the cold crystallization kinetics of PLLA in PLLA/PHB blends with high‐molecular‐weight PHB rather than in those with low‐molecular‐weight PHB. These findings suggest that the effect of physical aging on the crystallization behavior of the main component in a crystalline/crystalline blend with a small percentage of the second component is strongly dependent on the miscibility of the blend system. Enhanced chain mobility of PLLA in the interface region of PLLA matrix and PHB micro‐domains is proposed to explain the physical aging‐enhanced crystallization rate in immiscible PLLA/PHB blends with high‐molecular‐weight PHB. © 2013 Society of Chemical Industry     

Effect of hydrophilic and hydrophobic cyclodextrins on the release of encapsulated allyl isothiocyanate (AITC) and their potential application for plastic film extrusion

Allyl isothiocyanate (AITC), a natural pungent flavor from wasabi and horseradish, is well-known antimicrobial agents against foodborne pathogens. However, its highly volatile nature and low thermal stability restrict its application in the food packaging industry. Also, its strong organoleptic characteristics hinder its application at a higher dosage. We encapsulated AITC in β-cyclodextrin (β-CD) and triacetyl-β-CD (TA-β-CD) and evaluated the performance as slow releasing active compounds through low-density polyethylene (LDPE)–cyclodextrins (CDs) matrix. Also, the thermal, optical, mechanical, and barrier properties of two ternary blends, LDPE/β-CD/AITC(L-CDs) and LDPE/TA-β-CD/AITC(L-TACDs), were investigated to compare their compatibility under the plastic extrusion process. During the 15 days of the storage period, L-TACDs maintained more consistent AITC release and a higher concentration than L-CDs. Also, the blending of LDPE and TA-β-CD was more compatible with that of LDPE and β-CD. No significant optical, mechanical, and barrier property changes were observed in LDPE with less than 3% of TA-β-CD while L-CDs showed substantial agglomeration on the ternary blend films and the lower mechanical and barrier properties than pure LDPE. The results indicate that the LDPE films containing TA-β-CD/AITC can be applied as an effective antimicrobial packaging material for food and nonfood applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48137.     

Reinforcement on the mechanical‐, thermal‐, and water‐resistance properties of the wood flour/chitosan/poly(vinyl chloride) composites by physical and chemical modification

In this study, we aimed to physically and chemically modify wood flour (WF)/chitosan (CS) mixtures to reinforce the mechanical‐, thermal‐, and water‐resistance properties of WF/CS/poly(vinyl chloride) (PVC) composites with a three‐step modification process. This was a vacuum‐pressure treatment of sodium montmorillonite, inner intercalation replacement of organically modified montmorillonite, and surface grafting of glycidyl methacrylate (GMA). The untreated and modified mixtures were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy–energy‐dispersive spectroscopy, thermogravimetric analysis, and contact angle measurement. Meanwhile, the mechanical strengths and water absorption of WF/CS/PVC were estimated. The results indicate that the samples had a better performance after they were modified by montmorillonite (MMT) + GMA than when they were modified by only MMT. MMT and GMA showed a very synergistic enhancement to the mechanical‐, thermal‐, and water‐resistance properties of the WF/CS/PVC composites. Specifically, the maximum flexural and tensile strengths were increased by 10.59 and 12.28%, respectively. The maximum water absorption rate was decreased by 61.99%, and the maximum degradation temperature was delayed to the higher value from 314.3 and 374.9°C in the untreated sample to 388.8 and 412.8°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40757.