Artículos de revistas: "Aluminates de calcium hydraté"

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Madej, Dominika. "Strontium Retention of Calcium Zirconium Aluminate Cement Paste Studied by NMR, XRD and SEM-EDS". Materials 13, n.º 10 (21 de mayo de 2020): 2366. http://dx.doi.org/10.3390/ma13102366.

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This work concerns the hydration mechanism of calcium zirconium aluminate as a ternary compound appearing in the CaO-Al2O3-ZrO2 diagram besides the calcium aluminates commonly used as the main constitutes of calcium aluminate cements (CACs). Moreover, a state-of-the-art approach towards significant changes in hydraulic properties was implemented for the first time in this work, where the effect of structural modification on the hydration behavior of calcium zirconium aluminate was proved by XRD, 27Al MAS NMR and SEM-EDS. The substitution of Sr2+ for Ca2+ in the Ca7ZrAl6O18 lattice decreases the reactivity of Sr-substituted Ca7ZrAl6O18 in the presence of water. Since the original cement grains remain unhydrated up to 3 h (Ca7ZrAl6O18) or 72 h (Sr1.25Ca5.75ZrAl6O18) of curing period in the hardened cement paste structures, strontium can be considered as an inhibition agent for cement hydration. The complete conversion from anhydrous 27AlIV to hydrated 27AlVI species was achieved during the first 24 h (Ca7ZrAl6O18) or 7 d(Sr1.25Ca5.75ZrAl6O18) of hydration. Simultaneously, the chemical shift in the range of octahedral aluminum from ca. 4 ppm to ca. 6 ppm was attributed to the transformation of the hexagonal calcium aluminate hydrates and Sr-rich (Sr,C)3AH6 hydrate into the cubic phase Ca-rich (Sr,C)3AH6 or pure C3AH6 in the hardened Sr-doped cement paste at the age of 7 d. The same 27Al NMR chemical shift was detected at the age of 24 h for the reference hardened undoped Ca7ZrAl6O18 cement paste.

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2

Durczak, Karol, Michał Pyzalski, Tomasz Brylewski y Agnieszka Sujak. "Effect of Variable Synthesis Conditions on the Formation of Ye’elimite-Aluminate-Calcium (YAC) Cement and Its Hydration in the Presence of Portland Cement (OPC) and Several Accessory Additives". Materials 16, n.º 17 (3 de septiembre de 2023): 6052. http://dx.doi.org/10.3390/ma16176052.

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In the presented study, ye’elimite-aluminate-calcium (YAC) cement was synthesized. Complete synthesis of crystalline phases was achieved at a temperature of 1300 °C, which is 150 °C lower than the temperature standardly used in the processes of obtaining calcium aluminate cements (CAC). The greatest amount of ye’elimite phase (Klein complex), roughly 87% by mass, was acquired utilizing a sulphur ion transporter derived from artificial dihydrate gypsum obtained in the flue gas desulphurization process (variation I). In the case of anhydrite, the amount of synthesized crystalline ye’elimite in the clinker was 67% by weight (variant II). Depending on the synthesis conditions in the clinkers, the quantity of obtained calcium aluminates (C12A7, CA, and CA2) ranged from 20 to 40% by weight. Studies on the hydration process of YAC cement samples showed that the main products are hydrated calcium aluminates and dodecahydrate calcium alumino-sulphate. In sinters of YAC and OPC, no crystalline ettringite was observed. Hydration analysis of Chinese cement revealed the presence of crystalline ettringite and dodecahydrate calcium alumino-sulphate, as well as hydrated calcium silicates of the CSH type accompanied with pseudo-crystalline Al(OH)3. The obtained clinkers from variants I and II constitute a special binder, which, due to its phase composition after hydration, can be used in the construction of reactors for biogas production in eco-energy applications.

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3

Das, S. K., A. Mitra y P. K. Das Poddar. "Thermal analysis of hydrated calcium aluminates". Journal of Thermal Analysis 47, n.º 3 (septiembre de 1996): 765–74. http://dx.doi.org/10.1007/bf01981812.

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4

Liu, Peng, Zhi Wu Yu, Ling Kun Chen y Zhu Ding. "Study on Hydration Mechanism of Phosphoaluminate Cement". Materials Science Forum 675-677 (febrero de 2011): 701–4. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.701.

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Phosphoaluminate cement (PAC) is a kind of new cementitious material which has many special properties compared to Portland cement (PC). PAC sets quickly and develops early-high strength. In order to investigate the hydration mechanism, the hydration products and microstructure of PAC were studied with x-ray diffraction (XRD), electron scanning microscope (SEM) and electrochemical impedance spectroscopy (EIS). Heat evolution of PAC was also measured. The results show that the hydration mechanism of PAC is different from Portland cement, which is caused by the special minerals including CxP, CA(P), phase L, and so on. The main hydration products of PAC are calcium phosphorus aluminates hydrate (C-A-P-H), calcium phosphate hydrate (C-P-H), aluminates hydrate (C-A-H), the corresponding hydration microcrystal as well as gels. Also, there is no calcium hydroxide produced during hydration. The hydration procedure of PAC is divided into four stages which are dissolution and induction, acceleration, deceleration, stabilization.

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5

Dung Nguyen, Tien y Jean Ambroise. "Contribution of calcium aluminates to the water resistance of hydrated calcium sulfates". IOP Conference Series: Materials Science and Engineering 869 (10 de julio de 2020): 032051. http://dx.doi.org/10.1088/1757-899x/869/3/032051.

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6

Torréns-Martín, David, Lucia Fernández-Carrasco, Sagrario Martínez-Ramírez, Jordi Ibáñez, Lluis Artús y Thomas Matschei. "Raman Spectroscopy of Anhydrous and Hydrated Calcium Aluminates and Sulfoaluminates". Journal of the American Ceramic Society 96, n.º 11 (1 de octubre de 2013): 3589–95. http://dx.doi.org/10.1111/jace.12535.

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7

Segura Sierpes, Yasna, María Victoria Borrachero Rosado, José María Monzó Balbuena y Jordi Payá Bernabeu. "Preliminary studies on hydrated cement for its reuse in geopolymers". DYNA 83, n.º 196 (20 de abril de 2016): 229–38. http://dx.doi.org/10.15446/dyna.v83n196.54189.

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<p>The carbonation of hydrated ordinary Portland cement (OPC) allows the transformation of hydrated calcium aluminates and silicates into calcium carbonate and amorphous silica/ alumina. These carbonated materials are appropriate to being used as inorganic precursors for alkaline activation. The use of sodium silicate and hydroxide solutions enables the production of cementitious gels. Two ways of carbonation of hydrated cement were studied: in a dry environment, where relative humidity did not exceed 70% and in an aqueous medium at a temperature of 5 ± 1 ° C. Both materials were micro-structurally characterised and they have been used for the manufacturing of geopolymeric mortars. These mortars reached mechanical strength between 10 and 20 MPa, depending on the activating solution, the water/binder ratio and curing time/temperature. These results show the feasibility of reusing hydrated cement contained in construction and demolition wastes.</p>

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8

Dai, Lei y Xiao Xuan Deng. "The Relationship between Calcium Hydroxide Concentration in Pore Solution and the Strength of Stabilized Soils". Advanced Materials Research 989-994 (julio de 2014): 19–22. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.19.

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Under the same cement content, the stabilized soils, made of the soils with similar physical properties, may be significant difference in the strength. In this research, three groups of soils were selected, and the soils in each group are similar in physical properties. Strength and ions concentration in pore solution of the stabilized soils were investigated. The result reveals that calcium hydroxide (CH) concentration in pore solution of the stabilized soils might not reach to saturation due to soil consuming Ca2+and thus cause calcium silicate hydrates gels (C-S-H) and calcium aluminates hydrates gels (C-A-H) to form less. The cementitious hydrates are the main strength contributors of the stabilized soils. The Strengths of stabilized soils, the soils bearing similar physical properties, were almost identical as long as the CH concentrations in pore solution were saturated. The effect of chemical factors of soil on the strength of stabilized soil can be briefly attributed to the change of CH concentration in pore solution, and be further attributed to the influence of CH concentration on the amount of C-S-H and C-A-H formed in stabilized soils.

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9

Costa, C., P. Marques y P. A. Carvalho. "An SEM Investigation of the Pozzolanic Activity of a Waste Catalyst from Oil Refinery". Microscopy and Microanalysis 18, S5 (agosto de 2012): 75–76. http://dx.doi.org/10.1017/s1431927612013037.

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The most active phase of the fluid catalytic cracking (FCC) catalyst, used in oil refinery, is zeolite-Y which is an aluminosilicate with a high internal and external surface area responsible for its high reactivity. Waste FCC catalyst is potentially able to be reused in cement-based materials - as an additive - undergoing a pozzolanic reaction with calcium hydroxide (Ca(OH)2) formed during cement hydration. This reaction produces additional strength-providing reaction products i.e., calcium silicate hydrate (C-S-H) and hydrous calcium aluminates (C-A-H) which exact chemical formula and structure are still unknown. Partial replacement of cement by waste FCC catalyst has two key advantages: (1) lowering of cement production with the associated pollution reduction as this industry represents one of the largest sources of man-made CO2 emissions, and (2) improving the mechanical properties and durability of cement-based materials. Despite these advantages, there is a lack of fundamental knowledge on pozzolanic reaction mechanisms as well as spatial distribution of porosity and solid phases interactions at the microstructural level and consequently their relationship with macroscopical engineering properties of catalyst/cement blends.

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10

Mazur, Anton, Peter Tolstoy y Konstantinos Sotiriadis. "13C, 27Al and 29Si NMR Investigation of the Hydration Kinetics of Portland-Limestone Cement Pastes Containing CH3-COO−-R+ (R=H or Na) Additives". Materials 15, n.º 6 (8 de marzo de 2022): 2004. http://dx.doi.org/10.3390/ma15062004.

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The hydration kinetics of Portland-limestone cement pastes with organic additives in the form of acetic acid and sodium acetate were studied by using solid-state 13C, 27Al and 29Si NMR spectroscopy. The evolution of the relative content of various phases was monitored over the period of one month: amorphous and crystalline calcite (in 13C spectra), ettringite, aluminum in C-S-H gel, calcium aluminates and calcium hydroaluminates (in 27Al spectra), as well as alite, belite and silicon in C-S-H gel (in 29Si spectra). The retarding effect of the additives on cement hydration at early age was demonstrated. We show that the kinetics of phase assemblage formation is influenced by the acetate ion adsorption on the surface of the anhydrous cement components and hydrated phases. The kinetics of formation of ettringite in the cement paste, depending on the addition of acetic and or sodium acetate, is discussed in the context of potential thaumasite sulfate attack.

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11

Wang, Ru y Pei-Ming Wang. "Formation of hydrates of calcium aluminates in cement pastes with different dosages of SBR powder". Construction and Building Materials 25, n.º 2 (febrero de 2011): 736–41. http://dx.doi.org/10.1016/j.conbuildmat.2010.07.013.

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12

Holmes, Niall, Mark Russell, Geoff Davis y Mark Tyrer. "Comparing the Measured and Thermodynamically Predicted AFm Phases in a Hydrating Cement". Applied Sciences 12, n.º 19 (9 de octubre de 2022): 10147. http://dx.doi.org/10.3390/app121910147.

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In hydrating Portland cements, more than one of the AFm family of calcium aluminates may exist. Depending on the amount of carbonate and sulfate present in the cement, the most common phase to precipitate is monosulfate, monocarbonate and/or hemicarbonate. It has been reported in the literature that hemicarbonate often appears in measurements such as XRD but not predicted to form/equilibrate in thermodynamic models. With the ongoing use of commercial cements such as CEM I and CEM II containing more and more limestone, it is important to understand which hydrate solids physically precipitate and numerically predict over time. Using 27 cement samples with three w/c ratios analysed at 1, 3 and 28 days, this paper shows that although hemicarbonate was observed in a hydrating commercial Portland cement, as well as being predicted based on its carbonate (CO2/Al2O3) and sulfate (SO3/Al2O3) ratios, thermodynamic analysis did not predict it to equilibrate and form as a solid hydrate. Regardless of the w/c ratio, thermodynamic analysis did predict hemicarbonate to form for calcite contents < 2 wt.%. It appears that the dominant stability of monocarbonate in thermodynamic models leads to it precipitating and remaining as a persistent phase.

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13

Rahhal, Viviana Fátima, Mónica Adriana Trezza, Alejandra Tironi, Claudia Cristina Castellano, Milena Pavlíková, Jaroslav Pokorný, Edgardo Fabian Irassar, Ondřej Jankovský y Zbyšek Pavlík. "Complex Characterization and Behavior of Waste Fired Brick Powder-Portland Cement System". Materials 12, n.º 10 (21 de mayo de 2019): 1650. http://dx.doi.org/10.3390/ma12101650.

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Two waste fired brick powders coming from brick factories located in Argentine and Czech Republic were examined as alternative mineral admixtures for the production of blended cements. In pastes composition, local Portland cements (Argentine and Czech) were substituted with 8–40%, by mass, with powdered ceramic waste. For the ceramic waste-Portland cement system, workability, the heat released, pozzolanity, specific density, compressive strength, hydrated phases, porosity, and pore size distribution were tested. The relevance of the dilution effect, filler effect, and pozzolanic activity was analyzed to describe the general behavior of the pozzolan/cement system. The properties and performance of cement blends made with finely ground brick powder depended on the composition of ceramic waste and its reactivity, the plain cement used, and the replacement level. Results showed that the initial mini-slump was not affected by a low ceramic waste replacement (8% and 16%), and then it was decreased with an increase in the ceramic waste content. Brick powder behaved as a filler at early ages, but when the hydration proceeded, its pozzolanic activity consumed partially the calcium hydroxide and promoted the formation of hydrated calcium aluminates depending on the age and present carbonates. Finally, blended cements with fired brick powder had low compressive strength at early ages but comparable strength-class at later age.

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14

Marty, Nicolas C. M., Sylvain Grangeon, Catherine Lerouge, Fabienne Warmont, Olivier Rozenbaum, Thibauld Conte y Francis Claret. "Dissolution kinetics of hydrated calcium aluminates (AFm-Cl) as a function of pH and at room temperature". Mineralogical Magazine 81, n.º 5 (octubre de 2017): 1245–59. http://dx.doi.org/10.1180/minmag.2016.080.161.

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AbstractThe determination of reliable weathering/dissolution rates for cement phases is of fundamental importance for the modelling of the temporal evolution of both radioactive waste repositories and CO2 geological storage sites (e.g. waste matrix, plug in boreholes). Here, the dissolution kinetics of AFm-Cl (hydrated calcium aluminates containing interlayer Cl) has been studied using flow-through experiments conducted at pH values ranging from 9.2 to 13. Mineralogical (XRD) and chemical (EPMA, TEM) analyses have been performed to determine the evolution of the phases during the dissolution experiments. For pH values between 10 and 13, the dissolution of AFm-Cl is congruent (i.e. Ca/Al ratios close to 2 both for solids and outlet concentrations). In contrast, the precipitation of amorphous Al-phases and possibly amorphous mixed Al/Ca phases is observed at pH 9.2, leading to Ca/Al ratios in the outlet solutions higher than those of the initial solid. Therefore, at pH 9.2, even if Cl–/OH– exchange occurs, estimation of dissolution rate from released Cl appears to be the best proxy. Dissolution rates were normalized to the final specific surface areas (ranging from 6.1 to 35.4 m2 g−1). Dissolution rate appears to be pH-independent and therefore the far-from-equilibrium dissolution rate at room temperature is expressed as: logR(mol m–2 s–1) = –9.23 ± 0.18

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15

Ma, Qianwei, Wei Duan, Xiaofeng Liu, Peiying Fang, Ruifeng Chen, Tingyuan Wang y Zirui Hao. "Engineering Performance Evaluation of Recycled Red Mud Stabilized Loessial Silt as a Sustainable Subgrade Material". Materials 15, n.º 9 (9 de mayo de 2022): 3391. http://dx.doi.org/10.3390/ma15093391.

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Industrial solid waste red mud discharge has caused serious environmental problems. This study utilized red mud as an additive to loessial silt being used for roadway subgrade material. In this study, unconfined compressive test, direct shear test, electrical resistivity test, and hydraulic conductivity test were conducted on red mud stabilized loessial silt (RMLS) with different red mud dosage (DR) to investigate DR effect on mechanical-electrical-hydro properties. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were carried out to reveal the mechanism from micro perspective. The results showed addition of appropriate amount of red mud (30–42%) effectively improved unconfined compressive strength of treated loessial silt but reduced resistivity and hydraulic conductivity. Significant correlation between resistivity and strength performance of RMLS mixture was developed. Microscopic analysis indicates red mud addition will promote generation of hydration products such as calcium silicate hydrations (C-S-H), calcium silicate aluminates hydrations (C-A-S-H), and ettringite (Aft), which will tightly connect surrounding particles of loessial silt and hydrates. Red mud particles adhere to surface of soil particles and fill in pores between them improving a compact and stable structure. This study demonstrated the feasibility of using red mud as a stabilization material for roadway subgrade and proved that resistivity measurement is a nondestructive testing method to evaluate mechanical properties for RMLS mixture.

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Prathumsuwan, Thitarat, Alfred A. Christy y Rein Terje Thorstensen. "Hydration Chemistry of Cement Studied by Near Infrared Spectroscopy". Key Engineering Materials 765 (marzo de 2018): 309–13. http://dx.doi.org/10.4028/www.scientific.net/kem.765.309.

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Cement is a complex mixture of inorganic compounds which mainly composed of calcium silicates and calcium aluminates. Cement is mixed with water to form concrete. During the mixing calcium silicate hydrate (CSH) and calcium hydroxide are formed. The ratio of water/cement (w/c ratio) is important to obtain a mixture that gives optimum strength to the concrete. In this work, three different cement samples were mixed with water in four different ratios, including 0.35, 0.40, 0.45 and 0.55, respectively. The hydration process of cement was investigated by using near infrared (NIR) spectroscopy over a period of 28 days. The combination frequency of OH stretching and bending of water molecules gives rise to an absorption around 5200 cm-1. This peak contains contributions of overtones from several types of water molecules in the cement. Fourth derivatives spectra of all cement samples showed three peaks in the combination band region of 5300-5100 cm-1. These peaks indicated the presence of three distinct types of water molecules in the system. First, the characteristic peak at 5260-5240 cm-1 represented the hydrogen bond between water molecules and silinol group of calcium silicates. This peak indicated the formation of CSH from hydration of cement. Furthermore, this peak experienced a slight red shift after a period of seven days indicating stronger hydrogen bonding of water molecules with silinol groups. The peak at 5130 cm-1 corresponded to hydrogen bonding between water molecules and the peak at 5165 cm-1 corresponded to hydrogen bonding between free water and bound water. The suitable w/c ratio for cement-1 is at 0.35-0.45, cement-2, and cement-3 are 0.45. In addition, real concrete sample showed two characteristic peaks at 5250 cm-1 and 5165 cm-1, demonstrating the presence of CSH and free water within concrete, respectively. Near infrared spectroscopy in combination with fourth derivative technique can be used to investigate the hydration chemistry of cement and concrete.

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17

Pöllmann, H. y R. Kaden. "X-ray investigations of solid solutions of monocalcium aluminate and monostrontium aluminate important phases in cement and phosphorescence materials". Powder Diffraction 29, n.º 2 (15 de mayo de 2014): 141–46. http://dx.doi.org/10.1017/s0885715614000189.

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Calcium monoaluminate is the main phase in calcium aluminate cements and participates in the hydration, forming calcium aluminate hydrates. The amount of incorporation of foreign ions influences the hydration behaviour. Strontium aluminate is an important phase in producing phosphorescent materials when doped with rare-earth elements (REE) such as Eu, Dy, and La. These monoaluminates occur in different forms. Monocalcium aluminate forms a monoclinic and an orthorhombic modification, whereas monostrontium aluminate forms a monoclinic low-temperature and a hexagonal high-temperature form. Monoclinic calcium monoaluminate and monoclinic strontium aluminate form a partial solid-solution series. The hydration behaviour of different solid solutions was also investigated using calorimetry. The newly formed strontium aluminate hydrates could be identified while similar strontium aluminate hydrates are formed. Solid solutions of strontium- and calcium-aluminate hydrates will be investigated.

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18

Wang, Feng, Pingan Chen, Xiangcheng Li y Boquan Zhu. "Effect of Colloidal Silica on the Hydration Behavior of Calcium Aluminate Cement". Materials 11, n.º 10 (28 de septiembre de 2018): 1849. http://dx.doi.org/10.3390/ma11101849.

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The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO2 nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO2 nanoparticles.

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DEREVIANKO, V. M., N. V. KONDRATIEVA y H. M. HRYSHKO. "STRUCTURE AND PROPERTIES OF THE ETRINGITE PHASE". Physical Metallurgy and Heat Treatment of Metals, n.º 2 (101) (21 de octubre de 2023): 47–55. http://dx.doi.org/10.30838/j.pmhtm.2413.040723.47.983.

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Problem statement. Aluminate and sulfoaluminate cements are not produced in Ukraine, despite a rather significant need for binders of this class. The use of imported raw materials is limited by the high cost and certain disadvantages occurring during exploitation including rapid hardening, significant heat generation, which is associated with instability of some sulfoaluminates. At the same time, it is possible to highlight the following problems in the direction of expanding possibilities of using special cements of this type: stabilization over time and operating conditions of the hydrosulfate phase based on alumina cement, as well as modification of the compositions of mineral binders based on calcium sulfate dihydrate (CaSO4·2H2O) and development of binders of this class based on secondary production products. The main factor is that during hydration of sulfoaluminates and aluminates in the presence of gypsum (CaSO4·2H2O), a hydrosulfoaluminate phase is formed, which makes it possible to obtain a hardened cement paste structure with special properties. Then monocalcium hydrosulfoaluminate turns into hydrosulfoaluminate of the low-sulfate form С3А·СaSO4·12H2O with the release of gibbsite Al2O3·3H2O. Also, ettringite С3А·СaSO4·nH2O and 2(С2S)·nH2O is formed and hydrated calcium silicate CSH(B) can be formed. When gypsum is added to cement, ettringite is formed in this system. Etringite is one of the components. It is not formed initially, but through intermediate structures. During hydration reactions, ettringite is rearranged, neoplasms are formed, which can lead to gypsum corrosion. Etringite loses its stability. Herewith, the problem of primary and secondary ettringite arises. Primary ettringite creates conditions for strength. Secondary ettringite is formed already in the hardened system and leads to internal stresses. Formation of secondary ettringite can have both positive and negative consequences. The purpose of the atrticle is to investigate structure and properties of the ettringite phase. Conclusions. The hydration process depends on the Gibbs surface energy. Change in surface energy depends on the CaO/Al2O3 ratio. It was established that the surface energy increases with an increase in the CaO/Al2O3 ratio. The paper has studied influence caused by the ettringite phase on the main characteristics of alumina cement and gypsum in a modified gypsum binder. Studies have been conducted on formation of the maximum amount of ettringite phase. We have calculated the maximum amount of the ratio of alumina cement and gypsum to obtain the maximum amount of mineral – 70 % alumina cement and 30 % gypsum. The highest effect is achieved during the simultaneous use of С6АṤ3Н32 and АН3, which occurs during hydration of С4А3Ṥ. Taking into account the above, it is advisable to obtain clinker containing calcium sulfoaluminate and cements based on it.

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Ohya, Junichi, Hiroyuki Sango y Etsuo Sakai. "Immobilization Reaction of Chromate Ion Using Ca₄Al₂(OH)₁₂·Cl₂·4H₂O". Key Engineering Materials 617 (junio de 2014): 24–27. http://dx.doi.org/10.4028/www.scientific.net/kem.617.24.

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Hydrocalmite-like hydrate is one of calcium aluminate hydrated products. This hydrate has a layer structure and the principal layer, which is similar to calcium hydroxide define alternate with interlayer including divalent anions and water molecules. Their anions are able to react with outer anions by anion-exchange reaction. In this study, anion-exchange reaction between hydrocalmite-like hydrate including chloride anion (Ca4Al2(OH)12·Cl2·4H2O, Cl-HC) and chromate anion (CrO42-) is examined. CrO42- is immobilized in various hydrated forms, which are varied with an increasing in the additive ratio of CaCrO4 to Cl-HC. As the additive ratio of CaCrO4 to Cl-HC is below 1.0 in molar, Ca4Al2(OH)12·CrO4·nH2O (n=6 or 8, CrO4-HC) is formed. In this case, the concentration of chromate ion in solution is less than 1.0 ×10-3 mol·dm-3 and over 99% of chromium immobilize in solid phase. However, when the additive ratio of CaCrO4 is over 1.0, ettringite type hydrate including CrO42- (Ca6Al2(OH)12·3CrO4 ·26H2O) is generated and over 10 % of chromium is eluted from the solid phase.

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Morgun, Vladimir, Lyubov Morgun, Denis Votrin y Viktor Nagorskiy. "Analysis of the Synthetic Fiber Influence on the Cement Stone New Formations Composition in Foam Concrete". Materials Science Forum 1043 (18 de agosto de 2021): 43–48. http://dx.doi.org/10.4028/www.scientific.net/msf.1043.43.

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The relevance of the search for scientifically grounded tools, with the help of which it is possible to ensure the growth of crack resistance and strength of foam concrete, is noted. The systemic need of the building complex for energy-and resource-saving operationally reliable building materials is emphasized. The positive influence of the surface energy potential of the fibrous fiber of polymer and carbon composition on the possibility of forming an improved structure of the cement stone in the composition of the interpore partitions of foam concrete has been scientifically substantiated. The article provides information on the foam mixtures formulation and the timing of their hardening. The scans of the investigated materials’ X-ray diffraction patterns and the identification table of the detected hydration neoplasms of the cement stone are presented. The scientific substantiation reliability is experimentally confirmed by the results of the analysis performed, from which it follows that all foam concretes contain quartz, portlandite, hydro-aluminates and calcium hydro-silicates. It has been established that the introduction of fiber into the foam mixture formulation creates the prerequisites for the appearance of such varieties of the hydrated silicate phase as nekoite, which has a fibrous structure at the nanoscale, and foshagite, which has an acicular structure of crystals with increased hardness. The listed mineral hydrated new formations of cement stone, due to their individual properties, should contribute to the foam concrete operational properties’ improvement.

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22

Morejón-Alonso, L., Luis Alberto Santos y R. García Carrodeguas. "Influence of Mixing Liquid on the Properties of Calcium Aluminate Cement". Key Engineering Materials 396-398 (octubre de 2008): 241–44. http://dx.doi.org/10.4028/www.scientific.net/kem.396-398.241.

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The effect of using Na2HPO4 solution as mixing liquid in the physicochemical and mechanical properties of calcium aluminate cement (CAC), with a view to a possible reinforcement additive of conventional α-TCP-based CPC was studied. The results showed that the degree of the hydration reaction of CaAl2O4 (CA) increased when Na2HPO4 solution was used as mixing liquid. The porosity of cement was also lower (37.9 ± 1.3 %) than for H2O (33.2 ± 3.6 %). The values of compressive strength for cements prepared with both mixing liquids were lower than 3 MPa due to the excessive L/P ratio employed and large porosity. After immersion in SBF, only the Al(OH)3 hydrate is observed and no other crystalline hydrated calcium aluminate nor calcium phosphate was formed in any of the cements. Both cements released Ca ions to, and removed P ions from SBF, being this effect more remarkable when Na2HPO4 was used. As for other CAC, no Al was released to the SBF and no potential toxicity due to this ion should be expected.

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23

Hou, Dongshuai y Tao Li. "Influence of aluminates on the structure and dynamics of water and ions in the nanometer channel of calcium silicate hydrate (C–S–H) gel". Physical Chemistry Chemical Physics 20, n.º 4 (2018): 2373–87. http://dx.doi.org/10.1039/c7cp06985e.

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24

Rzepka, Marcin y Miłosz Kędzierski. "The Use of Nanomaterials in Shaping the Properties of Cement Slurries Used in Drilling". Energies 13, n.º 12 (16 de junio de 2020): 3121. http://dx.doi.org/10.3390/en13123121.

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For several decades, constant research has been performed in the world in order to obtain more durable, tighter, or less environmentally harmful binding materials which could be used to seal casing strings in boreholes. There is an increasing search for innovative solutions allowing the production of the highest possible class of binding cements. Since the beginning of the 21st century, one thing which has become synonymous with development is nanotechnology—a dynamically growing branch of science involving both the design, production, and testing of structures with the size of billionths of a metre. Among other things, a set cement stone is made of the grains of hydrated calcium silicates and calcium aluminates, between which there are pore spaces. Fine grains of nanoparticles can successfully settle inside these spaces, causing a decrease in the porosity and permeability of cement matrix. The paper presents the results of laboratory tests performed for formulas of cement slurries containing between 0.5% and 1% of nanosilica, between 1% and 3% of nanosized alumina and approximately 0.1% of carbon nanotubes. The resulting slurries had a density of approximately 1830–1920 kg/m3 and zero water settling. The thickening times of slurries were selected in accordance with the given geological and technical conditions. Early compressive strength amounting to 3.5 MPa (based on a test using an ultrasound cement analyser) was achieved by slurries after times between approximately 7 and 14 h. Upon setting of samples, cement stones produced from slurries featured a very low share of capillary pores. After 28 days of hydration, the compressive strength of the resulting cement stones took on very high values, reaching even up to 50 MPa. Photographs of cement stones containing nanomaterials (taken by means of scanning microscopy) are a confirmation of the exceptionally compact microstructure of the resulting samples.

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25

Roberts, M. H. "New calcium aluminate hydrates". Journal of Applied Chemistry 7, n.º 10 (4 de mayo de 2007): 543–46. http://dx.doi.org/10.1002/jctb.5010071004.

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26

Yoneyama, Akira, Heesup Choi, Masumi Inoue, Jihoon Kim, Myungkwan Lim y Yuhji Sudoh. "Effect of a Nitrite/Nitrate-Based Accelerator on the Strength Development and Hydrate Formation in Cold-Weather Cementitious Materials". Materials 14, n.º 4 (20 de febrero de 2021): 1006. http://dx.doi.org/10.3390/ma14041006.

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Recently, there has been increased use of calcium-nitrite and calcium-nitrate as the main components of chloride- and alkali-free anti-freezing agents to promote concrete hydration in cold weather concreting. As the amount of nitrite/nitrate-based accelerators increases, the hydration of tricalcium aluminate (C3A phase) and tricalcium silicate (C3S phase) in cement is accelerated, thereby improving the early strength of cement and effectively preventing initial frost damage. Nitrite/nitrate-based accelerators are used in larger amounts than usual in low temperature areas below −10 °C. However, the correlation between the hydration process and strength development in concrete containing considerable nitrite/nitrate-based accelerators remains to be clearly identified. In this study, the hydrate composition (via X-ray diffraction and nuclear magnetic resonance), pore structures (via mercury intrusion porosimetry), and crystal form (via scanning electron microscopy) were determined, and investigations were performed to elucidate the effect of nitrite/nitrate-based accelerators on the initial strength development and hydrate formation of cement. Nitrite/nitrate-AFm (aluminate-ferret-monosulfate; AFm) was produced in addition to ettringite at the initial stage of hydration of cement by adding a nitrite/nitrate-based accelerator. The amount of the hydrates was attributed to an increase in the absolute amounts of NO2− and NO3− ions reacting with Al2O3 in the tricalcium aluminate (C3A phase). Further, by effectively filling the pores, it greatly contributed to the enhancement of the strength of the hardened cement product, and the degree of the contribution tended to increase with the amount of addition. On the other hand, in addition to the occurrence of cracks due to the release of a large amount of heat of hydration, the amount of expansion and contraction may increase, and it is considered necessary to adjust the amount used for each concrete work.

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27

Petkova, Vilma, Ventseslav Stoyanov, Bilyana Kostova y Katerina Mihaylova. "EFFECTS OF ZEOLITE INCORPORATION AND INERT FILLERS ON THE CURING OF CEMENT MORTARS". Journal of Chemical Technology and Metallurgy 59, n.º 2 (3 de enero de 2024): 313–22. http://dx.doi.org/10.59957/jctm.v59.i2.2024.9.

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One of the main approaches to reducing the environmental impacts of the construction industry is the use of mineral additives reducing the use of cement in mortars and concretes for construction. The objects of this research are different cement composites with high content of inert mineral fillers (marble and quartz sand), the influence of zeolite incorporation on the microstructure, and low water-cement ratio, obtained after the hydration of white portland cement.In this study, the evolution of the curing processes and the crystal formation during up to 120 days of water-curing are investigated. Moreover, the effects of replacing up to 10 wt. % of white cement with natural zeolite are studied. Attention was focused on the general microstructural development during curing with special attention on the evolution and morphology of pore space and the observed calcium silicate hydrates (C–S–H), portlandite, and carbonate-containing phases.The phase composition (newly formed phases as well as the formation of C-S-H gel) is defined by using powder X-Ray diffraction and SEM. The experimental data shows that the cement composites with the inert marble filler as an additive lead to the creation of carbo-aluminates. The incorporation of up to 10 percent of clinoptilolite in concrete mixtures by mass of the total cementitious components is more efficient when used in lower strength mixes. A significant reduction in the workability of the fresh mortars is not observed, but the high surface area of zeolite reduces bleeding and accelerates setting without any strong effects on the other physical and technological properties of fresh mortars.

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28

Ashrit, Shrenivas, Ravikrishna V. Chatti, Udayabhanu G. Nair y Venugopal Rayasam. "Study of thermogravimetric curves of LD Slag size fractions in oxygen and nitrogen atmosphere and effect of FeO and free lime on weight loss at different temperatures". Metallurgical Research & Technology 115, n.º 4 (2018): 417. http://dx.doi.org/10.1051/metal/2018017.

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The thermogravimetric (TG) method offers a new approach to the study of the thermal degradation of LD Slag fines, which is a by-product produced in the Tata Steel plant, Jamshedpur during the steel making process. TG curves for LD Slag fines of different particle sizes in oxygen and nitrogen atmosphere from 100 to 900 °C were compared to each other to find the variation in the weight loss. Effect of FeO and free lime on weight loss of LD Slag fines was also discussed. Weight loss in the temperature range of 450–550 °C and then up to 700 °C confirmed the presence of calcium hydroxide, magnesium hydroxide, calcium silicate hydrate and calcite in LD Slag fines. Except −6.0 + 2.0 mm LD Slag fines, the weight loss in oxygen atmosphere is more than nitrogen atmosphere for other size fractions. The higher weight loss in nitrogen atmosphere than the oxygen atmosphere was attributed to the decomposition of calcium silicate hydrate and hydrated aluminate phases. Higher free lime values in finer LD Slag fractions than the coarser LD Slag fractions confirmed more volumetric stability of coarser LD Slag size fractions than the finer fractions due to powdering in the cooling process.

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29

Win, Thwe Thwe, Chinnapat Panwisawas, Pitcha Jongvivatsakul, Withit Pansuk y Lapyote Prasittisopin. "Effects of Fly Ash Composition to Mitigate Conversion of Calcium Aluminate Cement Composites". Buildings 13, n.º 10 (27 de septiembre de 2023): 2453. http://dx.doi.org/10.3390/buildings13102453.

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Calcium aluminate cement (CAC) is one of the alternative cements that is widely used for special applications. However, during the hydration process degradation of CAC microstructure, the so-called hydrate conversion process, hexagonal calcium aluminate hydrate (CAH10) transforms into a cubic (C3AH6) phase, resulting in increased porosity and reduced strengths. It is known that alternative means for stabilizing the CAC conversion are conducted by introducing fly ash (FA) in CAC, where its microstructure is attributed to aluminosilicates. However, no study has yet been conducted on different FA compositions influencing CAC performance. This study aims to evaluate the effects of different compositions of FA on CACs’ fresh and hardened characteristics. Results revealed that the microstructure was denser when CAC was mixed with FA. Regarding reactivity, CAC with calcium-rich FA systems is 13% faster than the silica-rich one. The higher the density and the lower the porosity of calcium-rich FA mixtures were found compared with silica-rich FA in both micro- and macro-structures. As seen in the microscopic structure, this is due to the calcium-rich phase formation.

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30

Bašić, Alma-Dina, Marijana Serdar, Ingrid Mikanovic y Gunther Walenta. "Impact of slag on carbonation rate of concrete based on calcium aluminate cement". MATEC Web of Conferences 364 (2022): 02020. http://dx.doi.org/10.1051/matecconf/202236402020.

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Throughout their service life, concrete structures are exposed to various environmental conditions that affect their durability. The cementitious matrix inevitably comes into contact with air, which leads to a progressive carbonation reaction. As a result of carbonation, changes occur in the microstructure and porosity of the cementitious matrix. Calcium aluminate cement is produced to increase the resistance of composites to aggressive environments, but its application is limited by the occurrence of conversion process. The addition of slag inhibits the conversion process of calcium aluminate cement and prevents a reduction in compressive strength due to the formation of C2ASH8 hydrate, while contributing to the net zero commitment of the cement industry. It remains an open question how these changes in microstructure caused by the addition of slag affect the carbonation rate of calcium aluminate cement-based concrete. Therefore, the objective of this study was to determine the effects of slag on the microstructure and porosity of calcium aluminate-based concrete before and after accelerated carbonation. For this purpose, the mechanical properties, porosity, and reaction product of a concrete mix containing 30% calcium aluminate cement replacement by slag were compared to calcium aluminate cement-based concrete before and after exposure to 3% CO2 for 7 and 28 days. Thermogravimetric analysis (TGA) and mercury intrusion porosimetry (MIP) were tested to understand the changes in reaction products and pore size distribution, respectively.

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31

Tan, Yan Ni, Liu Yong, Xiang He, Wen Wang, Dong Duan, Kai Yang Li, Hui Xia Li y Lan Lan Luo. "PGA Fiber Reinforced Calcium Aluminate Cement for Orthopaedic Application". Materials Science Forum 852 (abril de 2016): 1188–93. http://dx.doi.org/10.4028/www.scientific.net/msf.852.1188.

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Calcium aluminate cement (CAC) is a penitential candidate for bone replacements with good bioactivity but relative lower strength. In this study, biodegradable PGA fiber was incorporated into the CAC paste in order to improve the strength of the material. And MC3T3 cells were seeded on the surface of CAC and CAC/fiber to study their in vitro biocompatibility. The results indicate that the PGA fiber can improve the compressive strength of CAC without changing the crystalline phases and micromorphology. Calcium aluminate oxide hydrate, katoite and Gibbsite crystals were detected by XRD. Plate-like crystals can be observed under FESEM. The MC3T3 cells were attached well on both CAC and CAC/fiber composite, indicating their good in vitro biocompatibility. In summary, fiber reinforcement can be an effective way to improve the properties of calcium aluminate cement for orthopaedic application.

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32

Ahmad, Afnan, Muslich Hartadi Sutanto, Niraku Rosmawati Ahmad, Mazizah Ezdiani Mohamad y Mastura Bujang. "Microstructural Characterization of Fibric Peat Stabilized with Portland Cement and Silica Fume". Materials 16, n.º 1 (20 de diciembre de 2022): 18. http://dx.doi.org/10.3390/ma16010018.

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Peat is a renowned problematic soil and needs stabilization to enhance its engineering properties. Silica fume (SF) and Ordinary Portland Cement (OPC) were extensively adopted to increase the mechanical properties of peat; however, their microstructural analysis is lacking. Investigated herein is the microstructural evolution caused by the OPC and SF implementation in peat soil stabilization. Initially, the compositional analysis (elements and oxides) of peat and binders was carried out via energy-dispersive X-ray (EDX) and X-ray fluorescence (XRF). Subsequently, the microstructural changes that occurred in the stabilized peat were examined through a series of microstructural analyses. The analysis includes scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and thermogravimetric analysis (TGA) for morphological, mineralogical, functional group analysis, and bond thermal analysis, respectively. The SEM micrographs evidence the transformation of loosely packed with large micropores of untreated peat into a compact dense peat matrix. This transformation is due to the formation of newly developed minerals, i.e., calcium hydrates (CH), calcium silicate hydrates (C-S-H), calcium aluminate hydrate (CAH), ettringite (Aft) caused by the pozzolanic reaction of binders as recorded by the XRD. Similarly, different molecular functional groups were found in the FTIR analysis with the incorporation of SF and OPC. Finally, the percentage of mass loss was assessed through TGA analysis revealing the decomposition of stabilized in the second and third stages.

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33

Moncea, Andreea M., Ana M. Panait, György Deák y George Poteraș. "Binder Microstructures Developed during the Hydration Process in the System Portland Cement – Calcium Aluminate Cement – Calcium Sulfate". MRS Proceedings 1812 (2016): 71–76. http://dx.doi.org/10.1557/opl.2016.20.

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ABSTRACTLately, the investigations of binders from ternary system Portland cement (PC), calcium aluminate cement (CAC) and calcium sulfate ($C\overline S$), have gone through a larger stage of development due to their special properties such as fast setting and rapid hardening, early strength, non-efflorescence, etc. These special properties are ensured by the binder’s microstructure, developed through hydration processes and reactions between hydrate components, which allows us to use them in special environments (aggressive environments with very low or very high level of pH, environments with high temperature, etc.). The binders from this system were simply named “dry mortars”, and provide the final user with an easy processing. In order to explain the mechanical behavior of the specimens exposed in normal curing conditions (T = 20 ± 2 °C and R.H. ≈ 95%), and with different percentages of calcium sulfate (added as hemihydrate or anhydrite), research on the microstructure of the hardened system was performed using SEM and XRD investigation techniques. The analyses have been performed on the binder pastes, hydrated for 1 and 28 days. The tests results showed that the specimen with anhydrous $C\overline S$ content had the best mechanical behavior.

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34

Goñi, S., M. T. Gaztañaga y A. Guerrero. "Role of Cement Type on Carbonation Attack". Journal of Materials Research 17, n.º 7 (julio de 2002): 1834–42. http://dx.doi.org/10.1557/jmr.2002.0271.

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The carbonation of two hydrated ordinary portland cements of alkali content 1.03% or 0.43% Na2O equivalent and hydrated calcium aluminate cement (0.1% Na2O equivalent) was studied in a semi-dynamic atmosphere of 100% CO2, and 65% relative humidity at 20 ± 1 °C, for a period of 100 days. The changes of the microstructure before and during the carbonation were characterized by x-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy. The kinetics of the process was evaluated from the total CaCO3 content by means of thermogravimetric analysis. The changes of the mechanical flexural strength were also studied. The pore solution was collected and analyzed before and after different periods of time. The results were compared with those obtained under natural carbonation conditions. The results showed that the alkali content of cement does not influence the kinetics of the process when the carbonation is accelerated. In the case of natural carbonation, an induction period is produced in the ordinary portland cement of low alkali content and calcium aluminate cement. The carbonation rate of calcium aluminate cement is the slowest for accelerated and natural carbonation.

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35

Cecconi, Manuela, Costanza Cambi, Stefano Carrisi, Dimitri Deneele, Enza Vitale y Giacomo Russo. "Sustainable Improvement of Zeolitic Pyroclastic Soils for the Preservation of Historical Sites". Applied Sciences 10, n.º 3 (30 de enero de 2020): 899. http://dx.doi.org/10.3390/app10030899.

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Climate changes are inducing a modification of environmental loads on historical sites, requiring new actions towards their conservation. In the paper, the results of an experimental work on sustainable improvement of a pyroclastic soil belonging to the Orvieto cliff (Central Italy) have been investigated in the perspective of its preservation from degradation. The slightly coherent facies of Orvieto Ignimbrite (pozzolana) was treated with hydrated lime and the subsequent chemo-physical evolution was investigated by means of a multi-scale analysis. The beneficial effects obtained from the improvement in terms of mechanical behaviour were interpreted and correlated to the chemo-physical evolution of the system. Microstructural analyses, X-ray diffractometry, thermo-gravimetric analyses (DTG), SEM observations, mercury intrusion porosimetry performed on raw and treated samples, showed that the pozzolanic reactions develop since the very beginning in the system and that the observed mechanical improvement of the treated soil is mainly due to the formation of calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH). In the paper, the mechanical improvement is put in evidence by comparing the results of oedometer tests performed on both raw and treated samples.

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36

Moon, Ju-hyuk, Jae Eun Oh, Magdalena Balonis, Fredrik P. Glasser, Simon M. Clark y Paulo J. M. Monteiro. "Pressure induced reactions amongst calcium aluminate hydrate phases". Cement and Concrete Research 41, n.º 6 (junio de 2011): 571–78. http://dx.doi.org/10.1016/j.cemconres.2011.02.004.

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37

Raúl Fernández, Ana Isabel Ruiz y Jaime Cuevas. "Formation of C-A-S-H phases from the interaction between concrete or cement and bentonite". Clay Minerals 51, n.º 2 (mayo de 2016): 223–35. http://dx.doi.org/10.1180/claymin.2016.051.2.09.

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AbstractConcrete and bentonite are being considered as engineered barriers for the deep geological disposal of high-level radioactive waste in argillaceous rocks. Three hydrothermal laboratory experiments of different scalable complexity were performed to improve our knowledge of the formation of calcium aluminate silicate hydrates (C-A-S-H) at the interface between the two materials: concretebentonite transport columns, lime mortar-bentonite transport columns and a portlandite- (bentonite and montmorillonite) batch experiment. Precipitation of C-A-S-H was observed in all experiments. Acicular and fibrous morphologies with certain laminar characteristics were observed which had smaller Ca/Si and larger Al/Si ratios with increasing temperature and lack of accessory minerals. The compositional fields of these C-A-S-H phases formed in the experiments are consistent with Al/(Si+Al) ratios of 0.2– 0.3 described in the literature. The most representative calcium silicate hydrate (C-S-H) phase from the montmorillonite–cement interface is Al-tobermorite. Structural analyses revealed a potential intercalation or association of montmorillonite and C-A-S-H phases at the pore scale.

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38

Goñi, S., C. Andrade, J. L. Sagrera, M. S. Hernández y C. Alonso. "A new insight on alkaline hydrolysis of calcium aluminate cement concrete: Part I. Fundamentals". Journal of Materials Research 11, n.º 7 (julio de 1996): 1748–54. http://dx.doi.org/10.1557/jmr.1996.0219.

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In this work a hypothesis to explain the alkaline hydrolysis degradation process of calcium aluminate cement concrete (CACC) is presented. The hypothesis is based on x-ray diffraction (XRD) data of some samples taken from real Spanish CACC structures. The identification from XRD data of a hydrated alkaline aluminate could serve as a guide to differentiate both processes of normal carbonation and alkaline hydrolysis.

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39

Liu, Yong Jie, Lin Chen, Shi Quan Liu y Rui Xia Shi. "The Mineral Composition and Microstructure of MAC Cementing Material Prepared Using Hydrated Lime". Key Engineering Materials 575-576 (septiembre de 2013): 527–30. http://dx.doi.org/10.4028/www.scientific.net/kem.575-576.527.

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MAC cementing material was in-situ synthesized with different ratios of raw materials and sintering temperatures. The raw materials include hydrated lime, magnesite and alumina. X-ray diffraction analysis indicates that the major mineral phases in the MAC are monocalcium aluminate (CA), magnesium aluminate spinel (MA) and calcium aluminate (C7A12). The relative contents of the mineral and amorphous phase were simply calculated based on the relative diffraction peaks and MgO-Al2O3-CaO ternary phase diagram. SEM and EDS analysis indicate that the MAC cementing material includes layered structured CA, long strip C7A12 and octahedral MA.

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40

Hou, Zewang, Min Jiang, Kun-Peng Wang, Jianfei Xu, Ying Wang y Xinhua Wang. "Study on the control of inclusions in Al-deoxidized steel during LF-RH refining and the influence of calcium treatment in ladle furnace". Metallurgical Research & Technology 119, n.º 3 (2022): 302. http://dx.doi.org/10.1051/metal/2022033.

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In this paper, evolution of inclusions in an Al deoxidized specialty steel with basic slag refining in the LF-RH process were studied, taking into account of the influence of calcium treatment in the ladle furnace. It was found that inclusions would be modified from alumina into spinel then mainly into solid calcium magnesia aluminates after LF refining, and finally into calcium aluminates at the end of RH refining, irrespective of calcium treatment. When calcium treatment was carried out in the ladle furnace, solid calcium magnesia aluminates largely produced in the LF refining would be mostly modified into liquid calcium aluminates during the afterwards RH refining. By comparison, without calcium treatment, solid and liquid calcium aluminates were both formed in the RH refining. Importantly, when calcium treatment was used, big calcium aluminates as large as 40–50 μm were more frequently observed in steel and with a number density about 0.09–0.015 /mm2, which were bad to fatigue resistance.

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41

Zang, Jun, Chunlei Yao, Bing Ma, Zhiyuan Shao, Houhu Zhang, Jiaqing Wang, Binbin Qian, Hao Zhou y Yueyang Hu. "The Performance and Reaction Mechanism of Untreated Steel Slag Used as a Microexpanding Agent in Fly Ash-Based Geopolymers". Buildings 14, n.º 2 (7 de febrero de 2024): 463. http://dx.doi.org/10.3390/buildings14020463.

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Steel slag is an industrial by-product of the steelmaking process, which is under-utilized and of low value due to its characteristics. Alkali-activated technology offers the possibility of high utilization and increased value of steel slag. A geopolymer composition was composed of steel slag, fly ash, and calcium hydroxide. Four experimental groups utilizing steel slag to substitute fly ash are established based on varying replacement levels: 35%, 40%, 45%, and 50% by mass. The final samples were characterized by compressive strength tests, and Fourier-transform infrared spectroscopy measurements, thermogravimetric measurements, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, and mercury intrusion porosimetry were used to investigate the chemical composition and microstructure of the final products. Higher steel slag/fly ash ratios lead to a lower bulk density and lower compressive strength. The compressive strength ranges from 3.7 MPa to 5.6 MPa, and the bulk density ranges from 0.85 g/cm3 to 1.13 g/cm3. Microstructural and energy-dispersive X-ray spectroscopy analyses show that the final geopolymer products were a type of composite consisting of both calcium aluminate silicate hydrate and sodium aluminate silicate hydrate, with the unreacted crystalline phases acting as fillers.

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42

Bellmann, F., J. Majzlan, K. D. Grevel, E. Dachs y H. M. Ludwig. "Analysis of thermodynamic data of calcium aluminate monocarbonate hydrate". Cement and Concrete Research 116 (febrero de 2019): 89–94. http://dx.doi.org/10.1016/j.cemconres.2018.10.012.

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43

Lee, Yunsu, Seungmin Lim y Hanseung Lee. "Chloride Resistance of Portland Cement-Based Mortar Incorporating High Aluminate Cement and Calcium Carbonate". Materials 13, n.º 2 (12 de enero de 2020): 359. http://dx.doi.org/10.3390/ma13020359.

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Whether chloride resistance is highly influenced by chloride binding capacity remains unknown. In this study, the chloride resistance of Portland cement-based mortar incorporating aluminate cement and calcium carbonate was investigated considering the chloride binding capacity, pore structures and chloride diffusion coefficient from non-steady state chloride migration and natural chloride diffusion. The cement hydrates were investigated using X-ray diffraction and thermogravimetric analysis. The chloride binding capacity was evaluated based on the chloride adsorption from the solutions using the adsorption isotherm. The aluminate cement, as an available alumina source, can stimulate the formulation of layered double hydroxides, which in turn can increase the chloride binding capacity. The results of mercury intrusion porosimetry show that non-substituted (control) and substituted (only aluminate cement) specimens have capillary pore volume 8.9 vol % and 8.2 vol %, respectively. However, the specimen substituted with aluminate cement and calcium carbonate shows a higher capillary volume (12.9 vol %), which correlates with the chloride diffusion coefficient. Although the specimen substituted with calcium carbonate has a higher chloride binding capacity than the control, it does not necessarily affect the decrease in the chloride diffusion coefficient. The capillary pore volume can affect not only the chloride diffusion but also the chloride adsorption.

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44

Bagosi, S. y L. J. Csetényi. "Caesium immobilisation in hydrated calcium-silicate-aluminate systems". Cement and Concrete Research 28, n.º 12 (diciembre de 1998): 1753–59. http://dx.doi.org/10.1016/s0008-8846(98)00163-x.

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45

Trochez, Jenny Johanna, Janneth Torres Agredo y Ruby Mejía de Gutiérrez. "Study of hydration of cement pastes added with used catalytic cracking catalyst (FCC) from a colombian refinery". Revista Facultad de Ingeniería Universidad de Antioquia, n.º 55 (28 de febrero de 2013): 26–34. http://dx.doi.org/10.17533/udea.redin.14678.

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This paper analyzes the effect of the incorporation of industrial waste from an oil refinery in Colombia, known as used catalytic cracking catalyst (FCC), in the hydration process of cementitious pastes. For this purpose, ordinary Portland cement pastes (OPC) added in percentages of 10 and 20% of FCC were prepared. The pozzolanic reactivity of the material and type of hydration products were determined by X-ray diffraction (XRD) and thermogravimetric analysis (TG / DTG). Additionally, the heat of hydration released was determined based on the standard ASTM C186. The results indicate that the hydration process of FCC blended cement is strongly exothermic as a consequence of its pozzolanic activity. The main phases present in the blended cement system were the calcium silicate hydrates (CSH gel), calcium aluminate hydrates (CAH) y calcium aluminosilicate hydrates (CASH), similar to the products obtained in metakaolin blended cement pastes.

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46

Messersmith, Phillip B., Paul Osenar y Samuel I. Stupp. "Preparation of a nanostructured organoceramic and its reversible interlayer expansion". Journal of Materials Research 14, n.º 2 (febrero de 1999): 315–18. http://dx.doi.org/10.1557/jmr.1999.0044.

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We described previously the liquid phase synthesis and characterization of a nanostructured composite from an aqueous solution containing organic polymer and inorganic ions [J. Mater. Res. 7, 2599 (1992)]. The nanocomposite, termed an organoceramic, consisted of poly(vinyl alcohol) chains intercalated between the principal layers of a hydrated calcium aluminate ceramic. A key structural feature of the organoceramic is the polymer-induced expansion of the interlayer spacing by approximately 10 Å compared to the unmodified ceramic. In this paper, we describe the synthetic scheme that favors organoceramic formation and prove the existence of intercalated polymer by observation of reversible interlayer expansion and contraction in response to changes in ambient humidity. This property is unique to the organoceramic and is not observed in the unmodified calcium aluminate ceramic.

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47

Kobayashi, Mari, Keisuke Takahashi, Yuichiro Kawabata y Thomas A. Bier. "Physicochemical Properties of Portland Cement/Calcium Aluminate Cement/Calcium Sulfate Ternary Binder Exposed to Deep Seafloor". ce/papers 6, n.º 6 (diciembre de 2023): 1305–8. http://dx.doi.org/10.1002/cepa.2920.

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AbstractCementitious materials employed in deep‐sea marine engineering must have excellent durability. In this study, the durability of a ternary binder‐based paste composed of Portland cement, calcium aluminate cement, and anhydrite was investigated after deep‐sea exposure at a depth of 3515 m for 438 days. The recovered paste specimen showed significant expansion. However, the hydrate phases in the ternary binder exhibited no changes with the exception of the formation of Friedel's and Kuzel's salts. One reason for this was the transformation from unstable monosulfate to stable ettringite under low‐temperature seawater conditions. However, the additional ettringite formation could lead to significant expansion of the paste specimen.

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Kunhi Mohamed, Aslam, Pinelopi Moutzouri, Pierrick Berruyer, Brennan J. Walder, Jirawan Siramanont, Maya Harris, Mattia Negroni et al. "The Atomic-Level Structure of Cementitious Calcium Aluminate Silicate Hydrate". Journal of the American Chemical Society 142, n.º 25 (14 de mayo de 2020): 11060–71. http://dx.doi.org/10.1021/jacs.0c02988.

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Cui, Kewang, Zhen Feng, Tongwei Zhang y Zihao Yu. "Thermodynamic Simulation of Alkali-activated Processes of Tuff-Based Geopolymer". Journal of Physics: Conference Series 2679, n.º 1 (1 de enero de 2024): 012014. http://dx.doi.org/10.1088/1742-6596/2679/1/012014.

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Abstract The quantity of tuff powder is more than that of tuff mechanized sand in the dry process, which belongs to solid waste. In this paper, tuff from Gansu, Yunnan, Jiangxi, Sichuan, and Tibet was selected as the research object, and the composition of tuff in different areas was defined. Temperature and NaOH concentration were used as variables to conduct thermodynamic simulation, so as to explore the influence of both on the products after alkali-activated. The results show that the main products of alkali-activated tuff geopolymer are sodium silicate aluminate hydrate/calcium silicate aluminate hydrate (CNASH), magnesium silicate hydrate (MSH), Gibbsite, Goethite, and Quartz, except in the Jiangxi area. The amount of CNASH increases gradually with the increase of NaOH concentration, while the amount of Quartz decreases gradually with the increase of NaOH concentration. In the range of 20°C to 100°C, temperature has a significant effect on the production of CNASH and Quartz. The production of CNASH increases first and then decreases with the increase of temperature, and reaches the maximum at about 60°C. The production of Quartz increases with increasing temperature. The conclusion of this paper is helpful in understanding the alkali-activated mechanism of tuff powder.

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50

Wang, Ru y Pei Ming Wang. "Application of Styrene-Butadiene Rubber in Cement-Based Materials". Advanced Materials Research 306-307 (agosto de 2011): 588–93. http://dx.doi.org/10.4028/www.scientific.net/amr.306-307.588.

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This paper summarizes the function of styrene-butadiene rubber (SBR) in cement-based materials, focusing on the achievements of the authors in recent years. The effect of SBR on the properties of cement mortar is introduced, i.e. the workability of fresh mortar such as the water-reduction and water-retention effects of SBR, the mechanical properties of hardened mortar such as the tensile bond strength, flexural and compressive strengths, flexibility and anti-impacting capacity, the waterproofness such as the capillary water adsorption and anti-penetration capacity, the microstructure such as the matrix structure and interface structure, and the cement hydration such as the calcium silicate hydrates, calcium aluminate hydrates and polymerization of [SiO4]4- tetrahedron.

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