Articoli di riviste: "Monosulfoaluminate"

1

Hajilar, Shahin, e Behrouz Shafei. "Structure, orientation, and dynamics of water-soluble ions adsorbed to basal surfaces of calcium monosulfoaluminate hydrates". Physical Chemistry Chemical Physics 20, n. 38 (2018): 24681–94. http://dx.doi.org/10.1039/c8cp03872d.

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Yoon, Seyoon, Juyoung Ha, Sejung Chae, David Kilcoyne, Yubin Jun, Jae Oh e Paulo Monteiro. "Phase Changes of Monosulfoaluminate in NaCl Aqueous Solution". Materials 9, n. 5 (21 maggio 2016): 401. http://dx.doi.org/10.3390/ma9050401.

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Mesbah, Adel, Céline Cau-dit-Coumes, Guillaume Renaudin, Fabien Frizon e Fabrice Leroux. "Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate". Cement and Concrete Research 42, n. 8 (agosto 2012): 1157–65. http://dx.doi.org/10.1016/j.cemconres.2012.05.012.

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4

Renaudin, Guillaume, Rachid Segni, Dorota Mentel, Jean-Marie Nedelec, Fabrice Leroux e Christine Taviot-Gueho. "A Raman Study of the Sulfated Cement Hydrates: Ettringite and Monosulfoaluminate". Journal of Advanced Concrete Technology 5, n. 3 (2007): 299–312. http://dx.doi.org/10.3151/jact.5.299.

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5

Jiang, Yaqing, Sijia Zhang e D. Damidot. "Ettringite and Monosulfoaluminate in Polycarboxylate Type Admixture Dispersed Fresh Cement Paste". Advanced Science Letters 5, n. 2 (1 febbraio 2012): 663–66. http://dx.doi.org/10.1166/asl.2012.1798.

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6

Wang, Wei, Luping Zeng, Shuang Du, Min Qiao, Junsong Chen e Bosong Zhu. "The Influence of Alkali-Free Shotcrete Accelerators on Early Age Hydration and Property Development within Cement Systems". Materials 15, n. 19 (5 ottobre 2022): 6907. http://dx.doi.org/10.3390/ma15196907.

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Fluoride-containing alkali-free setting accelerators are a common type of admixture used in tunnel shotcrete but few studies in the literature focus on the effect of their fluoride compounds on the setting and hardening properties of accelerated cement paste under low environment temperatures. Tunnel shotcrete in cold regions or winter construction periods would be obviously influenced by low environment temperatures, especially for its fast setting and quick support applications. The objective of this work is to evaluate the early age hydration behavior of different accelerated cement pastes under 20 °C and 5 °C environment temperatures. In this study, setting time measurement, early age strength development, hydration ion leaching concentration, isothermal calorimetry, X-ray diffraction, and ESEM were performed on cement systems prepared with a non-fluoride alkali-free accelerator (aluminum sulfate solution with over 60% solid content) and a designed fluoride-containing alkali-free setting accelerator (aluminum sulfate and fluoride compound). The results showed that the fluorides obtained in alkali-free accelerators promote C3S dissolution and massive ettringite needles together with monosulfoaluminate (AFm) hydrate formation, thus leading to a quicker setting effect and low sensitivity to low environment temperatures than in non- fluoride groups. However, the rate of mechanical strength development of cement pastes hydrated within 24 h was decreased obviously when fluorine-containing alkali-free accelerator was used. This phenomenon is mainly related to the crystallization of thin-plate shape calcium fluoride (CaF2) formations and promoted conversion of ettringite to monosulfoaluminate hydrate in the accelerating period, thus weakening the denseness of C-S-H gel and inhibiting alite further hydration.

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Honorio, Tulio, Percy Guerra e Alexandra Bourdot. "Molecular simulation of the structure and elastic properties of ettringite and monosulfoaluminate". Cement and Concrete Research 135 (settembre 2020): 106126. http://dx.doi.org/10.1016/j.cemconres.2020.106126.

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Yao, Wu, e Man Jian Wu. "Solubility Behavior of the Hydration Products in the Pore Solution of Hydrated Cement Pastes". Key Engineering Materials 539 (gennaio 2013): 189–94. http://dx.doi.org/10.4028/www.scientific.net/kem.539.189.

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The concentrations of Ca, Al, Si, Na, K, SO42- and pH value in the pore solution of Portland cement were measured during the first 28 days of hydration at room temperature. A thermodynamic analysis of the elemental concentrations was used to predict saturation indices of various solid phases known to form in normal cement system. During the first 4 h the composition of pore solution is dominated by K+, Na+, SO42-and OH-. Large and rapid changes in the concentrations of Ca2+, SO42- and hydroxyl occurred between 4 h and 24 h, and thereafter the pore solution is essentially one of alkali hydroxides. Portlandite and calcium monosulfoaluminate was slightly supersaturated after the first few hours. Saturation indices calculations for ettringite and C-S-H indicate the high levels of supersaturation until 28 days.

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Zhuravel, Vitalii, Teresa Rucińska e Olga Borziak. "Investigation of the Diffusion of Chloride Ions in Blended Cement Pastes". ce/papers 6, n. 6 (dicembre 2023): 1265–68. http://dx.doi.org/10.1002/cepa.2970.

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AbstractWhen exposed to aggressive environments containing chlorides, the chlorine ion partially binds to the usual Portland cement mortar and changes its mineralogy. Chlorine ions entering the system displace sulfate from the monosulfoaluminate. Such systems form Kusel's salt at low chloride concentrations and Friedel's salt at higher concentrations. Unbound chloride ions remain dangerous for reinforcing steel, which diffuse deep into the concrete and destroy the passivating layer on the reinforcement. To assess the protective properties of concrete in relation to metal reinforcement, it is proposed to investigate the process of displacement of the diffusion front in cement composites of various compositions. It is also important to study changes in such characteristics as porosity and filtration properties, which significantly affect the penetration depth of an aggressive medium. The study of the structure, mineral and chemical composition is carried out in layers.

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Shiferaw, Natnael, Lulit Habte, Thriveni Thenepalli e Ji Whan Ahn. "Effect of Eggshell Powder on the Hydration of Cement Paste". Materials 12, n. 15 (5 agosto 2019): 2483. http://dx.doi.org/10.3390/ma12152483.

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Eggshells are one of the solid wastes in the world and are considered hazardous according to European Commission regulations. The utilization of solid wastes, like eggshells, will help create a sustainable environment by minimizing the solid wastes that are disposed into the environment. The utilization of eggshell powder in cement also helps to reduce the carbon dioxide emissions from cement factories by reducing clinker production. In this study, the effect of eggshell powder on the hydration of cement products was investigated using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). Pastes were made with 10% and 20% eggshell powder and examined for 1, 14, and 28 days of hydration. The addition of eggshell powder transformed ettringite to monosulfoaluminate and to monocarboaluminate. In 20% eggshell powder, the formation of monocarboaluminate was detected in the early stages and accelerated the hydration reaction. The CaCO3 from the eggshells reacted with the C3A and changed the hydration products of the pastes. The addition of eggshell powder provided nucleation sites in the hydration products and accelerated cement hydration.

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11

Jiang, Ya Qing, Ji Yin Zhang e Ming Zi Gong. "Action Mechanism of Sulfate Compatible Polycarboxylate Type Admixture". Advanced Materials Research 168-170 (dicembre 2010): 1875–80. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.1875.

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Interaction between cement and a kind of sulfate compatible polycarboxylate type admixture (PCA) and action mechanism of the novel water reducer were investigated. Experimental results indicate that adsorption amount of PCA on surfaces of cement particles is lower than that of polynaphthalene sulfonate condensate water reducer (PNS) because of the formation of more ettringite and calcium monosulfoaluminate, and calcium monocarboaluminate when CaCO3 presents in hydration system, even at initial period of hydration. Results from XRD analysis, derivative thermogravimetric (DTG) analysis and chemical analysis all verify the benificial effect of sulfate compatible PCA on initial and early age hydration of C3A. An establishment of electrostatic repulsion by grafting SO3- in molecule structure of PCA may result in a more negative zeta potential in the dispersion system. The improved dispersibility and fluidity retention are the result of a combination action mechanism of electrostatic repulsion cooperating with steric hindrance, and the acceleration effect of sulfate compatible PCA on initial and early age formation of ettringite and AFm phase. A combined high range water reducer mainly consisting of sulfate compatible PCA and PNS was made up based on the experimental and theoretical investigation results.

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12

Balde, Mamadou Yaya, Chantale Njiomou Djangang, Souleymane Balde, Eric Severin Simo Bakam e Philippe Blanchart. "Physicomechanical Properties of Mortars Based On Ordinary Portland Cement with Bauxite as Mineral Additives". European Journal of Advanced Chemistry Research 3, n. 3 (19 settembre 2022): 1–12. http://dx.doi.org/10.24018/ejchem.2022.3.3.105.

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Guinea has one of the world's main reserves of bauxite that can be used as an industrial mineral to produce low-cost building materials and other parts to address the housing and industrial development difficulties in this country. In this line, mortars were manufactured by replacing 5–25 wt.% of Portland cement with raw and 600 °C calcined. Workability and setting time of fresh mortars were measured. Hard products were characterized by linear shrinkage, porosity, and structural and microstructural investigations. The two mineral additives are chemically active since they favored the reduction of the workability and setting time of mortars. In the case of calcined bauxite, ettringite and monosulfoaluminate coexisted regardless of the rate of substitution due to the higher reactivity of alumina, whereas, for raw bauxite, ettringite is only found at 5 and 10 wt.%. Heterogeneous microstructures and increased porosity were revealed with the rate of cement replacement for raw bauxite, whereas for calcined bauxite, the porosity decreased. Even the minimum compressive strengths of both series of mortars, 13 MPa for raw bauxite and 17 MPa for calcined one, enabled their application as construction materials. Favouring the porosity increase, raw bauxite is more appropriate for applications using porous materials.

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13

Meller, Nicola, Konstantinos Kyritsis e Christopher Hall. "The hydrothermal decomposition of calcium monosulfoaluminate 14-hydrate to katoite hydrogarnet and β-anhydrite: An in-situ synchrotron X-ray diffraction study". Journal of Solid State Chemistry 182, n. 10 (ottobre 2009): 2743–47. http://dx.doi.org/10.1016/j.jssc.2009.07.029.

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14

Blandine, A., G. Bernard e B. Essaïd. "Use of thermodynamic chemical potential diagrams (µCaO, µCO2) to understand the weathering of cement by a slightly carbonated water". Cerâmica 54, n. 331 (settembre 2008): 356–60. http://dx.doi.org/10.1590/s0366-69132008000300014.

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Cement is a ubiquitous material that may suffer hazardous weathering. The chemical weathering of cement in natural environment is mostly characterized by the leaching of CaO and the addition of CO2. The different weathering zones that develop at the expense of the cement may be predicted by the help of chemical potential phase diagrams; these diagrams simulate the behaviour of systems open to some chemical elements. Some components have a so-called inert status, that is to say the system is closed for these components, their amount in the system remains constant; some other components have a mobile status, that is to say these components can be exchanged with the outside of the system, their amount can vary from one sample zone to another. The mobile components are represented in the model by their chemical potentials (linked to their concentrations) that are variable in the external environment. The main features of the weathering of a cement system open to CaO and CO2 are predicted in a phase diagram with µCaO et µCO2 as diagram axes. From core to rim, one observes the disappearance of portlandite, ettringite and calcium monosulfoaluminate, the precipitation of calcite and amorphous silica, the modification of the composition of the CSH minerals (hydrated calcium silicates) that see a decrease of their c/s ratio (CaO/SiO2) from the core to the rim of the sample. For the CSH minerals, we have separated their continuous solid solution into three compositions defined by different CaO/SiO2 ratios and called phases 1, 2 and 3: CaO = 0.8, 1.1, 1.8 respectively for one mole of SiO2 knowing that H2O varies in the three compositions.

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15

Wang, Ziwei, Minglei Guo, Chunlin Liu, Zhong Lv, Tengfei Xiang, Shunquan Zhang e Depeng Chen. "Chloride Binding Behavior and Pore Structure Characteristics of Low-Calcium High-Strength Cement Pastes". Materials 17, n. 13 (26 giugno 2024): 3129. http://dx.doi.org/10.3390/ma17133129.

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While Portland cement produces large amounts of carbon dioxide, low-calcium high-strength cements effectively reduce carbon emissions by decreasing the proportion of high-calcium minerals. In order to enhance the practical application value of low-calcium high-strength cement, the effects of mineral admixtures on the chloride binding capacity and pore structure characteristics of low-calcium high-strength cement pastes were investigated by equilibrium method and mercury intrusion method. The results showed that the chloride binding capacity of low-calcium high-strength cement pastes is superior to that of Portland cement. Fly ash and slag enhance this capacity by promoting monosulfoaluminate and C-S-H gel formation, with fly ash being more effective. Ground limestone also boosts chloride binding when incorporated at less than 10 wt%. However, sulfates have a more significant negative impact on chloride binding capacity in low-calcium high-strength cement pastes compared to Portland cement. The porosity of low-calcium high-strength cement pastes exhibits contrasting trends with the addition of fly ash, ground limestone, and slag. Fly ash and limestone initially coarsen the pore structure but later facilitate the transition of larger pores to smaller ones. In contrast, slag initially has little impact but later promotes the conversion of large capillary pores to medium ones, optimizing the pore structure. Notably, above 10 wt% fly ash, the critical pore diameter decreases with additional fly ash except at 10% where it increases for 3 days. Ground limestone enlarges the critical pore diameter, and this effect intensifies with higher content. During early hydration, slag decreases the critical pore diameter, but its impact diminishes in later stages.

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16

Rubinaite, Dovile, Tadas Dambrauskas, Kestutis Baltakys, Harald Hilbig e Raimundas Siauciunas. "Thermal stability assessment of calcium monosulfoaluminate 12-hydrate by applying the in-situ X-ray diffraction method at 25–1250 °C". Scientific Reports 13, n. 1 (7 marzo 2023). http://dx.doi.org/10.1038/s41598-023-30919-y.

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AbstractIn this study, the stability of synthetic calcium monosulfoaluminate and the reaction mechanism of its conversion into ye`elimite during the thermal treatment were examined. The monosulfoaluminate was produced referring to ye`elimite stoichiometry by applying the mechanochemical treatment (dry grinding at 900 rpm with 3 on–off cycles of 10 min) followed by the hydrothermal synthesis (for 8 h at 110 °C). The data indicated that the prepared sample consists of Ms12 (~ 54.8%), CaCO3 (~ 1.9%), Ms10.5/Hc (~ 0.7%) and amorphous content (~ 42.6%). Meanwhile, the thermal stability assessment by in-situ XRD analysis reveals that the dehydration of monosulfoaluminate interlayer water proceeds at 25–370 °C, where four different hydration states of monosulfoaluminate are identified. Additionally, the results suggest that the removal of water molecules from the main (octahedral) layers begins at ~ 200 °C. Finally, at 700–1250 °C, the solid-state reactions between CŜ, CA and CaO are observed, generating the formation of ye`elimite.

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17

Wang, Yang, Yong Ge, Haibo Fang, Yupo Pan, Xin Chen e Qinfei Li. "The Interaction between Monosulfoaluminate and Calcium Chloride Aqueous Solution". Advances in Cement Research, 22 giugno 2022, 1–17. http://dx.doi.org/10.1680/jadcr.21.00232.

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Scanning transmission X-ray microscope (STXM) and Ca L2,3-edge near-edge X-ray Absorption structure (NEXAFS) spectra investigate simultaneously the morphological and chemical information of various cement-based materials. The interaction between calcium chloride and monosulfoaluminate and the validation of intermediate phases were investigated. As the concentration of CaCl2 solution increases, calcium monosulfoaluminate (Ms) is converted into ettringite, Kuzel's salt (Ks) and Friedel's salt (Fs) in varying degree, while SO42- units in the ettringite and Kuzel's salt are continuously replaced by Cl2- in the solution, eventually forming Fs and gypsum. Based on Ca L2,3-edge NEXAFS absorption spectra, ettringite, Ms, Ks and Ms were greatly distinguished by the number and the shape of the leading peaks in the spectra since the difference in SO42- content among the interlayer structure of Ms, Ks and Fs. The present work is based on the references for the STXM study of the calcium (sulfo)aluminates, for demonstrating a more complete understanding of the phase evolution under chloride environments.

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18

Collin, Marie, Dale P. Prentice, Ross R. Arnold, Kirk Ellison, Magdalena Balonis, Dante Simonetti e Gaurav N. Sant. "Solubility behavior and thermodynamic modeling of sodium monosulfoaluminate (“U‐phase”) in cementitious systems". Journal of the American Ceramic Society, 10 giugno 2023. http://dx.doi.org/10.1111/jace.19257.

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19

McCarthy, G. J., P. J. Tikalsky, R. L. Carrasquillo, O. E. Manz e A. Thedchanamoorthy. "Factors Affecting the Ability of a Fly Ash to Contribute to the Sulfate Resistance of Fly Ash Concrete". MRS Proceedings 136 (1988). http://dx.doi.org/10.1557/proc-136-273.

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ABSTRACTThe objective of this summary is to report on work in progress that is examining parameters, measurable through chemical and XRD analyses, that could indicate whether a fly ash will enhance, degrade or have no effect on the sulfate resistance of fly ash concrete.Mehta [1–4] has discussed the factors that contribute to attack of sulfates on fly ash concrete. As noted in his review paper on this subject in the preceding volume in this series [1], the agents responsible for concrete expansion and cracking are alumina-bearing hydrates, such as calcium monosulfoaluminate and calcium aluminate hydrate, that are attacked by the sulfate ion to form ettringite, calcium trisulfoaluminate. Acidic type interactions between sulfate ions and calcium hydroxide also lead to strength and mass loss.

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20

Rubinaite, Dovile, Tadas Dambrauskas, Kestutis Baltakys e Raimundas Siauciunas. "Influence of water vapour pressure on the carbonation process of calcium monosulfoaluminate 12-hydrate". Journal of Thermal Analysis and Calorimetry, 27 maggio 2024. http://dx.doi.org/10.1007/s10973-024-13233-1.

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21

Mohamed-Nadjib, Brahim, Mechling Jean-Michel, Janvier-Badosa Sarah e Marchetti Mario. "Early stage ettringite and monosulfoaluminate carbonation investigated by in situ Raman spectroscopy coupled with principal component analysis". Materials Today Communications, febbraio 2023, 105539. http://dx.doi.org/10.1016/j.mtcomm.2023.105539.

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22

Diamond, Sidney, e David Bonen. "A Re-Evaluation of Hardened Cement Paste Microstructure Based on Backscatter Sem Investigations". MRS Proceedings 370 (1994). http://dx.doi.org/10.1557/proc-370-13.

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AbstractBackscattered electron imaging of polished cement paste specimens permits a re-evaluation of structural details of hydrated cement paste at the gim level. The primarily microstructural units comprise a highly porous groundmass and large distinct grains (“phenograins”) set in it. The groundmass is composed of several kinds of fine particles, with a significant content of easily detected gross pores. Phenograins are primarily large clinker grains hydrating in-situ, but may be distinct deposits of CH, or may be mineral admixture grains. Detailed EDS analyses indicated that hydrating cement in phenograins has a highly consistent composition, interpreted as C-S-H with a small but regular incorporation of sub-jim CH and calcium monosulfoaluminate. Groundmass particles are highly variable in composition, but appear to consist of C-S-H with variable and occasionally major contents of other hydration products on a sub-μm scale. Incorporation of fly ash does not appear to change the basic microstructure, but silica fume incorporated with superplasticizer drastically modifies the character of the groundmass. Some attempts at quantification of these features by application of image analysis are briefly described.

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23

Zenieris, Petros, e Joakim G. Laguros. "Fly Ash As A Binder in Aggregate Base Courses". MRS Proceedings 113 (1987). http://dx.doi.org/10.1557/proc-113-231.

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ABSTRACTThe benefit of adding up to 35 wt% Class C high calcium fly ash to various types of fine and coarse aggregate pavement mixes is described and quantified. The mixes, which were compacted to maximum dry density at optimum moisture content, had variable compressive strengths during the first 28 days of curing; after that they assumed a relatively uniform pattern of strength gain reaching values as high as 11 MPa (1600 psi). Mixes containing 15% fly ash gave unacceptably low strengths. XRD measurements indicated massive formation of ettringite, transforming to monosulfoaluminate and the poorly crystallized hydrated phases of C-A-H, C-A-S-H and C-S-H. This transformation helps explain the gain in strength of the mixes with extended curing. SEM observations depicted progressive packing and densification of the skeletal matrix as the hexagonal phases and C-S-H gained higher crystallinity and formed aggregated masses. Furthermore, these observations suggest that fly ash acts predominantly as a chemical binder and partly as a filler in the aggregate mixes tested.

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Zenieris, Petros E., e Joakim G. Laguros. "Similarities and Differences in Shale, Aggregate Mixes and Concrete Containing Fly Ash". MRS Proceedings 136 (1988). http://dx.doi.org/10.1557/proc-136-207.

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ABSTRACTFly ash technology has been very effective in providing stability in roadway base courses composed either of shale or aggregate materials, and also in partly replacing Portland cement in concrete. X-ray diffractometry and scanning electron microscopy observations indicate that there are certain similarities among these three types of mixes concerning the hydration process; on the other hand, there is evidence of distinct differences in the hydration products which are found to act either as a filler, a chemical agent, or both. Fly ash suppresses the intensity of the clay minerals in shale, speeds up the hydration process in concrete and acts partly as a filler in aggregate mixes. The net practical result is strength development which varies not only in terms of the maximum level attained, but also in regard to its rate. The conversion of ettringite to monosulfoaluminate proceeds at a rate which is considered high in concrete, moderate in aggregate mixes, and moderate to low in shale. X-ray diffraction analyses help to identify other dissimilarities in the minerals produced. The modification which takes place in the fabric and the matrix of the mixes is morphologically the same; in contrast, the growth of crystallites at the “particle”/fly ash interface is explicitly different. Preliminary quantification of matrix changes resulting from new hydration products is also explored.

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Articoli di riviste sul tema "Monosulfoaluminate"

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