Enthalpy of formation of ye’elimite and ternesite

Calcium sulfoaluminate clinkers containing ye’elimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for ye’elimite and ternesite (enthalpy of formation) have been determined experimentally using a combination of techniques: isothermal conduction calorimetry, X-ray powder diffraction and thermogravimetric analysis. The enthalpies of formation of ye’elimite and ternesite at 25 °C were determined to be − 8523 and − 5993 kJ mol−1, respectively

Influence of fly ash blending on hydration and physical behavior of Belite-Alite-Ye'elimite cements

A cement powder, composed of belite, alite and ye’elimite, was blended with 0, 15 and 30 wt% of fly ash and the resulting lended cements were further characterized. During hydration, the presence of fly ash caused the partial inhibition of both AFt degradation and belite reactivity, even after 180 days. The compressive strength of the corresponding mortars increased by increasing the fly ash content (68, 73 and 82 MPa for mortars with 0, 15 and 30 wt% of fly ash, respectively, at 180 curing days), mainly due to the diminishing porosity and pore size values. Although pozzolanic reaction has not been directly proved there are indirect evidences.This work is part of the Ph.D. of D. Londono-Zuluaga funded by Beca Colciencias 646—Doctorado en el exterior and Enlaza Mundos 2013 program grant. Cement and Building materials group (CEMATCO) from National University of Colombia is acknowledged for providing the calorimetric measurements. Funding from Spanish MINECO BIA2017-82391-R and I3 (IEDI-2016-0079) grants, co-funded by FEDER, are acknowledged

Impact of sodium gluconate on white cement-slag systems with Na2SO4

Sodium gluconate has been shown to compensate the impact of alkalis on the long term strength development of cement pastes. This work studies the impact of sodium gluconate combined with Na2SO4 on the microstructural development of white cement-slag systems compared to the addition of only Na2SO4 to better understand its effect on strength development. At long ages the addition of sodium gluconate in systems with Na2SO4 increases the strength compared to the systems with only Na2SO4. Differences in strength cannot be explained by changes in the degree of hydration of cement, degree of reaction of slag, phase assemblage or C-S-H morphology and chemical composition, since these parameters are not affected by sodium gluconate. H-1 NMR shows that sodium gluconate increases the water amount in C-S-H and image analysis confirms the formation of a less dense C-S-H, which can better fill the space. Consequently, the porosity decreases and strength development increases

Molecular understanding of tricalcium silicate hydration in absence and in presence of aluminate ions

Resumen del trabajo presentado 2nd Workshop Calcium-Silicate Hydrates Containing Aluminium (C-A-S-H II), celebrado en Empa, Dübendorf (Switzerland) del 23 al 24 de abril de 2018

Application of Raman spectroscopy to the study of the degree of reaction of mineral additions

Trabajo presentado en el Nanocem Open Meeting, celebrado en Praga (República Checa), los días 21 y 22 de abril de 200

Effect of cooling rates on the properties of Portland cement clinkers in the presence of Mg

In order to enhance the performance of Portland cement clinker, this study investigates the effect of cooling rates on the mineralogical composition of cement clinkers containing magnesium (Mg), which is the most common minor element in raw materials (e.g., limestone). Three cooling regimes were considered to simulate industrial kiln processing conditions. MgO contents of 0, 3, and 6 wt.% were considered in this study. After synthesis of the clinkers, quantitative X-ray diffraction is used to investigate the mineralogical composition, as well, the phase amounts using the Rietveld method. The results show that rapid cooling and Mg doping can promote the formation of alite, and monoclinic alite can be stabilized via Mg ions. Slow cooling and Mg incorporation can stabilize g- C2S, but a rapid cooling rate is still effective to restrain the transformation from b-C2S to g-C2S in MgO-doped clinker. The cooling rates do not influence the content of ferrite and C3A obviously, but the MgO incorporation can enhance the ferrite formation and reduce the C3A content. At a slow cooling rate, little Mg can dissolve in clinker phases, but the retention of MgO in clinker phases can be increased by a fast cooling rate. Therefore, the effect of MgO on the mineralization and the solubility of MgO is a function of cooling rates

Raman spectroscopy of anhydrous and hydrated calcium aluminates and sulfoaluminates

Recent investigations have revealed the great potential of Raman spectroscopy for the characterization of clinker minerals and commercial Portland cements. The usefulness of this technique for the identification of anhydrous, hydrated, and carbonated phases in cement-based materials has been demonstrated. In the present work, the application of micro-Raman spectroscopy for the characterization of the main clinker phases of calcium aluminate cements and calcium sulfoaluminate cement is explored. The main stable hydrated phases as well as several important carbonated phases are investigated. Raman measurements on the following phases are reported: (i) pure, unhydrated phases: CA, C12A7, CA2, C2AS, cubic-C 3A, C4AF, and C4A3S̄; (ii) hydrated phases: ettringite, monosulfoaluminate, and hydrogarnet (C 3AH6); (iii) carboaluminate phases: hemicarboaluminate and monocarboaluminate. The present results, which are discussed in terms of the internal vibrational modes of the aluminate, carbonate, and sulfate molecular groups as well as stretching O-H vibrations, show the ability of Raman spectroscopy to identify the main hydrated and unhydrated phases in the aluminate and sulfoaluminate cements. The Raman spectra obtained in this work provide an extended database to the existing data published in the literature. © 2013 The American Ceramic Society.This study was funded by the MINECO (Ministerio de Economıa y Competitividad) through BIA0767-2008 project.Peer Reviewe