97 research outputs found

    In‐Situ Early Age Hydration Characterization of LC3 binders

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    Ha sido una jornada en la que hemos expuesto los logros más importantes del grupo de la UMA "Cement Science Group" en relación a los cementos de arcillas calcinadas. In this workshop, we have exposed the most important achievements of the UMA group "Cement Science Group" related on calcined clay cements.PID2020‐114650RB‐I00 Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    XRD and Cements: from research to control quality

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    This keynote lecture was focused on the scientific background of the cement research group at UMA. Mainly all the research focused on the strategies for reducing CO2 emissions in the cement production. Moreover, the knowledge transfer to a spin-off was exposed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Clinkering and hydration study of non-active and active Belite-Alite-Ye'elimite (BAY) cements

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    The aim of AIM is to promote industry-driven, interdisciplinary research in material science and engineering in order to provide leading-edge, sustainable solutions to the challenges facing engineers in today’s changing society and environment. http://www.ucl.ac.uk/aim/conference-info/37ccsThe manufacturing process of ye'elimite rich cements emit about 15-37% less CO2 to the atmosphere than OPC. Cements that contain belite, ye’elimite and ferrite, known as BYF cements, are promising eco-friendly binders. However, belite, their main phase, shows a slow hydrating behaviour; therefore the corresponding mortars present lower mechanical strengths than OPC at early ages. To solve this problem, BYF clinkers can be activated by: i) forming alite jointly with belite and ye’elimite during clinkering, known as BAY clinkers. The alite and ye’elimite reaction with water should develop high mechanical strengths at early ages, besides, belite contributes to later curing times. ii) A second activation is based on the stabilisation of alpha forms of belite by dopants. The objective of this work is to obtain two types of BAY clinkers (standard and active BAY) using CaF2 as mineraliser and borax as dopant agent to stabilize alpha forms of belite phase. After that, anhydrite was added as sulphate source to obtain the corresponding cements. The hydration behaviour of these cements has been studied through rheological and x-ray diffraction measurements, the latter combined with Rietveld quantitative phase analysis. In addition, mechanical and dimensional properties of BAY mortars are also presented and discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Assessment of the quantitative accuracy of Rietveld/XRD analysis of crystalline and amorphous phases in fly ash

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    An internal standard method based on Rietveld/XRD whole-pattern fitting analysis of fly ash is used to assess the quantitative accuracy to determine its crystalline and amorphous phases under various conditions such as internal standards (types, SiO2 or Al2O3 and dosages, 10–50%), incident X-rays (laboratory or synchrotron) and refinement software (GSAS or TOPAS). The results reveal that the quantitative stability is quite sensible to minor phases, identical to the internal standard, in fly ash. Errors positively correlate with the weight fraction of that minor phase and negatively correlate with the dosage of an internal standard and amorphous phase content in fly ash. The original equation for the amorphous phase calculation is not applicable for a case with a higher inherent quartz content (>2.5%) in fly ash while the dosages of the internal standard is lower than 20%. The original equation is modified as proposed. Based on it, the quantitative results of five different patterns report a good reproducibility with the arithmetic mean errors and the standard errors of identified main phases of around 1%.The access to the beamline BL14B1 facilities at the SSRF is appreciated and the support of SSRF management, User Office and beamline staff is highly appreciated. This Research is supported by the National Natural Science Foundation of China (No. 51602126), the National Key Research and Development Plan of China (2016YFB0303505) and the Program for Scientic Research Innovation Team in Colleges and Universities of Shandong Province

    Reactivity of C3S and model cement in presence of Na2S2O3 and NaSCN

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    The impact of NaSCN and Na2S2O3 on the reactivity, microstructure and morphology of C3S and model cement (with a clinker containing 85% C3S and 15% C3A) pastes was systematically investigated. Results concluded that both alkali salts mainly act enhancing the reactivity of the C3S phase while not significant influence on the reactivity of C3A was measured. While both admixtures rose the reactivity of C3S over the studied 7 days of hydration, they only increased the reactivity of model cement pastes up to 14–20 h. NaSCN and Na2S2O3 did not modify the C–S–H stoichiometry but they influenced its morphology. In particular, thicker convergent C–S–H needles were formed in pastes containing Na2S2O3 compared to non-admixed systems, while a higher number of thinner C–S–H needles were formed in presence of NaSCN. Furthermore, greater portlandite clusters and intermixing of AFm and C–S–H were observed in admixed C3S and model cement pastes, respectively, compared to plain systems.Open Access funding provided thanks to the CRUECSIC agreement with Springer Nature. Consejería de Educación e Investigación (Comunidad de Madrid) is thanked for funding the 2016-T1/AMB-1434 project in the frame of ‘‘Ayudas de Atracción de Talento Investigador’’. Dr. Palacios also thanks CSIC for funding the PIE 202160I023 project. Prof. De la Torre thanks Junta de Andalucía for the P18-RT-720 research project (cofunded by ERDF)

    Advanced synchrotron studies of ye'elimite-based cement pastes

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    Synchrotron characterization techniques [1] are being used to study Portland-based cements and recently also CSA and related cements. A key property of these techniques is that they do not require sample preparation, so the microstructures of the pastes can be preserved. The classical application of synchrotron tools is powder diffraction used to determine the crystalline phase content evolution with hydration including the overall amorphous fraction. Furthermore, other most advanced techniques are being applied to ye'elimite-containing pastes such as i) Total Scattering Synchrotron Powder Diffraction (TS-SXPD), and ii) Ptychographic Synchrotron X-ray Computed Tomography (PSXCT). All these applications will be reviewed here. TS-SXPD data coupled with the Pair Distribution Function (PDF) analysis methodology [2] allows having a better insight about the nanocrystalline/amorphous atomic arrangements in the gels. It has been very recently shown that nanogibbsite with very small particles, 3nm, is the main constituent of ye'elimite-gypsum hydration paste [2]. Nanogibbsite particles being smaller than those originated from the hydration of monocalcium aluminate. In addition, PSXCT is a tomographic technique that profits from the partly coherent nature of the synchrotron beam to provide better (smaller) resolution, which can be lower than 100 nm. It also provides the mass densities if the chemical stoichiometries are known. This technique has been applied to ye'elimite hydration to determine the microstructure and chiefly the bulk densities of nanogibbsite [3]. The microstructure evolution at early age was also followed [4]. Figure 1 shows an example of a slide of the electron density tomogram for a ye'elimite paste at 8 days of hydration and the corresponding histogram for the full volume with all phases identified.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.This work has been supported by Spanish MINECO through BIA2014-57658-C2 and BIA2017-82391-R, which are co-funded by FEDER

    Rietveld Quantitative Phase Analysis of OPC Clinkers, Cements and Hydration Products

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    Universidad de Málaga. Campus de Excelencia Interacional. Andalucía Tech

    Synchrotron X-ray pair distribution function analysis of calcium silicate pastes

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    The analysis of nanocrystalline and amorphous phases in cement matrices which contain high amounts of crystalline phases is a very challenging task. In this respect, pair distribution function (PDF) methodology in combination with synchrotron radiation is very useful to characterize cement pastes. PDF data can give insight about the atomic local structure of the non-crystalline components such as C-(A)-S-H gels. This work is focused on the characterization of amorphous and nanocrystalline gels which are present in cement related pastes by total scattering PDF analyses in selected samples. In addition, the PDF approach also allows us to perform quantitative analysis in order to know the nanocrystalline and microcrystalline contents. [1] X-ray scattering data of different pastes were collected in BL04-MSPD beamline at ALBA Synchrotron (Barcelona, Spain). Three sets of hydrated samples have been studied and they will be reported: (i) tricalcium silicate, Ca3SiO5, the main component of Portland cements; (ii) dicalcium silicate, Ca2SiO4, the main component of belite cements; and (iii) tricalcium silicate samples mixed with different amounts of silica fume (as the simplest example of supplementary cementitious materials). For all the PDF analyses, a multi r-range approach was followed (see Figure below): the higher r-range (e.g. 40-80 Å) is used to determine the microcrystalline phase contents, for instance, portlandite and anhydrous phases; then, the intermedium r-range allows characterizing the atomic ordering in the nanocrystalline fraction of the C-S-H gel (e.g. 10-40 Å); and finally, the low r-range, below 10 Å, gives information about the chemical nature of the additional amorphous components [2].This work has been supported by PID2019-104378RJ-I00 research grant which is co-funded by FEDER. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Applications of synchrotron x-ray powder diffraction in hydrated cements: high-resolution and high-pressure studies

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    The main aim of this study is to apply synchrotron radiation techniques for the study of hydrated cement pastes. In particular, the tetracalcium aluminoferrite phase, C4AF in cement nomenclature, is the major iron-containing phase in Ordinary Portland Cement (OPC) and in iron rich belite calcium sulfoaluminate cements. In a first study, the hydration mechanism of pure tetracalcium aluminoferrite phase with water-to-solid ratio of 1.0 has been investigated by HR-SXRPD (high resolution synchrotron X-ray powder diffraction). C4AF in the presence of water hydrates to form mainly an iron-containing hydrogarnet-type (katoite) phase, C3A0.84F0.16H6, as single crystalline phase. Its crystal structure and stoichiometry were determined by the Rietveld method and the final disagreement factors were RWP=8.1% and RF=4.8% [1]. As the iron content in the product is lower than that in C4AF, it is assumed that part of the iron also goes to an amorphous iron rich gel, like the hydrated alumina-type gel, as hydration proceeds. Further results from the high-resolution study will be discussed. In a second study, the behavior of pure and iron-containing katoites (C3AH6 and C3A0.84F0.16H6) under pressure have been analyzed by SXRPD using a diamond anvil cell (DAC) and then their bulk moduli were determined. The role of the pressure transmitting medium (PTM) has also been studied. In this case, silicone oil as well as methanol/ethanol mixtures have been used as PTM. Some “new peaks” were detected in the pattern for C3A0.84F0.16H6 as pressure increases, when using ethanol/methanol as PTM. These new peaks were still present at ambient pressure after releasing the applied pressure. They may correspond to crystalline nordstrandite or doyleite from the crystallization of amorphous aluminium hydroxide. The results from the high-pressure study will also be discussed.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Acknowledgments: We thank CELLS-ALBA (Barcelona, Spain) for providing synchrotron beam time. We also thank the financial support by BIA2014-57658-C2-1-R and BIA2014-57658-C2-2-R (FEDER)
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