Preparation and hydration of model ecocement phases. Characterization by diffraction and cognate methods

La producción de cementos de sulfoaluminato de calcio (CSA, del inglés Calcium SulfoAluminate) es más respetuosa para el medio ambiente que la de los cementos Portland ordinarios (OPC, del inglés Ordinary Portland Cement) ya que libera menos CO2. Los cementos CSA presentan un amplio rango de ensamblaje de fases, pero todos contienen en torno a un 50% de ye'elimita además de belita, ferrito aluminato tetracálcico y otros componentes minoritarios. La ye'elimita es muy reactiva y la mayor parte del calor de hidratación se libera durante las ocho primeras horas. Durante la hidratación a edades tempranas, el principal producto cristalino que se forma, debido a la disolución de la ye'elimita en presencia de sulfato, es la fase etringita. Sin embargo, la fase monosulfato se forma cuando no hay una fuente de sulfato soluble en el medio. La ye'elimita, también está incluida (25% en peso) en los cementos belíticos de sulfoaluminato de calcio (BCSA, del inglés Belite Calcium SulfoAluminate). La formulación más común de estos cementos consiste en β-C2S, C4A3S y C4AF. El C2S presenta cinco formas polimórficas. Sin embargo, el polimorfo α'H-C2S es el más activo hidráulicamente, por ello su estabilización juega un papel importante en la preparación de los cementos activados tipo BCSA en el laboratorio y en ensayos industriales. Esta tesis doctoral se ha dividido en dos bloques: i) estudios estructurales de fases anhidras y ii) estudios de hidratación de fases seleccionadas. Para el estudio de la forma β del silicato dicálcico, se preparó la disolución sólida con fórmula general, Ca2Si1-2xAl2xO4-x x. Los materiales se caracterizaron determinándose el límite de la serie cercano a x=0.014. Por otro lado, la muestra α'H-Ca1.85Na0.15(SiO4)0.85(BO3)0.15 se seleccionó para estudiar la estructura cristalina del polimorfo α'H del silicato dicálcico. Para el caso de la ye'elimita, se han preparado dos muestras: una estequiométrica (Ca4Al6O12SO4) y otra dopada (Ca3.8Na0.2Al5.6Fe0.2Si0.2O12SO4) para caracterizar los polimorfos ortorrómbico y pseudocúbico, respectivamente. Mediante estudios termodifractométricos, calorimetría diferencial de barrido y medidas de permitividad se determinó la transición reversible que presentan. Los estudios de hidratación se han realizado usando difracción de rayos-X de polvo de laboratorio con la metodología del estándar externo (factor-G) y/o usando difracción de rayos-X sincrotrón de polvo con la metodología del estándar interno para determinar el ensamblaje de fases incluyendo el material amorfo. Los resultados obtenidos por ambas metodologías muestran una consistencia que permite entender las reacciones de hidratación en función del tiempo. Se ha determinado el papel del polimorfismo de la ye'elimita en los mecanismos de hidratación comparándose la reactividad de ambos polimorfos, obteniéndose importantes diferencias en su cinética y en sus mecanismos de hidratación. Además, se ha estudiado la hidratación de la ye'elimita en combinación con C4AF y con silicato dicálcico. En el caso del estudio de la hidratación con el silicato dicálcico, a los 6 meses, el α'H-C2S se disolvió totalmente, en cambio, se encontraron grandes cantidades de β-C2S sin reaccionar en todas las muestras. Finalmente, se ha determinado el comportamiento de hidratación de la fase C4AF en ausencia y presencia de yeso

Recent Advances in C-S-H Nucleation Seeding for Improving Cement Performances

Reducing cement CO2 footprint is a societal need. This is being achieved mainly by replacing an increasing amount of Portland clinker by supplementary cementitious materials. However, this comes at a price: lower mechanical strengths at early ages due to slow pozzolanic reaction(s). This is being addressed by using accelerator admixtures. In this context, calcium silicate hydrate nucleation seeding seems to have a promising future, as it can accelerate cement and pozzolanic reactions at early ages, optimising their microstructures, without compromising late strength and durability performances. In fact, these features could even be improved. Moreover, other uses are low temperature concreting, precasting, shotconcrete, etc. Here, we focus on reviewing recent reports on calcium silicate hydrate seeding using commercially available admixtures. Current knowledge on the consequences of nucleation seeding on hydration reactions and on early and late mechanical strengths is discussed. It is noted that other features, in addition to the classic alite hydration acceleration, are covered here including the enhanced ettringite precipitation and the very efficient porosity refinement, which take place in the seeded binders. Finally, because the seeded binders seem to be denser, durability properties could also be enhanced although this remains to be properly established.This research has been partly supported by PID2020-114650RB-I00 research grant, Spanish Government, which is co-funded by ERDF. Partial funding for open access charge: Universidad de Málag

Rietveld Quantitative Phase Analysis of Oil Well Cement: in Situ Hydration Study at 150 Bars and 150 °C

Oil and gas well cements are multimineral materials that hydrate under high pressure and temperature. Their overall reactivity at early ages is studied by a number of techniques including through the use of the consistometer. However, for a proper understanding of the performance of these cements in the field, the reactivity of every component, in real‐world conditions, must be analysed. To date, in situ high energy synchrotron powder diffraction studies of hydrating oil well cement pastes have been carried out, but the quality of the data was not appropriated for Rietveld quantitative phase analyses. Therefore, the phase reactivities were followed by the inspection of the evolution of non‐overlapped diffraction peaks. Very recently, we have developed a new cell specially designed to rotate under high pressure and temperature. Here, this spinning capillary cell is used for in situ studies of the hydration of a commercial oil well cement paste at 150 bars and 150 °C. The powder diffraction data were analysed by the Rietveld method to quantitatively determine the reactivities of each component phase. The reaction degree of alite was 90% after 7 hours, and that of belite was 42% at 14 hours. These analyses are accurate, as the in situ measured crystalline portlandite content at the end of the experiment, 12.9 wt%, compares relatively well with the value determined ex situ by thermal analysis, i.e., 14.0 wt%. The crystalline calcium silicates forming at 150 bars and 150 °C are also discussed.This research was funded by Spanish MINECO, grant number BIA2017‐82391‐R which is co‐funded by FEDER. We thank Marc Malfois for his help during the experiment performed at NCD‐SWEET beamline at ALBA synchrotron. We also thank Marcus Paul (Dyckerhoff GmbH) for providing the OWC sample with its characterization and helpful discussions

Water-to-cement ratio influence on low-carbon cements performances

Portland Cement (PC) is the most important active ingredient in most of the construction concrete. However, the PC production is associated with a high carbon dioxide release (around 1 ton of CO2 per ton of PC). One approach to reduce CO2 emissions consists on the reformulation of the clinker with less calcite demanding phases, such as, belite rich clinkers. The drawback of this kind of clinkers is the low reactivity of belite (beta-belite). In order to compensate this problem, belite rich clinkers can be prepared with ye’elimite and ferrite or with alite [known as belite-ye’elimite-ferrite (BYF) and belite-alite-ye’elimite (BAY), respectively]. In addition, it can be improved by using a high reactive belite polymorph, such as alpha-belite. In this work, the hydration and mechanical behaviour of BYF and BAY cements (with beta and/or alpha-belite) with different water-to-cement ratios have been studied. The clinkers were produced using natural raw materials, and were mixed with anhydrite (CaSO4) to prepare the corresponding cements. At early ages, the main hydration products of these cements were ettringite, calcium monosulfoaluminate and amorphous aluminium hydroxide. At later ages, stratlingite, katoite and amorphous C-S-H were found. The compressive strength values of the corresponding mortars were correlated with the mineralogy evolution of the pastes (mainly obtained by XRD and TGA).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. I3-Ramón y Cajal Universidad de Malag

Early hydration study of standard and doped Alite-Belite-Ye’elimite (ABY) cements through Synchrotron Radiation

The manufacturing of ye'elimite-rich cements releases from 15 to 37%, depending on their composition, less CO2 to the atmosphere than ordinary Portland cement (OPC). BYF cements containing belite, ye’elimite and ferrite as main crystalline phases, are promising eco-friendly binders. Nevertheless, belite, its main phase, shows a slow hydrating behaviour and the mechanical strengths are lower than OPC at early ages. Some alternatives to solve this problem are: i) forming alite jointly with belite and ye’elimite during clinkering, Alite Belite Ye’elimite (ABY) clinkers. The hydration of alite and ye’elimite would develop high mechanical strengths at early ages, and belite contributes to later curing times; ii) a second alternative is the stabilisation of alpha forms of belite using dopants such as boron named here after dABY. In this work, two different types of ABY clinkers (standard and doped) have been prepared and characterized to understand their different hydration mechanisms at the same water-to-cement (w/c) ratio. The clinkers have been prepared using CaF2 and ZnO as mineralizers, and borax as dopant agent to stabilize alpha forms of belite (’H-C2S). Afterwards, 14 wt% of anhydrite (as soluble sulphate source) was added to prepare the corresponding cements. Finally, the hydration study was performed at w/c ratio of 0.5. Here, an in-situ hydration study using synchrotron X-ray powder diffraction (SXRPD) for the first 14 hours of hydration is reported. Moreover, these results will be combined with the ex-situ laboratory X-ray powder diffraction study (LXRPD) at 1 day of hydration and calorimetric results. Rietveld quantitative phase analysis has been used to establish the phase evolution across the time.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. MINECO ( BIA2017-82391-R), co-funded by FEDER, and I3 [IEDI-2016-0079]

p53 loss and Kras mutation in an invasive murine model of colorectal cancer

For many years there have been many excellent mouse models of benign intestinal adenoma though not of later stage invasive disease. In this study we have attempted to generate a number of murine models that closely recapitulate the human disease by manipulating mutations that occur during colorectal cancer (CRC) progression. The p53 tumour suppressor gene is commonly mutated in sporadic CRC, though loss alone does not drive intestinal tumorigenesis. When we targeted p53 deletion to the adult murine intestine in concert with a single mutation in the Adenomatous Polyposis Coli (Apc) tumour suppressor gene, this led to an acceleration of tumorigenesis and an increase in the number of invasive tumours and more rarely metastasis. These invasive tumours closely resemble human tumours and importantly had many features of Epithelial to Mesenchymal Transition (EMT). Tumours in this background still formed at relatively long latencies suggesting other genetic events were occurring to drive the progression in the absence of p53. Up to 50% of colon cancers have a mutation in KRAS. Targeting mutant KrasG12D to the intestinal epithelium promotes hyperplasia though not tumorigenesis. In combination with Apc mutation there is an acceleration of tumorigenesis and a greater propensity to develop colonic tumours. To test whether Kras mutation caused a more marked phenotype in the background of p53 deficiency we generated VillinCreER+ Apcfl/+ p53fl/fl KrasG12D/+ mice. Remarkably these mice develop invasive and rarely metastatic tumours in as little as 50 days. Moreover even small tumours (less than 1mm) could be invasive. We believe these mouse models of invasive and metastatic intestinal adenocarcinoma will be an excellent tool to study the invasive and metastatic process in vivo. Moreover they should allow us to test the efficacy of drugs aimed to inhibit the invasion process

La construcción de la identidad profesional: el caso de los estudiantes de máster de cambio de carrera

[spa] El comienzo de este siglo ha traído consigo la normalización de la movilidad profesional debido a una realidad laboral más precaria e inestable. Ante esta nueva concepción menos lineal de la profesión, la formación continua en general, y los estudios de máster en particular se han convertido en herramientas que permiten adaptarse a estos cambios. Sin embargo, a pesar del aumento de las titulaciones de máster y de los diferentes tipos de estudiantes que acceden a estos programas, existe una falta de investigación sobre los másteres como mecanismo para construir una nueva identidad profesional. El objetivo principal de esta tesis es analizar y comprender los procesos de transición a los másteres y la construcción de la identidad profesional de los estudiantes que deciden cambiar de carrera a través de la realización de un máster en Formación del Profesorado en Cataluña. En cuanto a los objetivos específicos, pretendemos: a) profundizar en la trayectoria académica inicial de estos estudiantes de máster; b) conocer su experiencia profesional previa al máster; c) comprender el proceso de transición y los factores que lo desencadenan; d) examinar la evolución de su trayectoria durante el máster; y e) analizar el impacto que el máster ha tenido en su experiencia e identidad profesional posterior. El análisis teórico abarca los aspectos principales de esta investigación, que incluyen: la contextualización de la importancia de los másteres en el contexto de las transformaciones en la educación superior en el marco del Plan Bolonia; los modelos teóricos y la evidencia empírica del desarrollo de la carrera en adultos desde una perspectiva tradicional y actual; la identidad en general, y en particular la identidad profesional, a través de enfoques, teorías y modelos que la respaldan; y por último, la identidad profesional docente y los factores que influyen en su desarrollo y consolidación con especial énfasis en el colectivo objeto de esta tesis. El diseño metodológico da respuesta al objetivo de comprender el fenómeno del cambio de identidad analizado. A través de la metodología cualitativa se entiende dicho fenómeno desde la perspectiva de los protagonistas, utilizando historias de vida obtenidas a partir de entrevistas semiestructuradas realizadas a 10 profesores de secundaria. Estas entrevistas aportan datos sobre las vivencias y experiencias relacionadas con la transición. Además, se analizan las trayectorias a lo largo de varios años, se profundiza en las diferentes etapas vitales y momentos clave de los entrevistados, y se destaca el perfil heterogéneo del grupo en términos de edad, procedencia y período de finalización del máster, entre otros aspectos. El análisis del contenido se realiza tanto cada uno de los relatos de vida (intra-caso) como de manera transversal (inter-caso), permitiendo, así, establecer categorías relevantes. Los resultados revelan una diversidad de perfiles dentro del grupo en términos de profesión disciplinar previa y especialidad cursada en el máster de formación de profesorado, lo que confirma la heterogeneidad de este colectivo. Además, se observan diferencias en los factores y desencadenantes que motivan la transición hacia un cambio de identidad profesional. Mediante el estudio cualitativo intra e inter-caso se ha logrado profundizar en las diferentes etapas del ciclo de vida de los estudiantes, identificar características propias de cada etapa vital y determinar los factores personales y contextuales que influyen en el proceso de desarrollo de la identidad profesional docente. Los resultados obtenidos y su posterior discusión han llevado a establecer un marco de propuestas para mejorar esta transición específica tanto desde la perspectiva institucional como de la orientación.[eng] The beginning of this century has brought with it the normalization of professional mobility due to a more precarious and unstable work reality. Faced with this less linear conception of the profession, continuous education in general, and master's studies in particular have become tools that allow for adaptation to these changes. However, despite the increase in master's degrees and the different types of students accessing these programs, there is a lack of research on master's degrees as a mechanism for building a new professional identity. The main objective of this thesis is to analyze and understand the transition processes to master's degrees and the construction of the professional identity of students who decide to change careers through the completion of a Teacher Training Master's program in Catalonia. Regarding specific objectives, we aim to: a) delve into the initial academic trajectory of these master's students; b) understand their previous professional experience before the master's program; c) comprehend the transition process and the factors that trigger it; d) examine the evolution of their trajectory during the master's program; and e) analyze the impact that the master's program has had on their subsequent professional experience and identity. The theoretical analysis encompasses the main aspects of this research, which include: contextualizing the importance of master's degrees in the context of transformations in higher education within the framework of the Bologna Process; theoretical models and empirical evidence of career development in adults from both traditional and current perspectives; identity in general, and specifically professional identity, through supporting approaches, theories, and models; and finally, teacher professional identity and the factors that influence its development and consolidation, with special emphasis on the target group of this thesis. The methodological design responds to the objective of understanding the analyzed identity change phenomenon. Through qualitative methodology, this phenomenon is understood from the perspective of the individuals involved, using life stories obtained from semi-structured interviews conducted with 10 secondary school teachers. These interviews provide data on the experiences related to the transition. Additionally, trajectories over several years are analyzed, delving into different life stages and key moments of the interviewees, highlighting the heterogeneous profile of the group in terms of age, background, and period of completion of the master's program, among other aspects. Content analysis is conducted on both individual life narratives (intra-case) and in a cross-sectional manner (inter-case), allowing for the establishment of relevant categories. The results reveal a diversity of profiles within the group in terms of previous disciplinary profession and the specialization pursued in the teacher-training master's program, confirming the heterogeneity of this collective. Additionally, differences are observed in the factors and triggers that motivate the transition towards a change in professional identity. Through the qualitative intra- and inter-case study, it has been possible to delve into the different stages of students' life cycles, identify characteristics specific to each life stage, and determine the personal and contextual factors that influence the process of developing teacher professional identity. The obtained results and their subsequent discussion have led to the establishment of a framework of proposals to improve this specific transition, from an institutional and guidance perspective

La construcción de la identidad profesional: el caso de los estudiantes de máster de cambio de carrera

Programa de Doctorat en Educació i Societat[spa] El comienzo de este siglo ha traído consigo la normalización de la movilidad profesional debido a una realidad laboral más precaria e inestable. Ante esta nueva concepción menos lineal de la profesión, la formación continua en general, y los estudios de máster en particular se han convertido en herramientas que permiten adaptarse a estos cambios. Sin embargo, a pesar del aumento de las titulaciones de máster y de los diferentes tipos de estudiantes que acceden a estos programas, existe una falta de investigación sobre los másteres como mecanismo para construir una nueva identidad profesional. El objetivo principal de esta tesis es analizar y comprender los procesos de transición a los másteres y la construcción de la identidad profesional de los estudiantes que deciden cambiar de carrera a través de la realización de un máster en Formación del Profesorado en Cataluña. En cuanto a los objetivos específicos, pretendemos: a) profundizar en la trayectoria académica inicial de estos estudiantes de máster; b) conocer su experiencia profesional previa al máster; c) comprender el proceso de transición y los factores que lo desencadenan; d) examinar la evolución de su trayectoria durante el máster; y e) analizar el impacto que el máster ha tenido en su experiencia e identidad profesional posterior. El análisis teórico abarca los aspectos principales de esta investigación, que incluyen: la contextualización de la importancia de los másteres en el contexto de las transformaciones en la educación superior en el marco del Plan Bolonia; los modelos teóricos y la evidencia empírica del desarrollo de la carrera en adultos desde una perspectiva tradicional y actual; la identidad en general, y en particular la identidad profesional, a través de enfoques, teorías y modelos que la respaldan; y por último, la identidad profesional docente y los factores que influyen en su desarrollo y consolidación con especial énfasis en el colectivo objeto de esta tesis. El diseño metodológico da respuesta al objetivo de comprender el fenómeno del cambio de identidad analizado. A través de la metodología cualitativa se entiende dicho fenómeno desde la perspectiva de los protagonistas, utilizando historias de vida obtenidas a partir de entrevistas semiestructuradas realizadas a 10 profesores de secundaria. Estas entrevistas aportan datos sobre las vivencias y experiencias relacionadas con la transición. Además, se analizan las trayectorias a lo largo de varios años, se profundiza en las diferentes etapas vitales y momentos clave de los entrevistados, y se destaca el perfil heterogéneo del grupo en términos de edad, procedencia y período de finalización del máster, entre otros aspectos. El análisis del contenido se realiza tanto cada uno de los relatos de vida (intra-caso) como de manera transversal (inter-caso), permitiendo, así, establecer categorías relevantes. Los resultados revelan una diversidad de perfiles dentro del grupo en términos de profesión disciplinar previa y especialidad cursada en el máster de formación de profesorado, lo que confirma la heterogeneidad de este colectivo. Además, se observan diferencias en los factores y desencadenantes que motivan la transición hacia un cambio de identidad profesional. Mediante el estudio cualitativo intra e inter-caso se ha logrado profundizar en las diferentes etapas del ciclo de vida de los estudiantes, identificar características propias de cada etapa vital y determinar los factores personales y contextuales que influyen en el proceso de desarrollo de la identidad profesional docente. Los resultados obtenidos y su posterior discusión han llevado a establecer un marco de propuestas para mejorar esta transición específica tanto desde la perspectiva institucional como de la orientación.[eng] The beginning of this century has brought with it the normalization of professional mobility due to a more precarious and unstable work reality. Faced with this less linear conception of the profession, continuous education in general, and master's studies in particular have become tools that allow for adaptation to these changes. However, despite the increase in master's degrees and the different types of students accessing these programs, there is a lack of research on master's degrees as a mechanism for building a new professional identity. The main objective of this thesis is to analyze and understand the transition processes to master's degrees and the construction of the professional identity of students who decide to change careers through the completion of a Teacher Training Master's program in Catalonia. Regarding specific objectives, we aim to: a) delve into the initial academic trajectory of these master's students; b) understand their previous professional experience before the master's program; c) comprehend the transition process and the factors that trigger it; d) examine the evolution of their trajectory during the master's program; and e) analyze the impact that the master's program has had on their subsequent professional experience and identity. The theoretical analysis encompasses the main aspects of this research, which include: contextualizing the importance of master's degrees in the context of transformations in higher education within the framework of the Bologna Process; theoretical models and empirical evidence of career development in adults from both traditional and current perspectives; identity in general, and specifically professional identity, through supporting approaches, theories, and models; and finally, teacher professional identity and the factors that influence its development and consolidation, with special emphasis on the target group of this thesis. The methodological design responds to the objective of understanding the analyzed identity change phenomenon. Through qualitative methodology, this phenomenon is understood from the perspective of the individuals involved, using life stories obtained from semi-structured interviews conducted with 10 secondary school teachers. These interviews provide data on the experiences related to the transition. Additionally, trajectories over several years are analyzed, delving into different life stages and key moments of the interviewees, highlighting the heterogeneous profile of the group in terms of age, background, and period of completion of the master's program, among other aspects. Content analysis is conducted on both individual life narratives (intra-case) and in a cross-sectional manner (inter-case), allowing for the establishment of relevant categories. The results reveal a diversity of profiles within the group in terms of previous disciplinary profession and the specialization pursued in the teacher-training master's program, confirming the heterogeneity of this collective. Additionally, differences are observed in the factors and triggers that motivate the transition towards a change in professional identity. Through the qualitative intra- and inter-case study, it has been possible to delve into the different stages of students' life cycles, identify characteristics specific to each life stage, and determine the personal and contextual factors that influence the process of developing teacher professional identity. The obtained results and their subsequent discussion have led to the establishment of a framework of proposals to improve this specific transition, from an institutional and guidance perspective