Rheological and hydration characterization of calcium sulfoaluminate cement pastes

Calcium sulfoaluminate (CSA) cements are currently receiving a lot of attention because their manufacture produces less CO2 than ordinary Portland cement (OPC). However, it is essential to understand all parameters which may affect the hydration processes. This work deals with the study of the effect of several parameters, such as superplasticizer (SP), gypsum contents (10, 20 and 30 wt%) and w/c ratio (0.4 and 0.5), on the properties of CSA pastes during early hydration. This characterization has been performed through rheological studies, Rietveld quantitative phase analysis of measured x-ray diffraction patterns, thermal analysis and mercury porosimetry for pastes, and by compressive strength measurements for mortars. The effect of the used SP on the rheological properties has been established. Its addition makes little difference to the amount of ettringite formed but strongly decreases the large pore fraction in the pastes. Furthermore, the SP role on compressive strength is variable, as it increases the values for mortars containing 30 wt% gypsum but decreases the strengths for mortars containing 10 wt% gypsum.This work has been supported by Spanish Ministry of Science and Innovation through MAT2010- 16213 research grant, which is co-funded by FEDER, and Ramón y Cajal Fellowship (RYC-2008- 03523)

Hydration studies of calcium sulfoaluminate cements blended with fly ash

The main objective of this work is to study the hydration and properties of calciumsulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied parameters were: i) FA content, 0, 15 and 30 wt.%; and ii) water addition, water-to-CSA mass ratio (w/CSA = 0.50 and 0.65), and water-to-binder mass ratio (w/b = 0.50). Finally, compressive strengths after 6 months of 0 and 15 wt.% FA [w/CSA = 0.50] mortars were similar: 73 ± 2 and 72 ± 3 MPa, respectively. This is justified by the filler effect of the FA as no strong evidences of reactivity of FA with CSA were observed. These results support the partial substitution of CSA cements with FA with the economic and environmental benefitsThis work has been supported by Spanish MINECO through MAT2010-16213 research grant, which is co-funded by FEDER. I. Santacruz thanks a Ramón y Cajal fellowship, RYC-2008-03523

Inteligencia emocional y apego adulto: efectos del uso problemático del smartphone

Smartphone usage can become problematic when individuals have difficulties in emotional regulation. To clarify risk factors for problematic smartphone usage, the study had three objectives: To analyze the effect of emotional intelligence and attachment dimensions on smartphone usage; to evaluate differences by types and styles of attachment in problematic smartphone usage; to explore the roles of sex and age. For this purpose, the Smartphone Dependency and Addiction Scale, the Wong & Law Emotional Intelligence Scale, and the Adult Attachment Questionnaire were used. The study included 552 young adults (M = 21.79, SD = 2.66; 74.1% women) selected by purposive sampling, and classified in Generation Z and Millennials. The results showed that low awareness of one's emotions (emotional intelligence), poor self-esteem and need for approval, hostile conflict resolution, rancor, and possessiveness (attachment) predicted problematic smartphone usage. Furthermore, insecure type of attachment and negative styles such as fearfulness were closely related to smartphone addiction. Sex had some explanatory power with respect to device use, with women showing higher levels of problematic smartphone usage. In conclusion, the findings support the importance of the secure and positive attachment system, and being able to evaluate and regulate one’s own emotions for preventing problematic smartphone use.El uso del smartphone puede tornarse problemático cuando se presentan dificultades de regulación emocional. En la investigación se plantearon tres objetivos: analizar el efecto de las dimensiones de inteligencia emocional y el apego sobre el uso del smartphone; evaluar las diferencias en el uso problemático del móvil atendiendo a tipos y estilos de apego; explorar el efecto del sexo y la edad. Se utilizaron la Escala de Dependencia y Adicción al Smartphone, la Escala de Inteligencia Emocional de Wong & Law y el Cuestionario de Apego adulto. El estudio incluyó a 552 jóvenes (M = 21.79, SD = 2.66; 74.1% mujeres) seleccionados por muestreo intencional y clasificados en Generación Z y Millennials. Una baja conciencia de las propias emociones (inteligencia emocional), una pobre autoestima y necesidad de aprobación, la resolución hostil de conflictos, rencor y posesividad (apego) predecían el uso problemático. Además, el tipo inseguro de apego y los estilos negativos como el temeroso se relacionan más con este uso problemático. El sexo aportaba cierta capacidad explicativa, siendo las mujeres las que mostraron más problemas. Los hallazgos apoyan la relevancia de construir un apego seguro y positivo y de ser capaces de evaluar las propias emociones para prevenir los usos problemáticos del smartphone

Effect of calcium sulfate source on the hydration of calcium sulfoaluminate eco-cement

The availability of cements, including eco-cements, with tailored mechanical properties is very important for special applications in the building industry. Here we report a full study of the hydration of calcium sulfoaluminate eco-cements with different sulfate sources (gypsum, bassanite and anhydrite) and two water/cement ratios (0.50 and 0.65). These parameters have been chosen because they are known to strongly modify the mechanical properties of the resulting mortars and concretes. The applied multitechnique characterization includes: phase assemblage by Rietveld method, evolved heat, conductivity, rheology, compressive strength and expansion/retraction measurements. The dissolution rate of the sulfate sources is key to control the hydration reactions. Bassanite dissolves very fast and hence the initial setting time of the pastes and mortars is too short (20 min) to produce homogeneous samples. Anhydrite dissolves slowly so, at 1 hydration-day, the amount of ettringite formed (20 wt%) is lower than that in gypsum pastes (26 wt%) (w/c = 0.50), producing mortars with lower compressive strengths. After 3 hydration-days, anhydrite pastes showed slightly larger ettringite contents and hence, mortars with slightly higher compressive strengths. Ettringite content is the chief parameter to explain the strength development in these eco-cements.Universidad de Málaga. Campus de Excelencia Interncaional Andalucía Tech

Rietveld quantitative phase analysis with molybdenum radiation

Building materials are very complex samples of worldwide importance; hence quantitative knowledge of their mineralogical composition is necessary to predict performances. Rietveld quantitative phase analysis (RQPA) allows a direct measurement of the crystalline phase contents of cements. We highlight in this paper the use of laboratory X-ray powder diffraction (LXRPD) employing high-energy radiation, molybdenum (Mo), for attaining the RQPA of cements. Firstly, we evaluate the accuracy of RQPA employing a commercial calcium sulfoaluminate clinker with gypsum. In addition to MoKα1 and MoKα1,2 radiations, Cu and synchrotron patterns are also analyzed for the sake of comparison. Secondly, the assessment of the accuracy of RQPA results obtained using different radiations (synchrotron, Mo, and Cu) and geometries (reflection and transmission) is performed by analyzing two well-known commercial samples. As expected, for LXRPD data, accuracy in the RQPA results improves as the irradiated volume increases. Finally, three very complex aged hydrated cements have been analyzed using MoKα1-LXRPD and Synchrotron-XRPD. The main overall outcome of this work is the benefit for RQPA of using strictly monochromatic MoKα1 radiation. Best laboratory results arise from MoKα1 data as the effective tested volume is much increased but peak overlapping is not swelledUniversidad de Málaga. Campus de Excelencia Internacional. Andalucía Tech

A 16-week multicomponent exercise training program improves menopause-related symptoms in middle-aged women. The FLAMENCO project randomized control trial

Abstract Objective: To investigate the influence of a supervised multicomponent exercise training program on menopause-related symptoms, particularly vasomotor symptoms (VMS), in middle-aged women. Methods: A total of 112 middle-aged women (mean age 52 4 y old, age range 45-60 y) from the FLAMENCO project (exercise [n ¼ 59] and counseling [n ¼ 53] groups) participated in this randomized controlled trial (perprotocol basis). The exercise group followed a multicomponent exercise program composed of 60-minute sessions 3 days per week for 16 weeks. The 15-item Cervantes Menopause and Health Subscale was used to assess the frequency of menopause-related symptoms. Results: After adjusting for body mass index and Mediterranean diet adherence, the subscales measuring menopause-related symptoms and VMSs decreased 4.6 more in the exercise group compared to the counseling group (between-group differences [B]: 95% CI: -8.8 to -0.2; P ¼ 0.040). The exercise group also showed significant improvements in the subscales of couple relationships (between-group differences [B]: -1.87: 95% CI: -3.29 to - 0.45; P ¼ 0.010), psychological state (between-group differences [B]: -2.3: 95% CI: -5 to -0.2; P ¼ 0.035), and VMSs (between-group differences [B]: -4.5: 95% CI: -8.8 to -0.2; p ¼ 0.040) in the Cervantes Menopause and Health Subscale compared with the counseling group. Conclusions: A 16-week multicomponent physical exercise program showed a positive effect on menopauserelated symptoms especially in couple relationships, psychological state, and VMS, among 45 to 60 year old women

In-situ hydration study of sulfobelite eco-cements

ALBA User Meeting and VI AUSE Conferenc

Effect of different retarders on the hydration of calcium sulfoaluminate eco-cement pastes

VERSIÓN PRE-PRINTThe manufacture of Calcium SulfoAluminate (CSA) cements is more environmentally friendly than that of OPC [1] as their production releases up to 40% less CO2 than the latter. The main performances of CSA cements are fast setting time, good-chemical resistance properties and high early strengths. CSA cements are prepared by mixing CSA clinker with different amounts of a calcium sulfate set regulator such as gypsum (CaSO4•2H2O), bassanite (CaSO4•½H2O), or anhydrite (CaSO4), or mixtures of them. It is possible to modify the hydration process of CSA cements not only by its composition, but also by the selection of different quantities or sources of calcium sulfate [2,3]. The dissolution rate of the sulfate source is a key point to control the reactions during the hydration of CSA cements, and hence the mechanical properties of the corresponding pastes and mortars. The solubility of bassanite in water (0.88 g/100 mL) is 3-4 times larger than that for gypsum or anhydrite and hence, all the reactions start quickly, showing initial setting times as short as 20 min, which do not allow the preparation of homogeneous samples, with the consequent dramatic effect onto their mechanical strength values. However, the setting time can be controlled through the addition of small amounts of different additives/retarders. The objective of this work is to control the hydration, including setting time, of CSA cements prepared with bassanite and different retarders to obtain tailored CSA cements and mortars for different applications. The addition of these additives reduced considerably the viscosity of the bassanite-pastes to a minimum value which depends on the properties of the additive. The mechanical strength values of selected mortars have been correlated to those variables.- Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. - Spanish MINECO through MAT2010-16213 and MAT2010-15175 which are co-funded by FEDER. Junta de Andalucía through P11-FQM-07517 and FQM-1656 research projects. I. Santacruz thanks a Ramón y Cajal fellowship, RYC-2008-03523

Quantitative phase Analisis: A comparative study of Mo and Cu strictly monochromatic radiations

A comparison of the Rietveld quantitative phase analyses (RQPA) obtained using Cu-Kα1, Mo-Kα1, and synchrotron strictly monochromatic radiations is presented. The main aim is to test a simple hypothesis: high energy Mo-radiation, combined with high resolution laboratory X-ray powder diffraction optics, could yield more accurate RQPA, for challenging samples, than well-established Cu-radiation procedure(s). In order to do so, three set of mixtures with increasing amounts of a given phase (spiking-method) were prepared and the corresponding RQPA results have been evaluated. Firstly, a series of crystalline inorganic phase mixtures with increasing amounts of an analyte was studied in order to determine if Mo-Kα1 methodology is as robust as the well-established Cu-Kα1 one. Secondly, a series of crystalline organic phase mixtures with increasing amounts of an organic compound was analyzed. This type of mixture can result in transparency problems in reflection and inhomogeneous loading in narrow capillaries for transmission studies. Finally, a third series with variable amorphous content was studied. Limit of detection in Cu-patterns, ~0.2 wt%, are slightly lower than those derived from Mo-patterns, ~0.3 wt%, for similar recording times and limit of quantification for a well crystallized inorganic phase using laboratory powder diffraction was established ~0.10 wt%. However, the accuracy was comprised as relative errors were ~100%. Contents higher than 1.0 wt% yielded analyses with relative errors lower than 20%. From the obtained results it is inferred that RQPA from Mo-Kα1 radiation have slightly better accuracies than those obtained from Cu-Kα1. This behavior has been established with the calibration graphics obtained through the spiking method and also from Kullback-Leibler distance statistic studies. We explain this outcome, in spite of the lower diffraction power for Mo-radiation (compared to Cu-radiation), due to the larger volume tested with Mo, also because higher energy minimize pattern systematic errors and the microabsorption effect.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

In-situ early age hydration of cement-based materials by synchrotron X-ray powder diffraction

Cement based binders are building materials of worldwide importance. Since these samples are very complex, the knowledge/control of their mineralogical composition are essential to design and predict materials with specific/improved performance. Rietveld quantitative phase analysis (RQPA) allows the quantification of crystalline phases and, when combined with specific methodologies, as the addition of an internal standard or the external standard approach (G-factor), amorphous and non-crystalline phases can also be quantified. However, to carry out a proper RQPA in hydrated cementitious-materials, a good powder diffraction pattern is necessary. In this work, synchrotron X-ray powder diffraction (SXRPD) has been used, allowing in-situ measurements during the early-age hydration process. This work deals with the early hydration study of cement-based materials. The studied samples were: a laboratory-prepared belite calcium sulphoaluminate (BCSAF) clinker (non-active) mixed with 10wt% gypsum, labelled G10B0; two active laboratory-prepared BCSAF clinkers (activated with 2wt% borax), one mixed with 10wt% gypsum and the other one with 10wt% monoclinic-bassanite, hereafter named G10B2 and B10B2, respectively; and an environmentally-friendly cement sample from Henkel, composed of bassanite mixed with 15wt% Portland cement and 10wt% Metakaolin, labelled H1. Anhydrous G10B0 contains beta-belite and orthorhombic-ye'elimite as main phases, while alpha'H-belite and pseudo-cubic-ye'elimite are stabilized in G10B2 and B10B2, with the corresponding sulphate source. Anhydrous H1 contains monoclinic and hexagonal bassanite and alite as main phases. Ye'elimite, in the non-active BCSAF cement pastes, dissolves at a higher pace than in the active one (degree of reaction is α~25% and α~10% at 1 h, respectively) (both prepared with gypsum), with the corresponding differences in ettringite crystallisation (degree of precipitation is α~30% and α~5%, respectively). Moreover, the type of sulphate source has important consequences on the hydration of the active BCSAF cement pastes. Bassanite is quickly dissolved and it precipitates as gypsum within the first hour of hydration (in B10B2). At that time, ettringite starts to crystallize, and after 12 hours is almost fully crystallized, similar to G10B2. In H1, bassanite transforms into gypsum within the first hour, being the principal hydration product; ettringite starts to be formed just after few hydration minutes. These results are crucial in the understanding and development of improved cement materials.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech