Processing and characterisation of standard and doped alite-belite-ye'elimite ecocement pastes and mortars

Supplementary data to this article can be found online at https://doi.org/10.1016/j.cemconres.2019.105911.Cement and Concrete Research 127 (2020) 105911Here, we report the processing optimisation of two laboratory-prepared alite-belite-ye'elimite ecocements (standard and doped) that release to the atmosphere ~13% less CO2 than Portland Cement during fabrication. The processing was optimised through rheological measurements, where homogeneous pastes and mortars were finally prepared through the study and optimisation of both the superplasticiser content and the water-to-cement ratio. Both parameters were correlated with the phase assembly of selected pastes and compressive strength of the corresponding mortars. After optimisation, mortars with high compressive strengths (~72 and ~77 MPa for the standard mortar, and ~41 and ~75 MPa for the doped one, at 7 and 28 days, respectively) were prepared. Furthermore, the important increase in compressive strength from 7 to 28 days of the optimised mortar prepared from the doped ecocement is due to its composition (the higher content of belite jointly with the reaction of its active polymorph (α'H-belite)).This work is part of the PhD of Mr. Jesus D. Zea-Garcia. This research has been supported by Spanish MINECO and FEDER [BIA2017- 82391-R research project and I3 (IEDI-2016-0079) program]

RICORS2040 : The need for collaborative research in chronic kidney disease

Chronic kidney disease (CKD) is a silent and poorly known killer. The current concept of CKD is relatively young and uptake by the public, physicians and health authorities is not widespread. Physicians still confuse CKD with chronic kidney insufficiency or failure. For the wider public and health authorities, CKD evokes kidney replacement therapy (KRT). In Spain, the prevalence of KRT is 0.13%. Thus health authorities may consider CKD a non-issue: very few persons eventually need KRT and, for those in whom kidneys fail, the problem is 'solved' by dialysis or kidney transplantation. However, KRT is the tip of the iceberg in the burden of CKD. The main burden of CKD is accelerated ageing and premature death. The cut-off points for kidney function and kidney damage indexes that define CKD also mark an increased risk for all-cause premature death. CKD is the most prevalent risk factor for lethal coronavirus disease 2019 (COVID-19) and the factor that most increases the risk of death in COVID-19, after old age. Men and women undergoing KRT still have an annual mortality that is 10- to 100-fold higher than similar-age peers, and life expectancy is shortened by ~40 years for young persons on dialysis and by 15 years for young persons with a functioning kidney graft. CKD is expected to become the fifth greatest global cause of death by 2040 and the second greatest cause of death in Spain before the end of the century, a time when one in four Spaniards will have CKD. However, by 2022, CKD will become the only top-15 global predicted cause of death that is not supported by a dedicated well-funded Centres for Biomedical Research (CIBER) network structure in Spain. Realizing the underestimation of the CKD burden of disease by health authorities, the Decade of the Kidney initiative for 2020-2030 was launched by the American Association of Kidney Patients and the European Kidney Health Alliance. Leading Spanish kidney researchers grouped in the kidney collaborative research network Red de Investigación Renal have now applied for the Redes de Investigación Cooperativa Orientadas a Resultados en Salud (RICORS) call for collaborative research in Spain with the support of the Spanish Society of Nephrology, Federación Nacional de Asociaciones para la Lucha Contra las Enfermedades del Riñón and ONT: RICORS2040 aims to prevent the dire predictions for the global 2040 burden of CKD from becoming true

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Synchrotron pair distribution function approach applied to cement samples

The characterization of the nanocrystalline/amorphous materials is very challenging but the presence of these materials mixed with large amounts of crystalline phases makes the analysis even more complicated. This is the case of cement hydrated samples, since they contain high amounts of crystalline phases jointly with nanocrystalline and amorphous components, making challenging their full characterization. High-energy synchrotron X-ray scattering jointly with the pair distribution function (PDF) methodology is very useful to deeply study complex cement pastes. PDF data give information about the local structure (bonding environments) of the nanocrystalline and amorphous component phases such as cement gels. The main aim of this work is to characterize amorphous/nanocrystalline gels which are present in different cementitious pastes by the PDF approach. Moreover, the PDF technique also gives us quantitatively information about the nanocrystalline and microcrystalline contents. Firstly, the C-S-H gel obtained from the hydration of alite, Ca3SiO5, the main phase of Portland cement, is found to contain two components: a nanocrystalline defective clinotobermorite and an amorphous component which seemed to be monolayers of calcium hydroxide1. Figure below shows the PDF fit of a C-S-H gel formed from the hydration of alite in two selected r-ranges. Secondly, some ye’elimite Ca4Al6O12(SO4) -containing pastes with different sulfate contents have been also studied. The nanocrystalline hydrated phases, such as A-H gel and monosulfoaluminate (AFm) phases have been thoroughly analyzed in the different pastes and the diameters of these nanoparticles have also been reported2. Finally, we will also show here, PDF data for different cement samples (including the Ni sample as standard) that have been collected in two different experimental configurations, i.e., in ID15A beamline at ESRF and in MSPD beamline at ALBA synchrotron3Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. This work has been supported by Spanish MinCIU through BIA2014-57658-C2 and BIA2017-82391-R, which are co-funded by FEDER. We also thank CELLS-ALBA (Barcelona, Spain) and ESRF (Grenoble) for providing synchrotron beam time at BL04-MSPD and ID15A, respectively

Alite hydration mechanism in presence of ye’elimite related to BAY cements

One alternative to decrease CO2 emissions from ordinary Portland Cement (OPC) production consists on the development of a new kind of eco-cements composed by less calcite demanding phases. That is the case of Belite-Ye’elimite-Ferrite (BYF) cements, which have β-belite as a main phase and ye’elimite as a secondary phase. But the low reactivity of β-belite is well known, consequently these materials develop low mechanical strengths at early/intermediate hydration ages. A possible solution proposed to solve this problem consists on the production of cements which contain belite, alite and ye'elimite together, known as Belite-Alite-Ye’elimite (BAY) cements. Consequently, the reaction of alite and ye'elimite with water would develop cements with higher mechanical strengths at early ages, while β- belite will contribute to later ages. The main objective of this work is to better understand the hydration behavior of monoclinic alite in presence of ye’elimite (both stoichiometric and pseudo-cubic polymorphs), in order to be compared with a BAY eco-cement systems. The hydration of systems with selected alite/ye’elimite ratios were studied for the first 24 hours. The main techniques used for this study were in-situ synchrotron X-ray powder diffraction combined with Rietveld methodology and isothermal calorimetry.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. BIA17-82391-R Beca Colciencias 646—Doctorado en el exterior and Enlaza Mundos 2013 (Colombia

Synthesis and scaled-up of standard and active Belite-Alite-Ye'elimite clinker (BAY)

ABSTRACT: Clinkers with the coexistence of belite-alite-ye´elimite (BAY) are considered as eco-friendly cements due to the reduced CO2 emissions released during their manufacture. All BAY clinkering parameters have been optimized: raw materials, mineralizers/activators, clinkering conditions and scaled-up methodology. Two types of clinkers were prepared and scaled-up to have ~2 kg: i) standard-BAY (28.4 wt% of b-belite, 41.5 wt% of alite and 17.4 wt% of ye'elimite) by adding CaF2 and ZnO to the raw mixture; and ii) active-BAY (18.1 wt% of α'H-belite, 42.1 wt% of b-belite, 15.8(2) wt% of alite, and 7.7(2) wt% of ye'elimite) by using optimized amounts of CaF2, ZnO and B2O3. The microscopy[P1] study has revealed that primary particle size of belite is larger (~10 µm) in the active clinker than in the standard one (~5 µm). Moreover, ferrite and alite have incorporated most of the Zn and F in their structures in both clinkers, while belite (b and α’H forms) has preferentially incorporated sulphur

Phase-selective degree of hydration at setting: An in situ synchrotron diffraction study

Setting of Portland cements is still not well understood. Previous studies used techniques that analyse the pastes as a whole to correlate setting times with degree of hydration. Here, in-situ synchrotron X-ray diffraction analysed by the Rietveld method, with internal standard methodology, is used to derive alite dissolution rate and the crystallization kinetics of ettringite and portlandite in three commercial cements. Moreover, C–S–H gel precipitation pace has also been determined. C–S–H gel precipitation is key to account for setting. For grey Portland cements with w/c = 0.5, initial setting is attained when alite degree of hydration is close to 20% and the C–S–H gel content reached approximately 6 vol%.This research has been supported by Junta de Andalucía [UMA18-FEDERJA-095 and P18-RT-720] research projects, both cofunded by FEDER and I3 (IEDI-2016-0079) program

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

The analysis of nanocrystalline and amorphous components within cement pastes that contain high amounts of crystalline phases is very challenging. Synchrotron powder diffraction jointly with the pair distribution function (PDF) methodology is very useful to characterize complex cement pastes. PDF data can give information about the local structure and bonding environments of the non-crystalline components such as aluminate hydrate and calcium-(aluminum)-silicate-hydrate gels. The main goal of this work is to characterize amorphous and nanocrystalline gels which are present in cementitious pastes by total scattering PDF analyses in selected real-space ranges. Moreover, the PDF approach also allows quantitatively determining the nanocrystalline and microcrystalline contents. Several sets of tricalcium silicate pastes have been studied and the results are reported: (i) pastes from different tricalcium silicate polymorphs, such as monoclinic and triclinic; and (ii) the influence of selected parameters in triclinic tricalcium silicate pastes. For all the PDF analyses, a multi r-range approach was followed: the higher r-range (40 – 70 Å) is used to determine the microcrystalline phase contents, portlandite and unreactive alite; then, the intermedium r-range (10 – 25 Å) allows characterizing the atomic ordering in the nanocrystalline fraction of the C-S-H gel; and finally, the low r-range, below 10 Å, gives insight about the chemical nature of the additional amorphous component. It was concluded that for all the untreated tricalcium silicate pastes, the crystal structure of tobermorite-11 Å fits the nanocrystalline contribution of the C-S-H gel in the 10 – 25 Å r-region much better than tobermorite-14 Å.This work has been supported by Spanish MINECO through BIA2017-82391-R, which is co-funded by FEDER. Authors thank ESRF (Grenoble, France) for providing us with beam time at ID15A beamline. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Alite-Belite-Ye'elimite cements: effect of dopants on the clinker composition and properties

<p><strong>ABSTRACT:</strong> Clinkers with alite-belite-ye´elimite (ABY) are considered as eco-friendly cements. Clinkering (2 Kg) of two types of ABY clinkers was optimized: standard-ABY, with CaF₂ and ZnO as dopants (32.6 wt% alite, 30.4 wt% b-belite and 15.6 wt% ye'elimite) and αABY, with CaF₂, ZnO, B₂O₃, Na₂O (14.4 wt% alite, 37.1 wt% b-belite, 18.5 wt% α'_H-belite and 7.5 wt% ye'elimite). Zn and F were mainly incorporated in alite and ferrite, while S sulfur was mostly incorporated into Fluor-ellestadite, ye’elimite and, in lower percentages, in belite and ferrite, determined by EDS semi-quantitative. The effect of dopants on the hydration of the cement mortars has been tested. Thus, standard-ABY develops 29.9 MPa compressive strengths at 1 day while αABY does 16.8 MPa, mainly due to the higher amount of alite of the former. The presence of α’_H-belite in αABY increases mechanical strengths at 28 days of hydration from 44.7 MPa of standard-ABY to 74.9 MPa.</p