Carbonation mechanisms and kinetics of lime-based binders: An overview

The reaction of slaked lime with atmospheric CO2 in the presence of humidity leads to the formation of cementing carbonate phases in traditional aerial lime mortars and plasters. This carbonation reaction also affects the setting and degradation of hydraulic lime mortars and modern cement. Here, we present an overview of the existing knowledge on carbonation of lime-based binders, which are experiencing a revival as compatible material for the conservation of the built heritage and new sustainable construction. First, the carbonation reaction is defined and its importance in a range of technical and natural processes is outlined. This sets the ground for presenting a review of existing mechanistic models for the carbonation of lime-based materials, including the recent interface-coupled dissolution-precipitation model, and the understanding of carbonation in terms of non-classical crystallization theory. Kinetics models and experimental results for carbonation of lime-based binders (crystals and powder, as well as mortars/plasters) and its acceleration are presented and discussed. Finally, conclusions and future research directions are indicated.Spanish Government grant PID2021-125305NB-I00 funded by MCIN/ AEI /10.13039/ 501100011033ERDF A way of making EuropeJunta de Andalucía research group RNM-179 and grant P20_00675University of GranadaUnidad Científica de Excelencia UCE-PP2016-05European Commission, H2020 Programme, Marie Skłodowska-Curie Action European Training network – Innovative Training Network (ETN-ITN), SUBlime (grant agreement # 955986)Funding for open access charge: Universidad de Granada/CBU

On the Role of Poly-Glutamic Acid in the Early Stages of Iron(III) (Oxy)(hydr)oxide Formation

Nucleation of minerals in the presence of additives is critical for achieving control over the formation of solids in biomineralization processes or during syntheses of advanced hybrid materials. Herein, we investigated the early stages of Fe(III) (oxy)(hydr)oxide formation with/without polyglutamic acid (pGlu) at low driving force for phase separation (pH 2.0 to 3.0). We employed an advanced pH-constant titration assay, X-ray diffraction, thermal analysis with mass spectrometry, Fourier Transform infrared spectroscopy, and scanning electron microscopy. Three stages were observed: initial binding, stabilization of Fe(III) pre-nucleation clusters (PNCs), and phase separation, yielding Fe(III) (oxy)(hydr)oxide. The data suggest that organic–inorganic interactions occurred via binding of olation Fe(III) PNC species. Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed a plausible interaction motif and a conformational adaptation of the polypeptide. The stabilization of the aqueous Fe(III) system against nucleation by pGlu contrasts with the previously reported influence of poly-aspartic acid (pAsp). While this is difficult to explain based on classical nucleation theory, alternative notions such as the so-called PNC pathway provide a possible rationale. Developing a nucleation theory that successfully explains and predicts distinct influences for chemically similar additives like pAsp and pGlu is the Holy Grail toward advancing the knowledge of nucleation, early growth, and structure formation.Institute of Technical Sciences of SASA - Ministry of Education, Science and Technological Development of the Republic of Serbia (451-03-9/2021-14/200175)IAESTE Belgrade organization and DAA

Watchful waiting for depression using depathologization, advice and shared decision making

Background: Antidepressant use is on the rise, while the problem of depression on a population wide level is not being tackled. One of the hypothesis why this may be happening is the effect of adverse effects and withdrawal symptoms of antidepressants, as well as pathologization of normal sadness. Methods: In this study we did partial watchful waiting using (1) psychosocial advice; (2) depathologization; and (3) shared decision making. The study comprised of 83 consecutive non-suicidal out-patients with depressive symptoms. Results: The first among the three main findings of our study was that watchful waiting, when coupled with psychosocial advice, depathologization and shared decision making, was effective in 64.5 % of patients who ended up with no pharmaco- or psychotherapy after the three-month follow-up period. Severity of depression did not correlate with the efficacy of watchful waiting. Expectations from pharmacotherapy were the dominant factor influencing whether a patient will enter or finish the study without pharmacotherapy. Limitations: This was not a randomized control trial and the goal was to see if this approach is feasible. A randomized controlled trial comparing watchful waiting approach with pharmacotherapy could not factor in all parameters involved (i.e. self-fulfilling prophecy through pathologization, withdrawal and risk of chronicity). Conclusions: Our study showed that watchful waiting might be effective, particularly when coupled with depathologization, psychosocial advice and shared decision making, suggesting that this approach should be tested as the first-line of treatment in non-suicidal patients with depressive symptoms