0000000000461583
AUTHOR
Alejandro Fernandez-martinez
Impact of gluconate and hexitol additives on the precipitation mechanism and kinetics of C-S-H
The present paper investigates the influence of gluconate and hexitol additives on the precipitation mechanism and kinetics of C-S-H. To this end, wet chemistry C-S-H precipitation experiments were performed under controlled conditions of solution supersaturation, under varying silicate concentration, while the transmittance of the solution was followed. This allowed determining induction times for the formation of C-S-H precursors in the presence and absence of gluconate and three hexitol molecules. Characterization of the precipitates was performed via small angle X-ray scattering and cryo-transmission electron microscopy experiments, which allowed the identification of a multi-step nucle…
Two-Step Nucleation Process of Calcium Silicate Hydrate, the Nanobrick of Cement
Despite a millennial history and the ubiquitous presence of cement in everyday life, the molecular processes underlying its hydration behavior, like the formation of calcium–silicate–hydrate (C–S–H), the binding phase of concrete, are mostly unexplored. Using time-resolved potentiometry and turbidimetry combined with dynamic light scattering, small-angle X-ray scattering, and cryo-TEM, we demonstrate C–S–H formation to proceed via a complex two-step pathway. In the first step, amorphous and dispersed spheroids are formed, whose composition is depleted in calcium compared to C–S–H and charge compensated with sodium. In the second step, these amorphous spheroids crystallize to tobermorite-typ…
Gluconate and hexitols effects on C-S-H solubility
This study investigates the effect of gluconate, a carboxylate ion, and three uncharged hexitols, D-sorbitol, D-mannitol and D-galactitol on the solubility of C-S-H. Thermodynamic modeling was used to determine the kind and amount of Ca-organic-silicate-OH complexes that potentially form in the conditions studied. All the organics form complexes with calcium and hydroxide, In addition, heteropolynuclear organics complexes with calcium, hydroxide and silicate are observed at high pH values and high calcium concentrations with the exception of mannitol. The strength of complexation with silicate decreases from gluconate > sorbitol > galactitol. The adsorption of the selected organics on…
Monitoring a Mechanochemical Reaction Reveals the Formation of a New ACC Defect Variant Containing the HCO 3 – Anion Encapsulated by an Amorphous Matrix
Crystal growth & design 20(10), 6831 - 6846 (2020). doi:10.1021/acs.cgd.0c00912