The objective of this study is to evaluate the early age hydration mechanisms of accelerated CEM I pastes. Liquid phase analysis, conductimetry, isothermal calorimetry, in situ XRD and SEM were performed on cement pastes produced with equivalent doses of an alkaline accelerator (sodium aluminate solution) and of an alkali-free accelerator (aluminum sulfate solution). Results showed that the addition of these chemicals first changes the ionic equilibria of the medium by the consumption of Ca2+ and SO42- ions from the liquid phase. The alkali-free accelerator contributes to the rapid formation of ettringite, as well as to a faster rate of alite dissolution and hydration. The aluminate accelerator leads to AFt and AFm formation, rapidly depleting gypsum and filling up the space, inhibiting further alite hydration. According to the results, variations in cement hydration mechanisms caused by accelerators with different chemical.compositions are explained.Peer ReviewedPostprint (author's final draft
12 13 Hydration reactions of C 3 A with various amounts of calcium sulfate hemihydrate, 14 gypsum or a mixture of the two, were investigated by isothermal microcalorimetry, 15 and a monitoring of the ionic concentrations of diluted suspensions. This study 16shows that sulfate type used modifies the early C 3 A-CaSO 4 hydration products and 17 the rate of this hydration. The fast initial AFm formation observed before ettringite 18 precipitation in the C 3 A-gypsum system is avoided as soon as hemihydrate is 19 present in the suspension. This was attributed to.higher super saturation degrees and 20 then higher nucleation frequency with regard to the ettringite obtained in the 21 presence of hemihydrate. Moreover, replacement of gypsum by hemihydrate also 22 leads to an increase of the ettringite formation rate during at least the five first hours 23 under experimental conditions. 24 25
Nanoscale oxide-based negative electrodes are of great interest for lithium ion batteries due to their high energy/power density, and enhanced safety. The crystallinity effect of mesoporous TiO2 nanoparticle electrode was investigated in this work.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.