2026-05-31T08:21:51Zhttps://riuma.uma.es/rest/oai/request

oai:riuma.uma.es:10630/199912026-02-03T11:02:12Zcom_10630_2254col_10630_37953

Calcium aluminate cement conversion analysed by ptychographic nanotomography Shirani, Shiva Cuesta-García, Ana María Gómez-de-la-Torre, María de los Ángeles Díaz, Ana Trtrik, Pavel Holler, Mirko García-Aranda, Miguel Ángel Cemento - Aditivos Cemento - Densidad Construcción Calcium aluminate cements are used for special applications but are nowadays banned for general structural purposes due to the calcium aluminate hydrate conversion, that has led, for concretes fabricated with high water contents, to building collapses. The stoichiometries of these conversion chemical reactions are relatively well established but the consequences in porosity, key to predict durability, were unknown. Here, we have used hard X-ray ptychographic nanotomography to study the hydration of CaAl2O4 at different temperatures and chiefly, at 4ºC and then at 50ºC to provoke conversion similar to field conditions. The mass densities of the resulting Al(OH)3 gels were 1.94, 1.98 and 2.23 g.cm-3, for samples hydrated at 4, 20 and 50ºC, respectively. These values are lower than that of gibbsite, 2.42 g.cm-3. Above all, this 3D imaging technique has allowed measuring the secondary water porosity developed in the conversion, which has an average pore dimension close to 140 nm. 2020-10-15T12:44:17Z 2020-10-15T12:44:17Z 2020 2020-08-17 journal article Cement and Concrete Research 137 (2020) 106201 https://hdl.handle.net/10630/19991 10.1016/j.cemconres.2020.106201 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier