In situ time-resolved X-ray diffraction of tobermorite formation in autoclaved aerated concrete: Influence of silica source reactivity and Al addition

• Published in: Cement and concrete research 2011-05, Vol.41 (5), p.510-519
• Main Authors: Matsui, Kunio, Kikuma, Jun, Tsunashima, Masamichi, Ishikawa, Tetsuji, Matsuno, Shin-ya, Ogawa, Akihiro, Sato, Masugu
• Format: Article
• Language: English
• Subjects: Aerated; ALKALINE EARTH METAL COMPOUNDS; ALUMINIUM; Aluminum; Applied sciences; Autoclaving; BUILDING MATERIALS; Buildings. Public works; CALCIUM COMPOUNDS; Calcium silicate hydrate (C-S-H) (B); CALCIUM SILICATES; CEMENTS; CHERT; COHERENT SCATTERING; CONCRETES; Concretes. Mortars. Grouts; DIFFRACTION; DISSOLUTION; ELEMENTS; Exact sciences and technology; HYDRATES; Hydrogarnet (D); INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Lightweight concretes; MATERIALS; METALS; MINERALS; OXIDE MINERALS; OXYGEN COMPOUNDS; PORTLAND CEMENT; Portland Cement (D); QUARTZ; RADIATION SOURCES; REACTIVITY; RESOLUTION; ROCKS; Sand; SCATTERING; SEDIMENTARY ROCKS; SILICA; SILICATES; SILICON COMPOUNDS; Silicon dioxide; SYNCHROTRON RADIATION SOURCES; TIME RESOLUTION; TIMING PROPERTIES; Tobermorite (unlisted); X-RAY DIFFRACTION; X-ray diffraction (B); X-rays
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2011.01.022

The hydrothermal formation of tobermorite during the processing of autoclaved aerated concrete was investigated by in situ X-ray diffraction (XRD) analysis. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. To investigate the effects of the silica source, reactive quartz from chert and less-reactive quartz from quartz sand were used as starting materials. The effect of Al addition on tobermorite formation was also studied. In all cases, C-S-H, hydroxylellestadite and katoite were clearly observed as intermediates. Acceleration of tobermorite formation by Al addition was clearly observed. However, Al addition did not affect the dissolution rate of quartz. Two pathways, via C-S-H and katoite, were also observed in the Al-containing system. These results suggest that the structure of initially formed C-S-H is important for the subsequent tobermorite formation reactions.