Year: 2026
Type: preprint
Abstract: Strätlingite, Ca 2 Al(AlSi)O 2 (OH) 10 ·2.25H 2 O a phyllosilicate found in nature and in ancient Roman concrete, was investigated for its synthesis conditions, phase stability, and thermal and chemical degradation mechanisms. Contrary to previous reports, phase formation was observed to be complete after ~3 days of setting, using hand-ground precursors, while the applied water:solid ratio has only minimal effect on purity of the resulting strätlingite. The chemical stability field is rather narrow, and off-stoichiometry in the initial Ca:Si:Al ratio of the starting materials promotes the formation of poorly crystalline C-(A-)S-H side phases, which are difficult to detect by XRPD and may compromise complementary data interpretation. Thermogravimetry, variable humidity in situ XRPD and water sorption measurements reveal a reversible hydration below 100 °C, that is reflected in gradual changes of the lattice parameters and unit cell volume up to 2%. Above 100 °C irreversible changes to the crystal structure occur, resulting in the loss of the long-range order, which is complete at 200 °C and further. Strätlingite remains chemically stable during setting LC 3 cement formulations, making it a potential cement additive, provided the temperatures remain below 100 °C.
Source: ChemRxiv
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7215043097