Preliminary characterization of hydraulic components of low-temperature calcined marls from the south of Italy: Fid-Bau Portal

Preliminary characterization of hydraulic components of low-temperature calcined marls from the south of Italy

Gnisci, Andrea

Abstract Natural cement and hydraulic lime are considered proper candidates to be used in conservation and restoration of historical buildings cause their compatibility with original materials. Four marls with different percentage of calcite and clay were collected in the south of Italy and calcined at low temperatures (850 °C and 1050 °C). Unhydrated and hydrated products were characterized by X-ray diffraction and thermogravimetric analysis to identify hydraulic components; Rietveld analysis was performed to evaluate the amount of each phase; morphology and elemental composition of hydrated pastes were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Belite (β-C2S, α′-C2S) and amorphous aluminates resulted the principal hydraulic components. The presence in cement pastes of hydration products such as calcium hydroxide, ettringite and calcium silicate hydrates suggested the possibility to use the analyzed marls as hydraulic lime and natural cements for the restoration and conservation of historical buildings.

Highlights • Low temperatures are used for the calcination of marls from the south of Italy. • Belite and amorphous aluminates resulted the principal hydraulic components. • The marls were calcined to obtain hydraulic lime and natural cement. • XRD and SEM-EDX analysis were used to identify C-S-H and ettringite in cured pastes.