Structural investigation of carbonation and hydration process of hydraulic dolomitic binder

•Hydraulic dolomitic binder is synthesized from dolomite flour and clay.•The active phases of binder are CaO, MgO and an amorphous phase in the system CaO–SiO2–Al2O3.•Formation of crystalline magnesium carbonate phases starts at the fifth week of hardening.•Carbonation product of brucite – nesquehonite – form a dense network of prism-type crystals.•The binder is a perspective alternative for restoration of dolomitic Roman cement. The research deals with the microstructural examination of the hardening process of dolomitic binder synthesized from dolomite flour and clay. Such binder based on its suitable properties can be considered as a perspective alternative for restoration purposes of dolomitic Roman cement – a widely used construction binder in Riga during the late 19th and early 20th century. The structures formed during hydration and carbonation throughout the hardening are detected by using scanning electron microscopy (SEM) at every 7 days for 3 months. The low firing temperature of the binder ensures the formation of active and hydraulic phases – CaO, MgO and an amorphous phase in the system CaO-SiO2-Al2O3. The results of structural analysis showed that beginning with the fifth week of hardening a formation of a dense network of prism-type monolithic crystals – the carbonation product of brucite – takes place on the surface of samples. Such structure can contribute to an increased durability.