Method of preparation of a construction element by carbonation of cement

Method of preparation of a construction element by carbonation, comprising the consecutive steps of:

• a) preparing a composition containing a cement, water and chemical additives;
• then
• b) pre-drying the composition;
• then
• c) placing the pre-dried composition in a chamber of an incubator
• the chamber of the incubator contains at least one inlet and one outlet,
• the pre-dried composition is carbonated, in a carbonation step, by feeding into the chamber of the incubator, through the inlet, a flow of CO2 containing gas,
• variations of the CO2 concentration in the chamber of the incubator are kept below 10% of a reference value during the whole carbonation step,
• during the carbonation step, the pressure within the chamber of the incubator is atmospheric pressure or with slight overpressure, the relative humidity within the chamber of the incubator is above 80° % and the temperature within the chamber of the incubator is ranging from 20° C. to 80° C.,
• wherein the chemical additives in the composition comprise more than 0.05% in weight, compared to the total weight of the cement, of a cement hydration retarder,
• wherein the additives further contain a carbonation accelerator selected from the group consisting of triethylamine (TEA), triisopropanolamine (TIPA), calcium salts, sodium salts and mixtures thereof,
• the composition comprises from 0.1% to 3%, of the carbonation accelerator, the percentages are expressed in weight compared to the total weight of the cement.