Patent ID: 8709151

Claim:
A method of producing a carbonate bonded article by carbonation, the method comprising the steps of: providing a granular material having a pH higher than or equal to 8.3, the granular material comprising at least one alkaline earth metal silicate phase, compacting the granular material with a compaction pressure of at least 5 MPa to obtain a compact of the granular material, wherein the porosity of the compact is smaller than or equal to 37% by volume and wherein the intrinsic permeability of the compact is at least 1·10 −12 cm 2 , transporting the compact to a reactor, and reacting in the reactor the granular material in the compact with carbon dioxide in the presence of water to form at least 5% by weight of carbonates (CO 3 2− ) thus transforming the compact into the carbonate bonded article, wherein the compact is unsaturated with moisture at the beginning of reacting step, wherein the compact in the reactor is in an atmosphere comprising the carbon dioxide, wherein the atmosphere is at a temperature of at least 70° C. and at a pressure of at least 0.5 MPa so that the alkaline earth metal silicate phase contributes to formation of the carbonates, the pressure being higher than a saturated vapour pressure of water at the temperature, wherein the granular material is free of material having hydraulic binding properties or comprises an amount thereof such that a compressive strength of the carbonate bonded article is more than two times a strength of a same compact treated in a nitrogen atmosphere free of carbon dioxide under same conditions as in the reacting step following 28 days of aging subsequent to the reacting or nitrogen treatment step.