Production of a mainly carbonate bonded article by carbonation of alkaline materials

#This application is a National Stage Application of PCT/EP2009/055154, filed Apr. 28, 2009, which claims benefit of PCT/EP2008/055195, filed Apr. 28,2008 and which applications are incorporated herein by reference. To the extent appropriate, a claim of priority is made to each of the above disclosed applications.

#The present invention is related to a method of production of an article by carbonation of materials comprising reactive sources of alkaline earth metal silicates. The resulting article is bonded mainly by the carbonates formed during the carbonation reaction. In particular, the invention is related to methods of production of non cement-based articles. The method of the invention can be used for sequestering CO2 and/or for producing an article having high compressive strength and/or for recycling waste materials. The invention is also related to an article comprising carbonates and advantageously having a high compressive strength.

#The idea to stabilise cementitious materials and slags having pozzolanic or latent hydraulic binding properties by accelerated carbonation is known. Such accelerated carbonation aims mainly at accelerating the curing of the cementitious binder, by accelerating the hydration of tricalcium silicates (C3S) to calcium silicate hydrates (CSH), rather than forming a large amount of carbonates. The hydration of tricalcium silicates (C3S) forms portlandite (Ca(OH)2) as a by-product, which can be carbonated.

#FIG. 1 represents the particle size distribution of stainless steel (SSt) slag (residual fraction after extraction of metal fraction) and of sea sand. FIG. 1A represents the particle size distribution (particle size occurrence in % by volume) versus the particle size (μm) of three samples of stainless steel slag (R1, R2, R3). FIG. 1B represents the corresponding cumulative values (% by volume) versus the particle size (μm). FIG. 1C represents the particle size distribution (particle size occurrence in % by volume) versus the particle size (μm) of sea sand. FIG. 1D represents the corresponding cumulative values (% by volume) versus the particle size (μm).

#FIG. 2 represents XRD diffraction patterns of stainless steel slag. Pattern 21 refers to a compacted (182 kg/cm2) carbonated (140° C., 2 MPa, 18 hours) specimen and pattern 22 to a compacted non carbonated specimen. P=Portlandite (Ca(OH)2), L=Periclase (MgO), C=Calcite (CaCO3), A=Ankerite (Ca(Fe,Mg)(CO3)2), B=Bredigite Ca14Mg2(SiO4)8, M=Merwinite Ca3Mg(SiO4)2, K=Kirschsteinite (CaFeSiO4), G=Gehlenite (Ca2Al2SiO7) and/or Akermanite (Ca2Mg(Si2O7)), Q=Quartz (SiO2), D=Donathite (magnetite and/or chromite). Counts/s are set out against 2θ values (x-axis).

#FIG. 3 represents concentrations of Cr and Mo in solution (μg/l) after immersion of carbonated blocks (70 wt % SSt slag, 30 wt % sea sand) in a first solution for hours (D1) and a second solution for 18 hours (D2). Concentrations in the first and second solution were determined for blocks carbonated at 140° C. and at CO2 pressures (pCO2) identified on the graphs (1, 2, 5, 7.5, 10 and 14 MPa). Results of the same tests for non-carbonated compacts are indicated at 0 bar pCO2. FIG. 3A represents the concentration of Mo (μg/l) for the blocks as identified. FIG. 3B represents the concentration of Cr (μg/l) for the blocks as identified. FIG. 3C represents the pH of the solution after immersion of the blocks as identified. FIG. 3D represents the conductivity C (mS/cm) of the solution after immersion of the blocks as identified.

#Embodiments of the present invention will now be described in detail with reference to the attached figures, the invention is not limited thereto but only by the claims. Those skilled in the art can recognize numerous variations and modifications of this invention that are encompassed by its scope. Accordingly, the description of preferred embodiments should not be deemed to limit the scope of the present invention.

#Furthermore, the terms first, second and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

#It is to be noticed that the term “comprising” should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. Thus, the scope of the expression “a device comprising means A and B” should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, A and B are relevant components of the device.