METHOD FOR BINDING OF CARBON DIOXIDE

Abstract

The invention relates to a method for binding of carbon dioxide, comprising: providing a starting material which comprises sources for CaO and SiO.sub.2 and optionally also Al, Fe and/or Mg, hydrothermally treating the starting material in an autoclave at 50 to 300 C., tempering at 350 to 600 C., and hardening the resulting material with carbon dioxide. The invention further relates to building elements which are obtained by hardening a material according to the method.

Claims

1. A method for binding of carbon dioxide, comprising: providing a starting material which contains sources of CaO and SiO.sub.2, hydrothermally treating the starting material in an autoclave at 50 to 300 C., tempering the material obtained by hydrothermal treatment at 350 to 600 C., adding water or other fluids for adjusting the consistency, pouring in molds for the production of building elements or processing as mortar or cast-in-place concrete, and hardening the material obtained by hydrothermal treatment and tempering with carbon dioxide.

2. The method according to claim 1, wherein the starting material is selected from the group consisting of calcium hydroxide or oxide, quartz powder, microsilica, bauxite, clay/claystone, calcined clays, basalts, peridotites, dunites, ignimbrites, carbonatites, ashes/slags/ground granulated blast furnace slags, various stockpile materials, red and brown muds, natural sulphate carriers, desulphurisation muds, phosphogypsum, flue gas gypsum, titanogypsum and fluorogypsum.

3. The method according to claim 1, wherein a molar Ca:Si ratio in the starting material is set to be from 1.5 to 2.5.

4. The method according to claim 1, wherein the starting material comprises sources of Mg, wherein a molar ratio of Ca:Mg is set to be from 0.1 to 100.

5. The method according to claim 1, wherein the starting material comprises sources for Al and/or Fe, wherein a molar ratio (Al+Fe)/Si is set to be from 100 to 0.1.

6. The method according to claim 4, wherein a molar (Ca+Mg)/(Si+Al+Fe) ratio is set to be from 1 to 3.5.

7. The method according to claim 1, wherein that starting material mixture is seeded with 0.01 to 30% by weight of seed crystals, which contain at least one material selected from the group consisting of calcium silicate hydrate, Portland clinker, ground granulated blast furnace slag, magnesium silicate, calcium sulfoaluminate (belite) cement, water glass, and glass powder.

8. The method according to claim 1, wherein the hydrothermal treatment is carried out at a temperature of from 100 to 300 C.

9. The method according to claim 1, wherein the hydrothermal treatment is carried out at a water/solid ratio of from 0.1 to 100.

10. The method according to claim 1, wherein residence times of from 0.1 to 24 hours are set for the hydrothermal treatment.

11. The method according to claim 1, wherein, during the heat treatment, an additional holding time during heating of from 1 to 120 minutes at 400 to 440 C. is provided.

12. The method according to claim 11, wherein the heating rate during heat treatment is from 10 to 6000 C./min.

13. The method according to claim 11, wherein the residence time during the heat treatment is from 0.01 to 600 minutes.

14. The method according to claim 1, wherein the material is milled to a fineness of 2000 to 10,000 cm.sup.2/g, measured according to Blaine.

15. The method according to claim 1, wherein the material is mixed with a fluid, and shaped into a paste prior to hardening.

16. The method according to claim 1, wherein the material is mixed with rock particles prior to hardening.

17. The method according to claim 1, wherein the material is mixed with additives and/or addition agents, as well as clinker substitute material, prior to hardening.

18. A method for the production of a building element by hardening a material with carbon dioxide in the method according to claim 1.

19. The method according to claim 18, wherein the building element is a prefabricated part for construction.

Description

EXAMPLE 1

[0047] A starting material mixture was prepared from calcium hydroxide and colloidal silica with a molar ratio Ca:Si of 2 with the addition of water in a water/solids ratio of 2. The mixture was treated for 6 hours in an autoclave at 200 C. The product was tempered at 460 C. for 1 hour. The product contained 30.7% C.sub.2S (various polymorphs), 5.1% CaCO.sub.3, 22.2% dellaite, 2.6% afwillite and 39.4% X-ray amorphous phase.

[0048] Since the raw materials were already very fine, no grinding was necessary. To determine the potential of the material for reaction with carbon dioxide, 5.5 g of product were placed in a CO.sub.2-containing environment for 72 hours. For this purpose, 0.94 g of NaHCO.sub.3 was dissolved in 10 g of water and the product was immersed in the solution. The concentration of CO.sub.2 was 4.9%.

[0049] X-ray spectra of the material were recorded before and after the carbon dioxide hardening and a thermogravimetric analysis (DTG) was carried out. The measured values in Table 1 show that the decrease in the C.sub.2S content is associated with an increase in the formation of calcite. An increase in the content of the amorphous phase was also found. The DTG curves in FIG. 1 demonstrate the conversions during the carbon dioxide hardening.

TABLE-US-00001 TABLE 1 phase composition according to X-ray spectrum Phase Material Material after CO.sub.2 hardening CaCO.sub.3 5.1% 17.9% C.sub.2S 30.7% 9.3% Dellaite 22.2% .sup.16% Afwillite 2.6% Tobermorite 8.7% amorphous 39.4% 48.1%