Method for manufacturing binders hardening by hydration and carbonation
A method for manufacturing a binder of a hydratable material includes providing a starting material from one or more raw materials convertible by tempering at 600 to 1200° C. into the hydratable material, tempering the starting material to provide the hydratable material containing not more than 10% by weight monocalcium silicate and at least 15% by weight hydratable phases in the form of lime and dicalcium silicate, wherein the residence time and the tempering temperature are adapted to obtain the hydratable material by converting not more than 80% by weight of the starting material, and cooling the hydratable material to provide the binder comprising the hydratable material. The binder can be mixed with water and optionally one or more of aggregate, additives, admixtures to obtain a binder paste that is placed, hydrated and carbonated to produce a building product.
1. A method for manufacturing a binder comprising a hydratable material comprising the steps:
providing a starting material from one or more raw materials convertible by tempering at 600 to 1200° C. into the hydratable material, wherein the starting material has a Ca/Si molar ratio from 0.5 to 1.8 and contains no or up to 30% by weight of other elements than CaO and SiO 2 with regard to the total mass calculated as oxides,
tempering the starting material at a temperature in the range from 600 to 1200° C. during a residence time from 1 minute to 5 hours to provide the hydratable material containing crystalline hydratable phases, not more than 10% by weight monocalcium silicate and at least 15% by weight hydratable phases in the form of lime and dicalcium silicate, wherein at least 50% of the crystalline hydratable phases are dicalcium silicate,
wherein the residence time and the tempering temperature are adapted to obtain the said hydratable material by converting not more than 80% by weight of the starting material, and cooling the hydratable material to provide the binder comprising the hydratable material.
2. The method according to claim 1 , further comprising grinding the binder to a fineness characterized by a particle size distribution and a Rosin-Rammler Parameter (slope) n, wherein according to a determination of the particle size distribution of the binder by laser granulometry the binder has a D 90 ≤90 μm, whereby the Rosin-Rammler Parameter (slope) n can vary from 0.6-1.4.
3. The method according to claim 1 , wherein the hydratable material contains at least 15% by weight dicalcium silicate, less than 10% by weight monocalcium silicate, and from 20 to 80% by weight phases from the raw materials and/or formed during the tempering.
4. The method according to claim 1 , wherein the starting material has a Ca/Si molar ratio from 0.6 to 1.2.
5. The method according to claim 3 , wherein the tempering temperature ranges from 800 to 1100° C. and the residence time ranges from 5 minutes to 2 hours.
6. The method according to claim 1 , wherein the raw materials are selected from the group consisting of concrete fines, overburden from quarries, low quality limestone, marl, and dolomite.
7. The method according to claim 1 , wherein the tempering temperature is adjusted to range from 900 to 1100° C. for residence times from 5 minutes to 1 hour.
8. The method according to claim 1 , wherein the tempering temperature is adjusted to range from 800 to 1000° C. for residence times from 30 minutes to 2 hours.
9. The method according to claim 3 , wherein the starting material has a Ca/Si molar ratio from 0.6 to 1.3.
10. The method according to claim 4 , wherein the tempering temperature ranges from 850 to 1050° C. and the residence time ranges from 5 minutes to 2 hours.
11. The method according to claim 4 , wherein the tempering temperature is adjusted from 900 to 1100° C. for residence times from 5 minutes to 1 hour or to range from 800 to 1000° C. for residence times from 30 minutes to 2 hours.
12. The method for manufacturing a building element from a binder comprising a hydratable material comprising the steps:
providing a starting material from one or more raw materials convertible by tempering at 600 to 1200° C. into the hydratable material, wherein the starting material has a Ca/Si molar ratio from 0.5 to 1.8 and contains no or up to 30% by weight of other elements than Ca and Si with regard to the total mass calculated as oxides,
tempering the starting material at a temperature in the range from 600 to 1200° C. during a residence time from 1 minute to 5 hours to provide the hydratable material containing hydratable phases, not more than 10% by weight monocalcium silicate and at least 15% by weight hydratable phases in the form of lime and dicalcium silicate, wherein at least 50% of the hydratable phases are dicalcium silicate, wherein the residence time and the tempering temperature are adapted to obtain the said hydratable material by converting not more than 80% by weight of the starting material,
cooling the hydratable material to provide the binder comprising the hydratable material
grinding the binder to a fineness characterized by a particle size distribution and a Rosin-Rammler Parameter (slope) n, wherein according to a determination of the particle size distribution of the binder by laser granulometry the binder has a D 90 ≤90 μm, whereby the Rosin-Rammler Parameter (slope) n can vary from 0.6-1.4
mixing the binder with water to obtain a binder paste
placing the binder paste
hydrating the binder paste until an amount of bound water is at least 5% of hydraulic phases mass in dry binder and
carbonating the binder paste until an amount of additionally bound carbon dioxide is at least 150% of an initially bound water mass or the strength exceeds 2 MPa while still keeping the amount of bound water at at least 50% of the initially bound water mass.
13. The method according to claim 12 , wherein the building element is a precast concrete part or concrete good.
14. The method according to claim 12 , wherein placing comprises filling the binder paste into a mold or formwork.
15. The method according to claim 12 , wherein carbonation is carried out with gaseous carbon dioxide.
16. The method according to claim 15 , wherein the gaseous carbon dioxide is supplied with a pressure from atmospheric pressure to 6 bar, with a carbon dioxide concentration of at least 1% by volume.
17. The method according to claim 12 , wherein carbonation is carried out with carbon dioxide dissolved during the carbonation process in an aqueous alkaline solution.
18. The method according to claim 17 , wherein the solution has initially a pH in the range from 8 to 14 accounting for an activity index of OH − .
19. The method according to claim 12 , wherein carbonation is carried out with carbon dioxide dissolved during the carbonation process in an aqueous solution comprising substances improving dissolution of calcium ions.
20. The method according to claim 12 , wherein carbonation is carried out with carbon dioxide dissolved during the carbonation process in an aqueous solution comprising substances improving dissolution of carbonate ions.
21. The method according to claim 12 , wherein the fineness of the binder is D 90 <μm or the Rosin-Rammler Parameter n varies from 0.7 to 1.2 if the binder is coarser.
22. The method according to claim 16 , wherein the gaseous carbon dioxide is supplied with a pressure from 2 to 4 bar with a carbon dioxide concentration of at least 5% by volume.