System and method of applying carbon dioxide during the production of concrete

1. A method of carbonating concrete materials during mixing of the materials comprising

(i) placing a predetermined amount of concrete materials in a mixing chamber of a mixer, wherein the concrete materials comprise cement and water, and mixing the materials in the chamber;

(ii) starting addition of carbon dioxide to the mixing chamber so that carbon dioxide contacts the mixing concrete materials and reacts with the cement to produce carbonated concrete materials, wherein the carbon dioxide comprises solid carbon dioxide and gaseous carbon dioxide;

(iii) monitoring the amount of carbon dioxide added to the mixing chamber; and

(iv) stopping addition of carbon dioxide into the mixing chamber when a predetermined amount of carbon dioxide has been introduced, wherein the predetermined amount of carbon dioxide is between about 1 and about 27 pounds of carbon dioxide into the mixing chamber for each cubic yard of concrete mix in the mixer.

2. The method of claim 1 wherein the carbon dioxide comprising solid and gaseous carbon dioxide is produced by flowing liquid carbon dioxide from a container to the mixing chamber through an injection assembly, wherein the injection assembly is configured to cause the liquid carbon dioxide to convert to gaseous and solid carbon dioxide upon entering the mixing chamber.

3. The method of claim 1 wherein the amount of carbon dioxide added to the mixing chamber is monitored by a method comprising

(i) monitoring the weight of a carbon dioxide container that supplies the carbon dioxide added to the mixing chamber;

(ii) monitoring the time of addition of the carbon dioxide to the mixing chamber;

(iii) monitoring the mass of carbon dioxide added to the mixing chamber;

(iv) manually monitoring the carbon dioxide added to the mixing chamber;

or any combination thereof.

4. The method of claim 3 wherein the monitoring of steps (i), (ii), and/or (iii) is performed automatically by a control system.

5. The method of claim 1 wherein the concrete materials further comprise aggregate, admixture, other cementitious material, or any combination thereof.

6. The method of claim 5 wherein the other cementitious material comprises fly ash, pozzolan, ground granulated blast furnace slag, or any combination thereof.

7. The method of claim 1 wherein the predetermined amount of carbon dioxide added to the concrete materials in the mixing chamber is an amount that causes formation of a final concrete product, which product, when compared to uncarbonated concrete product of the same mix design, to have one or more of the following enhanced properties:

(i) increased break strength;

(ii) increased break strength consistency;

(iii) decreased permeability;

(iv) decreased degradation rate;

(v) decreased amount of cement in the concrete mix; and/or

(vi) decreased carbon footprint.

8. The method of claim 1 wherein the mixer is a tilt drum mixer, a single shaft compulsory mixer, a double shaft compulsory mixer, a paddle mixer, a pressurized mixer, a truck mounted mixer, or a transit mix truck continuous mixer.

9. The method of claim 1 wherein the addition of carbon dioxide to the mixing chamber occurs at a concrete production facility, a central mix batch plant, a job site, or a combination thereof.

10. The method of claim 1 wherein the carbon dioxide is added to the mixing chamber through an injection assembly configured to move relative to the mixer, and wherein the position of the injection assembly relative to the mixer is monitored.

11. The method of claim 10 wherein the addition of carbon dioxide to the mixing chamber is started only after the injection assembly is in an appropriate position relative to the mixer for injection of carbon dioxide into the mixer.

12. The method of claim 10 wherein the position of the injection assembly relative to the mixer is monitored automatically.

13. The method of claim 1 further comprising adding carbonated mix water to the mixing chamber.

14. The method of claim 13 further comprising carbonating water to produce the carbonated water added to the mix chamber.

15. The method of claim 2 further comprising ensuring that substantially all of the carbon dioxide transmitted to the injection assembly is in a liquid state.