Methods and compositions for concrete production

Abstract

The invention provides compositions and methods directed to carbonation of a cement mix during mixing. The carbonation may be in a stationary mixer or a transportable mixer, such as a drum of a ready-mix truck.

What is claimed is: 
     
         1 . A method for carbonating a concrete mix comprising a type of cement comprising delivering dose of CO2 to the concrete mix while it is mixing in a mixer, wherein the delivery of the carbon dioxide commences within 3 minutes of the start of mixing of the concrete mix, and wherein the duration of the delivery of the carbon dioxide is 10 seconds to 4 minutes. 
     
     
         2 . The method of  claim 1  wherein the dose of carbon dioxide is 0.01-1.0% by weight cement (bwc). 
     
     
         3 . The method of  claim 1  wherein the delivery of the carbon dioxide commences within 1 minute of the start of mixing of the concrete mix. 
     
     
         4 . The method of  claim 1  wherein the mixer comprises a transportable mixer. 
     
     
         5 . The method of  claim 4  wherein the mixer comprises a drum of a ready-mix truck. 
     
     
         6 . The method of  claim 1  wherein the dose of carbon dioxide is based on previous testing of a plurality of doses of carbon dioxide on a plurality of test mixes, wherein the test mixes comprise the type of cement in the concrete mix. 
     
     
         7 . The method of  claim 6  wherein at least three test doses of carbon dioxide are used in the previous testing. 
     
     
         8 . The method of  claim 6  wherein the plurality of doses of carbon dioxide used in the previous testing are all 0.01-1.0% bwc, and the dose of carbon dioxide delivered to the mixing concrete is 0.01-1.0% bwc. 
     
     
         9 . The method of  claim 1  wherein the carbon dioxide is delivered via a conduit to the surface of the mixing concrete. 
     
     
         10 . The method of  claim 9  wherein the conduit is positioned to be 5-200 cm from the surface of the mixing concrete, on average. 
     
     
         11 . The method of  claim 1  wherein the carbon dioxide is delivered as a mixture of solid and gaseous carbon dioxide. 
     
     
         12 . A method for carbonating a concrete mix in a drum of a ready-mix truck comprising
 (i) positioning a first conduit for delivery of components of the concrete mix to the drum, wherein the first conduit contains a second conduit for delivery of carbon dioxide to the concrete mix, and wherein the components of the concrete mix comprise at least cement and water;   (ii) delivering the components of the concrete mix to the drum via the first conduit to provide a concrete mix in the drum;   (iii) mixing the concrete mix; and   (iv) delivering a dose of carbon dioxide to the mixing concrete via an opening of the second conduit.   
     
     
         13 . The method of  claim 12  wherein the dose of carbon dioxide is 0.01-1.5% by weight cement. 
     
     
         14 . The method of  claim 12  wherein the carbon dioxide is a mixture of solid and gaseous carbon dioxide. 
     
     
         15 . The method of  claim 12  wherein the dose of carbon dioxide is based on previous testing of a plurality of doses of carbon dioxide on a plurality of test mixes, wherein the test mixes comprise the type of cement in the concrete mix. 
     
     
         16 . The method of  claim 15  wherein at least three test doses of carbon dioxide are used in the previous testing. 
     
     
         17 . The method of  claim 15  wherein the plurality of doses of carbon dioxide used in the previous testing are all 0.01-1.0% bwc, and the dose of carbon dioxide delivered to the mixing concrete is 0.01-1.0% bwc. 
     
     
         18 . The method of  claim 12  wherein the opening of the second conduit is positioned to be 5 cm to 200 cm, on average, from a surface of the mixing concrete. 
     
     
         19 . An apparatus for delivering carbon dioxide to a drum of a ready-mix truck comprising
 (i) a first conduit configured for delivery of components of concrete to the drum of the ready-mix truck;   (ii) a second conduit contained within or attached to the first conduit configured for delivery of carbon dioxide to the drum of the ready-mix truck.   
     
     
         20 . The apparatus of  claim 19  wherein the second conduit is made of material that is sufficiently flexible to move with the first conduit. 
     
     
         21 . The apparatus of  claim 19  wherein the second conduit contains a third conduit, wherein the third conduit is configured to be extended from the second conduit when the first conduit is positioned to deliver the components of the concrete to the drum, and to be retracted when the first conduit is moved from the drum of the ready-mix truck