Apparatus for carbonation of a cement mix

Abstract

The invention provides compositions and methods directed to carbonation of a cement mix during mixing. The carbonation may be controlled by one or more feedback mechanisms to adjust carbon dioxide delivery based on one or more characteristics of the mix or other aspects of the mixing operation.

What is claimed is: 
     
         1 . A method of carbonating a wet cement mix comprising exposing a wet cement mix comprising a type of cement to a dose of carbon dioxide while mixing for a duration of time sufficient to produce a carbonated cement mix, wherein the dose of carbon dioxide is determined by pretesting a carbonated mix comprising the type of cement to determine a dose of carbon dioxide that allows the flowability of the cement mix to be compatible with use of the cement mix in its intended operation. 
     
     
         2 . The method of  claim 1  wherein the intended operation is a wet cast operation. 
     
     
         3 . The method of  claim 2  wherein the wet cast operation is a ready mix operation and the flowability is compatible with the use of the wet cement mix at a job site. 
     
     
         4 . The method of  claim 1  wherein the wet cement mix comprises Portland cement comprising gypsum. 
     
     
         5 . The method of  claim 1  wherein the dose of carbon dioxide is such that a carbonation level of less than 2.0% by weight cement is achieved in the cement mix. 
     
     
         6 . The method of  claim 1  wherein the dose of carbon dioxide is such that a level of gaseous carbon dioxide or carbon dioxide reaction products of greater than 0.01% by weight cement is achieved in the wet cement mix. 
     
     
         7 . The method of  claim 1  wherein the dose of carbon dioxide determined by pretesting is further a dose of carbon dioxide that allows the strength of the cement mix at a time point after hardening to be within 50% of the same cement mix without carbon dioxide at the same time point. 
     
     
         8 . The method of  claim 7  wherein the strength of the cement mix at the time point is greater than the strength of the same mix without carbon dioxide. 
     
     
         9 . The method of  claim 1  wherein the carbon dioxide is delivered to the wet mix as a combination of gaseous and solid carbon dioxide. 
     
     
         10 . The method of  claim 9  wherein the dose of carbon dioxide is such that solid carbon dioxide is present in the mixing cement mix in an amount greater that 0.01% by weight cement. 
     
     
         11 . The method of  claim 1  wherein the carbon dioxide is supplied to the surface of the mixing cement mix via a flexible conduit. 
     
     
         12 . The method of  claim 1  wherein at least a portion of the dose of carbon dioxide is delivered as carbon dioxide-charged mix water. 
     
     
         13 . The method of  claim 1  wherein the dose of carbon dioxide is such that a carbonation level of less than 1.0% bwc is achieved. 
     
     
         14 . An apparatus for carbonating a wet cement mix comprising
 (i) a mixer for mixing the cement mix;   (ii) the cement mix in the mixer, wherein the cement mix comprises a type of cement;   (iii) a system for delivering carbon dioxide to the cement mix, wherein the system comprises
 (a) a source of carbon dioxide 
 (b) a conduit operably connected to the source of carbon dioxide and configured to deliver carbon dioxide to the surface of the mixing cement mix; 
 (c) a metering system for metering flow of carbon dioxide in the conduit; 
   (iv) an automatic controller, wherein the control system
 (a) receives information regarding flow of carbon dioxide and time of exposure to carbon dioxide; 
 (b) determines a total dose of carbon dioxide based on the flow and time; 
 (c) compares the total dose of carbon dioxide to a predetermined dose of carbon dioxide; and 
 (d) sends a signal to an actuator configured to modulate the flow of carbon dioxide when the total dose of carbon dioxide reaches the dose determined by pretesting. 
   
     
     
         15 . The apparatus of  claim 14  wherein the predetermined dose of carbon dioxide is a dose determined by pretesting a carbonated mix comprising the type of cement to determine a dose of carbon dioxide that allows the flowability of the cement mix to be compatible with use of the cement mix in its intended operation. 
     
     
         16 . The apparatus of  claim 14  wherein the cement mix comprises Portland cement and the type of cement is a type of Portland cement. 
     
     
         17 . The apparatus of  claim 14  wherein the dose of carbon dioxide is a dose that causes an amount of gaseous carbon dioxide or carbon dioxide reaction products to be present in the cement mix in an amount of at least 0.01% by weight cement (bwc). 
     
     
         18 . The apparatus of  claim 14  wherein the dose of carbon dioxide is a dose that causes a degree of carbonation of the cement mix that is less than 2% bwc. 
     
     
         19 . The apparatus of  claim 14  wherein the source of carbon dioxide comprises a source of liquid carbon dioxide, a source of gaseous carbon dioxide, or a combination thereof. 
     
     
         20 . The apparatus of  claim 14  wherein the conduit comprises a flexible conduit. 
     
     
         21 . The apparatus of  claim 14  wherein the source of carbon dioxide comprises a sources of carbon dioxide-charged water. 
     
     
         22 . The apparatus of  claim 14  wherein the mixer is a mixer that is open to the atmosphere. 
     
     
         23 . A carbonated wet cement mix composition wherein
 (i) the cement mix is fluid;   (ii) the cement mix comprises Portland cement comprising gypsum;   (ii) the cement mix comprises gaseous carbon dioxide or carbon dioxide reaction products in an amount of greater than 0.01% by weight cement.   
     
     
         24 . The carbonated wet cement mix of  claim 23  that is carbonated to a level of carbonation of less than 0.5% bwc. 
     
     
         25 . The carbonated wet cement mix of  claim 23  further comprising solid carbon dioxide in an amount of greater than 0.01% bwc.