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 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.

1 - 30 . (canceled) 
     
     
         31 . 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. 
     
     
         32 . The method of  claim 31  wherein at least two different doses of carbon dioxide are used in pretesting a carbonated mix. 
     
     
         33 . The method of  claim 31  wherein at least three different doses of carbon dioxide are used in pretesting a carbonated mix. 
     
     
         34 . The method of  claim 31  wherein the intended operation is a wet cast operation. 
     
     
         35 . The method of  claim 34  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. 
     
     
         36 . The method of  claim 35  wherein the flowability of the carbonated cement mix is within 50% of the flowability of an uncarbonated cement mix of the same mix design. 
     
     
         37 . The method of  claim 31  wherein the wet cement mix comprises Portland cement comprising gypsum. 
     
     
         38 . The method of  claim 31  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. 
     
     
         39 . The method of  claim 31  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. 
     
     
         40 . The method of  claim 31  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. 
     
     
         41 . The method of  claim 40  wherein the strength of the cement mix at the time point is greater than the strength of the same mix without carbon dioxide. 
     
     
         42 . The method of  claim 41  wherein the strength of the cement mix at the time point is 1-40% greater than the strength of the same mix without carbon dioxide. 
     
     
         43 . The method of  claim 31  wherein the time to set of the cement mix is earlier than the time to set of the same mix without carbon dioxide. 
     
     
         44 . The method of  claim 43  wherein the time to set of the cement mix is 0.5-50% earlier than the time to set of the same mix without carbon dioxide. 
     
     
         45 . The method of  claim 31  wherein the carbon dioxide is delivered to the wet mix as a combination of gaseous and solid carbon dioxide. 
     
     
         46 . The method of  claim 45  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. 
     
     
         47 . The method of  claim 31  wherein the carbon dioxide is supplied to the surface of the mixing cement mix via a flexible conduit. 
     
     
         48 . The method of  claim 31  wherein at least a portion of the dose of carbon dioxide is delivered as carbon dioxide-charged mix water. 
     
     
         49 . The method of  claim 31  wherein the dose of carbon dioxide is such that a carbonation level of less than 1.0% bwc is achieved. 
     
     
         50 . A carbonated wet cement mix composition wherein
 (i) the cement mix is fluid;   (ii) the cement mix comprises Portland cement comprising gypsum;   (iii) the cement mix comprises gaseous carbon dioxide or carbon dioxide reaction products in an amount of greater than 0.01% by weight cement.   
     
     
         51 . The carbonated wet cement mix of  claim 50  that is carbonated to a level of carbonation of less than 0.5% bwc.