Method For Treating Clay And Clay-Bearing Aggregates And Compositions Therefor

Abstract

The present invention provides compositions and methods involving the use of a carboxylate graft polymer having high molecular weight and low ratio of acid-to-polyoxyalkylene groups. Such clay-mitigation is particularly useful for treating clay and clay-bearing aggregates, particularly those aggregates used for construction purposes. The present invention minimizes the need to wash the aggregates, thus preserving fine aggregates (“fines”) content in construction materials, and thereby beneficiating the performance and/or properties of construction materials containing the clay-bearing aggregates.

1 . A carboxylate graft polymer composition for treating clay or clay-bearing aggregates, comprising:
 (A) a first component represented by the following structure:   
       
         
           
           
               
               
           
         
       
       wherein R 1 , R 2 , and R 3  each independently represent hydrogen, C 1 -C 3  alkyl, —COOH, —CH 2 COOH, or mixtures thereof; X represents hydrogen or an alkali metal; and
 (B) a second component represented by the following structure: 
 
       
         
           
           
               
               
           
         
       
       wherein R 4 , R 5 , R 6 , R 7 , and R 8  each independently represent hydrogen, C 1 -C 3  alkyl, —COOH, or mixtures thereof; Y represents —O—, —COO—, —OOC—, —COHN—, or —NHCO—; Z represents (CH 2 ) n  wherein “n” represents a whole number of 0 to 6; and “m” represents an integer of 25 to 200;
 (C) optionally a third component comprising a repeating unit of polymerized (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, 3-acrylamido-2-methylpropane sulfonic acid or its salts, and styrene sulfonic acid or its salt, or mixtures thereof; and 
 wherein the molar ratio of said first component A to said second component B is in the range of 50:100 to 100:40 and the weight-average molecular weight of the carboxylate graft polymer is in the range of 22,000 to 250,000; and 
 wherein, if the molar ratio of said first component A to said second component B is greater than 100:55, then the weight-average molecular weight of the carboxylate graft polymer is in the range of 70,000 to 250,000. 
 
     
     
         2 . The carboxylate graft polymer composition of  claim 1  further comprising at least one repeating unit of a polymerized (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, 3-acrylamido-2-methylpropane sulfonic acid or its salts, and styrene sulfonic acid or its salt, or mixtures thereof. 
     
     
         3 . The carboxylate graft polymer composition of  claim 1  or  2  wherein said molar ratio of said component A to said component B is between 0.6 and 1.8. 
     
     
         4 . The carboxylate graft polymer composition of  claim 3  wherein said molar ratio of said component A to said component B is between 0.7 and 1.5. 
     
     
         5 . The carboxylate graft polymer composition of any preceding claim wherein the weight-average molecular weight of said carboxylate graft polymer composition is in the range of 70,000 to 150,000. 
     
     
         6 . The carboxylate graft polymer composition of any preceding claim wherein the number-average molecular weight of said component B is in the range of 1,000 to 10,000. 
     
     
         7 . The carboxylate graft polymer composition of  claim 6  wherein the number-average molecular weight of said component B is in the range of 1,500 to 7,500. 
     
     
         8 . The carboxylate graft polymer composition of  claim 7  wherein the number-average molecular weight of said component B is in the range of 2,000 to 5,000. 
     
     
         9 . The carboxylate graft polymer composition of any preceding claim wherein, when mixed into a plastic hydratable cementitious composition, has a slump of 0-4 (using standard slump cone in accordance with ASTM C143). 
     
     
         10 . An aggregate composition comprising a plurality of clay-bearing aggregates and the carboxylate graft polymer composition of any preceding claim. 
     
     
         11 . The aggregate composition of  claim 10  wherein said plurality of clay-bearing aggregates natural or manufactured sand, crushed stone, crushed gravel, crushed rock, crushed shale, or mixtures thereof. 
     
     
         12 . The aggregate composition of  claim 10  or  11  further comprising a cementitious binder. 
     
     
         13 . The aggregate composition of  claim 10 ,  11  or  12  wherein said carboxylate graft polymer is contained in said plurality of clay-containing aggregates in an amount of 0.1% to 100% by weight based on dry weight of clay contained in said plurality of aggregates. 
     
     
         14 . The aggregate composition of  claim 13  wherein said carboxylate graft polymer is contained in said plurality of clay-containing aggregates in an amount of 1% to 50% by weight based on dry weight of clay contained in said plurality of aggregates. 
     
     
         15 . An admixture composition for modifying a cementitious composition, comprising:
 (i) at least one chemical admixture selected from the group consisting of water-reducing agent, set retarders, set accelerators, air entraining agents, air detraining agents, and mixtures thereof; and   (ii) A carboxylate graft polymer composition for treating clay or clay-bearing aggregates, comprising:
 (A) a first component represented by the following structure: 
   
       
         
           
           
               
               
           
         
         
           wherein R 1 , R 2 , and R 3  each independently represent hydrogen, C 1 -C 3  alkyl, —COOH, —CH 2 COOH, or mixtures thereof; X represents hydrogen or an alkali metal; and 
           (B) a second component represented by the following structure: 
         
       
       
         
           
           
               
               
           
         
         
           wherein R 4 , R 5 , R 6 , R 7 , and R 8  each independently represent hydrogen, C 1 -C 3  alkyl, —COOH, or mixtures thereof; Y represents —O—, —COO—, —OOC—, —COHN—, or —NHCO—; Z represents (CH 2 ) n  wherein “n” represents a whole number of 0 to 6; and “m” represents an integer of 25 to 200; 
           (C) optionally a third component comprising a repeating unit of polymerized (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, 3-acrylamido-2-methylpropane sulfonic acid or its salts, and styrene sulfonic acid or its salt, or mixtures thereof;
 wherein the molar ratio of said first component A to said second component B is in the range of 50:100 to 100:40 and the weight-average molecular weight of the carboxylate graft polymer is in the range of 22,000 to 250,000; and 
 wherein, if the molar ratio of said first component A to said second component B is greater than 100:55, then the weight-average molecular weight of the carboxylate graft polymer is in the range of 70,000 to 250,000. 
 
         
       
     
     
         16 . The admixture composition of  claim 15  further comprising at least one repeating unit of polymerized (meth)acrylamide, N-alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, 3-acrylamido-2-methylpropane sulfonic acid or its salts, and styrene sulfonic acid or its salt, or mixtures thereof. 
     
     
         17 . The admixture composition of  claim 15  or  16  wherein said at least one chemical admixture is a water reducer selected from the group consisting of lignin sulfonate, naphthalene sulfonate formaldehyde condensate, melamine sulfonate formaldehyde condensate, polycarboxylate comb polymers containing alkylene oxide groups, gluconates, and mixtures thereof. 
     
     
         18 . A method for modifying clay-bearing aggregates, comprising: introducing to a plurality of clay-bearing aggregates the carboxylate graft polymer composition of  claims 1  to  14 . 
     
     
         19 . A method for modifying cementitious materials containing clay-bearing aggregates, comprising: introducing to a cementitious binder and a plurality of clay-bearing aggregates the admixture composition of  claim 15 ,  16  or  17 . 
     
     
         20 . A method for modifying cementitious materials containing clay-bearing aggregates, comprising: introducing to cementitious binder and plurality of clay-bearing aggregates the carboxylate graft polymer composition of  claims 1  to  14 . 
     
     
         21 . A construction material, comprising: a plurality of aggregates, clay, and the carboxylate graft polymer composition of  claims 1  to  14 .