Methods of limiting hydroxyl ion concentrations or their effects in concrete pore solutions to interfere with alkali silica reaction

Abstract

Methods of reducing hydroxyl ions in concrete pore solutions are provided. Such methods are useful in providing resistance to gels which form in concrete due to the alkali-silica (ASR) reaction. The methods comprise adding a salt or mixture thereof to the concrete, in aqueous or solid form, the salt or salt mixture having cations higher in valence than the anions. The methods also comprise adding an acidic phosphate or a silicon-containing alkoxide to the concrete. The methods further comprise resisting and/or inhibiting ASR in airfield runway concrete pore solutions by applying a soluble salt or a mixture of soluble salts in solution or a deicing salt mixture in situ to the runway concrete. All of the above methods are useful in reducing hydroxyl ions in concrete. Such methods can be used to resist ASR in fresh concrete, in concrete that is setting, or in hardened concrete.

1 . A method of limiting or reducing alkali-silica reaction (ASR) in concrete pore solution, comprising applying to hardened concrete as an aqueous or non-aqueous solution or mixing with fresh concrete as a particulate solid or as an aqueous or non-aqueous solution, a soluble salt or mixture thereof, each of said salts comprised of a cation (Cat) and an anion (An), said Cat-An salt having a solubility in said concrete pore solution that is greater than Cat-OH, such that when said Cat-An salt precipitates as Cat-OH, the resulting alkali metal-An salt formed remains within said concrete pore solution or has a solubility in said concrete pore solution that is greater than that of said Cat-An salt. 
     
     
         2 . The method of  claim 1 , wherein the soluble salt or mixture thereof is formulated as a deicing salt mixture to be applied in situ to concrete in order to depress the freezing point of water as well as to prevent conditions in said concrete pore solution that would facilitate ASR, and wherein said deicing salt or mixture thereof exhibits an action in said concrete pore solution which contains alkali metal cations and hydroxyl ions, so as to reduce hydroxyl ions in said concrete pore solution. 
     
     
         3 . The method of  claim 1 , wherein the non-aqueous solution is an alcoholic solution. 
     
     
         4 . The method of  claim 1 , wherein the soluble deicing salt or mixture thereof is not harmful to aircraft alloys when used to interfere with ASR in runway concrete. 
     
     
         5 . The method of  claim 1 , wherein the soluble deicing salt or mixture thereof does not elevate the pH of said concrete pore solution to above about 13. 
     
     
         6 . The method of  claim 1 , wherein the cation of the soluble salt or mixture thereof is selected from the group consisting of sodium, potassium, magnesium, calcium and lithium. 
     
     
         7 . The method of  claim 1 , wherein the anion of each of the soluble salt or mixture thereof is selected from the group consisting of nitrates, nitrites, acetates, formates, phosphates and oxalates. 
     
     
         8 . The method of  claim 1 , wherein said cation has a higher valence than said anion. 
     
     
         9 . The method of  claim 1 , wherein the mixture of soluble salts is selected from the group consisting of potassium acetate, sodium acetate, potassium formate and sodium formate combined with a mixture of soluble salts selected from the group consisting of calcium nitrate, calcium nitrite, magnesium nitrate and magnesium nitrite. 
     
     
         10 . The method of  claim 1 , wherein the soluble salt or mixture thereof contains magnesium nitrite, said magnesium nitrite having the additional action of inhibiting corrosion of reinforcing steel contained in the concrete. 
     
     
         11 . The method of  claim 1 , wherein the soluble salt or mixture thereof contains a monobasic alkali phosphate. 
     
     
         12 . The method of  claim 11 , wherein the monobasic alkali phosphate is selected from the group consisting of NaH 2 PO 4  and KH 2 PO 4 . 
     
     
         13 . The method of  claim 1 , wherein the cations of the soluble salt or mixture thereof contain at least a divalent valence. 
     
     
         14 . (canceled) 
     
     
         15 . (canceled) 
     
     
         16 . (canceled) 
     
     
         17 . (canceled) 
     
     
         18 . (canceled) 
     
     
         19 . (canceled) 
     
     
         20 . (canceled) 
     
     
         21 . (canceled) 
     
     
         22 . A method of limiting or reducing alkali-silica reaction (ASR) in concrete pore solution comprising:
 adding an alkoxide containing silicon to fresh or hardened concrete;   reacting said alkoxide with water contained in said concrete pore solution to produce an alcohol and an acid, wherein said acid reduces the pH of said concrete pore solution.   
     
     
         23 . The method of  claim 22 , wherein the alcohol and acid is not harmful to aircraft alloys when used to interfere with ASR in runway concrete. 
     
     
         24 . A method of limiting or reducing alkali-silica reaction (ASR) in concrete pore solution comprising:
 adding a lithium alkoxide to fresh or hardened concrete;   reacting said alkoxide with water contained in said concrete pore solution to produce lithium hydroxide in situ within the concrete.   
     
     
         25 . A method of limiting or reducing alkali-silica reaction (ASR) in concrete pore solution by mitigating the effects of alkalis in said concrete pore solution, comprising:
 applying a mixture of lithium alkoxide and tetraethyloxysilane (TEOS) to concrete, wherein said mixture moves through said pore solution of the concrete;   hydrolyzing said TEOS with water contained in said concrete pore solution to form a lithium-containing silicate glass; and   reacting said lithium-containing silicate glass with alkali hydroxides present in said concrete pore solution, wherein said reaction prevents said alkali hydroxides from participating in an alkali-silica reaction (ASR).   
     
     
         26 . The method of  claim 25 , wherein the TEOS is partially hydrolyzed TEOS.