Methods of protecting concrete from freeze damage

Abstract

A method of protecting a cementitious mixture from freeze damage is provided. The method consists of incorporating an entrainment air composition into the cementitious mixture to form air voids in the concrete, and further adding an effective agent for nucleating ice, preferably, in the air voids, such that upon the freezing of concrete formed from the cementitious mixture, ice is nucleated in the air voids. In one embodiment, the air entrainment composition includes ceramic shells, which could be impregnated with an agent for nucleating ice such as metaldehyde.

What is claimed is:  
     
         1 . A method of protecting a cementitious mixture from freeze damage comprising incorporating an amount of air into the cementitious mixture to form air pores in the cementitious mixture, the cementitious mixture including an amount of an air entrainment agent and an effective agent for nucleating ice in the air voids upon the freezing of the cementitious mixture.  
     
     
         2 . The method of  claim 1  wherein the water nucleating agent comprises metaldehyde.  
     
     
         3 . The method of  claim 2  wherein the metadehyde consists of tetrameric units (CH 3 CHO) 4 .  
     
     
         4 . The method of  claim 2  wherein the air entrainment agent contains a surfactant.  
     
     
         5 . The method of  claim 2  wherein the metaldehyde is ground to expose the crystal planes that are most effective for nucleating ice.  
     
     
         6 . The method of  claim 2  wherein the air entrainment composition includes ceramic shells impregnated with metaldehyde.  
     
     
         7 . The method of  claim 2  wherein the amount of air is from about 3% to about 8% by volume.  
     
     
         8 . A method of protecting a cementitious mixture from freeze damage comprising incorporating an amount of air into the cementitious mixture to form air voids in the cementitious mixture, the cementitious mixture including an amount of an air entrainment composition and an effective amount of an agent for nucleating ice, selected from the group of metaldehyde, acetoacetanilide, p-bromoacetphenone, coumarin, m-nitoaniline, pthalic anhydride, and 2,4,6-trichloraniline for nucleating ice in the air pores.  
     
     
         9 . The method of  claim 8  wherein the air entrainment composition comprises ceramic shells impregnated with an agent for nucleating ice.  
     
     
         10 . The method of  claim 8  wherein the air entrainment composition comprises glass ceramic shells impregnated with an agent for nucleating ice.  
     
     
         11 . The method of  claim 8  wherein the air entrainment composition comprises shells of kaolin impregnated with an agent for nucleating ice.  
     
     
         12 . The method of  claim 8  wherein the air entrainment composition comprises clay shells inpregnated with an agent for nucleating ice.  
     
     
         13 . A method for protecting concrete from freeze damage comprising: 
 mixing an air entrainment composition into a cementitious mixture;    adding an agent for nucleating ice to the cementitious mixture; and    allowing the cemetitious mixture to form concrete.    
     
     
         14 . The method of  claim 13  wherein the agent for nucleating ice is added to the air entrainment composition before mixing the air entrainment composition with the cementitous mixture.  
     
     
         15 . The method of  claim 14  wherein the agent for nucleating ice comprises metaldehyde.  
     
     
         16 . A concrete composition including pores and air voids comprising a nucleating agent within the air voids for nucleating ice.  
     
     
         17 . The composition of  claim 16  wherein the nucleating agent comprises metaldehyde.  
     
     
         18 . A method of forming porous shells for use as an air entrainment composition for concrete comprising: 
 suspending particles in a slurry;    atomizing the slurry to form droplets;    drying the droplets; and    sintering the dried droplets to form shells with porous outer walls.    
     
     
         19 . The method of  claim 18  wherein the particles comprise ceramic material.  
     
     
         20 . The method of  claim 18  wherein the particles comprise clay.  
     
     
         21 . The method of  claim 18  wherein the particles comprise aluminum oxide.  
     
     
         22 . A method of protecting concrete from freeze damage by providing an air entrainment agent comprising mixing an amount of hollow porous shells into a cementitious mixture and allowing the cementitious mixture for form concrete, wherein the hollow porous shells allow water to pass thereinto.  
     
     
         23 . A concrete composition formed of a cementitious mixture with porous hollow shells mixed therein for allowing water to pass thereinto, to prevent freeze damage to the concrete composition.  
     
     
         24 . The composition of  claim 23  wherein the porous hollow shells are formed of a ceramic material.  
     
     
         25 . The composition of  claim 23  wherein the porous hollow shells are formed of clay.