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High performance PCC is a mix containing standard cement plus fly-ash, slag, and a medium-range water reducer. The additives ensure a mix that is readily workable and has low permeability.

 

The Iowa DOT has now used this specification to place overlays on dozens bridges. These bridges are reinforced with black steel which is common for county bridges. Adequate concrete cover is essential to preventing deterioration due to corrosion of the reinforcing steel.

   

The overlay process involves removing ¼-inch of concrete (plus any deteriorated concrete) and adding one inch of concrete above the nominal surface. This should result in close to three inches of cover over the steel. In addition the high performance concrete has very low permeability. So the steel should be well protected into the future. High performance concrete is an excellent option for counties that plan to perform bridge deck overlays. The high performance mix does not require special mixing or placement equipment and is widely available in Iowa. It provides very low permeability without the need for high cement percentages in the mix.

   
     
 
 

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Christensen Brothers, Inc.                                                      644 River Road, Cherokee Iowa 51012