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Effect of Superplasticizers on Form Pressures

Q.: To minimize bugholes in exterior walls we are considering using a high range water reducer to give us flowing concrete. Is there a way of calculating how much higher the formwork pressures would be?

A.: According to "Superplasticizing Admixtures in Concrete," a 1976 publication of the Cement and Concrete Association (England), wall and column forms to receive flowing concrete should be designed for full liquid pressure plus an impact surcharge of about 210 pounds per square foot if concrete is discharged from a height of 6.5 feet or more. The publication adds that if there are any cleanout openings in the forms, special care should be taken to see that their covers are well anchored.