Use of Class F Flyash to Mitigate Reactive aggregate
Use of Class F Flyash to Mitigate Reactive aggregate
(OP)
In our concrete specification we specifically exclude the use of reactive aggregates. During the bid process of a job we have received the following question:
"Can a fine aggregate be used that is potentially reactive if it is used in conjunction with a Class F Flyash to mitigate the reactivity?"
In checking in appears that flyash will mitigate the reactive aggregate, but I would like to know if anyone has experience with this. Is flyash 100% effective? What potential problems can be encountered in allowing this? Should it be allowed in certain situations? (ie footings, floors to be covered)
Any help would be appreciated.
"Can a fine aggregate be used that is potentially reactive if it is used in conjunction with a Class F Flyash to mitigate the reactivity?"
In checking in appears that flyash will mitigate the reactive aggregate, but I would like to know if anyone has experience with this. Is flyash 100% effective? What potential problems can be encountered in allowing this? Should it be allowed in certain situations? (ie footings, floors to be covered)
Any help would be appreciated.






RE: Use of Class F Flyash to Mitigate Reactive aggregate
If I recall correctly, ASTM C33 has an addendum that addresses ASR issues with Silicious aggregates.
RE: Use of Class F Flyash to Mitigate Reactive aggregate
To answer your question, it is not 100% effective.
Depending on the amount of reactive silica the result can range from surface popouts to extensive microcracking and deterioration of the concrete matrix. The quantity of either is not very predictable.