Posted on 06/15/2014 12:07:35 PM PDT by BwanaNdege
As an aside. several years back the epa ruled that solid components - the ash and fly ash - after combustion were to be considered emissions. It doesn't take long for a high quality steam coal, with 10% ash content, to produce a boat load of HAZMAT emissions.
As for Silica Fume, yes, it absolutely increases the strength of concrete, irrespective of the fly ash component. I'm sure it effects the compressive strength, but I don't have any idea how to plug in the numbers to determine if the rebar components should be adjusted to reflect a change in the tensile strength. Our engineers always added the Silica Fume just before the pour to manage the final product. Myself, I would add a bit if I were pouring a patio or foundation for a house. Just be darn sure to wear a well fitting respirator with an NBC filter while handling the bags.
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