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sulfate resistance comparison of slag, silica fume, fly ash
does anybody know how cement with class f flyash, slag, and silica fume compare in sulfate resistance? does anybody have links to such comparisons?
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i quickly checked a pca reference i have:
i got the following from a chart of scm additions considered to give high resistance (under astm 1012-95 expansion criteria at 6 months or 1 year) to sulfate attack. listed from higher resistance to lower using type 1 cement and with the given percentage of scm, (but all considered high resistance).
1. 20% class f fly ash
2. 35% slag
3. 6% silica fume
4. 15% metakaolin
other suggestions were to use type 2(moderate) or 5(high resistance) cement, and lower the w/cm ratio. don't use high calcium fly ash for sulfate resistance. search around on pca's site for more in depth information on sulfate resistance.
i use 50% slag cement and type ii cement. we can't get quality fly ash in pa. look in aci 318 or 350 chapter 4. they give guidelines. also look in aci 350. silica fume is good but unnecessary if you use 50% slag cement.
if you have project in mind, check out the ready-mix producers to see who has the experience and what materials are readily available and able to be used properly.
nothing is worse than specifying a mix type and find out the local producer does not have the facilities (extra silos, batching controls, etc.) and knowledge to reliably produce what is specified.
if you are in a major market, you should have little trouble because of the vertical integration of the cement industry and increased interest in performance and technical support.

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