Will shotcrete withstand the attack of black liquor from cellulose pulp production or does it have to be protected by some kind of lining?
Since so-called black liquor contains sodium sulfate it attacks any kind of portland cement in the shotcrete. Such shotcrete would have to be protected with a suitable coating such as coal tar epoxy. It would also be advisable to use a portland cement with a tricalcium aluminate content no higher than 5 percent. An alternative safety precaution would be to use a cement such as high alumina cement with very high sulfate resistance but this, too, should be protected for this severe exposure.