concrete for clarifier for acid mine remediation
 

concrete for clarifier for acid mine remediation
i am designing a concrete clarifier and treatment tanks for the remediation of a stream with acid mine drainage. i have read the aci articles 201.2, 318, 350 & 1515. they offer general guidelines but do not offer any specifics as to when i need to provide a protective barrier. i know the concrete will be exposed to a moderate sulfate attack. the acid is sulfuric acid which is highly corrosive to concrete. what is the cut-off for providing a protective barrier for acid attack? i am specifying type ii cement for moderate sulfate exposure, w/c ratio = 0.45, and fly ash astm c 618 class f. is this enough? or, do i need a chemically resistant barrier instead? this is the chemical composition of the water that the concrete will be permanently exposed to:
ph = 2.6-4.5
acidity = 177.8-271.8 mg/l
fe (total) = 21.9-45.9 mg/l
al = 12.8-18.2 mg/l
mn = 1.2-1.5 mg/l
so4 = 334.2-535 mg/l

with the ph you noted and the fact that it is high in sulfuric acid, you need a barrier.
the sulfuric acid will severely attack the concrete, even with type ii cement.
you can line the clarifier (t-lock) or coat it. but nothing is fool or contractor proof.
i'm guessing someone in the mining business will have some better suggestions.