Pothos is a clinger not a twiner.
I'd look for a solution in sealing the concrete (to provide a better clinging surface and stop the pH issue) and keeping its humidity up.
If that's impractical, then it's a labor of tying the vine up.
I suppose that a less elegant (but labor saving) solution might be a series of horizontal supports to help it deal with its own weight and to keep it from falling completely down each time (only part way down).
Rob
Zoo Horticulture
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