hairline crack in gunite shell, patched with hydraulic cement

[poolrex]

PB chiseled the crack and patched it with hydraulic cement (Hc), but the HC don't look very hard. does pebbletech will adhere to the HC?

[PoolDoc]

A high quality cement, like Thoro Waterplug should be fine, though you may need to acid etch it. If it's Lowes' special "Chinese - We make cheap junk" cement . . . all bets are off.

But really, it's a question for your finish contractor. If they are any good, they will know what they can bond to successfully.