Continuing this thought... does anyone have information on the effects of low pH on concrete pools?

Like a user in another thread, my pH really likes hanging around 6.8-7.0, even with boxfulls of Borax feeding it. I want to know if I need to stop fighting it for a concrete pool. If not, I'll jump over to that thread and join the battle!

TA=100
CYA=0 (this never goes up, even with the trichlor tabs for 5 years???)
FC=3
CC=.5 (gotta shock tonight)
CH=400
pH=7.0

I use trichlor tabs in a feeder, but BBB for shocking, ph, alk.

(According to the Taylor Wheel, my "saturation index" is only -.2 which shouldn't cause concern?)