Flew out of BCN to the US with the family on Sun 8/6, which was a security strike day. The strikes were scheduled ahead of time with specific hours. The schedule looked something like:
7.30AM - 8.30AM (strike)
10 AM - 11AM (strike)
2PM - 3PM (strike)
In between the strikes, there was a work slowdown. The premium and "with small child" lines were never on strike, but they were slow. Going through the premium line took ~45 minutes, and the screeners were REALLY slow about looking at electronics, etc, so I'd say you're safe leaving an hour extra cushion.
The lines were boring, and it was hot in the airport, but wasn't too bad.