What was the pitch rate? It suggests 50-80 g/hl.
It was a 5gal. batch. I used 2x 11,5g, which is equal to 1.6 to 2.5 times the pitching rate you posted.
That's plenty of yeast for a 1.084 beer. Have you calibrated your hydrometer in water to be sure it reads accurately ? And what thermometer do you use for mash temps? A cheap thermometer could've had you mashing several degrees warmer than you assumed. What mash temp?
Edit - And did you aerate thoroughly before pitching? Bigger beers need to be aerated even more thoroughly than average strength beers.
I`m not a very experienced brewer. This is only my 9th batch and I was concerned about the yeast`s ability in fermenting such high gravity wort, but obviously, I was wrong.
Actually, I used a regular hydrometer (not the fancy refractometer type) and it requires no calibration, I guess...
I used a digital, 0.1°C/F accurate thermometer. Mash temp. was between 142 and 152
Regarding aeration, I used a small duly sanitized aquarium air pump hose and stone with a 0.2micra air filter. I placed the stone in the fermentor before slowly transferring the wort to it, so that it was being aerated all the time (about 30 min.).
So, did I do something wrong here?