I will go as far as saying that 80 hours/week is definitely too much.
80 hours/week means 11.4 hours/day, working weekends or 16 hours/day working Monday-Friday.
Most contracts (and I assume you have one) state 35-40 hours/week (7-8/day not working weekends). However, this is generally just a "placeholder" when speaking of academic positions, where it is difficult to impose strict working hours. However, this does not mean that your supervisor can ask you to work an unreasonable amount of hours.
Directive 2003/88/EC of the European Parliament states that:
Member States shall take the measures necessary to ensure that, in
keeping with the need to protect the safety and health of workers:
(a) the period of weekly working time is limited by means of laws,
regulations or administrative provisions or by collective agreements
or agreements between the two sides of industry;
(b) the average working time for each seven-day period, including
overtime, does not exceed 48 hours.
This is surely implemented in the UK, France, and Italy (and I am sure most other EU states implemented the EU Directive).
I would say that, as a PhD student, there could be exceptional instances where you would need to work 80 hours/week (e.g. close to a deadline) but, for your own sake, that should NOT become a habit, but should instead be a very exceptional situation.
I have known people who had the "feeling guilty because I am not in the lab on a Sunday afternoon" syndrome. This is not healthy, and I hope for you that you do not reach that point. Working 80 hours/week means you'll soon become stressed, tired and overall less productive (as you will be more likely to make errors and will have to redo things several times). I know several people (unfortunately more than I would like to) who have had serious health problems because of this type of unreasonable request from their bosses.
You can work 40 hours/week and publish good papers. There are plenty of good people in academia who publish in very good journals, but have a life, a family, and hobbies during their free time. Do not believe those who tell you that working 24/7 you will publish more, because they are just trying to exploit you.
And always remember: just because you are passionate for your job that does not mean you should not have any right. You have the right to work reasonable hours, have the right to have holidays and you should be allowed to take them without having to beg or being considered lazy, and you should be reasonably paid. Just as in any other job.
A little edit on what to do :
- Speak with your supervisor and explain the situation. Try to be reasonable and see if you can both work out a solution
- If no solution can be found, look for another supervisor. Try not to make a bad brake up with your old supervisor, just explain that you are not confortable with the situation and that you feel it's better for both of you if you change supervisor.
- If things get particularly bad, remember that the university has an HR office, that is there also to deal with these things.