fsck is taking a lot of time?(buffer I/O error)

I had a irregular powercut 4-5 times in a row within an hour. My ubuntu suddenly went into busy box mode and showed there are errors on /dev/sda5. I then tried: fsck /dev/sda5 -y It has taken a lot of time more than an hour and still forcing rewrite. It seems that a lot of blocks are being repaired. Can someone describe what is going on or suggest any fix?