Can my Barbarian block attacks with a shield equipped while performing whirlwind?

If I have a shield equipped, will I have a chance to block incoming attacks while I'm in the middle of performing whirlwind through a group of enemies? Is my chance to block reduced in any way while performing whirlwind?

Yes you can block any attack while performing whirlwind and it doesn't seem to have any impact on the chance to block. You can test this with whirlwind in a big pack of enemies and have a close look at your combat text. If you have a high chance to block you can see the block text pop up quite fast. If you open up the detailpage of the inventory you can monitor your chance to block while performing whirlwind. by the way if you did not know yet, you can also use other abilities during the whirlwind animation.