Michigan
If I break one of the handbook rules my company has and don't tell them I broke it, am I guilty of fraudulent concealment?
From the lack of information you have provided, it is impossible to tell you if you are guilty of fraudulent concealment.
You can read the following Opinion from Michigan's Court of Appeals in "M&D, Inc et al v W.B. McConkey et al" and either read the whole case or scroll down to descriptions of common-law fraud, innocent misrepresentation and silent fraud (which is also called fraudulent concealment):
http://www.michbar.org/opinions/appeals/1998/073198/M&D.html
From the decision: " ... Michigan courts have recognized that silence cannot constitute actionable fraud unless it occurred under circumstances where there was a legal duty of disclosure."
If you had a legal duty to disclose this handbook rule violation, to perhaps prevent someone from being defrauded/injured, then you could be guilty of fraudulent concealment. If you have an intent to deceive or cheat to perhaps cause a financial loss to another or a financial gain for yourself, you could be guilty of fraudulent concealment. There are many more possible "ifs."
I suggest you read through the case at the link provided and see if you can see for yourself if your handbook rule violation comes anywhere close to silent fraud. I suspect it doesn't.