B 500MA stands, as far as I know, for reinforcement made of concrete bars, not fibers. However, I would strongly recommend that you simply confront the architect or structural engineer.
Oh please .... doesn't anyone think of recommending the OP a conversation with an expert on site? With his architect ... imho ...? Or external expertise?
The information from the OP is so rudimentary and amateurishly formulated that it is - from my point of view - negligent to even attempt to start an answer.