Polypropylene fiber is more and more widely used in our life, such as clothing, curtains, tent, etc., and there are some fibers can be used in the mortar, cement concrete, asphalt concrete and polyacrylonitrile fiber is one of the, in the construction and expansion agent can reduce and prevent concrete from cracking, increase the permeability resistance of concrete but they are different in different mechanism; Here's how they work, explained by expert luter: