Fiberglass fibers added to concrete for extra strength is commonly referred to as “fiber reinforced concrete”. When these fibers extend up through the surface, the concrete is sometimes called “fuzzy” or “hairy” concrete. These surface fibers, if not removed or encapsulated, could telegraph through the flooring material or present a problem when troweling adhesive and adhesive bonding to the concrete. In most cases these fibers are too tough to be sanded or ground away. Usually, the entire surface has to be leveled with a cement-based self-leveling underlayment product.