What is the difference between steel fibres and micro-synthetic fibres?
Micro-synthetic fibres are very thin short fibres primarily made of polypropylene (PP). Typical dosage rates are from 600 to 900 g/m³ of concrete. Unlike steel fibres, micro-synthetic fibres do not offer concrete post-cracking bearing capacities. Concrete with micro-synthetic fibres remains as brittle as plain concrete. Micro-synthetic fibres only have a positive influence on the fresh concrete. By reducing the amount of bleed water from fresh concrete, they reduce the plastic shrinkage of said concrete. After the concrete has hardened and is drying, they partially restore this water to the concrete, thus creating a curing effect. In other words, they slow the rate at which moisture evaporates from the surface of the concrete. The same effect can be obtained with steel fibres, by adding only the correct amount of allowable water for a given concrete mix, using adequate super-plasticizers as well as concrete mixes that are stable yet workable and by curing of the concrete based on state
