Monofire® micro synthetic fibers for concrete made from 100% virgin polypropylene. Designed specifically for use in concrete for fire resistance in concrete mix at tunneling applications. Monofire® is alkali resistant, non-absorptive and completely non-corrosive. Monofire® fibers have special treatment by production and have great mixing and homogenous distribution in concrete. Their use protects concrete from stresses which cause spalling during a rapid heat increase.