Abstract: An injection system for asphalt, asphalt-containing or other viscous compositions, comprising a mixing drum or receptacle, an injection device having a housing and mounted nozzle jet for preparation and discharge of a premix comprising such asphalt or other composition(s) admixed with staple fiber, means for supporting the injection device, and means for supplying composition and fiber components through the injection device in flowable condition, the composition flow pattern being arranged external and generally concentric to the fiber flow and in a downstream blocking flow pattern relative to the fiber flow to assure wetting and encapsulation thereof before discharge of the premix; and a method for introducing staple fiber and filler or other additives, as desired, into the asphalt composition by using the injection device.