USE OF FINELY GROUND RECYCLED CONCRETE FOR IMPROVEMENT OF INTERFACIAL ADHESION IN FIBER-REINFORCED CEMENTITIOUS COMPOSITES

This paper deals with an improvement and an assessment of a polymeric macro-fibers adhesion to the cement matrix. For this purpose, two approaches were employed – (i) roughening of fibers using a plasma treatment and (ii) an addition of finely ground recycled concrete (amount 30 wt. %) to the matrix ensuring the roughness of interfacial zones. Polyethylene terephthalate (PET) and polypropylene (PP) fibers, both ca. 0.3mm in a diameter, were used. These were surface roughened using a cold oxygen plasma treatment and then observed by means of the scanning electron microscopy. Consequently, pull-out tests of an individual fiber embedded 25mm in the matrix were performed, while the force needed for fiber pullout was recorded. Results have shown that plasma treated fibers reached on a better adhesion with the matrix by up to ca. 5% (PET) and 20% (PP), if compared to reference fibers. When recycled concrete was used, the adhesion increased further by about 5–10% for both fiber types.