Effects of the geometry of recycled PET fiber reinforcement on shrinkage cracking of cement-based composites

In this study, the reinforcing fibers were constructed with three different geometries, i.e., embossed, straight, and crimped, from waste polyethylene terephthalate (PET) bottles and used them to control plastic shrinkage cracking in cement-based composites. Pullout tests evaluated how the fiber geometry and fraction by volume (0.1–1.00%) affected the rate of moisture loss and controlled the plastic shrinkage cracking characteristics. The fiber geometry and fraction by volume did not affect the total moisture loss or moisture loss per hour; the moisture loss per hour exceeded 0.5 kg/m2/h in 5 h after casting, causing plastic shrinkage cracking. However, increased fractions of recycled PET fiber resulted in improved control of the plastic shrinkage cracking. At a fraction of 0.25%, the plastic shrinkage was reduced, but no further improvements were observed when the fraction of fiber was increased to 0.5%. Fiber geometry also affected the control of plastic shrinkage cracking up to a fiber fraction of 0.25%.