• A crack closure system for cementitious composite materials using knotted shape memory polymer (k-SMP) fibres

      Maddalena, R.; Bonanno, L.; Balzano, B.; Tuinea-Bobe, Cristina-Luminita; Sweeney, John; Mihai, I. (2020-11)
      Formation of cracks represents one of the major causes of concrete deterioration, which can lead to durability and safety issues. In this work, a novel crack closure system is developed, using polyethylene terephthalate (PET) polymer fibres embedded in a mortar mix. The PET polymer has shape memory properties and shrinks upon thermal activation, if free to do so, or otherwise exerts shrinkage restraint forces. A single knot was manufactured at each end of the PET fibres to provide mechanical anchorage into the mortar matrix. Mortar samples with embedded knotted fibres were pre-cracked and subsequently placed in an oven to thermally activate the polymers and induce the shrinkage mechanism into the fibres. Crack closure was measured in the range 45–100%, depending on the geometry, dimension and distribution of the fibres, and the size of the initial crack.