The detailed results obtained in this study lead to the following primary conclusions:
The density of hardened mortar is not significantly altered by incorporation of PET fibres in the volumes and sizes here studied.
The water capillary absorption determination prescribed by EN 1015-11 does not fit perfectly to the case of mortars with fibres such as those studied in this work, considering that the pullout of the fibres during the test undermines the structure adjacent to samples fracture faces;
The PET fibres incorporation does not significantly change the magnitude of the mortar compressive strength.
The PET fibre incorporation in the render reference mortar (1:1:6) increases the bending strength about 100% at 7 days, 30% at 28 days and the order of 50% at 63 days.
The volume of PET fibre of 1.5% is the optimum volume for the best performance of the mortar.
The residual strength factors values obtained for 1.5% fibre reinforced mortar leads, in all ages, to an optimum fibres amount that gives to the mortar a reinforced character with large energy absorption, especially at the ages of 7 and 63 days. These findings are indicative of good performance of the fibres and enable in part the recycling of PET packaging.