Martina Pezer

Shrinkage Behaviour of Fibre Reinforced Concrete with Recycled Tyre Polymer Fibres

Different types of fibres are often used in concrete to prevent microcracking due to shrinkage, and polypropylene fibres are among the most often used ones. If not prevented, microcracks can lead to the development of larger cracks as drying shrinkage occurs, enabling penetration of aggressive substances from the environment and reducing durability of concrete structures. The hypothesis of the present research is that polypropylene fibres, used in concrete for controlling formation of microcracks due to shrinkage, can be replaced with recycled polymer fibres obtained from end-of-life tyres. To test the hypothesis, concrete mixtures containing polypropylene fibres and recycled tyre polymer fibres were prepared and tested. Experimental programme focused on autogenous, free, and restrained shrinkage. It was shown that PP fibres can be substituted with higher amount of recycled tyre polymer fibres obtaining concrete with similar shrinkage behaviour. The results indicate promising possibilities of using recycled tyre polymer fibres in concrete products. At the same time, such applications would contribute to solving the problem of waste tyre disposal.

Utilization of polypropylene fibre reinforced cement composites as a repair material: A review

Environmental and structural loads cause stresses, deformations, and displacements in structures. According to the building codes, they have to be designed and built to safety resist all those actions during entire service life. When deteriorated, structures must be repaired and strengthen so that during usage they do not represent a risk for the users. Due to the low expenses and good mechanical characteristics, cement-based composites are often used for repairs. In structures susceptible to shrinkage and/or exposed to specific load conditions, used cement-based composites are improved with polypropylene fibres. These composites have many beneficial characteristics ; like as reduced occurrence of microcracks, positive effect on autogenous, plastic and restrained shrinkage, increased resistance to spalling during the fire, accessible price etc. Due to those characteristics, they are often used for repair of slabs, pavements and concrete overlays. Detailed state-of-the-art is presented and encompasses both fresh and hardened state properties. Also, a possibility for further improvement of repair materials is discussed.