Experiments on concrete test beams with recycled aggregates and natural fibers

To develop more sustainable concrete mixes, circular and bio-based constituents for the concrete mix are sought. As traditional concrete contains 70% aggregate by volume, using recycled aggregates is an attractive solution within the circular economy. To address concrete brittles, bio-based renewable fibers, such as abaca and coconut, can replace the traditional steel or polypropylene fibers. This study evaluates recycled aggregate concrete with natural fibers, comparing it to traditional polypropylene fibers in terms of mechanical properties. Concrete compressive strength, flexural strength, and dynamic modulus of reference and novel mixes were determined. The results of these experiments show that the compressive strength of the mixes with recycled aggregates is 65% of the control, and that the toughness of the beams with abaca is 48% of those with polypropylene fibers, and of the beams with coconut fiber are 29% of those with polypropylene fibers. The dynamic modulus of the discs with recycled aggregates is 30% of the control, whereas the modulus of the discs with abaca is 15% and those with coconut is 20% of the control. These first results show that concrete mixes using recycled aggregates and abaca fibers are a promising solution. These preliminary results will be used for further research geared towards the development of bio-based materials for tomorrow.