Improving the performance of recycled aggregate concrete using nylon waste fibers

The use of coarse recycled aggregates (CRA) as the replacement for natural aggregates is an eco-friendly solution to alleviate the extraction of natural resources and the harmful effects of demolition wastes on the environment. However, the mechanical and durability characteristics of CRA concrete are generally inferior compared to ordinary concrete. The performance of CRA concrete can be supplemented using different fibers and secondary binder materials. This study encourages the idea of using recycled nylon fiber (RNF) to upgrade the ductility of high-performance concrete (HPC) made with CRA. For this purpose, the effect of RNF on HPC properties was explored. RNF was introduced in HPC at four different volume fractions i.e., 0.1 %, 0.25 %, 0.5 % and 1 %. The experiments showed that RNF is generally harmful to the compressive strength and density of HPC. However, at 0.1 % volume, RNF showed a nominally positive effect on compressive strength. RNF addition was highly useful in enhancing the splitting tensile strength and crack resistance of HPC. The tensile strength loss of HPC due to 50 % and 100 % CRA incorporation can also be balanced using 0.25–0.5 % RNF. Water absorption and chloride permeability of HPC were marginally reduced at the incorporation of 0.1–0.25 % RNF. The recommended dosage of RNF is 0.25 %, considering the maximum tensile strength and low permeability of HPC. Owing to the addition of 0.5 % RNF, a CRA-based HPC can attain tensile strength higher than ordinary HPC. Thus, for tensile-loading applications, CRA-RNF-based HPC provides a ductile, and eco-friendly alternative to an ordinary plain HPC.