Fresh properties and rheological behavior of 3D-Printed cementitious composites incorporating recycled PVC and nylon fibers: An experimental approach

The increasing global use of plastic materials is leading to a corresponding rise in plastic wastes, posing significant environmental challenges. This research explores the effects of incorporating recycled plastic fibers (RPFs) derived from nylon and Polyvinyl Chloride (PVC) industry wastes into 3D-printed cementitious composites (3DPCC). The impact of using these two types of fibers on the fresh properties, rheological behavior, green strength, extrudability and buildability of 3DPCC is explored. The main variables in this study are fiber type, volume fraction (0.5 %, 1.0 %, and 2.0 %) and fiber length (6 mm and 12 mm). The results show that adding RPFs, particularly longer fibers, decreases the flowability and workability of 3DPCC, with PVC fibers having a more pronounced effect than nylon fibers. Utilizing RPFs in 3DPCC mixes increased plastic viscosity (PV) and yield stress (YS). At a volume fraction of 2 % and a length of 12 mm, PVC fibers increased the static yield stress by 214.5 %, the dynamic yield stress by 155.2 %, and the PV by 177.7 %. Furthermore, the results indicate that samples containing PVC fibers outperform those containing nylon fibers and samples without fiber content in terms of green compressive strength, crack pattern, and buildability. By using a fiber volume fraction of 2 % and 12-mm length, PVC fibers reduced structural failure by 36.8 %, allowing for the construction of 38 layers compared to 24 layers in the control sample.