Polyacrylonitrile fiber reinforced 3D printed concrete: Effects of fiber length and content

Abstract

Polyacrylonitrile (PAN) fibers significantly improve the toughness, strength, and crack resistance of conventional concrete. This research explores the impact of PAN fibers, in lengths of 6 mm and 12 mm and dosages of 0 %, 0.1 %, 0.2 %, 0.3 %, and 0.4 %, on the rheology, extrudability, buildability, mechanical performance, and anisotropic characteristics of 3D printed concrete. Scanning electron microscopy (SEM) was used to examine the fiber distribution in the concrete. The findings show that as the PAN fiber content increases, the flowability and extrudability of the 3D printed concrete decrease. Optimal buildability was achieved with 6 mm PAN fibers at dosages between 0.1 % and 0.2 %. Compressive strength initially increases and then decreases with higher PAN fiber content, whereas flexural strength continuously increases with fiber content. The 12 mm PAN fibers outperform the 6 mm fibers in enhancing flexural strength, with a maximum improvement of 42.41 %. Increased fiber length and content lead to greater anisotropy and weaker interlayer bonds in the 3D printed concrete, with specimens showing the highest compressive and flexural strengths in the X and Y directions, respectively. SEM results indicate that the distribution of fibers is the main factor causing the mechanical anisotropy.