Effects of Expanded Polystyrene Beads and Printing Direction on Printable Epscrete Properties

Abstract

This study investigates the effects of expanded polystyrene (EPS) beads and printing direction on the fresh and hardened properties of 3D printable lightweight concrete (epscrete) mixtures. In the experimental studies, control samples containing only sand, mixtures containing only EPS and sand-EPS mixtures with different ratios were prepared and various experiments such as workability, shape retention, unit weight, ultrasound transmission velocity, compressive strength, flexural strength and splitting tensile strength tests were performed on these specimens. In addition, the effects of printing and loading directions on the mechanical strength of epscrete mixtures were investigated. The results show that EPS beads improve the rheological properties of fresh concrete and increase workability, but cause a significant decrease in shape retention ability, especially at high EPS ratios. In terms of hardened concrete properties, it was determined that mechanical strength decreases as the EPS ratio increases, but sufficient load-bearing capacity can be provided with compressive strengths exceeding 30 MPa in all directions in mixtures containing 50% EPS. In addition, higher compressive strength is observed under loading perpendicular to the printing direction, while the strength is lower on the interlayer bonding surfaces. Microstructure analyses revealed that ettringite formations are intense in the transition zone between EPS and cement matrix and this increased porosity within the structure adversely affects the overall strength. These results show that lightweight concretes with EPS content, known for their advantages such as lightness and thermal insulation, have potential for 3D printable low-rise and lightweight building applications.