Mechanical and rheological properties of fiber-reinforced 3D printable concrete; in terms of fiber content and aspect ratio

The aim of this study is to improve the mechanical and dimensional stability properties of 3D printable concrete by using fibers. Ten mixtures containing polypropylene fiber in three different lengths (3, 6, and 12 mm) and ratios (0.2%, 0.4%, and 0.6%) were prepared. Rheological properties, compressive strength, three-point flexural strength, and drying-shrinkage performance of 3D printable concrete mixtures were examined in this study. Strength properties were determined by perpendicular and lateral loading. Thixotropic properties of the mixtures were determined using three different approaches (structural build-up development, hysteresis area and dynamic structural build-up). The dynamic yield stress value increased with fiber addition up to 0.4% of the total volume. It was determined that this value decreases with the use of fiber above this rate. In terms of mechanical and dimensional stability properties of 3D printable concrete, the optimum fiber length and utilization ratio were 6 mm and 0.4%, respectively. This parameters were adversely affected when fiber utilization ratio was 0.6% and length was 12 mm. Also, there is a strong correlation between structural build-up development and dynamic structural build-up.<br />