A Study of Early Age Shear Properties of 3D Printable Cementitious Mixes with Fiber Reinforcements

The use of Fiber Reinforcement in digitally manufactured concrete is not only one of the viable techniques in the otherwise difficult reinforcement strategy but also a segue to the use of highly durable Ultra High Performance Concretes in 3D printing. For this, the characterization of early age mechanical properties such as tensile, shear and compressive strength of printable Fiber Reinforced Concrete is very important in the design process. The printability of fresh concrete which is defined as combination of pumpability, extrudability and buildability can be characterized using the tensile strength of filament, the shear strength and the compressive strength of the freshly printed element. This study aims on defining the shear strength of 3D printable cementitious mortars at early ages focusing on the “printability window” highlighting the phase transitions in printed concrete. Highly cohesive mortar with high Sulfo-Aluminate cement content is cast with Basalt fibers in specially designed molds to understand these said properties at various times from casting namely, 30, 45, 60 and 90 min. Repeatability of the methodology has been established using 3 iterations of each experiment and crack - failure patterns have been studied closely. Further study on developing the Kupfer’s failure envelopes is underway by including the compressive strength study obtained through penetration tests and tensile strength study.