Design and analyses of printable strain hardening cementitious composites with optimized particle size distribution

Abstract

Since the advent of three-dimensional concrete printing (3DCP), several studies have shown the potential of strain hardening cementitious composites (SHCC) as a self-reinforcing printable mortar. However, only a few papers focus on achieving sufficient buildability when developing printable SHCC. This study investigates the role of the particle size distribution (PSD) in relation to the buildability properties of the mixture in the fresh state and strain hardening properties in the hardened state. To this end 6 mixtures were designed based on optimal particle packing with the application of the Modified Andreasen and Andersen Model. The two mix designs showed the highest displacement at maximum stress were selected for further development of their fresh state rheological properties. This was achieved by addition of a viscosity modifying agent (VMA) and a super plasticizer (SP) and through material analysis by means of ram extrusion tests. Further fresh material characterization on the final two 3DP-SHCC mix designs was attained by the deployment of uniaxial unconfined compression tests (UUCT), Vicat tests and Buildability tests. After successful printing of the two SHCC composites, the compressive strength, the 4-point bending strength and the uniaxial tensile strength and strain were determined at an age of 28 days. The research shows that optimization of the PSD in a 3DP-SHCC mix design results in an improvement of the buildability, but can introduce decreased pumpability and strain hardening capacity.