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

Anne Linde Van Overmeir,Stefan C Figueiredo,Branko Šavija,Freek P Bos,Erik Schlangen

doi:10.1016/j.conbuildmat.2022.126411

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.

Highlights

Three-dimensional concrete printing (3DCP) is one of the most common techniques of the additive manufacturing (AM) for concrete, in which the cementitious material is extruded layer upon layer, by a digitally controlled robot
Where the low fibre content printable mortars display clear failure planes that correspond with failure planes of hydrated concrete under compressional force, the strain hardening cementitious composites (SHCC) samples do not show these clear failure planes and the shape of failure is closer to those seen in the younger sample
The present study was designed to determine the effect of optimal particle size distribution on the buildability of 3D printable strain hardening cementitious composites

Summary

Introduction

Three-dimensional concrete printing (3DCP) is one of the most common techniques of the additive manufacturing (AM) for concrete, in which the cementitious material is extruded layer upon layer, by a digitally controlled robot. Despite the benefits that this additive manufacturing technique offers, it is not yet widely applied in practice, due to the multiple technical challenges that still need to be overcome [1,2,3], one being the mechanical properties of plain concrete, which is brittle by nature and lacks sufficient tensile strength. In traditional concrete this lack of tensile strength is overcome by the implementation of steel bar reinforcement.

Results

Discussion

Conclusion