Use of the Chemical and Mineral Admixtures to Tailor the Rheology and the Green Strength of 3D Printing Cementitious Mixtures

Abstract

Concrete 3D printing is an innovative manufacturing technic grasping a great interest in the construction industry. However, the materials engineering is still a challenge for an accurate large-scale 3D printing process. One promising solution is to tailor the rheological properties of the printing materials. Cementitious materials used for extrusion-based 3D printing should exhibit high static yield stress and well-adapted structuration (i.e. build-up) kinetics. These properties are mainly influenced by the mixture composition, including the use of the chemical and mineral admixtures. An experimental investigation was conducted to study the structuration kinetics of various mixtures by means of flowability and static yield stress evolution. Four mortar mixtures were developed using compatible chemical and mineral admixtures promoting the thixotropic behavior of printing materials. In addition, the green strength of mixtures was monitored up to 40 min after mixing. An empirical test setup and a novel sampling method were proposed to evaluate the behavior of the fresh 3D printed layers during the printing process.