Characterization of 3D printed concrete mixtures developed using local UAE materials based on rheological properties

Abstract

This paper investigates the fresh and rheological properties of 3D printed concrete mixes developed using locally available United Arab Emirates (UAE) materials. Thirty-two 3D printed concrete mixes were developed with various constituents. These constituents included: water to binder ratio (w/b), superplasticizer (SP), fly ash (FA), silica fume (SF), and two types of fibers: Stewathix 600 (ST600) fiber and Glass Short Cut - FGCS HP (HP6) fiber. A rating procedure was developed to qualitatively and quantitatively evaluate and rate the printability of 3D concrete mixes. This evaluation procedure employs a manual mortar gun that is suitable to be used for on-site assessment. Also, a printability chart relating dynamic yield stress to plastic viscosity was developed. A recommended printability box was identified suggesting that 3DPC mixes with plastic viscosity between 15 and 97 Pa.s and dynamic yield stress between 400 and 1500 Pa are likely to demonstrate adequate printability. This chart can aid in the design and quality control of 3D printing concrete mixes. The open time test was performed on four selected mixes. The results revealed that medium dosages of ST600 (0.11 %–0.22 %) and HP6 (0.15 %–0.22 %) fibers enhanced the extrudability of 3DPC mixes, while contributing to a reduction in flowability. These mixes fell within the defined printability box. A lower w/b ratio enhanced short-term printability, whereas a higher ratio was needed for longer durations. Microsilica improved early printability but led to reduced performance after 1 h. Finally, a large-scale laboratory printer was used to evaluate the printability of selected 3DPC mixes that fell within the identified printability box. The paper presents valuable practical insights for the construction industry in the UAE, which can foster the adoption of this technology in construction. Keywords 3D printing concrete, Rheology ,Dynamic yield stress, Slump flow