Understanding the rheological behavior of MSH (MgO-SiO2) binders for 3D concrete printing

• Main Author: Nu Nu Lwin
• Other Authors: En-Hua Yang
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/172673
• Institution: Nanyang Technological University

3D concrete printing represents an innovative approach in the field of construction, introducing advanced methods that transcend the limitations of traditional building techniques. This cutting-edge technology leverages the precision and automation of 3D printing to fabricate intricate and robust structures layer by layer. Moreover, 3D concrete printing offers a more efficient, cost-effective, and sustainable alternative. This study focuses on the use of both silica fume and metakaolin in the formation of MSH binders for 3D concrete printing. In contrast to the previous study, a PCE-based superplasticizer and aggregates are used in this study. Additionally, there has not been a systematic investigation of the effects of parameters on the rheological and mechanical properties. This study aims to fill this gap by providing a comprehensive exploration of these influential factors, thereby contributing to a more comprehensive understanding of the MSH binders for 3D concrete printing. The study evaluates the mix designs with four key parameters including the silica fume-to-binder ratio or metakaolin-to-binder ratio, water-to-binder ratio, sand-to-binder ratio, and superplasticizer dosage. The mix compositions include the respective silica source, MgO, water, sand, and superplasticizer. The Taguchi method is employed for experimentation, focusing on parameters influencing the rheological performance of MgO-SiO2 binders. The rheological properties and thixotropy analyses are carried out to provide crucial information about the flow behavior of the material during extrusion and its ability to regain viscosity after flow, which directly influences layer stability. Simultaneously, a slump and flow diameter test is conducted to evaluate the workability and consistency of the material during the 3D printing process. Comprehensive mechanical performance is investigated through the compressive strength test, to gain insights into the structural integrity of the MgO-SiO2 binders. To further enhance the understanding, microstructural analyses are investigated via x-ray diffraction (XRD) thermogravimetry/derivative thermogravimetry analysis (TGA/DTG), and Fourier-transform infrared spectroscopy (FTIR), to comprehensively characterise the composition, phase formations, and microstructural development of the binder.