Improving the mechanical properties of MgO-FCC based composite cement for 3D printing

• Main Author: Mok, Zong Han
• Other Authors: Qian Shunzhi
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/177672
• Institution: Nanyang Technological University

The utilisation of 3D concrete printing (3DCP) technology has garnered significant interest in the construction industry due to its potential for revolutionizing traditional construction methods. In recent years, MgO-fluid catalytic cracking (MgO-FCC) based cementitious composites have seen an increase in studies to investigate its feasibility to be used as the material for 3DCP printing. MgO gained its attention due to its lower calcination temperature as compared to Portland Concrete. FCC ash has received notice as it is also a common industrial waste product from the crude oil refinery process, and its inclusion would enhance the sustainability of 3DCP printing material. This has spurred several studies on its feasibility for use as a cementitious composite with MgO for 3DCP printing. However, the mechanical strength of this composite has shown to be limited as compared to regular Portland Concrete. This study aims to improve the mechanical properties and printing of MgO-FCC based cementitious composites by substituting the FCC ash with other supplementary cementitious materials (SCMs) like Silica Fume & Burnt Rice Husk ash, which studies have shown to enable higher compressive strength than control concrete. This study will conduct a systematic investigation of the rheological and mechanical properties of the proposed samples. Rheological properties and thixotropy analyses were carried out which had provided critical information on the materials flow behaviour during 3D concrete printing. Slump and slump flow tests were also conducted to evaluate the workability and flowability of the sample materials that would be used for 3D printing process. To gain insights into the mechanical performance of the material, the compressive strength test was also conducted. In the first half of the study, a suitable reducing agent was selected to help reduce the water-to-binder ratio of the concrete and to improve its workability. In the second part, several samples with varying ratios of FCC to SF & FCC to Burnt RHA were prepared for the experiment. Using an Anton Par Rheometer with a vane geometry, constant angular velocity protocol and creep recovery protocols, the rheological properties of fresh concrete samples were able to be obtained. The rheological properties mentioned will include static yield stress, dynamic yield stress and plastic viscosity. The outcome of this study is expected to contribute to the advancement of sustainable construction practices by providing insights into optimizing the material composition of MgO-FCC for 3DCP concrete printing.