Extrusion fabrication process for the 3D printing of sustainable concrete structures

Abstract

In recent times, an increasing amount of research and development has been put into 3D printing. Initially used to build small scale projects that are simple using basic materials like polyester, its usage and possibilities have expanded vastly over the years. It is now possible to construct a wide range from the micro scale used in the biomedical industry to super scale used in the building industry. This is possible as the investment in research and development of 3D printing has made it more affordable, efficient and highly accurate. This project focuses on the extrusion process for the 3D printing of sustainable concrete. The report investigates how different composition of cement will affect the rheological properties such as shear stress and viscosity. Different methods are designed to investigate different behaviours such as thixotropy, structural build up/recovery and stress growth rate. The concrete mixture is made up of Portland cement, fly ash (sembcorp), silica fume, sand and water. Understanding the rheological properties under different experimental methods is important to simulate crucial processes in 3D printing, namely pumping and extrusion. Smooth flow is required during the pumping process that occurs in a tube or pipe. And during extrusion from the nozzle, the material needs to be able to maintain its intended shape even before hardening. Therefore, experiments would be conducted to measure the rheological properties of the cement using a rheometer with a 4-blade vane geometry. Using ANOVA (Analysis of Variance) to find the exact relationship between compositions and rheological properties. Once the relationship is established, the prediction of rheological properties of new composition can be calculated without the need to conduct experiments, which can take up a lot of time and effort.