3D printing of sustainable concrete structures and characterisation

• Main Author: Lee, Hanzu
• Other Authors: Wong Teck Neng
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Civil engineering::Construction technology
• Online Access: http://hdl.handle.net/10356/78518
• Institution: Nanyang Technological University

This project aims to investigate the end-effect of a rotational cylindrical couette flow in an Anton Paar MCR 102 Rheometer under purely steady, laminar, and isothermal tangential flow conditions in the measurement of end correction lengths for non-Newtononian fluids. After which, the measured end correction length of a non-Newtonian fluid will be used to determine the corrected rheological properties of ordinary portland cement with superplasticiser mixtures following a Bingham model. A proposed set of equations is used to calculate the corrected yield stress values for Bingham type. The measured yield stress values of the cement paste are then compared with that of the corrected yield stress values after accounting for end effect. Finally, the magnitude of end effects on Newtonian and non-Newtonian fluids in concentric cylindrical couette flow are compared. With the corrected yield stress values and the calculated coefficients for fitting of the models in MatLab, an effort to model and simulate the early stages of the cement hydration process using Tomosawa’s and Avrami-Erofeyev’s hydration models is carried out. A comparison of the two hydration models and their respective models for the evolution of volume fraction of the hydrated cement over time and the evolution of the yield stress over time will also be accomplished with full consideration of the effects of superplasticizer oil content on the mixtures. All in all, it is found that the rheological properties of cement mixtures following the Bingham model such as yield stress differs by a value of 8.84% when accounting for end effects in a concentric viscometer. The difference in the degree of hydration during the early stages of cement particles for the both models are minute, resulting in minute differences in the volume fraction of the cement particles. For 0.2% of SP oil content, the evolution of yield stress is heavily depended on the structuration rate of the cement and for 0.1% and 0% of SP oil content in the cement mixtures, the increase in yield stress was mainly due to the initial yield stress of the cement which is solely affected particle size distribution pre-factor.