Investigation of the influence of temperature and relative humidity on the mechanical performance of sustainable cement binder-based concrete formulations

• Main Author: Lim, Sophia Suet Min
• Other Authors: Cise Unluer
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Civil engineering
• Online Access: http://hdl.handle.net/10356/71047
• Institution: Nanyang Technological University

With economic development and population growth, infrastructure demand has augmented. Consequently, the demand for cement, which is an essential raw material to infrastructure development, has also increased significantly thus resulting in large production of carbon dioxide (CO2). For instance, the annual production of 4.2 billion metric tons of cement has contributed to 5 to 7% of the current anthropogenic CO2 production. While reactive magnesia (MgO) cement might contribute to sustainability by sequestering CO2 production as compared to Portland cement, the former might be difficult and expensive to produce. This project aims to investigate an alternative and sustainable cement binder, dolomite, which could reduce its carbon footprint by determining the best curing conditions for it. Dolomite, which comprises of MgCO3 and CaCO3, was first calcined at 800˚C for 3 hours before it was grinded at 300 revolutions per minute for 10 minutes. In this study, MgO and dolomite concrete were subjected to different curing conditions of varying the curing temperature and relative humidity. After specific curing age (~7 and 14 days), mechanical properties and associated porosity test of concrete with different formulations were investigated. Meanwhile, microstructural analysis including X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy dispersive X-ray (EDX) were used to identify the hydration and carbonation product phases in selected samples. Preliminary results showed that there is a large reduction in porosity after carbonation for both dolomite and MgO concrete, meanwhile, at a higher curing temperature, a higher strength was achieved in MgO concrete but a lower strength was obtained for the dolomite concrete whereas for the relative humidity for both MgO and dolomite samples, a higher relative humidity curing conditions favors a higher strength gain. Corresponding microstructural analysis indicated that higher strength is associated with the formation of larger content of hydrated magnesium hydrates (HMCs). Based on the findings above, dolomite samples at curing conditions of 90% relative humidity, 30˚C at 10% CO2 and MgO concrete at curing condition of 90% relative humidity, 60˚C at 10% CO2 is recommended regarding mechanical performance.