Modification of marine clay for sustainable concrete application

• Main Author: Liu, Yuxin
• Other Authors: Qian Shunzhi
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/154395
• Institution: Nanyang Technological University

In recent years, the demand for aggregate, the main component in concrete, was kept increasing in the construction industry. Most construction sites were using natural aggregates, e.g., Rock and sand. As the natural resources were limited, and the depletion of natural resources became the principal concern. In this situation, it was an urgent call to apply sustainable engineering in every engineering discipline. On the other hand, it was expensive to import construction materials from other countries. Reusing locally available waste materials could help to reduce the cost. Moreover, during excavation, there was a stable supply of about 12-million-ton Marine Clay (MC) each year in Singapore, which made it necessary to investigate the use of local waste MC. Although fly ash or bottom ash has been broadly investigated as both filler or binder in concrete, there still existed more viable options to use marine clay due to local abundance and wide availability. (Zainuddin et al., 2019) Artificial aggregates have been broadly researched and applied so far, but MC has yet to be adopted in artificial aggregates fields due to its high liquid limit and water content. Consequently, it was hard to use MC as filler material in a geotechnical application or sand replacement in concrete. In this FYP research, local waste MC was adopted as the primary raw materials in producing artificial aggregates to improve sustainability. A cold bonding process was applied in this research, rather than the traditional sintering process considering the energy consumption during the sintering process. Finally, sustainable concrete with reasonable mechanical property can be produced with the incorporation of cold-bonding MC aggregates. In this study, various parameters, such as water addition rate and amount, air pressure, etc., were optimized to improve the pelletizing efficiency and performance of MC CBA (Cold Bonded Aggregates). Different MC: OPC ratios (from 0.95:0.05 to 0.6:0.4) were adopted to pelletize CBA, and their performance was compared accordingly. Aggregate particle crushing test and concrete cube compression test were conducted. It turned out that 70% MC as the main matrix with 30% cement obtained good particle crush strength and cube compression strength. In addition, an optical microscope and scanning electron microscopy (SEM) was employed to identify the morphology and microstructure of MC CBA. In addition, Calcinated MC (600 ℃) was also adopted in CBA. At 7 &28 days, calcined MC specimens showed better particle crushing strength and cube compression strength than raw MC ones. The compressive strength of the cube with calcinated MC CBA could achieve 40 MPa. Besides, the microstructure of calcinated MC CBA was denser with lower porosity.