Self-healing of MgO based strain-hardening fibre-reinforced cementitious composite (SHC)

• Main Author: Sai, Kaung Thura
• Other Authors: Cise Unluer
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Civil engineering::Construction technology
• Online Access: http://hdl.handle.net/10356/70875
• Institution: Nanyang Technological University

Engineered Cementitious Composites (ECC) are one of the most popularly used construction material. They are specially designed fibre-reinforced strain-hardening cementitious composites, which also known to possess self-healing properties. It was known that concrete itself was capable of healing cracks by sealing away with the formation of white crystalline substance. However, growing at an average annual rate of ~4%, Portland cement (PC) production contributes approximately 5-7% of anthropogenic carbon dioxide (CO2) emissions. Traditional ECC consumes a large quantity of PC as no aggregates are incorporated in binders. Therefore, development of alternative materials with lower net CO2 emissions is necessary. Recently reactive MgO gains its attention due to its lower calcination temperature and higher carbonation potential. In this report, the author investigated a way to promote formation of healing products by specific healing process. MgO-based strain hardening composites (SHC) were used to cast samples. The self-healing process included pre-cracking of samples and placing them in wetting-CO2 healing condition. The author also investigated repeatability in self-healing potential of MgO-based SHC in self-healing by pre-cracking and healing them for the second time. Results were verified using uniaxial tensile tests, resonance frequency, and microscopic observation to identify the performance of pre-cracked MgO-based SHC is recovered or even improved compared with original samples through specific improved healing condition. Preliminary results indicated that self-healing took place in MgO-based SHC reflected by the RF recovery and crack observation, and self-healing of pre-cracked samples outperformed control samples in ultimate tensile strength due to increased bond between the fibre and matrix. Through repeatability in self-healing, the healing efficiency reduces with the increased number of pre-crack-healing procedure by means of cracks observation. Finally, the crystals formed between cracks were hydrated magnesium carbonates by means of FESEM, indicating the self-healing potential of MgO-based SHC.