School of Engineering Department of Civil and Environmental Engineering 75 A Cement-free Novel Concrete That Absorbs Greenhouse Gas CO2 to Heal Itself and Improve Its Mechanical Performance Supervisor: QIU Jishen / CIVL Student: WONG Lok Yi / CIVL Course: UROP 1100, Fall UROP 2100, Spring There are mainly two ways to improve the mechanical performance of reactive magnesium cement (RMC): hydration and carbonation. We focused on improving its mechanical strength by increasing the carbonation degree. However, the carbonation degree is low if we only use RMC due to the low reaction rate constant of hydration of CO2 being only 1.7*10-3 at 25⁰C (Housecroft & Sharpe, 2005), and the dense hydrated magnesium carbonates (HMCs). We propose using hollow natural fiber (HNF) (i.e. Sisal fiber) to hold CA. Since sisal fiber can significantly improve the carbonation ability of RMC by providing a pathway for CO2 to diffuse. And sisal fiber has superior water absorption ability and a hollow lumen structure that can house CA. A Cement-free Novel Concrete That Absorbs Greenhouse Gas CO2 to Heal Itself and Improve Its Mechanical Performance Supervisor: QIU Jishen / CIVL Student: WU Tsz Yin Chloe / CIGBM Course: UROP 1100, Fall This study investigates the mechanical properties of fibrous cementitious materials, with a focus on improving traditional concrete mix by incorporating fiber and alternative cementitious materials. The use of natural fibers, for example sisal fiber, offer unique characteristics such as hollowness and the ability to allow carbon dioxide entry, together with better tensile strength. The study also explores the use of reactive magnesia cement (RMC) as an alternative to traditional cement, which exhibits rapid setting and hardening characteristics, as well as exceptional resistance to fire and chemical attack. The research involves experimental techniques, material characterization, and performance evaluation to develop highperformance fibrous cementitious materials. The study aims to enhance the tensile properties of concrete and provide insights for future research in this field. A Cement-free Novel Concrete That Absorbs Greenhouse Gas CO2 to Heal Itself and Improve Its Mechanical Performance Supervisor: QIU Jishen / CIVL Student: YU Wai Chung / CIVL Course: UROP 2100, Fall UROP 3100, Spring Cracking is an unavoidable phenomenon in cementitious composites, degrading the mechanical strengths of concrete and causing concerns of serviceability. This work aims at investigating the effects of incorporation of natural hollow fiber (HNF), e.g. sisal fiber (SF), on the healing efficiency of PVA-RMC. Lumens in SF can provide a channel for carbon dioxide to diffuse to the cracks in deeper regions, resulting in autogenous healing. In this study, results show longer wetting-air cycles (10WA) engaged better healing of tensile strength than (3WA) in single fiber pullout test and uniaxial tensile strength test. Due to the differences in sample size, specimens without adding SF perform greater tensile stress in fiber pullout test while specimens with 2% by volume of SF show maximum fiber-bridging strength in uniaxial tensile strength test.
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