| Graphene has attracted widespread attention because of its remarkable properties such as superior mechanical strength, excellent mobility of charge carriers and high thermal conductivity. Integration of graphene into cement-based materials plays an important role in developing multi-functional cementitious composites with better self-cleaning property, higher thermal energy storage capacity and improved mechanical behavior Graphene oxide (GO) is one of the most important graphene derivatives, which forms mono-layer of sp2 -hybridized carbon atoms decorated by a mixture of carboxyl, hydroxyl and epoxy functional groups. The hydrophilic, cost-effective and excellent chemical/physical properties make it more effective on reinforcing cement-based materials in mass production. The incorporation of GO into cement-based materials not only improves the mechanical properties, but also facilities the multi-functional behavior. In this thesis, the preparation and characterization of various GO modified composites were conducted in the context of photocatalytic, thermal and mechanical behavior.;Firstly, the reduction of GO to reduced graphene oxide (rGO) was conducted by the UV-assisted TiO2 method. Two key parameters, weight ratio of TiO2 to GO and UV irradiation time, have a great influence on the reduction degree of GO. The fabricated TiO2/rGO composites with various reduction degree of GO were then used to degrade the methyl orange (MO) to investigate the effect of rGO on the photodegradation efficiency of the TiO2/rGO composite. Finally, the optimized two parameters influencing the reduction of GO were given and the relationship between the reduction degree of GO and the photodegradation efficiency of the TiO2/rGO composite was established.;Secondly, the mechanical behavior and microstructures of GO reinforced cementitious materials, including the Ordinary Portland Cement (OPC), Strain Hardening Cementitious Composites (SHCCs) and Magnesium Potassium Phosphate Cement (MKPC), were investigated A certain amount of GO could enhance the mechanical behavior of OPC and MKPC by refining pore size, improving hydration and modifying microstructures. Moreover, it was found that the physical and chemical interactions between the polyvinyl alcohol (PVA) fiber and cement matrix in SHCCs were strengthened by GO. In addition, the dispersion of carbon nanotubes (CNTs) in GO solution was better than aqueous solution. The space interlocking mechanism of GO in enhancing the mechanical properties of the composites was investigated, and it was found that the flexural and compressive strength of cement paste were greatly increased by 21.13 % and 24.21 % with the incorporation of 0.025 wt. % CNTs/ 0.025 wt. % GO composites, which is much higher than that reinforced by 0.05 wt. % CNTs or 0.05 wt. % GO, respectively.;Finally, leakage problem of phased change materials (PCMs) composites was resolved by GO encapsulation due to its excellent thermal and impermeable properties. The thin layer coating of GO has showed an important effect on preventing PCMs composite from leakage after thermal cycling of 3000 times. It gave an innovative way to improve the work efficiency and durability of PCMs composites in terms of thermal energy storage.;The experimental results obtained in this thesis demonstrate that GO has a great potential to be used in photocatalytic, cementitious materials and PCMs composites. A small loading of GO can make a great enhancement on improving the physical and chemical properties of these materials. More importantly, it is worth fabricating cement-based materials by incorporating TiO2/rGO and PCMs/GO composites to achieve multifunctional construction materials with better mechanical behavior, satisfied self-cleaning performance and excellent thermal energy storage property. |
