University of Technology Sydney. Faculty of Engineering and Information Technology.Pozzolanic materials, like fly ash (FA) and ground granulated blast-furnace slag (GGBFS), are considered promising binder materials as they are industrial by-products, helping to decrease ordinary Portland cement (OPC) demands and further lessen greenhouse emissions. Therefore, the total or partial replacement of pozzolanic materials for OPC to fabricate sustainable and low-carbon cementitious composites (LCC) has garnered extensive attention for providing enormous environmental benefits for infrastructure and offshore construction. In addition, the durability of LCC under aggressive environmental deterioration (such as fire, acid, and marine environments) is a progressively significant property for concrete structures due to the increasing demand for extended service life and less maintenance.
For total pozzolanic materials replacement for OPC, this work has estimated the performance of fly ash/GGBFS-based geopolymer under combined mechanical loads and aggressive environmental conditions (fire and sulfuric acid attack). For partial pozzolanic materials replacement for OPC, this work has also assessed the performance of cementitious composites with GGBFS under the marine environment. The synergistic effects of seawater and undesalted sea sand on the properties of cementitious composites have been firstly analyzed. And then, the fire resistance of GGBFS-based cementitious composites with seawater and undesalted sea sand has been examined. Finally, the chloride-binding capacity of GGBFS-based cementitious composites in seawater and chloride solutions has also been observed.
The results showed that fly ash/GGBFS-based geopolymer with 20 wt.% GGBFS could be regarded as a remarkable alternative for OPC to achieve extraordinary fire resistance by considering the strength and compatibility variations. The fly ash/GGBFS-based geopolymer with cyclic preloading was also confirmed to exhibit less severe performance deterioration even after 18-month exposure to sulfuric acid attacks. In addition, the results illustrated that the chloride, sulphate, and magnesium ions in seawater and/or undesalted sea sand were assessed to lead to the phase changes of cementitious composites, including the formation of Friedel’s/Kuzel’s salts, magnesium hydroxide, and magnesium silicate hydrate, etc. The addition of 30 wt.% GGBFS and 1.0 wt.% glass fibers was also supposed to improve cementitious the fire resistance of cementitious composite with seawater and undesalted sea sand. Additionally, the cementitious composite with 30 wt.% GGBFS and 1.0 wt.% NS having the highest value of chloride-binding ratio was expected to enhance the long-term chloride-binding capacity.
Overall, this thesis improves the current understanding of the performance of low-carbon cementitious composites under aggressive environmental environments to produce more reliable data and ensure the reliability and sustainability of LCC-based construction
