Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 314-315). Also available in electronic version. Access restricted to campus users.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 177-196). Also available in electronic version.

Cement is the world's most popular building material, yet surprisingly its composition is not fully understood. Due to the complex nature of cement constituents, there is currently no reliable method to quantitatively determine the composition of cement. Partly this arises from the fact that the crystal structure of the main component of cement, tricalcium silicate, has not been fully determined. There has been an increase in the use of Rietveld refinement of powder diffraction data for the analysis of cement in recent years. The method has emerged as a valuable tool for the quantitative determination of the composition of cement. A further advantage of the method is its ability to refine complex crystal structures, such as tricalcium silicate. Despite the increased application of this method, few publications exist concerning the evaluation or improvement of the method for the purpose of cement analysis. In this work, the Rietveld method has been critically investigated as a tool for the identification and quantification of the different phases in cement clinker. Laboratory X-ray, synchrotron, neutron, and combined diffraction data are all used in the investigations. For the first time, comparisons of analysis results using various sources are made, rather than comparing the results from various methods. Inconsistencies in the results were found, and their causes were investigated and identified. The reliability of this method was shown to be dependent on the quality of the diffraction data, both in terms of the counting statistics and the resolution, and on the ability of the structures used in the Rietveld model to describe the phases in the sample. The only previously existing structural model for triclinic tricalcium silicate is shown, in this work, inadequate as a description of the form found in cement. Consequently, the triclinic crystal structures of tricalcium silicate were re-investigated. Using synchrotron powder diffraction data, the lattice dynamics during the T1-T2 transition were observed in detail for the first time. Superstructure reflections were observed for the two structures. The first model for the average sub-structure of the T2 form is presented. Structural modulation in the T1 form was re-investigated. The parent sub-structure, suitable for Rietveld refinement, corresponding modulation wave-vector, and superspace group of the superstructure, were identified.

Includes bibliographical references.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 120-125). Also available in electronic version. Access restricted to campus users.

Cement is the world's most popular building material, yet surprisingly its composition is not fully understood. Due to the complex nature of cement constituents, there is currently no reliable method to quantitatively determine the composition of cement. Partly this arises from the fact that the crystal structure of the main component of cement, tricalcium silicate, has not been fully determined. There has been an increase in the use of Rietveld refinement of powder diffraction data for the analysis of cement in recent years. The method has emerged as a valuable tool for the quantitative determination of the composition of cement. A further advantage of the method is its ability to refine complex crystal structures, such as tricalcium silicate. Despite the increased application of this method, few publications exist concerning the evaluation or improvement of the method for the purpose of cement analysis. In this work, the Rietveld method has been critically investigated as a tool for the identification and quantification of the different phases in cement clinker. Laboratory X-ray, synchrotron, neutron, and combined diffraction data are all used in the investigations. For the first time, comparisons of analysis results using various sources are made, rather than comparing the results from various methods. Inconsistencies in the results were found, and their causes were investigated and identified. The reliability of this method was shown to be dependent on the quality of the diffraction data, both in terms of the counting statistics and the resolution, and on the ability of the structures used in the Rietveld model to describe the phases in the sample. The only previously existing structural model for triclinic tricalcium silicate is shown, in this work, inadequate as a description of the form found in cement. Consequently, the triclinic crystal structures of tricalcium silicate were re-investigated. Using synchrotron powder diffraction data, the lattice dynamics during the T1-T2 transition were observed in detail for the first time. Superstructure reflections were observed for the two structures. The first model for the average sub-structure of the T2 form is presented. Structural modulation in the T1 form was re-investigated. The parent sub-structure, suitable for Rietveld refinement, corresponding modulation wave-vector, and superspace group of the superstructure, were identified.

Thesis (Ph. D.)--University of Technology, Sydney, 2003. / "Submited for the degree of Doctor of Philosophy, University of Technology, Sydney, Dept. of Chemistry, Materials and Forensic Sciences, August 2003" Bibliographic references: leaves 224-232.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references (leaves 212-220). Also available in electronic version. Access restricted to campus users.

The replacement of asbestos fibres with cellulose fibres in producing corrugated fibre reinforced cement sheets by the Hatschek process resulted in edge cracking for stacked sheets. This was due to the hydrophilic nature of cellulose, which increases its tendency for exchanging water with the surroundings. The drying process of corrugated sheets, in a stack, resulted in shrinkage hence edge cracking along the sheet. To reduce the magnitude of drying shrinkage and edge cracking potential, several mitigation strategies were proposed including the surface treatment of cellulose fibres, incorporation of wollastonite microfibres, addition of admixtures and superplasticizers, kaolin inclusion as partial replacement of cement and different exposure conditions. A fundamental understanding in mechanisms behind volume changes and how cracks form was crucial for optimization of the mitigation strategies. This thesis initially used a review approach to understand the mechanisms involved in different types of shrinkage and the role of different mitigation techniques. The ultimate goal was to achieve lower drying shrinkage and cracking risks in corrugated sheets along with reducing its economic impact. As a result, surface treatment of cellulose fibres, based on transforming the hydrophilic nature of cellulose to hydrophobic state, was investigated. Furthermore, inclusion of wollastonite/ kaolin as partial replacement of cement, were evaluated. Also, the potential of adding admixtures/ superplasticizers was explored. Finally, investigation on development of edge cracks in stacked corrugated fibrecement sheets was conducted under different exposure conditions. The results and findings of this research showed no significant improvement in permeability with cellulose surface treatment. Wollastonite microfibres promoted pore discontinuity hence significant reduction in permeability thus lower drying shrinkage. However, the resultant sheets were brittle. By reducing water content with addition of superplasticizers, density was enhanced thus reducing volume change from drying and wetting. Kaolin acted as internal restraint for shrinkage, refining the microstructure at the interfacial transition zone thus increasing density and its pozzolanic reaction enhanced mechanical properties. The inclusion of kaolin in the fibrecement mix in conjunction with controlling exposure conditions managed to eliminate edge cracking.