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.

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.

The necessity to reduce CO2 emissions has increased the driving force for the cement research community to develop alternatives to traditional Portland cement (PC). One of the alternative cements being investigated is calcium sulfoaluminate cement (CS ̅A), first developed commercially in China in the 1970's. CS ̅A cements are produced by clinkering together limestone, bauxite, clay and calcium sulfate to produce mainly ye'elimite (C4A3S ̅) and belite (C2S). Due to the presence of ye'elimite, SO3 content is typically between 6 – 10 wt%. The abundance of elemental sulfur arising from the desulfurisation of oil and gas and its use to produce CS ̅A clinkers were the starting points of the Green Concrete Project (GCP), which aimed to develop a novel approach to produce CS ̅A cement via the combustion of elemental sulfur, recycling this by-product and reducing the dependence on hydrocarbon fuels. Integrating the current knowledge on the production of CS ̅A, a new generation of CS ̅A belite calcium sulfoaluminate (BCS ̅A) and belite-ye'elimite-ternesite (BYT) clinkers incorporating the combustion of elemental sulfur has been successfully developed and produced in a pilot plant production process. A high-temperature thermodynamic model was developed to predict stable assemblages and to complement and validate experimental results. Within the frame of the GCP, the title thesis focused on collecting conditional thermodynamic data for ye'elimite and ternesite (enthalpy of formation) that were determined experimentally using isothermal conduction calorimetry. The enthalpies of formation of ye'elimite and ternesite at 25 °C were determined to be -8523 kJ/mol and -5993 kJ/mol, respectively. The thesis was also focus on characterising two clinkers of interest (designated BCS ̅A and BYT) obtained from a pilot plant trial (with the novelty of sulfur combustion). The obtained clinkers, BCS ̅A and BYT, have a distinctive mineralogy where alpha prime belite (α΄-C2S) and ternesite (C5S2S ̅) are present, respectively. Both phases are candidates to replace a significant amount of ye'elimite and therefore reduce the need of expensive bauxite to establish a more sustainable cement. The alpha prime polymorph of belite proved to be more reactive than the beta. However, actions had to be taken to control the fast setting of this BCS ̅A cement. To provide a solution to the fast setting problem a variety of retarders were investigated: 0.5 wt% citric acid with an additional 5 wt% gypsum showed the best results. A fundamental solution was also Abstract 5 investigated in order to avoid the use of any retarders. The results showed that the clinkering temperature should be around 1300 °C. The hydration of ternesite in the BYT cement was found to be moderate. Therefore, a thorough investigation was conducted to understand and find ways to enhance its reactivity. It was found that the addition/presence of 0.4 wt% MgO, 0.2 wt% K2O and 0.1wt% Na2O in the raw meal required for the synthesis of ternesite, can increase its reactivity. Furthermore, it was found that particle size distribution above 600 m2/kg can also accelerate its reactivity. Single-phase chemically activated ternesite hydrated rapidly at 25 °C, achieving compressive strengths of ≈ 30 and ≈ 65 MPa at 28 and 90 days respectively, with C-S-H and gypsum as hydration products.

Thèse doctorat : Génie Civil : Villeurbanne, INSA : 2005. / Titre provenant de l'écran-titre. Bibliogr. p. 254-260.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 231-238)

Thèses (M.Sc.A.)--Université de Sherbrooke (Canada), 1997. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Thèse doctorat : Images et Systèmes : Villeurbanne, INSA : 2001. / Titre provenant de l'écran-titre. Bibliogr. p. 136-144.

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1940. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed March 9, 2010) Includes bibliographical references (p. 60-62) and index (p. 63-64).

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographic references (p.269-278).