Call number: LD2668 .T4 1953 M85 / Master of Science

Published Article / Corrosion of rebar in concrete is commonly associated with the free chloride in the pore water in the cement matrix. Knowing the quantity of chloride in concrete is important because chloride can promote corrosion of steel reinforcement when moisture and oxygen are present. The problem ofphysical extraction and the measurement of the free chloride content in pore water solutions extracted from cement pastes has received attention in literature but has not been explained in full detail. However, the variability of results obtained from the different methods used by various investigators only serves to confuse the issue. This investigation describes the use of a tumbler designed to prepare homogeneous samples and the use of a pore water expression device designed to extract free chloride in cement paste and concrete samples.

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Lam Lik. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 107-112). / Chapter Chapter 1. --- Introduction --- p.1 / Chapter 1.1. --- Chemistry of portland cement manufacture --- p.1 / Chapter 1.2. --- Classical methods of cement analysis --- p.7 / Chapter 1.3. --- Application of instrumental methods in cement analysis --- p.12 / Chapter 1.3.1. --- X - ray fluorescence spectrometry --- p.12 / Chapter 1.3.2. --- Atomic absorption spectrometry --- p.16 / Chapter 1.3.3. --- Other instrumental methods --- p.22 / Chapter 1.4. --- Treatment of data --- p.25 / Chapter 1.5. --- Dissolution techniques for AAS analysis --- p.28 / Chapter 1.5.1 --- Hydrofluoric acid decomposition --- p.28 / Chapter 1.5.2 --- Fusion --- p.30 / Chapter 1.6. --- Research objective --- p.34 / Chapter Chapter 2. --- Analysis of Cement and Raw Meal Samples --- p.35 / Chapter 2.1. --- Experimental --- p.36 / Chapter 2.1.1. --- Reagents --- p.35 / Chapter 2.1.2. --- Instrumental --- p.37 / Chapter 2.1.3. --- Procedure --- p.37 / Chapter 2.1.3.1. --- "Sample solutions for the determination of SiO2, A1203, Fe2O3, Ti02, Na20 and K20" --- p.37 / Chapter 2.1.3.2. --- Sample solutions for the determination of CaO and MgO --- p.38 / Chapter 2.1.3.3. --- "Standard solutions for the determination of SiO2, Al2O3， Fe203, TiO2, Na2O and K2O" --- p.33 / Chapter 2.1.3.4. --- Sample solutions for the determination of CaO and MgO --- p.41 / Chapter 2.1.3.5. --- X-ray briquettes --- p.42 / Chapter 2.2. --- Results and discussion --- p.43 / Chapter 2.2.1. --- The proposed fusion system --- p.43 / Chapter 2.2.2. --- Instrumental conditions --- p.47 / Chapter 2.2.3. --- Accuracy --- p.56 / Chapter 2.2.4. --- Interferences studies --- p.61 / Chapter 2.2.5. --- "Calibration graph, detection limits and precision" --- p.69 / Chapter 2.2.6 --- Real sample analysis --- p.80 / Chapter Chapter 3. --- Analysis of Siliceous Materials and Coal --- p.84 / Chapter 3.1. --- Experimental --- p.84 / Chapter 3.1.1. --- Reagents and instruments used --- p.84 / Chapter 3.1.2. --- Procedure --- p.85 / Chapter 3.1.2.1. --- "Sample solutions for the determination of SiO2, A1203, Fe2O3, Ti02, Na20 and K20" --- p.85 / Chapter 3.1.2.2. --- Sample solutions for the determination of CaO and MgO --- p.85 / Chapter 3.1.2.3. --- "Standard solutions for the determination of Si02, Al2O3, Fe2O3,TiO2, Na20 and K20 in siliceous material and coal" --- p.86 / Chapter 3.1.2.4. --- Standard solutions for the determination of CaO and MgO --- p.87 / Chapter 3.1.2.5. --- X - ray briquettes --- p.88 / Chapter 3.2. --- Results and discussion --- p.88 / Chapter 3.2.1. --- Fusion of siliceous materials --- p.88 / Chapter 3.2.2. --- Fusion of coal --- p.93 / Chapter 3.2.3. --- Accuracy and precision --- p.95 / Chapter 3.2.4. --- Real sample analysis --- p.99 / Chapter Chapter 4. --- Conclusion --- p.103 / Chapter 4.1. --- Comparison of XRF and AAS as analytical means in the cement industry --- p.103 / Chapter 4.2. --- The proposed fusion system --- p.105 / References --- p.107

Most of the hydrocarbon reservoirs in the world are carbonates, and most of these carbonate reservoirs are fractured. Fractures can form due to tectonic activity, mainly associated with fold and faults, and as a result of diagenesis. In many cases, the fractures in carbonates are cemented due to fluid flow, where these fluids precipitate cements. The presence of fractures can enhance reservoir fluid flow if the fractures were open and connected. This thesis focuses on carbonate reservoir fractures, and understanding the evolution of fluids from the cements that have precipitated within them. This thesis relates regional tectonic events to the formation of fractures, and of the environment and temperature of the fluids of precipitation in cement fractures the Early Cretaceous Thamama Group, in the United Arab Emirates (UAE). First, samples were studied from the subsurface in a highly faulted oil Field (A) located in South East Abu Dhabi. Core samples were taken from wells close to major faults in the field in both oil and water legs. Second, fractures in outcrop in Wadi Rahaba, Ras Al Khaima (RAK) in the Northern Emirates were studied where the Upper Thamama Group is exposed. The field study in the outcrop included the fracture orientation and cement types. The fractures in the outcrop were divided into two main generations, F1, (en-echelon) and F2 and they were both fully or partially cemented. The main tectonic events that affected the fracture formation in the Thamama Group are foreland autochthon in the Precambrian to Lower Cretaceous, a frontal triangle zone in Neogene and Dibba zone which consists of Hawasina units (Triassic to Cretaceous), and the Sumeini units (Lower to Middle Cretaceous). F1 is related to the NS orientation fracture system consistent to the Arabian Trend sets caused by Cenozoic compression. F2 is related to the EW orientation fracture system matching Tethyan extensional trend sets. Petrographic analysis of the subsurface thin sections revealed the presence of three main sets of fractures. Fracture Set 1 (cemented), Fracture Set 2 (open) and Fracture Set 3 (cemented, only in Lower Thamama). The fracture cement included equant and blocky calcite as well as saddle dolomite. Cathodoluminescence (CL) analysis assigned the number of cement zones in each cement type in the fractures, and revealed more cement zones in the Lower Thamama reservoirs than the Upper. The most important diagenetic events were cementation and dissolution, which took place towards the end of the paragenetic sequence. The reservoirs contained significant amounts of stylolites, dissolution seams and bitumen, which were associated with most of the dissolution events. mMg/mCa obtained from in situ elemental analysis showed variation through the calcite and dolomite cement zones in the different reservoirs of the Thamama Group. This was inferred to be due to temperature changes. The Upper Thamama Reservoirs (A, B, and C) show lower mMg/mCa (0.072-0.48) than the Lower Thamama reservoirs (F,G) (0,4-1.3), meaning that the Upper Thamama fracture calcite cements were precipitated at higher overall temperatures than the Lower Thamama reservoirs. Mn-Fe analysis allowed an understanding of the redox index through the different cement zones, in both Fracture Set 1 and Fracture Set 3. Analysis of Sr showed the absence of exotic fluids role in the diagenetic system. In-situ (SIMS) δ18OVPDB values were obtained for the calcite cementation history of the two fracture sets in the five reservoirs of the Thamama Group. The δ18OVPDB analysis indicated that Fracture Set 1 has a longer cementation history than Fracture Set 3, and has wider range of temperatures (58-128°C). A comparison of the outcrop analysis results and the subsurface reservoir was established at the end to distinguish the similarities and differences between the subsurface and outcrop in fracture types, fracture cement types and characteristics of the elemental analysis curve behaviours. The fracture cement in both subsurface and outcrop seemed to be precipitated at deep burial environment.

Thesis (Doctor of Engineering in Civil Engineering)--Cape Peninsula University of Technology, 2018. / Rheological properties of most ordinary Portland cements are dictated by the hydration reactions that their different phases experience. Cement clinker has four main phases with aluminate being the most reactive. Once in contact with water, the aluminate phase reacts rapidly and generally impedes the early hydration of other cement compounds such as calcium silicates that are responsible for the strength of cement systems. Consequently, the obtained matrix is stiff without much strength. Alternatively, calcium sulphate bearing materials are added within the clinker as set regulators of the aluminate phase hydration. For this purpose, natural gypsum is moslty gound with cement clinker as a source of sufficient sulphate, thereby keeping the cement paste plastic for a certain amount of time, allowing the hydration of silicate phases that are responsible for the early and later strength. However, the heat generated within the mill during the grinding process of clinker and gypsum causes a partial dehydration of natural gypsum into hemihydrate. The final ground cement product is thus comprised of two unexpected types of calcium sulphate bearing materials in an unpredictable proportion. Due to the difference in their solubility, the hydration of the aluminate phase can variably be altered which consequently affects the rheokinetics of the cement paste. Currently, the effect of the available amount of hemihydrate and natural gypsum in the cement sulphate phase, on both the hydration and rheology of ordinary Portland cements (OPC), are not well-understood. An ordinary Portland cement clinker was sampled during the production process of CEM I under stable kiln operations at a local cement plant. This was ground without any form of calcium sulphate bearing material and the final product was considered as relatively pure cement clinker. The degree of natural gypsum degeneration was achieved by partially replacing fractions of hemihydrate with those of natural gypsum. Firstly, the individual effect of these calcium sulphate bearing materials on the hydration kinetics was studied by varying their concentrations from 2-7% within the cement system. Secondly, the effect of their mix proportions at an optimum calcium sulphate concentration on cement paste rheokinetics was investigated. This research confirmed the findings of previous investigations relative to the effect of calcium sulphate on the hydration kinetic , giving new insight on the rheokinetics of cement paste with mix proportions of various calcium bearing materials. Results showed that the reaction rates of cement systems with hemihydrate were faster than those with natural gypsum and generally tended to decrease with the increase in their concentrations. Cements with hemihydrate experiencing shorter dormant durations than those with natural gypsum, likely due to the fact that the consumption rate of calcium sulphate was higher in cement systems with hemihydrate than those with natural gypsum. Consequently, before the exhaustion of sulphate ions, cement systems with hemihydrate had higher degrees of hydration and became almost similar thereafter. More ettringite and portlandite were formed in cement systems with hemihydrate as compared to those with natural gypsum. The amount of ettringite increased with the increase in calcium sulphate concentration up to 4% and thereafter remained constant. Conversely, the amount of portlandite decreased with the increase in calcium sulphate and also remained unchanged after 4%. The strength development of the cement microstructure depended on the concentration of hemihydrate within the suspension. The rigidification of the newly formed network was affected at higher hemihydrate fractions. Rheological parameters were more pronounced when the concentration of hemihydrate exceeded 50%. Below this hemihydrate concentration, cements had almost similar flow properties as those with only natural gypsum. Large changes in yield stress values and variation in plastic viscosity values of approximately 50% were observed. The trend of mixes dynamic yield stress were similar to their corresponding strength rate developments. This rheological behaviour was primarily attributed to the morphology change of ettringite that was triggered by the presence of a higher hemihydrate concentration. It was also noticed that physical performances of cement systems depended on their respective microstructure developments.

With my research in Concrescence planters I was able to design set of planters using specific methods that I generally use in designing. The methods that I utilized the most are the Golden Rectangle and the Fibonacci sequence as Golden Rectangle talks about the symmetry and design in nature and how I apply the same systems to my own design to make it as natural for human interaction. The research also utilized some of the same design techniques and element that then to translate from one design to another which make the design process simpler and fluid.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 119-121). Also available in electronic version.

In order to keep up with the world’s energy demands, oil and gas producing companies have taken the initiative to explore offshore reserves or drill deeper into previously existing wells. The consequence of this, however, has to deal with the high temperatures and pressures encountered at increasing depths. For an oil well to maintain its integrity and be produced effectively and economically, it is pertinent that a complete zonal isolation is achieved during well completion. This complete zonal isolation can be compromised due to factors that come into play when oil well cement experiences cyclic loading conditions which can lead to fatigue failure as a consequence of extensive degradation of the microstructure of the cement material depending on stress levels and number of cycles. There have been a lot of research and experimental investigations on the mechanism of fatigue failure of concrete structures but the fatigue behavior of oil well cement is still relatively unknown to engineers. Research in the area of oil well cement design has led to improved cement designs and cementing practices but yet many cement integrity problems persist and this further strengthens the need to understand the mechanism of cement fatigue. This research seeks to develop a better understanding of the performance of the casing cement bond under HPHT well conditions that can lead to best practices and a model to predict well life. An analytical model, which can be used to evaluate stresses in the cement sheath based on actual wellbore parameters, was developed and combined effectively with finite element models to evaluate the fatigue and static loading behavior of a well. Based on the findings of this investigation, the mechanical properties of the casing, cement and formation as well loading conditions play a very big role in the static and fatigue failure of well cement. Finally, recommendations for future work on this subject were also presented in order to understand all tenets of cement fatigue and to develop governing equations.