Fly ash has been used extensively to control deleterious alkali-silica reaction in concrete. The majority of fly ashes can be used to control ASR induced expansion. Fly ashes with high CaO contents are less effective at reducing expansion and fly ashes with high alkali contents can be counter active. Class C fly ashes are less effective at reducing the pH of the pore solution because they are less pozzolanic. The pozzolanic reaction in Class F fly ashes enhances the ability for the hydration products to bind alkalis. This prevents the availability of these alkalis for ASR. This project aims to characterize fly ash in a way that best predicts how it will perform in concrete with an emphasis on ASR. Fly ashes with a variety of chemical compositions were evaluated using a range of analytical and characterization techniques. Research data from several universities were used to correlate their long term data with this project’s accelerated tests. This research aimed at evaluating the mineralogical, chemical, and physical characteristics that most affect the ability of a given fly ash to prevent ASR-induced expansion and cracking. / text

Leakage of CO₂ saturated fluid along wellbores has critical implications for the feasibility of geologic CO₂ storage. Wells, which are ubiquitous in locations ideal for CO₂ storage, develop leaks (e.g. fractures) for many reasons and at different points in their age. Small leaks pose the most significant risk to geological CO₂ sequestration because they are difficult to detect and provide a direct pathway through which fluid can escape the storage formation. This dissertation shows that due to complex coupling between reaction and flow, leaking wells will tend to self-seal via secondary precipitation of calcium carbonate in the open pathway. Residence time, fluid reactivity, and initial fracture aperture all play a key role in determining the time required to seal the leakage pathway. To test the self-sealing hypothesis, laboratory experiments were conducted to inject reactive fluids into naturally fractured cement. Restriction of the leakage pathway, i.e., the fracture, was inferred from the relationship between flow rate and pressure differential. Precipitation was observed in both constant flow rate and constant pressure differential experiments. In the former precipitation resulted in an increasing pressure differential, while precipitation caused a decrease in flow rate in the latter. Analysis by electron microprobe and x-ray diffraction, and corroborated with effluent chemical analysis, showed that the reacted channel was depleted in calcium and enriched in silicon relative to the original material. The remaining silicon rich material prevents widening of the reacted channel and development a self-enhancing (e.g. wormhole) behavior. Self-limiting behavior is caused by calcium mixing with carbonate ions in high pH slow flow regions where local residence time is large and calcium carbonate is insoluble. Secondary precipitation initially develops next to the reacted channel and then across the fracture surface and is the source of pathway restriction and the self-sealing behavior. Results from the experiments are used to develop a simple analytical model to forecast well scale leakage. Future work is needed to test a broader range of experimental conditions (e.g. brine salinity, cement formulations, cement-earth interface, effect of CO₂ saturation, pressure, and temperature), to improve our understanding of both the fundamental behavior and the leakage model. / text

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Project Completion Report OWRT Project No. A-075-ARIZ / Agreement No. 14-34-0001-7006 / Project Dates: July 1976 - June 1977 / "The work upon which this report is based was supported by funds provided by the United States Department of the Interior, Office of Water Research and Technology as authorized under the Water Resources Research Act of 1964, the State of Arizona, and the Arizona Department of Transportation and Federal Highway Administration

This thesis describes and discusses the application of System Dynamics methodology as a basis for formulating diversification strategy and control policies of the largest diversifying cement company in the 'United Kingdom. The problems of the industry such as stagnant growth, cyclic and seasonal variations in cement demand, and overcapacity are described. The formulation of a SD model of the situation which captures these problems together with its equations system are presented. The model also simulates the planning and control processes for the selection, initiation and completion of both expansion and diversification investment projects. It is argued and demonstrated that the fact that these processes consist of feedback loops should and could be utilized for understanding these processes, advancing complementary theoretical concepts, and designing and formulating more 'effective systems and decision rules. An intensive analysis of the model in SD frameworks further supports these arguments. These analyses reveal the nature of the system's dynamic properties and its likely developments, the dynamic and situational nature of diversification effectiveness, and the importance of several diversification decision factors. These analyses also show how complex the formulation of a thorough and effective diversification strategy may become together with the ways and means of dealing with these complexities.. It is concluded that the thrust of an effective diversification lies with the broadening of the conventional theoretical concepts and analysis to include the dynamic characteristics of the system. It is also concluded and shown that System Dynamics methodology can provide a strong analytical basis for achieving these ends.

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Tanzania is one of the world’s poorest countries. But it has a lot to offer and in recent years both tourists and companies have realised this. This thesis focuses on the companies and takes a closer look at the growth performance and the inflow of Foreign Direct Investments (FDI) to Tanzania. By presenting a case on the cement industry in Tanzania the thesis also provide some insight in the mechanisms of FDI on a more practical level. The findings conclude that the FDI and growth have both increased extensively since the 1990’s, but I refrain from comments on the causality of this relationship. The economic reforms that the country underwent in the 1990’s are thought to have played a key role in the development of the country. From the case presented we draw the conclusion that a FDI can affect the value chain as well as the whole country in numerous ways.

CO2 absorption behaviour of four commonly used cement based building products: cement paste, concrete block, expanded polystyrene bead (EPB) and cement-bonded cellulose fiberboard are studied. Cement products are manufactured following industry formulation and process, and carbonation curing takes place in a chamber under a pressure of 0.5 MPa, at ambient temperature, for durations of mostly 2 to 8 hours with both pure carbon dioxide gas and flue gas. The flue gas of 13.8% CO2 content is collected from a typical cement kiln without separation. Influencing factors on carbon uptake, long-term strength as well as microstructure development are studied. / It is found that the CO2 uptake ability of those cement-based products follows the same order when exposed to either pure gas or flue gas: fiberboard has the highest uptake capacity, followed by cement paste, bead board and concrete. For fiberboard, the best CO2 uptake in flue gas is 8.1%, it reaches 23.6% if pure gas used. Introduction of cellulose fiber in the fiberboard significantly increases voids volume and cement paste surface area through dispersing the paste onto fiber surface, effectively increasing carbonation reaction sites and thus CO2 uptake. / For pure gas carbonation with high reaction rate, it takes longer time for carbonated products to further develop strength from subsequent hydration, due to the high water loss during carbonation, the densified cement matrix structures and even fast decalcified cement minerals. Fast carbonation with pure gas is detrimental to cement paste in its long-term strength. For flue gas carbonation, both immediate strengths and long-term strength of the products are comparable with those by pure gas carbonation, although with less CO 2 uptake ability. / Five CO2 uptake determination methods are evaluated. Weight gain method is suitable for both pure gas and flue gas carbonation systems. Mass curve method is more suited for pure gas carbonation. For flue gas carbonation, CO2 concentration method agreed well with the weight gain method. Pressure drop method is relatively less accurate because of water vapor generation during carbonation.

Solidification/Stabilization (S/S) is a low cost remedial technology that is being used with success to remediate sites that contain higher molecular weight organic compounds, leading to a need to research the interaction of organic contaminants with cement-based S/S materials. The objective of this study was to examine the sorption levels of naphthalene to cement-based S/S materials. Batch testing was performed with S/S materials containing different amounts of organic carbon to investigate the sorption of naphthalene. It was found that sorption values varied, but appear to be dependent on the organic carbon present. Dynamic leach test (ANS16.1 methodology) and SPLP analysis results are presented for intact cement-based S/S materials. Contaminant migration modeling was performed to use the information obtained in the study to compare the sorption capacity of cement-based S/S systems. It was shown that cement-based S/S remediation systems can provide long-term protection against naphthalene contaminant migration.