Yes / Bond between substrate and overlay concretes is a key factor for the success of the repair method and significantly influences the structural performance of the repaired element. This study investigated the effect of fly ash and the surface preparation method on the bond strength of repaired concrete after exposure to high temperatures, that has not been comprehensively studied in the literature. For this purpose, overlay concretes containing 0, 5, 10, 15, and 20% fly ash as a replacement by weight of cement were cast on the original concrete surface prepared by four methods namely, as-cast, wire brushed, grooved and grooved-wire brushed. The bond strength of the interface between concrete substrate and overlay concrete was evaluated after exposure to 23, 200, 400, and 600oC temperatures for 1 hour. The results showed that partial replacement of cement by fly ash in the overlay concrete increased the bond strength of repaired concrete by up to 71%, depending on the amount of fly ash used, surface preparation method, and the temperature to which the sample was exposed. The maximum increase of bond strength was recorded for concrete containing 20% fly ash when the wire brushed preparation method was adopted at temperature of 200oC. However, surface preparation was the most influential parameter, achieving a bond strength gradual increase in order from as-cast, wire brushed, grooved to grooved-wire brushed methods. The results also showed that for most of the samples having similar surface preparation and the same percentage of fly ash, bond strength decreased with the increase of exposure to temperature; for example, for overlay concretes without fly ash, in as-cast and wire brushed surface preparation methods at temperatures of 400 and 600 oC, the bond strength has reached zero. On the other hand, for grooved and grooved-wire brushed surface preparation methods, the bond strength reduction was about 63%, when temperature increased from 23 to 600oC. / The full-text of this article will be released for public view at the end of the publisher embargo, 12 month from first publication.

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Yes / Increasing infrastructure growth has forced the construction industry to look for wasteful, cheap, and suitable materials for construction. An investigation into the geotechnical utilization of fly ash was carried out in the present study. Practical applications normally involve the use of large quantities of fly ash, so proper mixing of the fly ash with other materials may not be significantly achieved. Therefore, the present paper investigates the behaviour of a fly ash–bentonite layered system with different ratios. The physical properties and chemical composition of fly ash and bentonite were determined. SEM and energy dispersive X-ray experiments were also used to investigate the morphology and phase compositions of fly ash and bentonite. A series of consolidated undrained (CU) triaxial tests on fly ash–bentonite were carried out to investigate shear strength characteristics. Fly ash (F) and bentonite (B) were used in the following ratios: 1:1 (50% F:50% B), 2:1 (67% F:33% B), 3:1 (75% F:25% B), and 4:1 (80% F:20% B), with different numbers of interfaces (N), i.e., 1, 2, and 3 for each ratio. The deviator stress and cohesion value were found to increase with the number of interfaces for each ratio. The angle of shear resistance changed marginally with the increase in the fly ash–bentonite ratios and varying interfaces.

<p>Validerat; 20111223 (anonymous)</p>

Results are reported from a series of experiments simulating the combustion and expansion processes of a heavy-duty combustion turbine engine burning a heavy residual fuel oil. The tests were carried out in a turbine simulator device, consisting of a combustion chamber and a turbine first-stage nozzle cascade sector. Both film, air-cooled and closed-circuit, water-cooled nozzle sectors were tested. These sectors were four-vane, three-throat sections with throat cross-sectional areas of approximately 50 (10⁻⁴) m². The test fuel was simulated by adding the appropriate contaminants to no. 2 fuel oil. A series of seven full-length tests were performed, ranging in length from 22.5 to 88.2 hours. Four of the tests involved the watercooled nozzle sector and the remaining three used the air-cooled nozzle. The principle objectives of the tests were to assess the rate at which ash accumulates in the turbine nozzle and the relative difficulty in removing these deposits. The variable used to evaluate the extent of the ash deposit on the nozzle was the effective throat area, determined using the calculated gas flow rates, turbine nozzle inlet temperature, and the measured combustion chamber pressure. The parameters varied in the test program, other than the nozzle sectors, were the gas temperature and the gas pressure. The gas pressure variations served to vary the gas path surface temperatures at constant gas temperature. The test conditions were nominal turbine firing (nozzle exit) temperatures of 1283 and 1394 K and combustor pressures of 3 and 6 atmospheres. A 2-to-l pressure ratio was maintained across the nozzle to insure sonic conditions at the throat sections. With the exception of one test, the data show that the deposit rates in the water-cooled turbine nozzle were lower than in the air-cooled nozzle. The effect of increasing the gas temperature was to dramatically increase the ash deposition rates. Decreased gas pressures (and hence surface temperatures) resulted in reduced deposition rates. Ash cleanability was enhanced by water-cooling. Heat transfer data were analyzed from the water-cooled tests and gave significant insight into the ash deposit formation and removal phenomena. One of the more significant conclusions drawn from these data was that the major portion of the effective area decrease observed in a turbine nozzle because of ash deposits is due to the pressure face deposits. A computer simulation of a combustion turbine engine was developed to aid in the evaluation of the turbine simulator test data. Results from field tests of full-sized production engines burning residual oil were used in the simulation to determine the relationship between the extent of ash deposition (throat area reduction) and turbine efficiency. This result was then combined with data from the turbine simulator tests to produce a real-time computer simulation of full-sized combustion turbine engines having air- and water-cooled first-stage turbine nozzles. It was found that water-cooling of the turbine nozzle would result in an increase in engine availability of 27 per cent when operating on heavy residual fuel oil. / Ph. D.

no abstract provided by author / M.S.

In recent years there has been considerable development along the lines or using coal powdered to a fineness resembling talcum powder for the production of power in practically all the new and larger power plants. This pulverized coal burns similarly to gas when blown into the combustion chamber. Because or the fineness of the individual particles of coal, a very fine ash termed "fly ash" is formed when combustion occurs, a large portion of which is carried on up and out the smoke stack. The "fly ash," if allowed to go up the stack and out over the surrounding territory, becomes a health hazard as well as a nuisance to the cleanliness of the community. The average fly ash is about fifty per cent silica (SiO₂) which should classify it as a silicosis hazard. To avoid this nuisance and hazard, the fly ash may be collected in one of several ways, the most important being by electrostatic precipitation, wet scrubbing, and with cyclone separators. It must then either be used or disposed of. Several attempts have been made to use fly ash for some useful purpose, but it is not adaptable for filling in, for road construction, or for similar uses made of clinker ash. In this investigation, an attempt has been made to determine the optimum conditions of both the process and composition which should be used in the manufacture or a building material from fly ash, and special reference will be made to the ash of the Virginia Polytechnic Institute Power Plant, Blacksburg, Virginia. / M.S.

Traditionally, coal combustion residuals (CCRs) were disposed of with little engineering consideration. Initially, common practice was to use a wet-scrubbing system to cut down on emissions of fly ash from the combustion facilities, where the ash materials were sluiced to the disposal facility and allowed to sediment out, forming deep deposits of meta-stable ash. As the life of the disposal facility progressed, new phases of the impoundment were constructed, often using the upstream method. One such facility experienced a massive slope stability failure on December 22, 2008 in Kingston, Tennessee, releasing millions of cubic yards of impounded ash material into the Watts Bar reservoir and damaging surrounding property. This failure led to the call for new federal regulations on CCR disposal areas and led coal burning facilities to seek out geotechnical consultants to review and help in the future design of their disposal facilities. CCRs are not a natural soil, nor a material that many geotechnical engineers deal with on a regular basis, so this thesis focuses on compiling engineering characteristics of CCRs determined by different researchers, while also reviewing current engineering practice when dealing with CCR disposal facilities. Since the majority of coal-burning facilities used the sluicing method to dispose of CCRs at one point, many times it is desirable to construct new "dry-disposal" phases above the retired ash impoundments; since in-situ sampling of CCRs is difficult and likely produces highly disturbed samples, a sample reconstitution technique is also presented for use in triaxial testing of surface impounded CCRs. / Master of Science

Yes / Fly ash is a toxic industrial waste, mainly consisting of silica and alumina particles, that has been found discharged into the environment. It is proposed that alginate, a naturally occurring biopolymer, can bind to these minerals and thus play a role in water purification. The binding forces involved in this process consist of weak interactions, such as van der Waals forces and electrostatic interactions. Although the attachment of alginate to mineral surfaces is mainly governed by its carboxylate groups, hydroxyl moieties could play a role in the interaction between the polymer and minerals. This work aims to use the SiO2 and Al2O3 particles as models for fly ash and to show the use of alginate biopolymers (fluorescently labelled with an aminonaphthaline sulfonate fluorophore (AmNS)) to coagulate them. The addition of simple electrolytes like NaCl and CaCl2 encourages the coiling of the polymer chain at high pH values which has an effect on its capability to bind to the inorganic particles. A combination of fluorescence and ICP-MS demonstrated that alginate has a considerable adsorption affinity for Al2O3, whereas it attracts SiO2 weakly. The adsorption process is pH dependent: strong adsorption was observed at low pH values. The dependence of adsorption on the mineral (Al2O3 and SiO2) concentration was also examined under different pH conditions: the adsorption amount was observed to increase by increasing the solid concentration. Adsorption isotherms obtained at low and high mineral concentrations were found to be Henry in type.