Alkali silica reaction (ASR) is detrimental to concrete. It is a time-dependent phenomenon, which can lead to strength loss, cracking, volume expansion, and premature failure of concrete structures. In essence, it is a particular chemical reaction involving alkali hydroxides and reactive form of silica present within the concrete mix. Geopolymer is a type of alkaline activated binder synthesized through polycondensation reaction of geopolymeric precursor and alkali polysilicates. In this thesis, three types of reactive aggregates with different chemical compositions were used. Systematic laboratory experiments and microstructural analysis were carried out for the geopolymer concrete and the OPC concrete made with the same aggregates. The result suggests that the extent of ASR reaction due to the presence of three reactive aggregates in geopolymer concrete is substantially lower than that in OPC based concrete, which is explained by the pore solution change and verified through their microstructural variations and FTIR images.

This is a diverse collection of narrative nonfiction, which includes personal essays, reportage, nature writing, and short columns. Its major themes include boxing and fly-fishing. Many of the pieces are set in and around the state of Oregon.

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A preliminary experiment was conducted during the horn fly season at Blacksburg, Virginia from May through September, 1959, to determine the relationship of weather conditions to horn fly populations on 3 breeds of dairy heifers. Daily records of the fly populations on 10 animals selected at random from a mixed herd of Holstein, Guernsey, and Jersey yearling heifers were made. In addition, the daily minimum and maximum macrotemperatures and relative humidities, the approximate wind direction, and the amount of sunlight or cloud coverage were recorded. Usually there was a significant difference between the number of horn flies on Holstein and that on Guernsey and Jersey heifers. Horn flies generally preferred the dark colored areas of bicolored cattle during the hours of daylight, and they preferred the black of the Holstein rather than the tan of the Guernsey. When the macrotemperature was above 85°F, many of the flies were found on the white skin of the belly and udder area of a heifer. During inclement weather the flies were observed on both the white and dark colored areas of all the heifers. Macrotemperature and relative humidity influenced the horn fly populations within the biocenose. Light rain and winds of less than 20 miles per hour were found to have a negligible effect on the number of flies in the populations; however, significant population decreases were attributed to heavy rain, wind in excess of 20 miles per hour. Often, when the macrotemperature was below 55°F, light rain or wind of low velocity influenced movement of the flies to more sheltered areas on the host. The apparently preferred macroclimate for horn flies was: temperature of 73 to 80°F; relative macrohumidity of 65 to 90%; scattered light showers; and no wind. During the horn fly season of 1960, a second experiment was conducted to correlate the effect of the macro-environment on the micro-environment within the ½ inch mantle of the animal, and also to correlate the locations of horn flies within this mantle with various factors of the micro-environment. (Daily macro-environmental data, including air temperature, relative humidity, wind direction and velocity, amount of cloud coverage, and precipitation, were recorded as in the preliminary experiment of 1959.) Methods for measuring the micro-environment were devised, and the data obtained were analysed statistically and interpreted. Accordingly, the effects on horn fly populations of dark skin color, low temperature, and low humidity were highly significant at the 1% level; the effects on horn fly populations of high humidity and precipitation were significant at the 5% level; and the effect of high temperature on horn flies was not significant at the 5% level. According to the results of the second experiment, the horn flies apparently sought certain micro-environmental conditions which were most commonly observed on Holstein heifers. Within the mantle of micro-environment, horn flies appeared to prefer an air temperature of about 85°F, a skin temperature of about 97°F, and a relative humidity of about 65%. When such conditions were not available to the horn flies on the sides and backs of Holstein heifers, the flies usually found near optimum conditions along the belly midline for each of the 3 breeds of heifers. / Ph. D.

Larval mortality of the face fly, Musca autumnalis De Geer, due to the biotic environment in Virginia was determined to be approximately 62.7% during the sumer of 1967 in preliminary studies. This was based on the difference in numbers of pupae resulting from an insect~accessible tray and an insect~proof tray, Each was filled with bovine manure and both contained approximately equal numbers of eggs or new first—instar larvae when placed in the field, Pupae of the major species of coprophagous Diptera resulting from pasture droppings of bovine feces were collected in sandboxes and furnels from three areas of Montgomery County, Virginie during 1967. The pupae were separated according to species, incubated, and examined afterwards to determine the fate of each pupas, Special emphasis was placed on the parasites involved and the portion of total porasitization contributed by each species, Primary interest was in biological reculation of face fly populations, Other flies were studied for comparison and to determine natural reservoirs of parasites, Comparisons of data from sandboxes with those from funnels showed a higher over-all rate of parasitism in the sandboxes than in the funnels. Other techniques for attempting to obtain new parasites of the face fly were also employed, Adult face flies were examined for nematodes, Heterotylenchus autumnalis Nickle. Approximately 16% of the natural population were infested during 1966-7. Available data for mortality during different life stages were combined into a preliminary life table for the face fly. Muscidifurax raptor Girault and Sanders, a pteromalid parasite, was recovered in low numbers from face fly pupae during 1966 field studies, It has been successfully propagated in the laboratory on face fly pupae by mechanically cracking the fly puparia to aid emergence of the parasites, Parasitism is normally accomplished by penetration of the ovipositor throush the posterior spiracles of the host, The ovipositor of one female was observed to penetrate the anterior spiracle of a face fly pupa. Muscidifurax ravtor is not limited to the spiracles for penetration of house fly pupae. Muscidifurex raptor was found on several hosts in nature. Eucoila sp., Xyalophora quinouelineata (Say), Aleochora tristis Gravenhorst, and A. bimaculata Gravenhorst, which are parasites of coprophagous Diptera, were hyperparasitized by M. raptor. Studies on the biology and behavlor of M. raptor were conducted in the laboratoiy, Its effectiveness in parisitizing different hosts was compared on house fly and face Fly pupae. / Ph. D.

An economical process for the elimination of nutrients to receiving waters.is a major problem now facing modern wastewater treatment. The purpose of this investigation was to determine the feasibility of soluble phosphate removal in a flyash contact system. The investigation consisted of experiments involving batch adsorption studies and continuous flow studies. Removal kinetics and relationships between contact time, “t” , and flyash concentration, “D_f”, were evaluated using batch adsorption techniques. Of the two flyash samples tested the high alumina content flyash exhibited the best rate of phosphate removal. The high alumina content flyash yielded an average removal capacity of 2.47 x l0⁻⁴ grams of phosphorus per gram of flyash, whereas the low alumina content flyash yielded an average capacity of only 1.61 x 10⁻⁴ grams of phosphorus per gram of flyash. Continuous flow operations were conducted using both types of flyash so as to observe the removal in an actual process situation. The phosphate removal was concluded to be both physical and chemical in nature, with two removal mechanisms predominating. The primary physical mechanism involved the phosphate adsorption on the alumina surface found in the flyash. The chemical removal mechanism was postulated to be the precipitation of phosphate as Mg₃(PO₄)₂ and Ca₃(PO₄)₂ at pH levels above 8.0. / Master of Science

A laboratory study on the face fly reported herein was conducted at Blacksburg, Virginia, from July through September, 1962, to ascertain the biology of each stage of the life cycle, and to determine the relationship of certain environmental factors on the fly activity under laboratory conditions. Morphological descriptions of each life stage were made in order to distinguish this insect from other related muscoid flies. Temperature and humidity were found to be two essential environmental factors which influenced the development and activities of the face fly. Rate of development in each stage under different ranges of temperature was emphasized. Similarly, observations were also made to determine the characteristic behavior of both larvae and adults in response to these environmental factors. Little has been published on food habits of this insect; thus, emphasis was laid on a study of the effect of diet on sexual development and reproduction. Results obtained have shown that sugar and milk appeared to be two vital nutrients for the adult fly, and that bovine blood could increase sexual maturation and egg production. Considerable attention was also given to the relationship between illumination and sexual development and reproduction. It was found that increased illumination resulted in acceleration of sexual maturation and increased egg production. / Master of Science

Call number: LD2668 .T4 1985 E46 / Master of Science