No / It is known that lime was added to historic Roman cement render mortars. The focus of this work is the influence of the combination of NHL5 and CL90 with Roman cement in mortars for restoration; however, the results indicate a wider potential for render applications in general. It is shown that simply adding lime to Roman cement does not retard its hydration and yields mortars where the binding action of the cement is compromised by the mixing process. If the cement is retarded by means of a pre-hydration process, hybrid mortars can be produced with improved workability and workable life as well as permitting the fine control of strength and moisture transport.

Master of Science

The effects of electron beam radiation on the rheological behavior of a polystyrene/poly(vinyl methyl ether) blend as a function of absorbed dose, composition, and temperature, were investigated. The purpose of this research has been to modify the viscosity of polystyrene by studying the influences of the addition of a small amount of poly(vinyl methyl ether), combined with the exposure of the blends to low radiation doses. It is shown that the crosslinking behavior, in terms of the changes in the viscosity, is more pronounced and significant for the highest PVME content system composed of 10 wt % PVME. The other blends under consideration in this study do not display significant modifications in their rheological response after irradiation. The effects of radiation and composition on the temperature dependence of the viscosity is illustrated using the Arrhenius Law. The results obtained, in terms of flow activation energy, Ea, show that no real changes occurred due to radiation. On the other hand, it is found that the flow activation energy is strongly dependent on the blend composition. The phase separation temperature as a function of radiation dose and composition is also examined. It is shown that the most noticeable change occurs at a radiation dose of 10 Mrads, the phase separation temperature increasing also as PVME content increases in the blend composition. / Master of Science

Results indicate that the durability of the concrete mixes using poor aggregates can be improved to a considerable extent by moist-curing. / Master of Science

The flue curing process for tobacco is practiced today in nearly the same manner as when tobacco first became of commercial importance, with no definite procedure being followed. A scientific study has proved that the curing process is accurately defined within narrow limits, and that control rather than art may be more definitely relied upon. Tobacco curing differs from a true drying process in that both physical and chemical changes are involved. Since it is impractical to evaluate the chemical changes because of their complexity, the physical changes were investigated, for they govern both the chemical and physical changes which take place. Drying rate curves for each period of the curing process were obtained over a wide range of constant conditions of temperature, relative humidity, and air velocity. Correlation of these curing curves indicate the narrow limits of the conditions required for satisfactory curing, and the critical points beyond which resulted in poorly cured tobacco. From the results obtained, air conditioning improves the process by (1) reducing the time approximately one-half, thus doubling the capacity of the barns; (2) the production of uniform quality tobacco completely eliminating loss from improper curing; and (3) large reductions in labor and fuel requirements. / Master of Science

The purpose of this work was to study the heating and curing rate of polymers with continuous and pulsed microwave radiation and compare with conventional thermal energy. The heating rate of poly(ethylene glycol) and poly(propylene glycol) has been studied as a function of molecular weight with pulsed as well as continuous microwave radiation, at constant average power. The curing rate of poly(amic acids) have also been studied with thermal energy, continuous and pulsed microwave radiation to better understand the interaction between pulsing the microwave and the polymeric material. Results from the heating rate studies indicate that the enhancement in heating rate with pulsed microwave radiation depends on the low frequency absorption spectrum (i.e., less than 10,000 Hz) of the polymer. The heating rate of poly(propylene glycol), which has a low frequency absorption, was enhanced by pulsing the microwave energy whereas the heating rate of poly(ethylene glycol), which does not have a low frequency absorption, remained the same when compared to continuous wave. Also results from the curing rate studies with poly(amic acids) indicate that the enhancement in curing rate observed in samples cured by microwave radiation as opposed to those thermally cured may be partially due to microwave power distribution in the cavity. This has been tested by agitating the sample to reduce any temperature gradient arising from the power distribution in the cavity. According to the experimental results, as the agitation rate was increased, the rate of imidization of poly(amic acids) with microwave radiation approached the rate of thermal imidization, at constant temperature. However, more research is required to clarify this complex phenomenon. / Master of Science

The problem considered in this study arose from the need for an emperlcal analysis of the sale value of land to determine if the increased price benefits of the governmental flue-cured tobacco program have been absorbed by higher land rents. If acreage allotments giving the right to produce tobacco under the program are capitalized into farmland values to an appreciable extent, the program objective of increasing farm incomes would be partially defeated through higher rents. The objective of this study was to determine the extent to which allotments have been capitalized into land values. Data on sale value of farms and factors expected to influence the farm sale value were secured from primary public record sources for the four-year period from 1954 to 1957 in two distinctly different flue-cured tobacco regions--Pittsylvania County, Virginia, and Wilson, Greene, and Pitt Counties, North Carolina. These data were analyzed by a multiple regression statistical technique designed to measure the value of an acre of tobacco allotment es a right to produce. The statistical coefficients indicated that an acre of tobacco allotment increased in value from $962 in 1954 to $1,673 in 1957 for Pittsylvania County and from $1,830 to $3,308 for Wilson, Greene, and Pitt Counties. The size of the values for an acre of tobacco allotment as well as the increase in values over the four-year period during which allotments were reduced under the program by 33 percent indicate that an appreciable proportion of the price·rais1ng benefits of the program have been capitalized into land values. / Master of Science

Two flue-cured tobacco varieties (Nicotiana tabacum L.) and eight harvesting and curing methods were simultaneously evaluated. Harvesting variables involved the removal of different leaf numbers on different schedules. Curing methods included single or separate barn conventional curing and a bulk curing method. Certain agronomic, physical, and chemical factors were measured. The modified harvesting methods in which the leaves were removed in less than the conventional number of harvests caused a reduction in yield and value, but not in price. Bulk curing also resulted in lower yield and value per acre as well as dollars per hundredweight than conventionally cured leaves, but there were no differences associated with curing leaves from different stalk positions in separate barns. When considering stalk positions, modification of the harvesting methods from the normal method caused a reduction in yield and an increase in filling value for the lower leaves from each harvest section. Bulk curing caused an increase in filling value in comparison to conventionally cured leaves. Leaves from the modified harvest treatments were higher in amino nitrogen and lower in nicotine concentration than normally harvested tobacco. Leaf extracts were less acidic for leaves which were harvested in one day than for normally harvested leaves. With increases in stalk position, the nitrogenous factors and water soluble acids increased, while the pH value decreased. Reducing sugars were highest for midstalk tobacco and decreased in leaves from the extremities. Plants that were harvested three times were not greatly altered in agronomic, physical, or chemical factors from those harvested conventionally, but the bulk curing of the leaves (as operated in 1970) did alter these factors. / Master of Science

Fresh hams were skinned, boned, and fat removed to tolerance. Three curing mixtures were applied at the rate of 5% of the boneless weight. The curing mixtures consisted of (1) .1% sodium nitrite, 14.2% white sugar, and 85. 7% salt, (2) .2% sodium nitrite, 14.2% white sugar and 85.6% salt, (3) 10% v/v nitric oxide gas in nitrogen, 14.2% white sugar and 85.8% salt. The entire amount of the curing mixture was applied immediately prior to the tumbling treatment. Hams were tumbled for 180 minutes (3 hours) continuously at 22 R.P.M. at 2l.1°C. The hams were held 12 hours at 4.4°C for salt equalization, smoked for four hours and cooked to an internal temperature of 71.1°C for 15 minutes and then aged for 14 days at 60% humidity and 15.5 to 21.1°C. Organoleptic evaluations were made, and slices were analyzed for salt, moisture, and residual nitrite. Panel scores were similar for all treatments, all were acceptable except for control which could not be evaluated. Percent salt and moisture were similar for the three treatments but the control (non-tumbled) had the lowest percent salt. Variations occurred in nitrite levels, the lowest level detected was in the control (non-tumbled) hams and the highest level detected was in the hams treated with the nitric oxide. Residual nitrite levels for the hams treated with 0.1% sodium nitrite and 0.2% sodium nitrite showed no statistical differences. / Master of Science

Based on the results of this investigation certain conclusions were arrived at relative to Portland cement concrete using Dolomitic limestone sand as the fine aggregate. The most important of these are as follows: 1. Fresh concrete continues to gain strength while in the frozen state. 2. Freezing and then thawing of fresh concrete does not have an appreciable effect on the twenty-eight day ultimate strength, and the concrete, if given time to recover, will compare favorably with concrete cured under normal conditions. 3. Freezing of concrete immediately after pouring has a greater effect on the twenty-eight day ultimate strength of the concrete than has freezing for the same period at a more advanced age within the twenty-eight days. 4. Concrete cured at 65°C. tends to increase its twenty-eight day ultimate strength, providing the water lost through evaporation is replaced. 5. High early strength concrete can be obtained by curing ordinary Portland cement concrete at high temperatures. Based on the results of compression tests performed in this investigation, Dolomitic limestone sand has been found to be satisfactory as the fine aggregate for Portland cement concrete; verifying what Messrs. Broyles and Brown had said in 1936 and 1937 respectively. What has been done in the way of concrete research at Virginia Polytechnic Institute is satisfactory for relatively new concrete using Dolomitic limestone sand as the fine aggregate; but it is wondered how this concrete will stand up over a long period of time. Professor Hartman and Dr. Holden have inaugurated some long time studies at the Institution, but there is still much room for further investigation. Dolomitic limestone rock has proven itself worthy when used as the coarse aggregate for Portland cement concrete. It is up to time and future research to prove the worth of its sand used as the fine aggregate. / Master of Science