Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Mar. 3, 2010). Bibliography: leaves 87-91.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 120-125). Also available in electronic version. Access restricted to campus users.

The deterioration of today's infrastructure particularly roadways and bridge decks has continued to increase over the years due to the larger axle loads, higher traffic volumes of densely populated cities. These highly congested areas have required the need to repair and rehabilitate the affected pavements in a timely manner with minimal traffic interruptions. Different rapid hardening binders were tested in this project to evaluate and characterize their performance when subjected to concrete distresses such as alkali-silica reaction, delayed ettringite formation, corrosion, freezing and thawing, salt scaling, sulfate attack, material incompatibility and volume changes. Among the cements tested were calcium aluminate cement, calcium sulfoaluminate cement, accelerated portland cement, alkali-activated fly ash, and three other proprietary blends available to the public. This thesis will summarize the preliminary findings of a comprehensive laboratory study focusing on rapid repair materials -- the final results of this study will be included in future publication (theses and final project report). / text

Foamed cement is widely used in the oil and gas industry to provide zonal isolation. Foamed cement provides various advantages vs. pure cement. The primary purpose of foamed cement is to reduce the density of the cement mixture. Consequently, foamed cement can be used in weak formations were reduced exerted hydrostatic pressure is needed to prevent/control cement circulation loss into the formation. However, Due to gas compressibility, foamed cement’s gas injection rate has to be constantly adjusted in order to create a constant density slurry through the height of the cement column. Furthermore, foamed cement’s properties include higher ductility, constant pressure exertion to the formation during cement transition time (gelling) and lower thermal conductivity. The ability of solid silica nanoparticles to generate stable gas/water foams was researched for foamed cement applications. Solid nanoparticles have been shown to permanently stabilize foams by assembling into layers at the gas/water interface. A potential decrease in compressibility of the gas phase by the presence of these armoring bubble layers was investigated. Enhancement of cement’s splitting tensile strength and compressive strength by silica nanoparticles was also investigated. The addition of uncoated silica nanoparticles at various concentrations did not appear to enhance neither cement’s splitting tensile or compressive strength. In most tests with varying silica nanoparticles concentrations, the samples with nanoparticles exhibited a slightly reduced splitting tensile and compressive strength. The exception being the compressive strength of the samples mixed with the highest nanoparticle concentration tested. However, the strength improvement was small vs. its pure cement counterpart. An apparatus to test the compressibility of nanoparticle stabilized foams was built for this research. The functionality of the apparatus was validated using various test fluids. The validation process allowed for the establishment of a compressibility benchmark to compare the compressibility of nanoparticle stabilized foams. A vital conclusion of this process was that generating the particle stabilized foams under pressure would allow for greater discernment between the existence of the armored bubble effect and gas dissolution into the water phase. A type of nanoparticle was identified as having the capacity to generate long term stable foams without the need of surfactant. Partially hydrophobic surface treated silica nanoparticles were utilized to generate gas/water foams under pressure and subsequently their compressibility was measured. The compressibility of these foams did not appear to show the armored bubble effect behaving as an equivalent ideal gas + water mixture. An additional surfactant and particle stabilized foam recipe was tested and displayed the same results. It was concluded that either the particle layers were not fully forming in the foam or in the case they were forming; either foam geometry was not conductive to the distribution of forces or they likely had limited rigidity and buckled when compressed. If the latter was true, the apparatus was not sensible enough to measure the limited rigidity. / text

This research project concentrated on determining whether or not a correlation existed between laboratory aggregate tests and observed aggregate field performance. For this purpose, aggregate samples were collected from the majority of the U.S. states as well as several Canadian provinces and subjected to a variety of strength, soundness, and intrinsic particle property tests. Additionally, performance data on the aggregates was obtained by contacting multiple DOT's where aggregates were in use in several categories - hot-mix asphalt, portland cement concrete, base course, and open-graded friction course. Numerical and qualitative analyses were performed to evaluate the success of separating good performers from fair and poor performers using the micro-Deval test alone as well as the micro-Deval test combined with another test. Furthermore, attempts were made to determine if a correlation exists between any two tests.

No description available.

The work describes various physical and chemical treatments to eliminate the deleterious effects of impurities in phosphogypsum on the delayed setting time and impaired strength development behaviour of cement to which it was added as a set regulator. The physical treatments included washing, milling, and ultrasonic treatment of the material, while the chemical treatments dealt with acidic and basic additions to the phosphogypsum during the washing stage. It was found that chemical treatment with a milk of lime solution, which is often recommended in literature, was ineffective in reducing set retardation. Treatment with ammonium hydroxide or sulphuric acid was more effective in this regard. Intergrinding phosphogypsum with slaked lime improved its effectiveness in reducing set retardation, but the use of unslaked lime was less effective and also resulted in marked reductions in compressive strengths. A combined treatment of wet milling phosphogypsum with a lime slurry in a ball mall was derived from these experiments and is recommended for full-scale plant applications.

Superplasticisers are used to improve the flow properties of fresh cement and offer undoubted benefits to the construction sector. There is concern in the nuclear industry, however, that organic additives may increase the solubility of radionuclides when in contact with cementitious grouts or backfill. The research presented in this thesis describes the effect of a commercial polycarboxylated poly ether comb type superplasticiser on the behaviour of U (VI), Th (IV), Eu (III) and Ni (II) in blended cements. Both Blast Furnace Slag (BFS) and Pulverised Fly Ash (PFA) blends with Ordinary Portland Cement (OPC) were investigated. Solubility experiments approached from oversaturation were conducted in a range of high pH aqueous solutions that are representative of the respective cement pore waters. Results show that the as received superplasticiser is responsible for an increase in solubility of all the metals investigated, however, the extent of solubility enhancement is dependent on the metal investigated and the nature of the high pH solution. U (VI) and Eu (III) display solubility enhancement over several orders of magnitude while Ni (II) and Th (IV) solubility is enhanced to a lesser extent. Batch experiments of Ni (II) and Eu (III) uptake onto BFS:OPC and PFA:OPC cement were investigated from two view points i. By regarding the superplasticiser as a ligand where batch experiments of metal uptake on crushed cement are carried out with increasing concentrations of free superplasticiser in solution. ii. By investigating metal uptake in cements prepared with superplasticiser already present. Results of the batch experiments show that the presence of free superplasticiser in solution reduces uptake of Ni (II) and Eu (III) by both BFS:OPC and PFA:OPC. Further, metal bound in the presence of free superplasticiser is readily remobilised on exposure to fresh cement solution. Conversely, metal uptake is quantitative and irreversible when exposed to crushed cement prepared with superplasticiser in the original mix. Leaching of U (VI), Th (IV) and Ni (II) from hardened cement with and without the addition of superplasticiser was investigated by the preparation of monolithic BFS:OPC and PFA:OPC cement samples. BFS:OPC samples prepared with superplasticiser suffered from bleed and a significant proportion of the original metal inventory was found in the BFS:OPC bleed water after 48 hours, varying from 19% in the case of nickel to 32% for uranium. Autoradiography of the monoliths showed accumulation of uranium and thorium in the region adjacent to, and in contact with, the bleed water. Therefore, the bulk of the metal inventory had not been incorporated into the cement. The stability of the superplasticiser under conditions likely to be present in a Geological Disposal Facility (GDF) was investigated by exposing the superplasticiser to chemical, thermal and radiolytic attack. Several analytical techniques were assessed for their ability to characterise the products of these experiments. Whereas Infra-Red (IR) spectrometry provided comparative information regarding the functionality of the superplasticiser before and after exposure, Gel Permeation Chromatography with Refractive Index Detection (GPC-RID) was found to be the best technique available to observe changes to the superplasticiser. Under chemical (alkali) attack by exposure to 0.1 mol dm-3 NaOH and 95% saturated Ca(OH)2 , the superplasticiser samples were found to decrease in molecular weight, a result consistent with alkaline hydrolysis of the polymer chains. Little change to the superplasticiser were observed on heating to 80ºC, however, on exposure to gamma radiation (60Co), further polymerisation and cross-linking of the polymer chains was initiated, with a significant increase of the polymer s molecular weight. Solubility experiments on U (VI), Th (IV), Eu (III) and Ni (II) were repeated to investigate the effect of irradiated superplasticiser. As with the as received material, the results show that the presence of irradiated superplasticiser causes an increase in solubility of all the metals investigated. In this case however, Th (IV) and U (VI) display a much greater enhancement in solubility, whereas Eu (III) and Ni (II) show solubility enhancement similar to that observed in the non-irradiated samples. The results presented in this thesis give a representation of the behaviour of metals in the presence of polycarboxylated poly ether comb superplasticiser and highlight the importance of considering the consequences of the use of cement additives in the concept of the GDF. The metals studied encompass a range of oxidation states from Ni (II), through Eu (III) and Th (IV) to U (VI). The behaviour of these metals here is of potentially great significance as it may indicate similar behaviour by other actinide species, most notably the behaviour and apparent mobility of Th (IV) may suggest analogous behaviour of tetravalent Pu (IV) and Np (IV).

No description available.