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Alkali silica reaction (ASR), a reaction which occurs between reactive siliceous mineral components in the aggregate and the alkaline pore solution in concrete, is responsible for substantial damage to concrete structures in the U. S. and across the world. Lithium admixtures, including lithium nitrate (LiNO3), have been demonstrated to mitigate ASR damage, and are of particular interest for use in concrete airfield pavement construction, where ASR damage has been recently linked to the use of certain de-icing chemicals. Although the effectiveness of lithium admixtures at ASR-mitigation is well-researched, relatively less is known regarding the potential effects, including negative effects, on overall concrete behavior. The goal of this research is to better understand the influence of LiNO3 admixture on early age concrete behavior, and to determine if a maximum dosage rate for its use exists. Isothermal calorimetry, rheology and bleed water testing, time of setting, chemical shrinkage, autogenous shrinkage, free and restrained concrete shrinkage, and compressive and flexural strength were measured for pastes and concretes prepared with a range of LiNO3 dosages (i.e., 0, 50, 100, 200, and 400% of the recommended dosage). In addition, the interaction of LiNO3 with cement was evaluated by comparing results obtained with six cements of varying alkali and tricalcium aluminate (C3A) contents. Additionally, one of these cements, was examined alone and with 20% by weight Class F fly ash replacement. Results indicate that the hydration of the tricalcium silicate and tricalcium aluminate components of cement are accelerated by the use of LiNO3, and that low alkali cements (typically specified to avoid damage by ASR) may be particularly susceptible to this acceleration. However, inclusion of Class F fly ash at 20% by weight replacement of cement (also common in applications where ASR is a concern) appears to diminish these possibly negative effects of LiNO3 on early age hydration acceleration and heat generation. Dosages higher than the current standard dosage of LiNO3 may have minor effects on fresh concrete workability, causing slight decreases in Bingham yield stress, corresponding to slightly higher slump. Fresh concrete viscosity may also be affected, though more research is necessary to confirm this effect. LiNO3 had no effect on quantity of bleed water in the mixes tested. Generally, LiNO3 had no effect on initial and final setting times, although increasing dosages caused faster set times in the lowest alkali (Na2Oeq = 0.295%) cement examined. In shrinkage testing, higher LiNO3 dosages appeared to cause initial expansion in some sealed paste specimens, but in all cases the highest dosage led to greater autogenous shrinkage after 40 days. In concrete specimens, however, the restraining effect of aggregates diminished shrinkage, and no effect of the LiNO3 was apparent. In no cases, with any dosage of lithium tested, with or without fly ash replacement, did restrained shrinkage specimens show any cracking. Strength testing produced mixed results, with laboratory specimens increasing in 28-day compressive strength, but companion specimens cast in the field and tested by an outside laboratory, exhibited lower 28-day compressive strength, with increasing lithium dosages. Flexural specimens, also cast in the field and tested by an outside laboratory, appeared to show an increase in 28-day flexural strength with increasing lithium dosages. However, because of the conflicting results when comparing the various strength data, further research is necessary for conclusive evidence of LiNO3 effects on concrete strength.

The undesirable expansion of concrete because of a reaction between alkalis and certain type of reactive siliceous aggregates, known as alkali-silica reactivity (ASR), continues to be a major problem across the entire world. The renewed interest to minimize distress resulting from ASR has emphasized the need to develop predictable modeling of concrete ASR behavior under field conditions. Current test methods are either incapable or need long testing periods in which to only offer rather limited predictive estimates of ASR behavior in a narrow and impractical band of field conditions. Therefore, an attempt has been made to formulate a robust performance approach based upon basic properties of aggregate and concrete ASR materials derived from dilatometry and a kinetic-based mathematical expressions for ASR behavior. Because ASR is largely an alkali as well as a thermally activated process, the use of rate theory (an Arrhenius relationship between temperature and the alkali solution concentration) on the dilatometer time-expansion relationship, provides a fundamental aggregate ASR material property known as “activation energy.” Activation energy is an indicator of aggregate reactivity which is a function of alkalinity, particle size, crystallinity, calcium concentration, and others. The studied concrete ASR material properties represent a combined effects of mixture related properties (e.g., water-cementitious ratio, porosity, presence of supplementary cementitious materials, etc.) and maturity. Therefore, the proposed performance-based approach provides a direct accountability for a variety of factors that affect ASR, such as aggregate reactivity (activation energy), temperature, moisture, calcium concentration, solution alkalinity, and water-cementitious material ratio. Based on the experimental results, the following conclusion can be drawn concerning the performance-based approach to evaluate ASR potential of aggregate and concrete using dilatometer method; (i) the concept of activation energy can be used to represent the reactivity of aggregate subjected to ASR, (ii) the activation energy depends on the reactivity of aggregate and phenomenological alkalinity of test solution, and (iii) The proposed performance-based model provides a means to predict ASR expansion development in concrete.

The unsaturated polyester/silica hybrids have been synthesized via sol-gel process and characterized in an effort to obtain a transparent hybrid material in this study, with emphasis on the effects of silica precursors and coupling agents. Chemical properties, thermal properties, and morphology of the hybrids were investigated by Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that silica particles can be dispersed homogeneously in the UP matrix; also, physical and chemical interactions at the interface between UP and silica can be enhanced by adding coupling agents into the system. From the thermal and chemical properties measurement, the decomposition temperature of UP backbone and the heat distortion temperature (HDT) of UP/Silica hybrid were higher than pure UP. Solvent-resistance of UP/Silica hybrid was also enhanced by adding coupling agents. A model illustrating the chemical and physical interaction at the interface due to the addition of coupling agents is proposed to explain the resulted obtained.

¡@¡@The purpose of thesis is to study the responses of nanoindentation in fused silica. By experiments the mechanical properties of intrinsic fused silica were obtained. From the finite element simulation the response of material was estimated. Our main work is on simulation. This part includes the effects of different coefficient of friction, different indentation depth, tip rounding, and substrates of thin films. ¡@¡@First, the experimental load¡Vdisplacement curves were obtained through the nanoindentation sensing system. Then, a three-dimensional finite element was successfully modeled through the comparison of the load¡Vdisplacement curves of the experiment and the simulation. The yield stress and the strain-hardness trend of intrinsic fused silica were obtained. ¡@¡@For different coefficient of friction and different tip radii, no significant differences were found through the load¡Vdisplacement curves and von Mises stress distributions. For different indentation depths, varied trends were found through the load¡Vdisplacement curves and von Mises stress distributions. For substrate effect, no significant differences could be found through the normalized hardness. The intrinsic film hardness could be obtained for indentation depth less 20% of the total indentation depth.

Microphyll morphology of 16 Taiwanese species of Selagienlla was observed under light microscopy and scanning electron microscopy. Features studied include microphyll arrangement, epidermal cell morphology, stomal distribution, shape arrangement and distribution silica body on microphyll surface. Microphyll are dimorphic and 4-ranked arrangement, with ventral microphylls larger than the dorsal microphylls. The epidermal cells at dorsal side of dorsal microphylls and at ventral side of ventral microphylls are similar, which are tetragonal or oblong in shape and sinuolate or sinuate in anticlinal cell walls. The epidermis at ventral side of dorsal microphylls and dorsal side of ventral microphylls are similar, which are sub-square or rectangular in shape and straight or sinuolate in anticlinal walls. Stomata are mainly distributed on dorsal side of dorsal microphylls and ventral side of ventral microphylls. Four distribution patterns of are found on microphyll silica body, which are microphyll margin, midrib, homogeneity and nil patterns. Four types of arrangement of silica body on epidermal cells were recognized, namely single row, multi-row, mixed and globulate types. In Taiwan, the characters appeared in epidermal cell morphology and stomal distribution of microphyll are useful for species identification in Selaginella, while those of distribution at patterns and arrangement types of silica bodies on epidermal cells are valuable for the species identification under subgenus.

Thesis (M.S.)--University of Nevada, Reno, 2008. / "December 2008." Includes bibliographical references (leaves 57-59). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Dissertation (Ph.D.)--Auburn University,2006. / Abstract. Vita. Includes bibliographic references (p.138-140).

Thesis (M. Sc.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 11, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Chemicals and Materials Engineering, University of Alberta." Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 242-256).