Thesis (M.S. - Renewable Natural Resources)--University of Arizona, 1984. / Includes bibliographical references (leaf 69).

Les mortiers projetés sont formulés de manière très complexe, afin de notamment répondre aux exigences imposées par leur procédé de mise en place. La caractérisation et l’interprétation des leurs propriétés rhéologiques représentent ainsi un grand challenge, faisant appel à diverses thématiques de la matière molle : suspensions granulaires, dispersions colloïdales, solutions de polymère, mousses, etc. Nous considérons l’influence de divers paramètres de formulation, toutefois, le cœur de cette étude concerne l’influence des épaississants organiques, en particulier les éthers de cellulose (EC). Ces polysaccharides sont utilisés dans la pratique principalement pour leurs propriétés de rétention d’eau, mais ils ont également un fort impact sur la rhéologie. Nos résultats montrent que les EC augmentent considérablement la consistance du mortier, mais leur influence sur le seuil d’écoulement est plus complexe : celui-ci augmente pour les faibles dosages puis diminue jusqu’à s’annuler pour des dosages élevés. L’impact de l’EC sur la rhéologie du mortier a été relié à son influence sur les propriétés de la solution aqueuse interstitielle, en invoquant notamment ses aspects associatifs. La rhéologie est influencée par des facteurs externes (température, ajout de tensioactif) ainsi par la structure chimique du polymère. Avec la rhéologie oscillatoire, nous avons analysé l’impact de certains types d’épaississants sur l’organisation microstructurale du mortier. Nous avons établi une corrélation nette entre propriétés viscoélastiques et rétention d’eau. Plus l’épaississant augmente, plus les aspects dissipatifs augmentent et plus la rétention d’eau s’améliore. / Machinery rendering mortars are characterized by a highly complex mix-design, due to several requirements related to their placement process that need to be fulfilled. It is therefore a challenge to characterize their rheological properties. Indeed they display most of the features encountered in the field of soft matter. We consider the influence of several mix-design parameters on most of the fresh state properties of the mortars. However the main focus is the impact of organic thickening admixtures, in particular cellulose ethers (CE), on the rheological behavior. These admixtures are used for their water retention capacity, yet they have also a high impact on the rheological properties. CEs significantly increase the consistency, while their effect on the yield stress is more complex: when increasing CE dosage rate the yield stress first increases, and then decreases beyond a critical dosage rates. The impact of CE on the mortar rheological behavior is discussed in relationship to its effect on the properties of the interstitial aqueous solution. The associative feature of the CE polymer is particular referred to explain our results. Several parameters that may affect this property are considered. Small amplitude oscillatory shear rheology is used to probe mechanically the influence of CEs on the microstructure of the mortar. By comparing the effect of different thickening admixtures on the viscoelastic properties of the mortars a clear correlation between these properties and water retention is established. The more the admixture introduces viscous dissipation as compared to elasticity into the system, the more it increases its water retention capacity.

Tanto no meio rural como urbano as novas tendências são de buscar uma melhoria de técnicas e de uso de materiais alternativos buscando-se uma maior sustentabilidade. A utilização de plantas nas paredes e telhados é um dos mais recentes campos da pesquisa ambiental e busca encontrar uma solução ecológica e sustentável para melhorar a qualidade de vida urbana e rural. Uma cobertura verde consiste de um substrato leve e de uma vegetação apropriada, plantada sobre uma base impermeável. Podem conter também camadas adicionais, tais como, um sistema de drenagem e irrigação e uma barreira anti-raízes. Os efeitos positivos da vegetação sobre o ambiente urbano já são bem conhecidos e neste caso da cobertura, diminuem as enxurradas, filtro biológico, redução da poluição do ar, amenizam o calor nas edificações durante o verão e o conservam durante o inverno. Há também benefícios para a fauna, com retorno de espécies que mantêm o equilíbrio biológico local. Essas coberturas podem ter muitas aplicações, como em indústrias, residências, escritórios e outras propriedades comerciais e rurais. Uma criteriosa seleção de plantas permite que a cobertura verde tenha sucesso em condições adversas. Por outro lado, são necessárias pesquisas no sentido de assegurar um meio de cultura que retenha água e ao mesmo tempo proporcione uma boa drenagem para que as raízes não apodreçam, permitindo uma maior gama de espécies de plantas na cobertura. Neste sentido, realizou-se um estudo dos substratos mais abundantes na região, buscando tecnologias apropriadas para a confecção dos telhados verdes e identificando as melhores técnicas de aplicação, de acordo com a necessidade de cada ambiente. Para a realização deste trabalho foram utilizados dez tipos de substratos que foram pré-selecionados de acordo com a disponibilidade no mercado, de mais fácil obtenção e de melhor custo beneficio ambiental. As análises estatísticas utilizam o delineamento experimental inteiramente ao acaso, em esquema fatorial com três repetições e utilizando o programa estatístico SAS para auxiliar na análise e confecção dos gráficos e discussões. Na avaliação do conjunto de características, a turfa marrom (TM) apresentou o menor valor de densidade seca, maior porosidade total, maiores valores de água facilmente disponível, água disponível e capacidade de retenção de água, e mesmo valor de espaço de aeração daquele sugerido como referência sendo um bom material para o uso em telhados verdes, formando compostos com outros materiais e buscando as melhores características e sustentabilidade do sistema. Dentre os substratos comerciais estudados, o substrato para espécies hortícolas (SH) apresentou os maiores valores de capacidade de retenção de água e água disponível para as plantas, possibilitando um maior intervalo entre irrigações ou chuvas, características importantes para o uso em telhados verdes. No entanto, tornam-se necessários mais estudos com a finalidade identificar mais materiais e substratos apropriados para o uso em telhados verdes, levando-se em conta as diferentes características de cada local, tipo de vegetação escolhida, capacidade de suporte da edificação, dentre outro fatores. / Rural and urban new trends seek an improvement in techniques and use of alternative materials for greater sustainability. The use of plants on walls and roofs is one of the newest fields of environmental research, looking for a green and sustainable solution to improve the quality of urban and rural life. A green cover consists of a substrate and appropriate vegetation planted on an impermeable base. It can also contain additional layers, such as a system of drainage and irrigation with an anti-root barrier. The positive effects of roof vegetation on urban environment are well known, as reducing the runoff,acting as a biological filter, reducing air pollution, minimizing heat inside the buildings during summer and maximizing during the winter. There are also benefits to fauna, with the return of various species, maintaining the local biological balance. The coverage can be adapted to industries, homes, offices and other commercial and rural properties. Careful selection of plants allows the green roof to succeed in adverse conditions. In addition, research is necessary to ensure a culture medium that retains water that the same time provides good drainage to prevent root rot, allowing a wider range of plant species in the cover. In this sense, a study was conducted involving the most abundant substrates of our region, seeking appropriate technologies for the manufacture of green roofs and identifying the best application techniques, according to the needs of each environment. For this work ten types of preselected substrates were used according to market availability, easier to obtain and with a better environmental cost/benefit ratio. Statistics of the experimental design was completely randomized in a factorial format with three replications and using the SAS statistical software to assist in the analysis and construction of graphs and discussions. In evaluating the feature of the cover set, brown peat (TM) presented the lowest value of dry density, higher porosity, higher values of easily available water, available water capacity and water retention, and even the amount of aeration space, suggested TM as being a good reference material for use in green roofs. Among the studied commercial substrates, the substrate for horticultural species (SH) showed the highest values of water holding capacity and water available to plants, allowing a longer interval between irrigations or rainfall, an important characteristic for its use on green roofs. However, more studies are needed in order to identify the most suitable materials and for use in green roof substrates, taking into account the different characteristics of each site, vegetation type, bearing capacity of the building, among other factors.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisors: Jack B. Gingrich and Charles E. Mason, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Ecology, Evolution and Natural Resources." Includes bibliographical references (p. 41-47).

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2002. / Includes bibliographical references (leaves 62-65).

Thesis (M Eng) -- University of South Australia, 1993

Thesis (M Eng) -- University of South Australia, 1993

Long term storage of bauxite residue materials requires a capping stratum which will limit erosion while stabilizing slopes, limit deep infiltration of water into storage piles, and be aesthetically acceptable to the surrounding community. A diverse native vegetative community capable of surviving seasonal drought, low plant available water and nutrient constraints has the best potential of satisfying most, if not all of these requirements. Current and past rehabilitation of residue disposal areas (RDAs) using species native to southwest Western Australia has exhibited varying success. Current practices at Alcoa World Alumina Australia’s (Alcoa) Western Australia refineries have bauxite residue fines (< 150 ìm) stored within impoundments, in which the outer embankments are constructed with bauxite residue sands (> 150 ìm). The residue sands are also used as the growth media in the capping stratum for vegetation establishment on the disposal sites. Despite the inherently hostile properties of residue sand (pH > 10, EC(1:5) > 4 dS m-1, and ESP > 50), reductions in alkalinity (pH), salinity (EC) and sodicity (ESP) are corrected, through freshwater leaching, to a greater extent than is possible with residue fines. Although leaching can reduce the hostile character of residue sand, additions of phosphogypsum are typically added to expedite the removal of Na and alkalinity, and inorganic fertilizers are incorporated to improve the nutrient status of the growth media. However, due to the inconsistencies in vegetation establishment, which are attributed to poor water retention, inherent nutrient deficiencies and rapid loss of nutrients within residue sands (because of high hydraulic conductivity), further amendments are required. The aim of this study was to determine if amending the residue sand capping layer with residue fines would enhance its overall growth potential for vegetation establishment. Additions of fines to residue sands were predicted to increase water retention, add nutrients and increase the ability of the growth media to retain nutrients. Comparisons were made between the treated residue fines (seawater washed, carbonated, or unaltered) at a series of fines additions (1 - 20 % w/w) and a control(residue sand) amended with 2% (w/w) phosphogypsum and inorganic fertilizer. Comparisons were to determine the differences in 1) water retention, 2) nutrient concentrations and nutrient retention, and 3) plant growth responses and plant biomass nutrient concentrations between the growth media treatments. Four experiments were set up to measure differences in these variables which included: a glasshouse study involving the growth of Acacia saligna; a germination and emergence study (A.saligna); a two year field study in Western Australia; and a glasshouse column leaching study. Water retention increased with increasing percentage of residue fines addition. Plant available water (PAW) increased up to 110 %, with a 20 % increase in fines, representing an increase of 0.026 m3 PAW m-3 residue growth media, when compared to the residue sand only. This increase in PAW was attributed to changes in pore space distributions, due to the increasing fines contents altering the sandy texture to loamy sand texture class. However, initially much of this increase in PAW may not be realized, due to estimated temporary increases in osmotic potential associated with the high salt contents of residue sand and fines. Fines materials have much greater salt contents, and thus need to be leached to a greater extent than sands to remove the associated osmotic potential effects. Essential plant nutrients (P, K, S, Ca, Mg, and B) were increased with additions of residue fines in the glasshouse studies, although many nutrients (Mg, Zn, Mn and B) were still marginal for sustainable plant growth and development. Seawater treated residue fines additions produced the greatest increases in growth media nutrients with substantial increases in soluble (> 7 mg L-1) and exchangeable (> 0.10 cmolc kg-1) Mg, being up to 400 % greater than all other treatments. Along with these necessary nutrients, concentrations of Na were also increased in all fines additions treatments. Added Na may offset the benefits of fines additions, at least in the short term, due to inhibitions of cation uptake from Na competition. However, in the column leaching study soluble and exchangeable Na was lost rapidly from the profile, due to Ca and K displacement of Na from exchange sites during leaching. Soluble Na was removed from the profile to < 5 % of initial concentrations, after only three pore volumes of leaching, and exchangeable Na was removed from charge sites to less than 25 % of the initial concentration. Fines additions did increase concentrations of Mg and K on exchange sites, thus reflecting increased nutrient retention capacity relative to that in residue sand only. Plant growth responses and plant biomass nutrient concentrations were altered with the additions of residue fines to residue sands. The germination and emergence study demonstrated that the emergence of native seedlings was affected by additions of fines, due to the increased salinity and sodicity of the materials. Acacia saligna seedling emergence was inhibited by EC(1:5) > 2 dS m-1, which was highly correlated with a Na/Ca ratio of > 40, for all treatments, except the seawater fines additions. Seeds sown in seawater treatments emerged from growth media with EC(1:5) as high as 3.33 dS m-1 and appeared to be better correlated with Ca/Mg ratios than any other variable. Native vegetation growth responses showed mixed results in fines treated residues in the field. In the greenhouse study, plant growth tended to decrease with fines additions. Poor plant growth with increasing fines additions occurred despite the increased water retention and increased nutrients. This was attributed to the addition of Na associated with the residue fines, as increases in Na, EC and ESP in fines treatments all appear to have limited growth of Acacia saligna in the glasshouse over three months. Seawater fines additions had elevated Mg and B concentrations in plant biomass, and performed better than the carbonated or unaltered fines treatments, but still had reduced growth compared to the residue sand, which contained lower Na concentrations. Additional plant growth limitations may have occurred, due to possible plant nutrient deficiencies including: Mg, Zn, Mn and B and Na toxicity. Incorporation of residue fines into residue sands did increase water retention, nutrient concentrations and the nutrient retention capacity, but did not enhance the overall growth potential for vegetation, at least in the short term. Reductions in germination and emergence of seedlings and reduced plant growth were attributed to increases in Na concentrations introduced from the fines. Seawater washed residue fines had lower ESP and greater concentrations of nutrients, thus reducing the negative impacts from the additional Na introduced, and showed the greatest promise as a fines amendment. As leaching occurs over the first few initial months of rehabilitation, it is expected that the majority of the Na will be removed, from a system with an addition of 5 to 10 % fines, and the positive benefits of the fines additions will than be realized. Findings also illustrate that delaying the planting of vegetation on RDAs, until adequate leaching has occurred to reduce the Na concentrations, will substantially increase vegetation emergence and establishment.