Over the past years, levee failures during floods have caused significant losses of lives and properties in the nation. Majority of these failures were induced by seepage through granular foundation soils underneath the top soil on which the levees were built. One of methods to mitigate this phenomenon includes the treatment of the granular soil deposits with an engineered fluid delivered by permeation (permeation grouting), resulting in a less pervious deposit. Since the conventional cement-based suspensions and chemical solutions may cause groundwater contamination due to long term reaction with groundwater, clay suspension such as bentonite suspension can be an alternative in terms of environmental friendliness and long-term safety. Moreover, the suspensions, after being permeated, are expected to be stable in the pore space due to the thixotropic nature of bentonite. The main challenge in this approach is being able to permeate a concentrated suspension through the pores of a granular material. To achieve a significant reduction in the hydraulic conductivity, concentrated bentonite suspensions should be used; however, concentrated suspensions can have low mobility, resulting in a low penetration depth and little practical application. The main objective of this study is to investigate the permeation of concentrated bentonite suspensions by controlling their rheological properties. The first portion of this research focuses on measuring the rheological properties of the various engineered bentonite suspensions over time. The second point of focus of this research is the parameters affecting the flow of the bentonite suspensions through granular soils, and the final focal area is determining the hydraulic performance of the grouted granular soils. In order to achieve these objectives, an experimental program was developed in this research. First, rheological tests were performed with the bentonite suspensions with and without various concentrations of sodium pyrophosphate (SPP); SPP is an ionic additive that is used to reduce the initial yield stress and viscosity of bentonite suspensions. A stress controlled test with the vane geometry produced rheological parameters with a minimal disturbance. Suspensions were stored in sealed cups and tested at various times to measure the long term thixotropic changes in yield stress and viscosity. Second, the various concentrations of the bentonite suspensions were injected at a constant pressure through clean sands which were prepared at various conditions (relative density, fine contents, and grain size) in order to investigate soil and suspension parameters affecting the flow of the bentonite suspensions. The results from these experimental tests were utilized to develop a groutability criterion of bentonite suspensions for practical purposes. Finally, the saturated hydraulic conductivity of the treated soils was measured using falling and rising head method. The traditional concept of “clay void ratio” was re-examined. The results from this study showed that the modified bentonite suspensions could be used as an alternative grout in permeation grouting to improve hydraulic performance of the permeable granular soils. / text

Thesis (Ph. D.)--Columbia University, 1934. / Vita.

O objetivo deste trabalho foi avaliar in vitro e in situ o potencial erosivo do suco de laranja modificado por cálcio e alguns polímeros alimentares. Este estudo foi dividido em quatro fases. Na primeira, as seguintes substâncias: lactato de cálcio (Ca), goma xantana (XG), hexametafosfato de sódio (HMP), tripolifosfato de sódio (STP), pirofosfato de sódio (PP) e suas combinações, foram adicionadas a um suco de laranja, disponível comercialmente, criando 15 sucos modificados. O suco sem aditivos foi utilizado como controle negativo (C-), e um suco de laranja modificado com cálcio (disponível comercialmente), como controle positivo (C+). Os sucos tiveram o seu potencial erosivo avaliado com o método do pH-stat. A variável resposta foi o volume de titulador necessário para manter o pH dos sucos nos valores iniciais. Após, seis sucos foram selecionados e testados na segunda fase, com um modelo de ciclagem de erosão-remineralização. Na terceira fase, os episódios de erosão e de remineralização foram estudados independentemente. A variável resposta para essas duas fases foi a microdureza de superfície (MDS) para esmalte, e a perfilometria ótica, para esmalte e dentina. Na quarta fase, os sucos Ca, Ca+HMP e HMP, mais os controles, foram testados com um modelo de erosão in situ, crossover, cego, de 5 fases, envolvendo 10 voluntários. Em cada fase, os voluntários inseriam aparelhos palatinos contendo espécimes de esmalte na boca e, após 5min, realizavam os desafios erosivos nos tempos experimentais de 0 (controle), 10, 20 e 30min. Dois espécimes eram aleatoriamente removidos dos aparelhos, após cada tempo. A variável resposta foi a alteração da microdureza de superfície (em %). Antes dos procedimentos clínicos, em cada fase, os voluntários realizaram um teste cego de sabor, onde o suco modificado designado a aquela fase foi comparado cegamente com C-. Na primeira fase, todos os aditivos foram capazes de reduzir o potencial erosivo do suco, com exceção da adição de XG isoladamente. Na segunda fase, não houve perda de estrutura de esmalte detectável quando Ca, HMP e Ca+HMP foram adicionados ao suco; XG, STP e PP apresentaram uma perda de esmalte similar ao grupo C-. Ca+HMP apresentaram a menor redução da MDS, seguido por Ca; todos os outros grupos apresentaram uma redução da MDS similar ao grupo C-. Para dentina, somente Ca+HMP apresentou uma redução na perda de estrutura. Na terceira fase, Ca, HMP e Ca+HMP protegeram contra erosão e nenhum dos compostos interferiu com o processo de remineralização. Na quarta fase, Ca e Ca+HMP reduziram a erosão, sem diferenças significantes entre esses grupos; o HMP não apresentou efeito protetor. 5/10 voluntários notaram uma diferença no sabor de C+, 4/10 para Ca e 2/10 para C-. Conclui-se que, in vitro, tanto o HMP, quanto o Ca, nas concentrações testadas, reduziram a erosão causada pelo suco em esmalte e a combinação desses aditivos aumentou seus efeitos protetores. Para dentina, apenas a combinação Ca+HMP reduziu a erosão. In situ, Ca reduziu a erosão provocada pelo suco, porém, alterações no sabor foram notadas por alguns voluntários. HMP não apresentou efeito protetor. / The aim of this study was to evaluate in vitro and in situ the erosive potential of the orange juice modified with calcium and some food-approved polymers. This study was divided into four fases. In the first, the following substances: calcium lactate (Ca), xanthan gum (XG), sodium hexametaphosphate (HMP), sodium trypoliphosphate (STP), sodium pyrophosphate (PP) and some of their combinations were added to a commercially available orange juice, creating 15 modified juices. The juice without additives was used as a negative control (C-) and a commercially available calcium-modified juice as positive control (C+). These juices were tested for erosive potential using pH-stat. The response variable was the volume of titrant needed to maintain the pH of the juices in their baseline values. After, six selected juices were tested in the second phase with an erosion-remineralization cycling model. In the third phase, the erosion and remineralization episodes were tested independently. The reponse variable for these phases was surface microhardness for enamel and optical perfilometry for enamel and dentin. In the fourth phase, the juices Ca, Ca+HMP and HMP, plus the controls were tested with an erosion in situ model, consisting of a 5-phase, single blind crossover clinical trial involving 10 subjects. In each phase, subjects inserted custom-made palatal appliances containing enamel specimens in the mouth and, after 5 min equilibration period, performed erosive challenges for total of 0 (control), 10, 20, and 30 min. Two specimens were randomly removed from the appliances, after each challenge period. The reponse variable was the percentage of surface microhardness change. Before the procedures, in each phase, the subjects performed a taste test, where the modified juice assigned to that phase was blindly compared to C-. In first phase, all the additives were able to reduce the erosive potential of the juice, except the addition of XG alone. In the second phase, no detectable enamel loss was observed when Ca, HMP and Ca+HMP were added to the juice; XG, STP and PP had enamel loss similar to C-. Ca+HMP showed the lowest reduction in the surface microhardness, followed by Ca;all the other groups presented a reduction in the surface microhardness similar to C-. For dentin, only Ca+HMP reduced surface loss. In the third phase, Ca, HMP and Ca+HMP protected against erosion; and none of the tested compounds seemed to interfere with the remineralization process. In the fourth phase, Ca and Ca+HMP reduced erosion, with no difference between them. HMP did not show any protective effect. 5/10 subjects noticed a difference in the taste of C+; 4/10 for Ca; and 2 /10 for C-. In conclusion, in vitro, HMP and Ca, in the concentrations tested, reduced erosion on enamel and this effect was enhanced by their combination. For dentin, only the combination Ca+HMP caused a significant reduction. In situ, Ca reduced the erosion caused by the juice; however, taste changes were noticed by some volunteers. HMP did not show any protective effect.

O objetivo deste trabalho foi avaliar in vitro e in situ o potencial erosivo do suco de laranja modificado por cálcio e alguns polímeros alimentares. Este estudo foi dividido em quatro fases. Na primeira, as seguintes substâncias: lactato de cálcio (Ca), goma xantana (XG), hexametafosfato de sódio (HMP), tripolifosfato de sódio (STP), pirofosfato de sódio (PP) e suas combinações, foram adicionadas a um suco de laranja, disponível comercialmente, criando 15 sucos modificados. O suco sem aditivos foi utilizado como controle negativo (C-), e um suco de laranja modificado com cálcio (disponível comercialmente), como controle positivo (C+). Os sucos tiveram o seu potencial erosivo avaliado com o método do pH-stat. A variável resposta foi o volume de titulador necessário para manter o pH dos sucos nos valores iniciais. Após, seis sucos foram selecionados e testados na segunda fase, com um modelo de ciclagem de erosão-remineralização. Na terceira fase, os episódios de erosão e de remineralização foram estudados independentemente. A variável resposta para essas duas fases foi a microdureza de superfície (MDS) para esmalte, e a perfilometria ótica, para esmalte e dentina. Na quarta fase, os sucos Ca, Ca+HMP e HMP, mais os controles, foram testados com um modelo de erosão in situ, crossover, cego, de 5 fases, envolvendo 10 voluntários. Em cada fase, os voluntários inseriam aparelhos palatinos contendo espécimes de esmalte na boca e, após 5min, realizavam os desafios erosivos nos tempos experimentais de 0 (controle), 10, 20 e 30min. Dois espécimes eram aleatoriamente removidos dos aparelhos, após cada tempo. A variável resposta foi a alteração da microdureza de superfície (em %). Antes dos procedimentos clínicos, em cada fase, os voluntários realizaram um teste cego de sabor, onde o suco modificado designado a aquela fase foi comparado cegamente com C-. Na primeira fase, todos os aditivos foram capazes de reduzir o potencial erosivo do suco, com exceção da adição de XG isoladamente. Na segunda fase, não houve perda de estrutura de esmalte detectável quando Ca, HMP e Ca+HMP foram adicionados ao suco; XG, STP e PP apresentaram uma perda de esmalte similar ao grupo C-. Ca+HMP apresentaram a menor redução da MDS, seguido por Ca; todos os outros grupos apresentaram uma redução da MDS similar ao grupo C-. Para dentina, somente Ca+HMP apresentou uma redução na perda de estrutura. Na terceira fase, Ca, HMP e Ca+HMP protegeram contra erosão e nenhum dos compostos interferiu com o processo de remineralização. Na quarta fase, Ca e Ca+HMP reduziram a erosão, sem diferenças significantes entre esses grupos; o HMP não apresentou efeito protetor. 5/10 voluntários notaram uma diferença no sabor de C+, 4/10 para Ca e 2/10 para C-. Conclui-se que, in vitro, tanto o HMP, quanto o Ca, nas concentrações testadas, reduziram a erosão causada pelo suco em esmalte e a combinação desses aditivos aumentou seus efeitos protetores. Para dentina, apenas a combinação Ca+HMP reduziu a erosão. In situ, Ca reduziu a erosão provocada pelo suco, porém, alterações no sabor foram notadas por alguns voluntários. HMP não apresentou efeito protetor. / The aim of this study was to evaluate in vitro and in situ the erosive potential of the orange juice modified with calcium and some food-approved polymers. This study was divided into four fases. In the first, the following substances: calcium lactate (Ca), xanthan gum (XG), sodium hexametaphosphate (HMP), sodium trypoliphosphate (STP), sodium pyrophosphate (PP) and some of their combinations were added to a commercially available orange juice, creating 15 modified juices. The juice without additives was used as a negative control (C-) and a commercially available calcium-modified juice as positive control (C+). These juices were tested for erosive potential using pH-stat. The response variable was the volume of titrant needed to maintain the pH of the juices in their baseline values. After, six selected juices were tested in the second phase with an erosion-remineralization cycling model. In the third phase, the erosion and remineralization episodes were tested independently. The reponse variable for these phases was surface microhardness for enamel and optical perfilometry for enamel and dentin. In the fourth phase, the juices Ca, Ca+HMP and HMP, plus the controls were tested with an erosion in situ model, consisting of a 5-phase, single blind crossover clinical trial involving 10 subjects. In each phase, subjects inserted custom-made palatal appliances containing enamel specimens in the mouth and, after 5 min equilibration period, performed erosive challenges for total of 0 (control), 10, 20, and 30 min. Two specimens were randomly removed from the appliances, after each challenge period. The reponse variable was the percentage of surface microhardness change. Before the procedures, in each phase, the subjects performed a taste test, where the modified juice assigned to that phase was blindly compared to C-. In first phase, all the additives were able to reduce the erosive potential of the juice, except the addition of XG alone. In the second phase, no detectable enamel loss was observed when Ca, HMP and Ca+HMP were added to the juice; XG, STP and PP had enamel loss similar to C-. Ca+HMP showed the lowest reduction in the surface microhardness, followed by Ca;all the other groups presented a reduction in the surface microhardness similar to C-. For dentin, only Ca+HMP reduced surface loss. In the third phase, Ca, HMP and Ca+HMP protected against erosion; and none of the tested compounds seemed to interfere with the remineralization process. In the fourth phase, Ca and Ca+HMP reduced erosion, with no difference between them. HMP did not show any protective effect. 5/10 subjects noticed a difference in the taste of C+; 4/10 for Ca; and 2 /10 for C-. In conclusion, in vitro, HMP and Ca, in the concentrations tested, reduced erosion on enamel and this effect was enhanced by their combination. For dentin, only the combination Ca+HMP caused a significant reduction. In situ, Ca reduced the erosion caused by the juice; however, taste changes were noticed by some volunteers. HMP did not show any protective effect.