O uso de adições minerais no concreto como substituição parcial ao cimento Portland ajuda a preservar os recursos naturais poupando a matéria-prima, reduzindo o consumo de energia necessária para a produção do cimento e reciclando rejeitos que se lançados no meio ambiente causariam problemas ambientais e de saúde pública. A adição mineral que vem tendo muito destaque devido à sua alta reatividade, considerada por vários pesquisadores como uma superpozolana, é a sílica ativa (SA), um subproduto da fabricação de silício metálico ou ligas de ferro-silício. A sílica ativa se caracteriza por uma elevada finura e alta área específica e um alto teor de sílica vítrea, estes fatores somados garantem à SA a alta reatividade com o hidróxido de cálcio, transformando-o em silicato de cálcio hidratado. A casca do arroz vem sendo pesquisada como uma fonte alternativa de sílica ativa. A sílica ativa extraída da casca de arroz contém um alto teor de SiO2 e, dependendo do processo de extração, possui propriedades adequadas para a utilização na confecção de concretos de elevado desempenho. Este trabalho visa estudar a atividade pozolânica da sílica da casca de arroz produzida no laboratório de materiais avançados à base de cimento. Para avaliar as características das sílicas, foram realizados ensaios tanto para determinação das suas propriedades físicas quanto para a determinação de sua composição química e pozolanicidade. Os ensaios realizados foram:composição química, pozolanicidade (método Chapelle modificado), área superficial B.E.T., distribuição granulométrica, distribuição do tamanho de partículas via MEV, amorficidade (por difratometria de raio X), massa específica e determinação do índice de atividade pozolânica com cimento Portland (NBR-5752). Os ensaios de caracterização demonstraram que a sílica da casca de arroz possui um alto grau de amorficidade e elevada área superficial, que garantiram uma maior reatividade nas idades iniciais, porém em idades avançadas apresentou a mesma eficiência que a sílica de ferro-silício. / The use of mineral additions in concrete in order to partially replace Portland cement helps to protect natural resources by saving raw material, reducing energy consumption in cement production and recycling industrial waste that could otherwise cause environmental and public health hazards. One mineral addition that has drawn considerable attention due to its high reactivity is silica fume (SF), a byproduct of the manufacturing process of metallic silicon or iron-silicon alloys and considered by many researchers as a superpozzolan. Silica fume is characterizated by high fineness, high specific area and high content of vitreous silica. The sum of these factors provides SF high reactivity with calcium hydroxide, which is transformed into hydrated calcium silicate. Rice husk ash has also been investigated as an alternative source of silica fume. The silica from rice husk ash contains a high percentage of SiO2 and, depending on the extraction process, has adequate properties to be employed in the manufacturing of high-performance concrete. The objective of this work is to study the pozzolanic activity of silica from rice husk ash produced at the Laboratório de Materiais Avançados à Base de Cimento. In order to evaluate the characteristics of silica samples from rice husk, assays were performed to determine their physical properties as well as their chemical composition and pozzolanicity. The assays performed were: chemical composition,pozzolanicity (modified Chapelle method), B.E.T. surface area method, granulometric distribution, particle size distribution by Scanning Electron Microscope (SEM), amorphicity by X-ray diffractometry (XRD), specific mass and pozzolanic activity index determination with Portland cement (NBR-5752). The characterization assays showed that the silica from rice husk ash has a high amorphicity level and a high surface area, which yield higher reactivity at initial ages. However, at advanced ages it pesented the same efficiency as that of silica from iron-silicon.

In recent decades, much research has investigated the efficiency of Phase Change Materials (PCMs) in improving the thermal performance of buildings and pavements. In buildings, increasing the thermal inertia of structural elements by incorporating PCMs decreases the energy required to keep the inside temperature in the comfort range. In concrete pavements, using PCMs decreases the number of freeze/thaw cycles experienced by the pavement and thus increases service life. However, PCMs cannot be added to cementitious binders directly, because they interfere with the hydration reactions between cement and water that produce strength-bearing phases. Therefore different carriers have been proposed to indirectly incorporate PCMs in cementitious materials. Lightweight Aggregate (LWA) is one of the materials that has been proposed as PCM carrier agent. However, it was not studied in depth before. Various experiments were conducted to investigate the problems associated with incorporating LWA presoaked in PCM in cementitious media. The results show that a portion of PCM leaks out of the LWA’s structure and subsequently affects different chemical, physical, and mechanical properties of the binder. In addition, the applicability of Rice Husk Ash (RHA), a common material never before used to encapsulate PCM, as a PCM carrier agent was investigated. The results show that RHA can absorb and contain liquids in its porous structure; and regarding its compatibility with the cementitious media, it can be used as PCM carrier. Different computational simulations using Typical Meteorological Year data were conducted to evaluate the efficiency of PCMs in improving the thermal performance of buildings. Utilizing PCM-incorporated gypsum boards was shown to be a promising strategy to achieve the governmental plans of “Zero Net Energy� buildings. The results show that using a PCM with a melting point near the occupant comfort zone delays and reduces the inside peak temperature, increases the duration of time during which the inside temperature stays in the comfort zone, and decreases the cost and energy required by HVAC system to keep the inside temperature in this range. However, PCMs’ efficiency is completely dependent on the input temperature profile.

Submitted by Fabricia Fialho Reginato (fabriciar) on 2015-08-05T00:01:47Z No. of bitstreams: 1 DaianeCalheiro.pdf: 5982937 bytes, checksum: 0a11f48bf6517b673d6c2163ae6ae2e7 (MD5) / Made available in DSpace on 2015-08-05T00:01:47Z (GMT). No. of bitstreams: 1 DaianeCalheiro.pdf: 5982937 bytes, checksum: 0a11f48bf6517b673d6c2163ae6ae2e7 (MD5) Previous issue date: 2011-03-03 / Banco Santander / Banespa / FINEP - Financiadora de Estudos e Projetos / De acordo com os novos paradigmas ambientais, a busca pelo desenvolvimento sustentável é imprescindível para o prolongamento das reservas naturais e a redução da poluição. No intuito de minimizar os impactos ambientais negativos, cada vez mais se investe em pesquisas que englobam o uso eficiente de recursos naturais não renováveis. A agroindústria é um grande gerador de resíduos e devido a esse fato, está começando a perceber a importância de destiná-los corretamente. A cinza de casca de arroz (CCA), que é proveniente da queima da casca utilizada para a geração de energia, é um resíduo gerado em grandes quantidades e de baixa densidade, dificultando o gerenciamento, pois necessita de um grande espaço para o armazenamento e o descarte. Desta forma, a reciclagem destas cinzas torna-se uma excelente alternativa para minimizar o impacto ambiental provocado pelo seu descarte inadequado e reduzir os custos de disposição em aterros controlados. A CCA possui um grande teor de sílica em sua composição, podendo se tornar um co-produto para vários segmentos industriais como: construção civil, cerâmica, química, vidros e siderurgia. No intuito de incentivar a inserção desse resíduo como um co-produto de maior valor agregado, o trabalho visa contribuir para aumentar a eficiência da moagem da cinza da casca de arroz. Neste sentido, aditivos foram utilizados para facilitar a moagem para sua adequação como co-produto, considerando a qualidade do material obtido, o tempo e a economia do processo. Para a elaboração deste trabalho, a CCA foi moída sem e com uso de aditivo em 4 tempos diferentes (30min., 1h, 2h e 4h) e foram adicionados dois tipos de aditivos, um comercial e um resíduo do setor metal-mecânico. Estes aditivos foram adicionados em 3 concentrações diferentes: 0,03%, 0,045% e 0,06% para o comercial e 2%, 6% e 10% para o resíduo. Para avaliar o processo de moagem foram realizadas caracterizações química, física e estrutural de todas as amostras: CCA Bruta, CCA Segregada e as CCA moídas. A caracterização da CCA utilizada nesta dissertação mostrou um material mais adequado comparado a trabalhos anteriores confirmando a influência do aumento da eficiência energética da queima da casca na qualidade da CCA como coproduto. Com relação ao uso dos aditivos SIKA-GRIND 200 e pó de granalha, os resultados indicaram que estes não reduziram significativamente o diâmetro médio das partículas. Entretanto, o uso de aditivos para reduzir o tamanho de grão da CCA deve ser melhor estudado para qualificá-la como matéria prima na construção civil. / According to the new environmental paradigms, the pursuit of sustainable development is essential for the lengthening of natural reserves and reduction of pollution. In order to minimize negative environmental impacts, ever more investments are made in research about the efficient use of nonrenewable natural resources. Agribusiness is a major generator of waste and due to that fact, begins to realize the importance of proper disposal. Rice husk ash (RHA), which proceeds from the burning of the husk for energy generation, is generated in large quantities and low density, making it difficult to manage, as it requires a large space for storage and disposal. Thus, recycling this ash becomes an excellent alternative to minimize the environmental impact caused by its inappropriate disposal and reduce landfill disposal costs. RHA has a high content of silica in its composition, making its use possible as a by-product to several industries such as: construction, ceramics, chemical, glass and steel. To encourage the placement of this waste as a by-product with higher aggregated value, this study aims to contribute to increase the efficiency of rice husk ash milling. In this way, additives were used to facilitate the milling for its suitability as a by-product, considering the quality, time and process economy. To elaborate this study, the rice husk ash was ground with and without additives in four different times (30min., 1h, 2h and 4h) and two types of additives were used, a commercial additive and a solid waste from the metal-mechanic industry (cleaning cast parts dust). These additives were added in three different concentrations: 0.03, 0.045 and 0.06% for the commercial additive and 2, 6 and 10% for the dust. To evaluate the milling process, chemical, physical and structural characterizations were carried out for all samples: as received RHA, segregated RHA and grounded RHA. The characterization of RHA, used in this dissertation, showed a material more adequate, when compared to former works using RHA from the same source, confirming the influence of the energetic efficiency of the rice shell burning on the RHA quality as by-product. In relation to the additives SIKA-GRIND 200 and granalha dust, the results indicated that they did not influence significantly in the decreasing of medium diameter of RHA particles. However, the use of additives to reduce the size of the RHA grains must be better studied to qualify RHA as a raw material to civil construction.

Um grande passivo ambiental da atualidade refere-se à contaminação dos recursos hídricos por hidrocarbonetos. Os atuais sistemas de remediação buscam a utilização de adsorventes alternativos para remoção destes poluentes. O objetivo desta tese de doutorado foi avaliar o uso da cinza de casca de arroz (CCA) e de carvão ativado (CA) na adsorção de BTEX – benzeno, tolueno, etilbenzeno e xileno em soluções aquosas. A CCA foi gerada a partir do processo de queima de casca de arroz para aproveitamento energético e o CA obtido comercialmente. As propriedades físicas, químicas e microestruturais da CCA e do CA foram caracterizadas através de análises de distribuição granulométrica, área superficial, porosidade, massa específica, capacidade de hidratação, pH, ponto de carga zero, perda ao fogo, carbono total, composição química elementar, determinação de fases cristalinas, determinação de grupos funcionais e análise de imagem. Estudos de adsorção cinéticos e de equilíbrio (isotermas) foram efetuados com soluções padrões de benzeno, tolueno, xileno e etilbenzeno em sistemas monocompostos e em misturas BTEX. A quantificação foi realizada por por cromatografia gasosa com detector de ionização de chama. Na cinética de adsorção, foram avaliadas as variáveis: tempo de contato adsorvente-adsorbato (15, 30, 60, 120 e 240 minutos); concentração inicial do adsorbato (1, 5, 10 e 20 mg/L) e dosagem do adsorvente (10 e 20 g/L). Os modelos cinéticos de Pseudo-primeira ordem, Pseudo-segunda ordem e Difusão intrapartícula foram ajustados aos dados experimentais. Isotermas experimentais foram obtidas para cada composto e para a mistura BTEX. Os modelos de Langmuir, Freundlich e Sips foram ajustados aos resultados experimentais para os sistemas com monocompostos. A caracterização das amostras indicou que o CA apresenta microestrutura uniforme com grande área superficial formada por micro e mesoporos e alto teor de carbono. Já a CCA apresenta uma microestrutura heterogênea formada por macroporos e com alto teor de sílica. Os estudos cinéticos demonstraram que a CCA e o CA apresentam capacidades de adsorção altas e semelhantes no tempo de equilíbrio de 120 minutos. De forma geral, a remoção de cada composto na mistura foi menor que a remoção obtida quando em sistemas de monocompostos, onde a capacidade de adsorção se deu na seguinte ordem (em massa de adsorbato por massa de adsorvente): etilbenzeno > xileno > tolueno > benzeno. O modelo cinético de Pseudo-segunda ordem apresentou a melhor correlação para todos os ensaios. As isotermas experimentais obtidas para os monocompostos caracterizam a adsorção em superfícies porosas com formação de monocamada. Os ajustes aos modelos teóricos não apresentaram unanimidade, observando em algumas situações uma correlação adequada para Langmuir e Freundlich. Nas misturas BTEX, as isotermas experimentais para a CCA indicam uma competição pelos sítios ativos do adsorvente entre benzeno/tolueno e entre etilbenzeno/xileno. Os resultados obtidos sugerem que a adsorção de BTEX ocorre preferencialmente através de efeito hidrofóbico já que o CA é um material carbonoso e a CCA configura-se como uma matriz de sílica com fração carbonosa. Os valores de remoção ficaram entre 78,8 e 100%, demonstrando que a CCA apresenta-se como um material alternativo para a adsorção de benzeno, tolueno, etilbenzeno e xileno presente em solução aquosas. / The contamination of water resources by hydrocarbons is considered a significant environmental impact. The remediation systems currently search alternative adsorbents to remove this pollutants. The aim of this work was to investigate the use of rice husk ash (RHA) and activated carbon (AC) in the removal of BTEX (benzene, toluene, ethylbenzene, and xylene) from aqueous solutions. The RHA used was generated as a byproduct of the combustion of rice husk for energy generation, while AC was purchased from the market. Samples of both materials were characterized based on physical, chemical, and microstructural standards (grain size distribution, surface area, porosity, specific weight, hydration capacity, pH, zero load test, loss on ignition, total carbon, chemical composition, crystalline phases, functional groups, and image analysis). The adsorption assays were carried out using standard benzene, toluene, xylene, and ethylbenzene individually and mixed. Quantification of compounds was conducted by gas chromatography with Flame Ionization Detector. Adsorption kinetics was evaluated based on the variables contact time between adsorbent and adsorbate (15, 30, 60, 120, and 240 min), initial adsorbate concentration (1, 5, 10, and 20 mg/L), and adsorbent dose (10 and 20 g/L). The kinetic models pseudo 1st order, pseudo 2nd order, and intra-particle diffusion were adjusted to experimental data. Experimental isotherms were obtained for each compound and for the BTEX mixture. The Langmuir, Freundlich, and Sips models were adjusted to the experimental results for the systems that used one compound at a time. Sample characterization revealed the differences in composition, microstructure, surface area, and pore size between RHA and AC. Kinetic studies showed that RHA and AC have high and similar adsorption capacities at the equilibrium time of 120 min. Generally, the amount of each hydrocarbon removed from the mixture was lower than the removal achieved in the single-compound systems, for which removal rate followed the sequence (adsorbate mass/ adsorbent mass) ethylbenzene > xylene > toluene > benzene. The pseudo 2nd order kinetics model presented the best correlation for all assays. The experimental isotherms obtained for single-compound systems characterized the adsorption on porous surfaces, forming monolayers. No overall concordance was observed in the adjustment of the theoretical models, and in some situations the Langmiur and Freundlich models presented appropriate correlation coefficients. Considering the BTEX mixtures, the experimental isotherms constructed for RHA indicated the existence of competition for active sites of the adsorbent material between benzene and toluene and between ethylbenzene and xylene. The results obtained suggest that BTEX adsorption occurs preferentially through the hydrophobic effect, since AC is a carbonaceous material, while RHA is composed mainly of silica, with a carbonaceous fraction. Removal rates were between 78.8% and 100%, indicating that RHA is an interesting alternative in the removal of benzene, toluene, ethylbenzene, and xylene from aqueous solutions.

White cement has currently received increasing attention due to potential for use in sustainable concrete structures. Based on the U.S. Green Building Council certification practice, the LEED Green Building Rating System for New Construction and Major Renovation (LEED-NC) considers that the reflective quality of white surfaces may help to improve lighting efficiency and reduce temperature fluctuations, resulting in lower heating and cooling with reduction of related energy costs. In addition to the environmental impact, white concrete represents a valuable tool for the aesthetic acceptability of a structure, and can also offer important practical benefits in terms of safety (i.e., light reflection in the dark). In this thesis white concrete was combined with off-white rice husk ash and with a glass fibers reinforced polymer to obtain an innovative composite system able to: a) reduce the energy used for the production of the primary materials, b) decrease the temperature fluctuation in the building resulting in less energy needed for heating and cooling, and c) increase the life of the structure and thereby reduce energy usage for material disposal. It is evident that in applications where aesthetics is the driver, a great deal of attention needs to be devoted to the concrete mixture, but also to durability properties. To further improve the durability of white concrete, novel methodologies were introduced to study the corrosion mechanism of steel embedded in concrete and its effect on the color degradation of white surface. This study demonstrates the validity of the sustainable system made by white cement, OWRHA, and GFRP, and of the methodology introduce to evaluate corrosion and color degradation of reinforced concrete.

Η Τέφρα Φλοιού Ρυζιού (ΤΦΡ) είναι ένα από τα κυριότερα γεωργικά απόβλητα και προέρχεται από την καύση του φλοιού ρυζιού (ΦΡ) στις ορυζοβιομηχανίες για παραγωγή ενέργειας ή και μείωσης του όγκου των αποβλήτων. Η τέφρα φλοιού ρυζιού αποτελεί περίπου το 18-20% του φλοιού του ρυζιού, ο οποίος αποτελεί περίπου το 20% του ακατέργαστου ρυζιού ενώ συνήθως είναι κρυσταλλική. Καθώς ο παγκόσμιος όγκος της ετήσιας παραγωγής σε ρύζι και κατ’ επέκταση σε τέφρα φλοιού ρυζιού αυξάνεται διαρκώς, εγείροντας περιβαλλοντικά και οικονομικά ζητήματα, η ανεύρεση ενός αποδοτικού και οικολογικού τρόπου εκμετάλλευσης της είναι θέμα μείζονος σημασίας. Παράλληλα, τα υψηλά ποσοστά της ΤΦΡ σε διοξείδιο του πυριτίου την καθιστούν πιθανή πηγή πυριτίου για πολλές εφαρμογές, μία από τις οποίες είναι και οι σύνθεση ζεόλιθων. Στην παρούσα εργασία μελετήθηκε η αξιοποίηση κρυσταλλικής ΤΦΡ στην σύνθεση τεσσάρων τύπων ζεόλιθων και συγκεκριμένα των MFI, FAU, BEA και LTA. Για τον σκοπό αυτό αρχικά χαρακτηρίστηκε η πρώτη ύλη, δηλαδή η ΤΦΡ, τόσο ως προς την χημική της σύσταση και περιεκτικότητα σε άκαυτο άνθρακα όσο και ως προς την κρυσταλλική δομή της. Στη συνέχεια εξακριβώθηκαν οι συνθήκες καύσης του ΦΡ οι οποίες οδηγούν στην μετατροπή από την άμορφη στην κρυσταλλική δομή του διοξειδίου του πυριτίου, η οποία ονομάζεται χριστοβαλίτης. Εφόσον αυτή η κρυσταλλική δομή είναι ακατάλληλη για την παραγωγή ζεόλιθων, μελετήθηκε η δυνατότητα διαλυτοποίησης της ΤΦΡ σε υδατικό διάλυμα καυστικού νατρίου ώστε να καταστραφούν οι κρύσταλλοι και να παραληφθεί άμορφο διοξείδιο του πυριτίου. Για το σκοπό αυτό, επιλέχθηκαν οι μοριακές αναλογίες των πρώτων υλών που οδηγούν στη σύνθεση καθενός από τους τέσσερεις τύπους ζεόλιθων και η ΤΦΡ επεξεργάστηκε με την κατάλληλη αναλογία καυστικού νατρίου σε υδατικό διάλυμα σε διάφορες θερμοκρασίες και συνθήκες. Παρατηρήθηκε κρυστάλλωση του επιθυμητού τύπου ζεόλιθου σε κάθε μία από τις περιπτώσεις που εξετάστηκαν, ενώ το ποσοστό της διάλυσης του χριστοβαλίτη βρέθηκε ότι είχε την σημαντικότερη επίδραση στην απόδοση της διεργασίας και την καθαρότητα του προϊόντος. Ταυτόχρονα διαπιστώθηκε ότι το ποσοστό της διάλυσης του χριστοβαλίτη εξαρτάται κυρίως από την αναλογία μαζών RHA/NaOH και βρέθηκαν οι κατάλληλες τιμές. Καθώς το μεγαλύτερο ποσοστό διαλυμένου χριστοβαλίτη παρατηρήθηκε στην περίπτωση της σύνθεσης του ζεόλιθου LTA, η οποία επιπλέον δεν χρειάζεται οργανικό παράγοντα δομής ούτε υψηλές θερμοκρασίες, επιλέχθηκε να χρησιμοποιηθεί για την μελέτη και την βελτιστοποίηση της διεργασίας. Συγκεκριμένα, εξετάστηκαν διαφορετικές μέθοδοι επεξεργασίας της ΤΦΡ με καυστικό νάτριο, σε μεγάλο θερμοκρασιακό και χρονικό εύρος, ώστε να μελετηθεί η κινητική της διάλυσης του χριστοβαλίτη και να βρεθεί η ενέργεια ενεργοποίησης της. Στη συνέχεια μελετήθηκε η επίδραση της θερμοκρασίας και της διάρκειας στην κρυστάλλωση του ζεόλιθου LTA ώστε να μελετηθεί η κινητική της αντίδρασης και να βρεθεί η ενέργεια ενεργοποίησης της καθώς και οι βέλτιστες συνθήκες απόδοσης της διεργασίας και καθαρότητας του τελικού προϊόντος. Τέλος, εξετάστηκε η επίδραση δύο σημαντικών παραμέτρων, της θερμοκρασίας σύνθεσης και της ταχύτητας ανάδευσης στην ποιότητα του τελικού προϊόντος και βρέθηκαν οι βέλτιστες τιμές τους. Τα αποτελέσματα και τα συμπεράσματα από την παρούσα εργασία, έχουν κατατεθεί στον Οργανισμό Βιομηχανικής Ιδιοκτησίας (Ο.Β.Ι.), για την χορήγηση Διπλώματος Ευρεσιτεχνίας (Δ.Ε.), με αριθμό αίτησης: 20120100391. / Rice husk ash (RHA) is one of the major agricultural wastes and results from the combustion of rice husk (RH) at rice in milling facilities for energy production or waste volumes reduction. Rice husk ash is about 18-20% of the cortex of the rice, which is approximately 20% of raw rice and is usually in its crystalline form. As the global volume of annual production in rice and hence rice husk ash is increasing, raising environmental and economic issues, finding an efficient and ecological way of RHA exploitation is a major issue. In addition, the high rates of RHA on silica render possible silicon source for many applications, one of which is the synthesis of zeolites. In this study, the use of crystalline RHA in the synthesis of four zeolite types, namely MFI, FAU, BEA and LTA was investigated. For this purpose, the raw material, i.e. RHA, was characterized both in terms of its chemical composition and unburned carbon content as well as its crystalline structure. Afterwards, the combustion conditions of RH which lead to the conversion from the amorphous to the crystalline structure of silica, called cristobalite, were determined. Since this crystalline structure is unsuitable for the production of zeolites, the possibility of solubilizing RHA in aqueous sodium hydroxide solution was investigated, in order to destroy the crystals and receive amorphous silica. For this purpose, the molar ratios of the raw materials which would result in the synthesis of each of the four types of zeolites were selected and RHA was treated with the appropriate amount of sodium hydroxide in aqueous solution at various temperatures and conditions. The crystallization of the desired zeolite type in each of the cases examined was verified, while the rate of dissolution of cristobalite was found to have the most significant effect on the process efficiency and the product purity. Simultaneously, it was found that the rate of dissolution of cristobalite mainly depends on the mass ratio of RHA / NaOH and the most suitable values were determined. As the majority of dissolved cristobalite was observed in the case of LTA synthesis, which moreover does not require organic structure directing agent nor high temperatures, it was chosen to be used for the study of design and optimization process. Specifically, several methods of RHA treatment with sodium hydroxide at high temperature and time range were examined, in order to study the kinetics of dissolution of cristobalite and to find the activation energy. Then, the influence of temperature and duration on the crystallization of LTA was examined in order to study the kinetics of the reaction and to determine the activation energy as well as the optimum conditions of the process in terms of efficiency and final product purity. Finally, the effect of two important parameters, the temperature of the synthesis and the stirring speed, on the final product quality was investigated and the optimal values were found. The results and the conclusions of this study, have been submitted to the Hellenic Industrial Property Organization for the grant of Patent with application number: 20120100391.

Na primeira etapa deste trabalho foi avaliada a potencialidade do uso da cinza de casca de arroz como carga em polipropileno (PP) comparando-a com o talco que é a carga mineral mais utilizada em polímeros. Esta comparação foi feita utilizando os compósitos formados por polipropileno com 20% da cinza de casca de arroz assim como, os formados por polipropileno com 20% de talco, determinando as suas propriedades. Apesar das propriedades do compósito de PP com a carga de 20% de cinza de casca de arroz apresentarem resultados inferiores em relação àqueles quando se utilizou o talco como carga, pode-se dizer que a cinza de casca de arroz pode ser usada como carga para outros usos menos nobres do PP. Desta forma se está dando um destino para esse resíduo que hoje é descartado no meio ambiente contribuindo assim, para a preservação do mesmo, além de reduzir o custo do produto. Este trabalho também teve como objetivo estudar o efeito da radiação ionizante nas propriedades destes compósitos de PP com 20% de cinza de casca de arroz. Utilizou-se o agente de acoplagem, anidrido maleico, para verificar se houve melhora na homogeneização das amostras. Em virtude do PP ser um polímero semicristalino, quando exposto ao processo de irradiação, tem sua morfologia modificada devido aos mecanismos de cisão das cadeias poliméricas. Este fato é atribuído aos mecanismos de cisão das cadeias poliméricas, que está de acordo com a literatura. / In the first step of this work, it was evaluated the possibility of using rice husk ash as a filler in polypropylene (PP) making a comparison with talc which is the most used mineral filler in polymers. This comparison was made by using polypropylene with 20% rice husk ash as well as polypropylene with 20% talc measuring their properties. Despite the properties of the PP with 20% rice husk ash decreased compared with the composite of polypropylene with 20% talc it can be said that the rice husk ash can be used as filler for or other utilization less noble of PP . This way it is being given a destination for this residue that it is disposable in the environment contributing to its preservation, moreover reducing the product cost. This work had also as an aim to study the ionizing radiation effect in the properties of these composites. It was used the coupling agent, maleic anhydride , to verify a best sample homogenization. According to the results it can be said that PP is a semicrystalline polymer, and so it has its morphology modified when exposed to the irradiation process. This fact is due to the scission mechanisms of the polymeric chains which it is in compliance to the literature.

Apesar do avanço tecnológico crescente na construção civil, a falta de durabilidade das estruturas de concreto, tanto em edificações como pavimentação, tem sido constatada com acentuada assiduidade e proporção. O compósito cimentício de elevada deformação, também conhecido como Engineered Cementitious Composites (ECC), foi difundido a partir do conceito de concretos de alto desempenho reforçado com fibras, visando suprir o comportamento frágil do concreto convencional e problemas relacionados à falta de durabilidade gerada, principalmente, devido à propagação de fissuras. Neste contexto, o Laboratório de Ensaio de Modelos Estruturais (LEME) da Universidade Federal do Rio Grande do Sul (UFRGS) consolidou, nos últimos cinco anos, um grupo de pesquisa voltado ao estudo do ECC aliado a utilização de materiais nacionais. A concepção tem sido baseada na aplicação de materiais que proporcionem custos mais baixos e fomentem questões de sustentabilidade ambiental. Assim, foram incorporados ao material, fibra de polipropileno (2% em volume) e substituição parcial do cimento por 30% (em volume) de cinza de casca de arroz residual. O presente trabalho visa analisar questões de durabilidade destes compósitos (com e sem a incorporação de cinza), e compará-los a concretos convencionais, através de ensaios relacionados ao estudo da estrutura de poros (absortividade, absorção e índice de vazios, absorção e água por capilaridade, absorção de água pelo método do cachimbo e microscopia eletrônica de varredura), penetração e difusão de íons cloretos, retração livre e restringida, e, por fim, resistência à abrasão. Os resultados obtidos indicam que a incorporação de cinza de casca de arroz melhorou significativamente as propriedades do compósito relacionadas à conexão e solução dos poros, dificultando a passagem de cloretos, além de apresentar resistência à abrasão semelhante ao compósito de referência. Sua desvantagem está relacionada às maiores aberturas de fissuras ocasionadas devido à retração restringida. Entretanto, o trabalho evidencia a viabilidade e vantagem do uso de cinza de casca de arroz na produção do compósito, em termos de durabilidade. / Despite the increasing technological advances in construction, the lack of concrete structures durability, both in buildings and pavement, have been found with severe attendance and proportion. The high strain cementitious composite, also known as Engineered Cementitious Composites (ECC), was widespread from the concept of high performance fiber reinforced concrete, in order to supply the fragile behavior of conventional concrete and problems related to lack of durability generated mainly due to crack propagation. In this context, the Laboratório de Ensaios e Modelos Estruturais (LEME) of the Federal University of Rio Grande do Sul (UFRGS) consolidated over the last five years, a research group focused on the ECC study allied with the use of national materials. The design has been based on the application materials that provide lower costs and promote environmental sustainability issues. Thus, they were incorporated into the material polypropylene fibers (2% by volume) and partial cement replacement of 30% (by volume) of residual rice husk ash. This study aims to examine durability issues of these composites (with and without rice husk ash), and compare them to conventional concretes, through tests related to the study of pore structure (absorptivity, absorption and void ratio, water absorption by capillarity, water absorption by the pipe method and scanning electron microscopy), penetration and diffusion of chloride ions, free and restrained shrinkage, and, finally, abrasion resistance. The results indicate that the incorporation of rice husk ash significantly improved material properties related to connection and pores solution, hindering the chloride ingress, and presents abrasion resistance similar to the reference composite. Its disadvantage is related to the larger cracks due to restrained shrinkage. However, the work demonstrates the viability and advantage of use rice husk ash in the composite production in terms of durability.

A pesquisa relatada nesta dissertação teve por objetivo analisar a viabilidade técnica de estabilizar-se um solo sedimentar arenoso do Uruguai com cinza de casca de arroz (CCA) e cal. O solo utilizado apresenta baixo poder suporte, sendo pouco adequado para camadas de sub-base e base de pavimento rodoviário. Também não é adequado para ser estabilizado com cal e sua estabilização com cimento é muito custosa. Dois tipos básicos de CCA foram utilizados: uma cinza residual do processo de queima de casca de arroz em um forno sem controle de temperatura, e cinzas produzidas em laboratório por incineração de casca de arroz a diferentes temperaturas controladas. Foram realizados ensaios de difratogramas de raios-X, compactação, capacidade de suporte (ISC), compressão simples, tração por compressão diametral e durabilidade do solo, das CCA e das misturas solo-CCA-cal. Determinaram-se as influências do tempo de cura, dos teores de CCA e cal e dos tipos de CCA nos parâmetros de compactação, no ISC, no comportamento tensão-deformação e nas resistências à compressão simples e à tração por compressão diametral. Analisaram-se os efeitos da demora entre mistura e compactação no comportamento tensão-deformação e na resistência à compressão simples nas misturas com CCA residual e cal, além da sua durabilidade a ciclos de molhagem e secagem. As CCA produzidas a temperatura controlada entre 650°C e 800°C mostraram uma maior atividade pozolânica devido a sua estrutura amorfa. Os valores máximos de módulo de deformabilidade e resistência à compressão simples foram obtidos para as misturas com CCA a temperatura controlada. As misturas solo- CCA residual-cal desenvolveram resistência à tração demonstrando a ocorrência de reações pozolânicas. A estabilização do solo sedimentar arenoso com CCA e cal mostrou-se eficaz, permitindo o uso destes materiais em camadas de sub-base de pavimentos. / This MSc thesis was carried out with the purpose of analysing the technical feasibility of stabilizing a Uruguayan sandy soil with rice husk ash (RHA) and lime. The soil utilized present low bearing capacity and is not suitable for road pavement bases and sub-bases. It does not react to lime by itself and its stabilization with Portland cement is prohibitively expensive. Two kinds of RHA were used: a residual ash produced in the process of incinerating rice husk in an oven without temperature control, and ashes produced in laboratory by incineration of rice husk at different controlled temperatures. X-ray diffraction, compaction and bearing capacity (CBR), unconfined compression, split tensile and durability tests were carried out in the soil and in RHA samples and also in soil-RHA- lime mixtures. The influence of curing time, RHA and lime contents and RHA types in compaction parameters, CBR, strain-stress behaviour and unconfined compressive and split tensile strength were evaluated. The effects of the compaction delay on the stress-strain behaviour and the unconfined compression strength of the mixtures with residual RHA and lime were analysed. In order to investigate the mixtures durability, compacted specimens were submitted to wetting and drying cycles. Due to this amorphous structure, the RHA produced at controlled temperatures (650°C to 800°C) showed to be a more reactive concerning pozzolanic activity. The highest strain modulus and unconfined compression strength values were obtained for the mixtures with controlled temperature RHA. The soil-residual RHA-lime mixtures also developed tensile strength proving that pozzolanic took place. The stabilization of the sandy sedimentary soil with RHA and lime proved to be efficient, allowing the use of these materials in pavement sub-base layers.

O compósito cimentício de elevada capacidade de deformação é um tipo especial de compósito cimentício de alto desempenho reforçado com fibras, cuja principal característica é a alta ductilidade, devido à capacidade de gerar fissuração múltipla quando em carregamento. Este compósito também é conhecido como Engineered Cementitious Composite (ECC), desenvolvido pelo Pesquisador Professor Victor Li na Universidade de Michigan, nos Estados Unidos. Nos últimos cinco anos, o Laboratório de Ensaios e Modelos Estruturais (LEME) vem desenvolvendo uma linha de pesquisa com o objetivo de adaptar o ECC com materiais locais. Neste intuito, fibras de polipropileno têm sido utilizadas em conjunto com cinza da casca de arroz visando o desenvolvimento de misturas mais viáveis economicamente e mais ambientalmente sustentáveis. Este estudo teve como finalidade avaliar a possibilidade da utilização da cinza de casca de arroz residual (moída em laboratório por 1, 2, 4, 6 e 8 horas) como material pozolânico para substituição parcial de cimento. A caracterização da cinza foi realizada por meio dos ensaios de difração de raio-x, fluorescência de raio-x, perda ao fogo, índice de desempenho, massa especifica e distribuição granulométrica. Este estudo caracterizou compósitos cimentícios de elevada capacidade de deformação contendo 10%, 20% e 30% (em volume) de substituição de cimento por cinza de casca de arroz residual, analisando o comportamento mecânico quanto à tração direta e flexão a quatro pontos. Na busca de um indicativo de durabilidade foram avaliados a absorção e índice de vazios destes compósitos. Além disso, foi realizada a análise da curva de liberação de calor de hidratação para verificar o efeito retardador que a cinza de casca de arroz possa gerar no compósito. E como possível utilização deste compósito como material de reparo, foi analisada a aderência pelo método de cisalhamento oblíquo e pelo método de arrancamento e avaliada a reflexão de fissuras juntamente com a realização de microscopia eletrônica de varredura destes compósitos. Os resultados obtidos mostraram-se satisfatórios para os compósitos com 30% de cinza de casca de arroz moída por 8 e 4 horas, apresentando bons resultados quanto à ductilidade e resistência à propagação de fissuras. / The high strain cementitious composite is a special type of fiber reinforced high performance cementitious composite which main characteristic is the high ductility achieved through the ability to generate multiple cracking under loading. This composite is also known as Engineered Cementitious Composites (ECC), which was first developed by Professor Victor Li at the University of Michigan, in the United States. Over the last five years, the Laboratory of Testings and Structural Models (LEME) of UFRGS has developed a research area aiming to adapt ECC with local materials. In this context, polypropylene fibers were used to substitute PVA fibers and rice husk ash was used to partially replace cement, aiming to develop more cost attractive and greener mixtures. This study analyzed the use of non-processed rice husk ash (grinded in laboratory for 1, 2, 4, 6 and 8 hours) as a pozzolanic material by means of x-ray diffraction tests, x-ray fluorescence, fire loss, performance index, specific mass and particle size distribution. This study characterized, in terms of mechanical behavior, the high strain cementitious composites with 10%, 20% and 30% (by volume) of non-processed rice husk ash as cement replacement. The experimental tests were carried out in terms of direct tensile and four points bending tests. Aiming to obtain a first indication of durability, absorption and void rate tests were performed. Other tests were performed to obtain the hydration heat curve aiming to determine a possible retarding effect that the rice husk ash may cause to the composite. Finally, in order to analyze the use of the composite as a reinforcement material, tests were carried out to obtain the bond behavior in terms of oblique shear and pullout methods. The reflection of cracks was also evaluated along with scanning electron microscopy of the composites. The results were satisfactory for composites with 30% of rice husk ashes grinded for 8 and 4 hours, presenting good results in terms of ductility and resistance to crack propagation.