Academic literature on the topic 'Rice Husk Ash and SCM'

This document studies the stabilization of the soil used as a subgrade, by adding locally available materials such as rice husk ash (RHA) and sugarcane bagasse ash (SCBA). These aggregates were added to the soil in substitution by weight between 5%, 7.5% and 10%. By adding these, the expansiveness is reduced while the maximum dry density increases, in addition the tendency of CBR is increasing and then tends to decrease proportionally to the addition of the aforementioned aggregates. This indicates a peak in CBR and expandability. The best result obtained from CBR was 33.75% with the 5% replacement mixtures.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Os problemas à saúde acarretados pela exposição às fibras minerais do amianto (asbesto) têm motivado esforços para a substituição destas fibras nos diversos componentes que as empregam como matéria prima. Devido às propriedades físicas e mecânicas e estabilidade química do amianto, bem como sua afinidade natural com a matriz cimentícia, o cimento- amianto é um compósito com excepcionais características de resistência e durabilidade a um custo relativamente baixo. Tais características fazem da busca por um reforço alternativo ao asbesto um desafio, mobilizando indústria e pesquisadores desde a década de 70. Neste contexto, considerando sua disponibilidade e características mecânicas, as fibras celulósicas se mostram como alternativa viável, tendo sido empregadas industrialmente como reforço em fibrocimentos há mais de duas décadas. Entretanto, mesmo com a industrialização, alguns aspectos de seu comportamento, principalmente aqueles relacionados à durabilidade, são ainda foco de intensos esforços de pesquisa (no Brasil, o estudo do emprego de fibras celulósicas como alternativa ao amianto teve início em 79, com os trabalhos pioneiros realizados na PUC-Rio). Considerando os principais mecanismos causadores de degradação nos fibrocimentos, todos eles relacionados ao transporte de fluidos pela rede porosa do material, tem-se que o principal método empregado para melhoria nas características de durabilidade é a substituição parcial do cimento por aditivos com alto teor de sílica amorfa finamente moídos. As melhores características assim obtidas decorrem de modificações na estrutura da matriz e, principalmente, da interface. A casca de arroz, é um resíduo agrícola produzido em grande quantidade no Brasil. Quando não empregada como combustível no próprio eneficiamento do arroz ou em outras atividades rurais, a casca de arroz é disposta sem qualquer controle, apresentando-se assim como um problema ambiental. Entretanto, se queimada em condições controladas, a casca de arroz resulta em cinza, CCA, com alto teor de sílica (80- 90 por cento) altamente amorfa, apresentando boa reatividade com o cimento. Portanto, a CCA foi empregada neste trabalho como material de substituição parcial do cimento em compósitos reforçados por polpas de bambu, buscando com isso melhorar as características relacionadas à durabilidade destes fibrocimentos. Foi observado que o emprego de até 30 por cento de CCA com baixo teor de carbono como substituição parcial do cimento resultou em um substancial decréscimo na porosidade da matriz e interface do compósito. Por conseqüência, estes compósitos apresentaram permeabilidade significativamente inferior à daqueles produzidos sem CCA. Com o emprego de CCA com alto teor de carbono (simulando a cinza obtida de queima não controlada, como a realizada no beneficiamento do arroz) é possível obter resultados semelhantes, uma vez que o compósito seja submetido à cura acelerada em autoclave. Neste caso, devem ser empregadas taxas ainda maiores de substituição parcial do cimento por CCA, com os melhores resultados observados em compósitos cujas matrizes compunham-se por 50 por cento da CCA. Além destes aspectos intimamente ligados aos principais mecanismos de degradação dos compósitos, foi observado que a CCA também favorece a aderência interfacial nos compósitos, acarretando em maior resistência mecânica.<br>Asbestos is regarded as a hazardous material since the 60 s, motivating the efforts for the replacement of these mineral fibres in the vast range of materials in which they are applied as a raw material. Asbestos-cement was the first building material produced in large scale applying natural fibres as reinforcement in cement-based materials. Due the physical and mechanical behaviour and chemical stability of asbestos fibres, as well as their natural affinity with the cementitious matrix, asbestos-cement presents remarkable strength and durability, associated to a relative low cost. Such characteristics make the search for a suitable replacement to asbestos in fibre-cements a challenge, mobilizing industry and researchers since the early 70 s. Considering their availability and mechanical strength, cellulose fibres have proven to be a viable alternative to asbestos, being employed by the industry as reinforcement in fibre-cements for more than two decades. However, in spite of their well established production and commercialization in many parts of the world, some aspects of the cellulose-cement composites behaviour still motivates research efforts, which are mainly focused on durability aspects. The main deterioration mechanisms acting in cellulose-cement composites are all related to fluid transport within the pore network of the composites and the most applied treatment method is the partial replacement of cement by finely ground admixtures with high active silica content. The improvements in the durability aspects of composites are achieved by modifying the characteristics of the matrix and, mainly, the interfacial region. Rice husk is an agricultural residue produced in large scale in Brazil. If not applied as fuel in the rice mills or in others rural activities, the rice husk is disposed without control, resulting in an ecological problem. However, the pyrolysis of rice husk yields ash with high silica content, (80-90 percent). When burned in a proper way, this silica remains amorphous, presenting high reactivity with cement. Due to these characteristics rice husk ash, RHA, is applied in this PUC-Rio - Certificação Digital No 9924941/CA research as the treatment method in cement composites reinforced by bamboo pulp. It was observed that blended cement with up to 30 percent RHA with low carbon content resulted in a significant decrease in the porosity of the matrix and interface of the composite. As a consequence, these blended-cement composites presented water permeability expressively lower than that of the composites produced without RHA. High carbon content RHA was also applied, simulating the use of ash obtained by a non-controlled burning process. Similar results as those observed in composites with low-carbon-content RHA were achieved, once accelerated autoclave curing was applied to the composites. In this case, for better composite properties, higher RHA content must be used, with the best results being observed in composites with 50 percent RHA. Also, besides these aspects closely related to the main deterioration mechanisms of the composites, it was observed that RHA enhances the fiber-matrix interaction in the interface, improving the mechanical behaviour of the composites.

The construction of road works in the world has always been a challenge for engineering, especially in areas where the conditions and types of soil are not adequate for the execution of this type of projects. The present investigation has as main objective to determine the influence that has the rice husk ash (RHA) to stabilize the subgrade layer of a pavement, composed of a low resistance clayey soil. RHA is a waste and pollutant material for the environment; therefore that its use can be considered as an economic and ecological alternative. Thus, several tests were carried out where it proved the value of CBR increased from 4.30% to 20.70%, by adding a 20% RHA dosage, achieving its optimum value to be considered a very good subgrade. In this way, it is possible to affirm that the addition of RHA improves the geotechnical properties of the soil.

The continuous population increase in recent years requires a greater number of households to be built quickly, with good materials and produced under quality standards that guarantee their manufacturing process. The prefabricated concrete, produced and supplied by concrete plants, is poured into the different structural elements, the mezzanine slabs being the most careful surfaces in the appearance of fissures; because being horizontal and having larger dimensions, the dimensional changes in the concrete appear more frequently due to the rapid loss of water from the surface of the concrete before setting; which generates superior stresses to the resistant capacity of the concrete at early ages, which affect the durability and reduce the resistance of the structures, causing greater economic expenses in maintenance and repairs. In the present investigation, 5%, 10% and 15% of rice husk ash was used as a replacement for cement and 900g/m3 of polypropylene fiber; The results indicate that as the percentage of rice husk ash increases, there is a reduction in the slump and the crack fissures, and that the resistance to compression and flexion decreases, with respect to the concrete pattern.

O uso do carvão ativado (CA) no tratamento de águas e efluentes possui importante papel na eliminação de cor, odor, mau gosto e remoção de compostos orgânicos, fenólicos e substâncias que diminuem a qualidade da água e pode ser obtido de diferentes fontes de origem vegetal com alto teor de carbono tais como coco, café, casca de arroz, entre outros. No Brasil são produzidos anualmente cerca de 12 milhões de t/ano de arroz em casca, que quando beneficiados geram aproximadamente 2,4 milhões de t/ano de casca de arroz, a qual tem sido queimada em termoelétricas para a geração de energia elétrica, sobrando como resíduos a cinza da casca de arroz (CCA). Visando a obtenção de um adsorvente através de um resíduo abundante para utilização como filtro de tratamento de água e de efluente, o presente trabalho apresenta um estudo de caracterização do CA produzido a partir do resíduo de cinza da casca do arroz (CACCA) para verificar as condições de utilização do mesmo como filtro de tratamento de água e de efluentes. Para tanto, o CACCA foi caracterizado por: Área Superficial, Fluorescência de Raios X, Difração de Raios X e Microscopia Eletrônica de Varredura, Teor de Cinzas, pH e comparado a cinza de casca de arroz (CCA) e ao produto comercial (COM) atualmente utilizado. Após a constatação de que o mesmo possui características de um CA e similares ao comercial, foram analisadas a sua efetividade em melhorias de propriedades físico-químicas e biológicas (cor aparente, turbidez, pH, DQO, absorção de sódio e coliformes) de quatro amostras selecionadas para verificar os resultados comparados ao produtos comercial, demonstrando a sua eficiência como adsorvente.<br>Urban agglomerations and water consumption have been increased. As a consequence, its necessary to construct structures for capture, transport and storage of water and even develop treatment techniques for the different water sources in order to provide quality water for the population (FUNASA , 2007). However, Brazilian governament doesn t invest enough to supply improvements in basic infrastructure, and that generates deficits in the sanitation sector. According to Brazilian National Sanitation Information System (SNIS, 2013), only 48.6 percent of the population has sewage collection and only 39 percent are treated. 7 percent of the urban population does not have access to the supply network of water. These indexes indicate the reality of sanitation in Brazil, but the current numbers of official information systems do not analyze the quality of these water.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 73-76).<br>Cement is a very valuable commodity as it can be used to construct structurally sound buildings and infrastructure. However, in many developing countries cement is expensive due to the unavailability of local resources to produce enough cement in-country to meet the demand for this material, and therefore it has to be imported. In rice-producing countries rice husk ash-a material naturally high in silica-can be used as a supplementary cementitious material and can substitute a portion of Portland cement in concrete without sacrificing the compressive strength. This study investigates the use of Cambodian rice husk ash in 10, 20 and 30% replacements of Portland cement by mass in mortar, without optimization of the ash by controlled burning. Five ashes collected from different sources in Cambodia were assessed for their suitability for use in rural Cambodian construction via compression strength testing of 2" (50 mm) mortar cubes. A 20% replacement of unprocessed Cambodian rice husk ash was deemed appropriate for use in small-scale, rural structural applications. Low-tech methods of grinding the ash were also investigated and were found to drastically increase the compressive strength of RHA-cement mortars in comparison to mortars made with unground RHA.<br>by Dorothy Kamilah Brown.<br>S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 188-195).<br>Cement global production stands at 3 Giga tons making concrete the most consumed structural mateial worldwide. This massively produced material comes with a heavy environmental footprint rendering the cement industry contributing about 5% to global CO₂ emission. Rice Husk Ash (RHA) among many other silicious materials, has the potential to partially replace cement and enhance the properties of the final product. The goal of this thesis is an investigation of the fundamental properties of RHA cement. For a set of RHA cement paste samples, we investigate at the nano-scale the effect of RHA incorporation on chemical and mechanical properties of cement. RHA is found to have high pozzolanic properties through its reaction with portlandite to form different types of calcium silicate hydrate (C-S-H). It is found that C-S-H in RHA cement has lower Ca/Si ratios compared to pure ordinary portland cement (OPC) samples prepared under the same conditions. Incorporation of RHA has minor effect on the mechanical properties of cement paste at the nano scale for low water-to-binder ratios while significant improvement in mechanical properties is found at high water-to-binder ratios. We arrive at these conclusions as a result of a dual chemical-mechanical analysis at the nanoscale in which electron probe microanalysis (EPMA) and nanoindentations are employed.<br>by Muhannad Abuhaikal.<br>S.M.

Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, School of Engineering, System Design and Management Program, Engineering and Management Program, 2014.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 87-[90]).<br>As the world's second largest rice grower, India can generate up to 5 million MT of ash from burning rice husk for fuel. The material that remains after combustion, known as Rice Husk Ash (RHA), is high in silica content, provides good insulation, and has a large surface areas for chemical reactions. These characteristics of RHA allow it to be used in a variety of applications such as insulation in steelmaking, substitute for raw material in the cement and brickmaking industry, water filtration, pest control, and the production of precipitated silica. While RHA is currently used in the steel industry in India, and to a smaller degree, in the cement industry, there are many waste-to-wealth opportunities to use RHA which are currently not being leveraged. This results in a loss of land for RHA disposal and more importantly, wasted opportunities to extract value from RHA. There has been a large amount of research conducted on using RHA. The publications around this research have typically been broad and qualitative, describing the potential applications of RHA on a high level, or focused on technical details pertaining to a specific set up using RHA. While the information currently available is extremely important, it is not easily leveraged by entrepreneurs who would be interested in increasing their use of RHA. There seems to be a lack of studies which compare the various applications for RHA qualitatively. The purpose of this thesis is to help current and potential RHA entrepreneurs to apply available research in making decisions about how to make use of RHA, by creating a framework to assess the applications of RHA economically. While this paper is focused on RHA, it is intended that the framework can be used in assessing opportunities to use other biomass ash material.<br>by Lesley Yu.<br>S.M. in Engineering and Management

There are many studies about how the addition of lime and rice husk ash (RHA) gives the soil a better mechanical behavior, particularly on clayey soils, where usually fine particles reach more than 75%. However, the soils with a small presence of fine particles (59-60%) do not have much research. This analysis evaluates the influence that RHA has on this kind of soil stabilized with 3% of lime. After the initial mix of soil-lime, CBR increased 11.2 times its initial value; within the addition of the ash, the CBR averaged between 45-50% up until 28% of RHA was added, where the results decreased considerably. Soil workability improved and the specimens with more ash resulted in a more granular material, with a group index value 0 following the AASHTO standards. The greatest CBR record was obtained with the specimen of 16% RHA, 3% lime and soil, reaching a 51.3% CBR, 1.58g/cm3 of MDD and 16.5% of OMC. Yet, it only showed a 1.55% more resistance than the lime-soil specimen. The CBR with more presence of RHA tends to decrease its value, therefore for silica-rich clayey soils, the addition of lime by itself should be enough for an adequate performance.