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Master's Dissertation
DOI
https://doi.org/10.11606/D.74.2021.tde-15102021-122328
Document
Author
Full name
Alda Renata dos Santos Martinho Capelo
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Pirassununga, 2021
Supervisor
Committee
Rossignolo, João Adriano (President)
Akasaki, Jorge Luís
Santos, Sérgio Francisco dos
Title in Portuguese
Cimento à base de óxido de magnésio e cinza da casca do arroz
Keywords in Portuguese
Alcalinidade
CCA
Cimento magnesiano
Pozolana
Sílica reativa
Abstract in Portuguese
Em certas aplicações técnicas, as fibras celulósicas são usadas em matrizes cimentícias para a produção de compósitos. No entanto, sua utilização é limitada devido à precoce degradação causada pela elevada alcalinidade do meio, quando a matriz é a base de cimento Portland. Deste modo, a presente pesquisa avaliou como solução alternativa a reação da sílica originária da cinza da casca do arroz (CCA) em presença do óxido de magnésio (MgO), para a produção de cimento magnesiano de reduzida alcalinidade. Foram produzidas cinzas com diferentes tratamentos térmicos, diferindo nas temperaturas de 500, 550, 600 e 650 °C e submetidas a uma avaliação inicial da pozolanicidade por meio da condutividade elétrica. Foram preparadas pastas com formulação 50% MgO-50% CCA, expostas a cura térmica em diferentes idades, sobre as quais se realizaram as análises de difratometria de raios X (DRX), termogravimetria (TG) e avaliação do pH. Com a cinza de maior reatividade foram produzidas pastas em 3 formulações (60% MgO-40% CCA, 70% MgO-30% CCA e 80% MgO-20% CCA). Por fim, se moldaram corpos de prova cilíndricos e submetidos ao ensaio de compressão axial. A cinza produzida a 500 oC foi a que se mostrou mais reativa, com condutividade elétrica final de 800 µS/cm e perda de massa residual de 82,11%, na idade inicial, o que se refletiu na maior formação do composto MSH pela presença da região mais amorfa e menor pH, (entre 9,62 e 9,94) ao longo do tempo. Os resultados do ensaio de compressão axial mostram de modo geral que não houve diferença estatística na resistência mecânica entre a CCA 500 e SA. Com valores de 19,02 15,90 MPa respetivamente, para a formulação 50% MgO-50% CCA.
Title in English
Cement based on magnesium oxide and rice husk ash
Keywords in English
Alkalinity
CCA
Magnesian cement
Pozzolana
Reactive silica
Abstract in English
In certain technical applications, cellulosic fibers are used in cementitious matrices to produce composites. However, its use is limited due to the early degradation caused by the high alkalinity of the medium, when the matrix is based on Portland cement. Thus, the present research evaluated as an alternative solution the reaction of silica originating from rice husk ash (CCA) in the presence of magnesium oxide (MgO), for the production of low alkalinity magnesian cement. Ashes were produced with different heat treatments, differing at temperatures of 500, 550, 600 and 650 °C and submitted to an initial evaluation of pozzolanicity by means of electrical conductivity. Pastes were prepared with a 50% MgO-50% CCA formulation, exposed to thermal curing at different ages, on which X-ray diffractometry (DRX), thermogravimetry (TG) and pH evaluation were analyzed. With the highest reactivity ash, pastes were produced in 3 formulations (60% MgO-40% CCA, 70% MgO-30% CCA and 80% MgO-20% CCA). Finally, cylindrical specimens were molded and submitted to the axial compression test. Ash produced at 500 oC was the most reactive, with final electrical conductivity of 800 µS/cm and loss of residual mass of 82.11% at initial age, which was reflected in the greater formation of the MSH compound by the presence of the more amorphous region and lower pH, (between 9.62 and 9.94) over time. The results of the axial compression test show, in general, that there was no statistical difference in mechanical strength between CCA 500 and SA. With values of 19.02 to 15.90 MPa, respectively, for the 50% MgO-50% CCA formulation.
 
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ME10650064COR.pdf (2.61 Mbytes)
Publishing Date
2021-10-15
 
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