Estudo de propriedades de pastas de cimento Portland modificadas com nanopartículas de dióxido de titânio - TiO2
Data
2022-09-16
Autores
Ribeiro, Paulo Henrique [UNIFESP]
Orientadores
Santos, Elias Barros [UNIFESP]
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Esta dissertação é referente à análise da influência da adição de nanopartículas de TiO2 (TiO2NPs) em pastas de cimento Portland. Com isso, foram preparadas três pastas de cimento Portland com diferentes concentrações de TiO2NPs em relação a massa de cimento, sendo 0% (CP0), 0,1% (CP01) e 0,5% (CP05). Nesse trabalho foram utilizadas nanopartículas comerciais e o cimento Portland CP II-E. Com o objetivo de favorecer apenas TiO2 na fase anatásio, as nanopartículas foram tratadas termicamente a 400°C durante 4h em forno mufla. As TiO2NPs foram caracterizadas por espectroscopia UV-Vis, espectroscopia Raman e microscopia eletrônica de transmissão. Sequencialmente, as pastas de cimento aditivadas com TiO2NPs foram caracterizadas por microscopia eletrônica de varredura com espectroscopia de energia dispersiva (MEV/EDS) e por espectroscopia Raman. Adicionalmente, as amostras passaram pelo ensaio de resistência à compressão axial. Posteriormente, a porosidade das amostras foram analisadas por B.E.T e, por fim, foram feitos testes de resistência à penetração de íons cloretos, de ataque ácido e alcalino. A caracterização das nanopartículas por espectroscopia Raman evidenciou que o tratamento térmico foi efetivo em garantir apenas a fase cristalina do TiO2 anatásio. Em adição, a microscopia eletrônica de transmissão apresentou uma distribuição média de tamanho das TiO2NPs de 32,5 nm (média ± 8,3 nm). O ensaio de resistência à compressão axial não evidenciou um aumento da resistência das amostras e nem decréscimo. A análise de B.E.T apresentou os mesmos valores de porosidade nas três diferentes amostras, mostrando que as nanopartículas não influenciaram na porosidade das diferentes pastas de cimento Portland. Pela imagem de MEV, é possível observar a presença de poros de diferentes dimensões em todas as amostras. A partir da análise de EDS é possível identificar a presença de Ti nas amostras aditivadas. Ainda, em comparação a amostra CP01, é possível observar a formação de pequenos aglomerados de TiO2NPs ao longo da região analisada do CP05. A partir do teste de penetração de cloretos foi possível observar uma
redução da penetração de cloretos nas amostras em função do aumento da porcentagem de TiO2, de 0% a 0,5%, mostrando que as TiO2NPs estão conferindo uma proteção superficial as amostras. Semelhantemente, pelo teste de ataque ácido, a mesma proteção superficial foi percebida conforme o aumento da concentração de TiO2 nas amostras, sendo o ataque ácido foi menos agressivo no CP05 em relação ao CP0. Finalmente, a aplicação de TiO2NPs em pastas de cimento Portland apresentou resultados satisfatórios em relação à propriedade de superfície, resultando na proteção das amostras contra ataque ácido e contra a penetração de íons cloretos. Esses resultados são um excelente campo a ser explorado, uma vez que as pesquisas se concentram em analisar apenas as propriedades mecânica e microestrutural desses materiais.
This dissertation is related to the analysis of the influence of the addition of TiO2 nanoparticles (TiO2NPs) in Portland cement pastes. With this, three Portland cement pastes were prepared with different concentrations of TiO2NPs in relation to the cement mass, 0% (CP0), 0.1% (CP01), and 0.5% (CP05). In this work, commercial nanoparticles and Portland cement CP II-E were used. To favor only TiO2 in the anatase phase, the nanoparticles were heat treated at 400°C for 4h in a muffle furnace. TiO2NPs were characterized by UV-Vis spectroscopy, Raman spectroscopy, and transmission electron microscopy. Sequentially, cement pastes added with TiO2NPs were characterized by scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and Raman spectroscopy. Additionally, the samples passed the axial compressive strength test. Subsequently, the porosity of the samples was analyzed by B.E.T, and, finally, tests of resistance to the penetration of chloride ions, acid, and alkali attack were carried out. The characterization of the nanoparticles by Raman spectroscopy showed that the heat treatment was effective in guaranteeing only the crystalline phase of anatase TiO2. In addition, transmission electron microscopy showed a mean size distribution of TiO2NPs of 32.5 nm (mean ± 8.3 nm). The axial compressive strength test did not show an increase in the strength of the samples or a decrease. The B.E.T analysis showed the same porosity values in the three different samples, showing that the nanoparticles did not influence the porosity of the different Portland cement pastes. Analyzing the SEM image, it is possible to observe the presence of pores of different dimensions in all samples. From the EDS analysis, it is possible to identify the presence of Ti in the modified samples. Also, in comparison to the CP01 sample, it is possible to observe the formation of small clusters of TiO2NPs along the analyzed region of CP05. From the chloride penetration test, it was possible to observe a reduction in the chloride penetration in the samples due to the increase in the percentage of TiO2, from 0% to 0.5%, showing that the TiO2NPs are providing surface protection to the samples. Similarly, by the acid etch test, the same surface protection was perceived as the TiO2 concentration increased in the samples, with the acid etch being less aggressive in CP05 compared to CP0. Finally, the application of TiO2NPs in Portland cement pastes showed satisfactory results in relation to the surface property, resulting in the protection of the samples against acid attack and against the penetration of chloride ions. These results are an excellent field to be explored since research focuses on analyzing only the mechanical properties and microstructure of these materials.
This dissertation is related to the analysis of the influence of the addition of TiO2 nanoparticles (TiO2NPs) in Portland cement pastes. With this, three Portland cement pastes were prepared with different concentrations of TiO2NPs in relation to the cement mass, 0% (CP0), 0.1% (CP01), and 0.5% (CP05). In this work, commercial nanoparticles and Portland cement CP II-E were used. To favor only TiO2 in the anatase phase, the nanoparticles were heat treated at 400°C for 4h in a muffle furnace. TiO2NPs were characterized by UV-Vis spectroscopy, Raman spectroscopy, and transmission electron microscopy. Sequentially, cement pastes added with TiO2NPs were characterized by scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) and Raman spectroscopy. Additionally, the samples passed the axial compressive strength test. Subsequently, the porosity of the samples was analyzed by B.E.T, and, finally, tests of resistance to the penetration of chloride ions, acid, and alkali attack were carried out. The characterization of the nanoparticles by Raman spectroscopy showed that the heat treatment was effective in guaranteeing only the crystalline phase of anatase TiO2. In addition, transmission electron microscopy showed a mean size distribution of TiO2NPs of 32.5 nm (mean ± 8.3 nm). The axial compressive strength test did not show an increase in the strength of the samples or a decrease. The B.E.T analysis showed the same porosity values in the three different samples, showing that the nanoparticles did not influence the porosity of the different Portland cement pastes. Analyzing the SEM image, it is possible to observe the presence of pores of different dimensions in all samples. From the EDS analysis, it is possible to identify the presence of Ti in the modified samples. Also, in comparison to the CP01 sample, it is possible to observe the formation of small clusters of TiO2NPs along the analyzed region of CP05. From the chloride penetration test, it was possible to observe a reduction in the chloride penetration in the samples due to the increase in the percentage of TiO2, from 0% to 0.5%, showing that the TiO2NPs are providing surface protection to the samples. Similarly, by the acid etch test, the same surface protection was perceived as the TiO2 concentration increased in the samples, with the acid etch being less aggressive in CP05 compared to CP0. Finally, the application of TiO2NPs in Portland cement pastes showed satisfactory results in relation to the surface property, resulting in the protection of the samples against acid attack and against the penetration of chloride ions. These results are an excellent field to be explored since research focuses on analyzing only the mechanical properties and microstructure of these materials.