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Abstract(s)
Com o objectivo de evitar anomalias nas argamassas de revestimento, muitos investigadores têm procurado soluções para que isso não aconteça. Como tal, a adição de fibras acrílicas em argamassas pode ser vista como uma boa solução para que se evite muitas das anomalias que normalmente aparecem em matrizes cimentícias, sobretudo aquelas advindas das deformações nas primeiras idades. Foi com esse intuito que se levou a cabo este trabalho de estudar o desempenho reológico e mecânico de argamassas de revestimento reforçadas com
adição de fibras acrílicas. Um plano factorial experimental 23 foi desenvolvido tendo em conta o comprimento, diâmetro e o volume de fibras como variáveis independentes. Este plano experimental foi realizado a partir de uma matriz cimentícia com traço 1:3 (cimento/areia) e uma relação de 0,5 água/cimento, adicionaram-se diferentes tipos de fibras acrílicas em que se fez variar o comprimento, o diâmetro e o teor de fibras adicionados. Com o intento de ser possível estudar a reologia das argamassas de revestimento, foi ensaiada uma nova matriz cimentícia, com agregados mais finos e com um traço 1:0,5 (cimento/areia) e uma relação água/cimento de 0,4.
O comportamento reológico das argamassas no estado fresco foi avaliado através dos ensaios de espalhamento (Flow Table) e através do reómetro Viskomat NT para determinação dos parâmetros relacionados a tensão de cedência e a viscosidade plástica. Para a avaliação do comportamento mecânico foram realizados ensaios no estado endurecido relativos à resistência à flexão e à compressão, ao módulo de elasticidade dinâmico, à retracção livre, à massa volúmica e à absorção de água por capilaridade.
Como resultados, verificou-se que a adição de fibras acrílicas na matriz cimentícia original influência a reologia das argamassas devido às suas características geométricas, visto que ao serem introduzidas na matriz, modificam fortemente as características da matriz cimentícia
original. Constatou-se assim que a adição de fibras que apresentam uma relação l/d muito
elevada, apresentam uma menor trabalhabilidade. A resistência à flexão é influenciada pelo comprimento e volume das fibras, enquanto a resistência à compressão sofre influência da relação l/d. A absorção de água por capilaridade é sensivelmente influenciada pelo volume de fibras e pela interacção entre o comprimento, o diâmetro e o volume das fibras. Já o módulo de elasticidade dinâmico é mais fortemente influenciado pelo volume de fibras. Com a aplicação do Método dos Planos Experimentais foi possível identificar os factores mais influentes nas propriedades estudadas e elaborar modelos matemáticos de previsão de comportamento da argamassa reforçada com fibras acrílicas.
In order to avoid anomalies in renders mortars, many researchers have studied solutions to prevent them. How one of the proposed solutions is the fibers incorporation in renders mortars this study is developed with the acrylic fibers addition that can be seen as a good solution to avoid the anomalies that typically appear, during early ages, in cementitious matrices. It was with this in mind that this work was carried out observing the rheological and mechanical performance of render mortar reinforced with acrylic fibers. A factorial experimental plan 23 was developed taking into account the length, diameter and fibers volume as independent variables. This experimental plan was done with a cement-based mortar weight proportion 1:3 (cement/sand) with a water/cement ratio 0.5 was prepared with different aspect ratio and volume of acrylic fibers. The follow mortar hardened properties was determined: flexural and compressive strengths, dynamic modulus of elasticity, free mortars shrinkage, capillarity water absorption and the dry bulk density. A mortar weight proportion 1:0.5 (cement/sand) with a water/cement ratio 0.4 was specifically prepared for the mortar rheological study. As result, it was found that the acrylic fibers addition in original cementitious matrix influence the mortar rheology due to their geometric characteristics. Since being introduced in the matrix, the fibers strongly modify the original characteristics of the cementitious matrix. It was found that a high l/d ratio of fibers lead the mortars to present a lower workability. The flexural strength is influenced by the length and volume of fibers, while the compressive strength is influenced by the l/d ratio. Water absorption by capillarity is significantly influenced by the volume of fibers and interaction between length, diameter and fibers volume. The dynamic modulus of elasticity is stronger influenced by the volume of fibers. By applying a Factorial Experimental Plans Method it was possible to identify the most influential factors in the properties studied and elaborate mathematical models to predict the acrylic fibers reinforced mortar behavior.
In order to avoid anomalies in renders mortars, many researchers have studied solutions to prevent them. How one of the proposed solutions is the fibers incorporation in renders mortars this study is developed with the acrylic fibers addition that can be seen as a good solution to avoid the anomalies that typically appear, during early ages, in cementitious matrices. It was with this in mind that this work was carried out observing the rheological and mechanical performance of render mortar reinforced with acrylic fibers. A factorial experimental plan 23 was developed taking into account the length, diameter and fibers volume as independent variables. This experimental plan was done with a cement-based mortar weight proportion 1:3 (cement/sand) with a water/cement ratio 0.5 was prepared with different aspect ratio and volume of acrylic fibers. The follow mortar hardened properties was determined: flexural and compressive strengths, dynamic modulus of elasticity, free mortars shrinkage, capillarity water absorption and the dry bulk density. A mortar weight proportion 1:0.5 (cement/sand) with a water/cement ratio 0.4 was specifically prepared for the mortar rheological study. As result, it was found that the acrylic fibers addition in original cementitious matrix influence the mortar rheology due to their geometric characteristics. Since being introduced in the matrix, the fibers strongly modify the original characteristics of the cementitious matrix. It was found that a high l/d ratio of fibers lead the mortars to present a lower workability. The flexural strength is influenced by the length and volume of fibers, while the compressive strength is influenced by the l/d ratio. Water absorption by capillarity is significantly influenced by the volume of fibers and interaction between length, diameter and fibers volume. The dynamic modulus of elasticity is stronger influenced by the volume of fibers. By applying a Factorial Experimental Plans Method it was possible to identify the most influential factors in the properties studied and elaborate mathematical models to predict the acrylic fibers reinforced mortar behavior.
Description
Keywords
Argamassas de revestimento Argamassas de revestimento - Comportamento mecânico Argamassas de revestimento - Reologia Argamassas de revestimento - Fibras acrílicas Argamassas de revestimento - Retracção Argamassas de revestimento - Ligantes