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Caracterização e desenvolvimento de argamassas de revestimento para fortalezas em taipa militar no Alentejo
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O trabalho realizado teve como objetivo a caracterização de amostras de argamassa de
revestimento pertencentes à fortaleza de Juromenha, importante estrutura em taipa militar do
Alentejo (Portugal), e a proposta e estudo de potenciais argamassas de substituição.
Para tal, foi desenvolvido um amplo programa experimental, que começou com a recolha das
amostras de argamassa de vários locais da fortaleza, as quais foram depois limpas e
devidamente catalogadas. Posteriormente, procedeu-se à sua caracterização através da
realização de ensaios colorimétricos e físicos (absorção de água por capilaridade, porosidade
aberta, massas volúmicas real e aparente, absorção de água às 48 horas) e foi também avaliada
a sua composição através dos ensaios de dissolução ácida para obtenção do traço aproximado
e peneiração do resíduo insolúvel. Com base nos resultados anteriores, foram definidas e
estudadas argamassas de substituição, sujeitas também elas aos mesmos ensaios colorimétricos
e físicos, bem como a ensaios de caracterização mecânica (resistência à tração por flexão e
resistência à compressão).
A caracterização efetuada às amostras de argamassa antiga permitiu verificar que estas eram
constituídas por cal aérea e areia siliciosa, com traços aproximados em massa que variavam
entre 1:2 e 1:4 (cal:agregado), sendo os traços mais ricos em agregado correspondentes às
argamassas mais antigas. Foram então definidas e estudadas duas argamassas de substituição,
produzidas com materiais semelhantes aos originais e com traços iguais aos extremos do
intervalo de traços obtido anteriormente (1:2 e 1:4). Os resultados da sua caracterização
mostraram que estas apresentavam características físicas, em geral, dentro da gama de valores
da apresentada pelas amostras antigas. Contudo, no que diz respeito à resistência mecânica, as
argamassas de substituição poderão ser demasiado resistentes, especialmente a argamassa 1:2.
Também a cor das argamassas de substituição revelou ser mais clara e menos amarelada do que
a das argamassas antigas.
The aim of the work carried out was the characterization of samples of rendering mortars belonging to the fortress of Juromenha, an important structure in military rammed-earth in Alentejo (Portugal), and the proposal and study of potential replacement mortars. To this end, a broad experimental program was developed, which began with the collection of mortar samples from various locations in the fortress, which were then cleaned and catalogued. Subsequently, their characterization was made by carrying out colorimetric and physical tests (water absorption by capillarity, open porosity, real and bulk densities, water absorption at 48 hours), and their composition was evaluated through acid dissolution tests and the sieving of the insoluble residue. Based on these results, replacement mortars were defined and studied, and subjected to the same colorimetric and physical tests, as well asto mechanical tests (flexural tensile strength and compressive strength). The characterization of the old mortar samples from the fortress allowed verifying that they were composed of aerial lime and siliceous sand, with approximate lime:aggregate ratios (by mass) that varied between 1:2 and 1:4. The richest ratios in aggregate were found to correspond to the older mortars. Two replacement mortars, produced with similar materials and with lime: aggregate ratios equal to the extremes of the range obtained (1:2 and 1:4) were then studied. The results of their characterization showed that these presented physical characteristics, in general, within the range of values presented by the old samples. However, with regard to mechanical strength, replacement mortars may be too resistant, especially the 1:2 mortar. The color of the replacement mortars also turned out to be lighter and less yellowish than that of the old mortars.
The aim of the work carried out was the characterization of samples of rendering mortars belonging to the fortress of Juromenha, an important structure in military rammed-earth in Alentejo (Portugal), and the proposal and study of potential replacement mortars. To this end, a broad experimental program was developed, which began with the collection of mortar samples from various locations in the fortress, which were then cleaned and catalogued. Subsequently, their characterization was made by carrying out colorimetric and physical tests (water absorption by capillarity, open porosity, real and bulk densities, water absorption at 48 hours), and their composition was evaluated through acid dissolution tests and the sieving of the insoluble residue. Based on these results, replacement mortars were defined and studied, and subjected to the same colorimetric and physical tests, as well asto mechanical tests (flexural tensile strength and compressive strength). The characterization of the old mortar samples from the fortress allowed verifying that they were composed of aerial lime and siliceous sand, with approximate lime:aggregate ratios (by mass) that varied between 1:2 and 1:4. The richest ratios in aggregate were found to correspond to the older mortars. Two replacement mortars, produced with similar materials and with lime: aggregate ratios equal to the extremes of the range obtained (1:2 and 1:4) were then studied. The results of their characterization showed that these presented physical characteristics, in general, within the range of values presented by the old samples. However, with regard to mechanical strength, replacement mortars may be too resistant, especially the 1:2 mortar. The color of the replacement mortars also turned out to be lighter and less yellowish than that of the old mortars.
Descrição
Palavras-chave
Argamassas de cal aérea Conservação do património Fortalezas em taipa militar Caracterização física Caracterização mecânica Aerial lime mortars Conservation of the built heritage Military rammed-earth fortresses Physical characterization Mechanical characterization