Desempenho do revestimento de argamassas reforçadas com telas: estudo de fissuração e do comportamento mecânico

Abstract

Resumo A utilização das telas para reforço da camada de revestimento em fachadas tem se tornado uma excelente aliada na prevenção e redução de fissuras, pois podem absorver as tensões que surgem no sistema de revestimento. Esta pesquisa busca avaliar a incidência de fissuras de revestimentos reforçados com telas, submetidos à variação térmica, visando contribuir para o conhecimento do desempenho e comportamento das telas nos revestimentos argamassados. Para tanto, foi avaliada a resistência à tração direta de três telas (uma de polietileno e duas galvanizadas) a serem empregadas como reforço em argamassas analisadas quanto à resistência à compressão, tração, flexão e cisalhamento. Em seguida, foram construídos protótipos de fachadas revestidos com reboco reforçado com tela observando-se o comportamento do sistema após carregamento térmico (38 ºC e 80 ºC) por meio de termografia, mapeamento de fissuras e resistência ao impacto, avaliando-se, ainda, a eficiência de duas metodologias de reparo de fissuração (tela poliéster com massa acrílica e resina epóxi). Os resultados revelaram que a tela galvanizada eletrossoldada apresentou melhor desempenho ao absorver parte das tensões e reduzir as aberturas das fissuras, garantindo ao conjunto melhor resistência à flexão, e ambas as metodologias de reparo analisadas apresentaram desempenho adequado ante a exposição térmica.

Mesh reinforcement in masonry mortar coatings: a systematic literature review

“…The EMS with 1.24 mm wire and 25x25 mm opening presented the highest tensile strength, an order of magnitude higher than the polymer meshes, with reported wire strength between 400 and 600 MPa. The studied WMH presented a sensible gain of strength with smaller mesh openings and wire diameter due to the higher number of wires in a same-size specimen [17,21,27]. AFG meshes were close in strength to EMS, although they had smaller openings.…”

“…The resulting stress state often causes fractures, cracking, and detachments [21]. Reinforcement meshes are applied in various situations, especially corners of openings and transition zones between different materials, acting as distributors of punctual stresses and giving ductility to the coating, reducing the large cracking to smaller, distributed, and sometimes harmless, microcracks [17,27]. Only one study [20] presented an analytical model for the determination of the coating stress state, considering the occurrence of cracking in the structure under the coating.…”

“…The mortars utilized had flexural strength varying from 0.61 to 2.79 MPa, with a reported elastic modulus of 7.58 GPa [20,21]. Mortar strength seems to significantly affect reinforcement behavior [27]. Some authors [21] suggest that the closer the elastic moduli between mesh and mortar, the better the interaction between both.…”

“…Only two documents tested with a smaller thickness, but the difference between materials and test conditions is such that any comparison is hindered. The major mesh position was in 2/3 of the layer from the base, followed by the middle of the layer [20,21,27]. Some authors [17] found more contribution for flexural strength using the mesh in the external part of the layer, while others [15] found no significant variation along the height.…”

“…There is also an absence of guidelines and specifications for the design and execution of such procedures, resulting in high variability in real applications and endorsing the need for in-depth studies about efficiency, methodology, and performance [20,22]. Also, the development of analytical and simulation models for reinforcement design is hampered due to the intrinsic heterogeneity of such materials and the numerous amount of variables that affect its behavior, such as mesh's material, wire diameter, durability, grid format and spacing, mortar's type and mechanical properties, the use of connectors, type of masonry, and loading conditions [20,27].…”