Abstract
The tensile bond strength is one of the main properties of rendering mortars. It represents the adhesiveness ability between the mortar itself and the substrate. This property depends on several factors, such as the proportion and characteristics of the mortar materials and the substrate, along with the mode of application and climate conditions. The purpose of this paper was to analyze the tensile bond strength between three rendering mortar proportions in volume – 1: 1: 6, 1: 2: 9, and 1: 6 (with plasticizer additive) – each one applied on two substrates, ceramic structural blocks with roughcast and concrete structural blocks. The rendering mortars had their physical properties evaluated in fresh and hardened stages, as well as their compressive and tensile strengths in flexure. The tensile bond strength was determined by a pullout test on ceramic and concrete masonry walls exposed to external weather. The results showed that the 1: 1: 6 mixed mortar exhibited higher tensile bond strength in both substrates of ceramic blocks with roughcast and concrete blocks without preparation. Besides, among 1: 2: 9 and 1: 6 mortars there is no significant difference in tensile bond strength considering both substrates. Another conclusion was that the substrate type did not affect the final bond strength between the mortars.
Highlights
In buildings, rendering mortars perform an important role as an insulating element of the structure
For T3, the chosen plasticizer additive was Quartzolit from Weber Company, which is widely used in constructions in the city of Palmas-TO
For ceramic and concrete blocks substrates submitted to the Palmas-TO climate, mixed rendering mortars with T1 proportion (1: 1: 6 in volume) presented greater tensile bond strength compared to T2 and T3 - 1 : 2: 9 and 1: 6, respectively
Summary
In buildings, rendering mortars perform an important role as an insulating element of the structure. Numerous researchers, such as (Antunes and Masuero, 2016), (Stolz and Masuero, 2018), (Kabagire et al, 2017), (Jiao et al, 2017), (Zanelatto et al, 2013) concluded that there are determining factors in the tensile bond strength of rendering mortars Those are the characteristics of the mortar (proportion of materials, granulometry, rheology and presence of additives), the substrate (capillarity, water absorption, and surface roughness), the executive process (surface treatment, application energy, quality of the mixture, type of application and curing process), in addition to the climatic conditions the coating system is subjected (temperature, relative air humidity, and wind). The use of high amounts of sand, as well as greatly coarse or fine sands, affects its adherence, so the use of medium sands with good granulometric distribution is the recommendation (De Freitas and Gonçalves, 2008)
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