AC Ambiente Construído Ambiente Construído 1415-8876 1678-8621 Associação Nacional de Tecnologia do Ambiente Construído - ANTAC Resumo O uso da alvenaria racionalizada na construção de edifícios cresce pela otimização dos processos e redução de desperdícios, com desempenho atrelado à qualidade e interação dos materiais. Esta pesquisa analisou a influência das propriedades das argamassas de revestimento mista, industrializada e estabilizada, aplicadas sobre prismas de dois blocos cerâmicos. As argamassas foram caracterizadas no estado fresco e endurecido, e o seu comportamento reológico foi avaliado pelo método squeeze-flow sobre três diferentes superfícies. A resistência de aderência à tração das argamassas foi determinada e os prismas, sem e com revestimentos, foram submetidos à compressão. Os resultados revelaram que um maior espalhamento da argamassa não impactou diretamente na aderência e mostraram um aumento na resistência à compressão dos prismas com a aplicação da camada de revestimento, sendo mais pronunciado nas argamassas com melhor desempenho mecânico, de forma não proporcional. O modo de ruptura dos prismas, na maioria dos casos, ocorreu de forma dúctil, acompanhada pelo descolamento dos revestimentos de argamassa. Essas constatações contribuem para compreensão do desempenho das alvenarias e para a mitigação de problemas decorrentes de falhas nos sistemas de revestimento. Introduction The pursuit of cost minimization in structural masonry construction, coupled with inadequate quality control in components and construction procedures, and the absence of specific design codes, can lead to a range of pathologies and accidents in this construction system (Oliveira et al., 2018). Masonry structures primarily experience compressive stresses, making the compressive behavior of masonry crucial for design and safety assessment purposes (Mohamad; Lourenço; Roman, 2007; Barbosa; Lourenço; Hanai, 2010). One of the challenges in structural masonry design codes is how to evaluate the strength and strain capacity of hollow masonry elements for structural purpose. Mainly due to their difficulties to manufacturer, transport, costs, requiring considerable capacity of reaction frames for applying and measuring the compression capacity of masonry specimens in prototype dimensions (Milani et al., 2021). The compressive strength of masonry not only has considerable effects on structural safety but can also significantly impact construction costs (Zhou; Wang; Zhu, 2016). It is influenced by various factors, including the strength of the mortar and units, the height-to-thickness ratio of the units, the orientation of the units concerning the direction of applied load, and the thickness of mortar joints (Fortes et al., 2017; Ravula; Subramaniam, 2017; Garzón-Roca; Marco; Adam, 2013). Masonry prisms have been widely used in research and quality control of masonry structures due to their simplified models, ease of construction and testing, considering operational and economic aspects, which can represent the interaction between different masonry components (Nalon et al., 2021; Abasi et al., 2020). The mechanical performance of prisms under compression is directly affected by failure modes associated with the mechanical properties of their constituent materials. Factors such as the relative strength between their components, preparation/test conditions, arrangement of the mortar joint, curing procedures, loading rate, geometric properties, also influence their performance (Parsekian et al., 2012; Gumaste et al., 2007; Sumanthi; Mohan, 2014). Numerous studies have been conducted on the behavior of masonry prisms under axial compression (Ewing; Kowalsky, 2004; Kaushik; Rai; Jain, 2007a; 2007b; Caldeira et al., 2020; Padalu; Singh, 2021; Baghi et al., 2018), however, few studies consider the mortar coatings on prisms. Milani et al. (2021), for example, studied the failure mode of masonry specimens, which was found to be highly similar between full and small scales. This suggests that, for blocks, prisms, and wallettes, these components could be utilized to represent the strength and strain behavior of masonry under compression. Oliveira et al. (2018) discusses masonry buildings constructed in Pernambuco and their relationship to several failures that have occurred, some of which included the death of inhabitants. Its content analyses in depth, experimentally, the behaviour of single bricks, prisms and wallets that allow the identification and quantification of the influence of several mortar coating layers on the load capacity of elements tested. Azevedo et al. (2019) describes an experimental study carried out prisms of two and three ceramic blocks, with and without cement mortar coating and some samples reinforced with mesh, subjected to axial compression in order to enhance the capacity of masonry. The experimental results indicate an increase both in the compressive load capacity of the coated prisms and in those that use coatings based on reinforced mortar. Despite their extensive historical use, mortar coatings, widely used in masonry walls, particularly in Brazil, for both internal coatings and facades (Botas; Veiga; Velosa, 2017), still exhibit several pathological manifestations, including cracking and detachment due to a lack of adhesion between the constituent layers of a building’s coating system, contributing to a decrease in the useful life of structures (Nogueira; Pinto; Gomes, 2018). It is crucial for the mortar used in wall rendering to possess adequate strength to ensure durability and impermeability while contributing to stability (Álvarez-Pérez et al., 2020). The conditions of mortar preparation and application to the substrate significantly impact the hardening process and characteristics relevant to in-service performance (Starinieri; Hughes; Wilk, 2015; Válek; Skruzná, 2019). Additionally, the interaction between applied mortar and the substrate, through the adhesion mechanism, also plays a role in mortar performance (Starinieri; Hughes; Wilk, 2015; Torres; Veiga; Freitas, 2018). Adhesion is a very complex property that is dependent on several factors, namely: the characteristics and properties of the porous material in contact with the mortar; the characteristics of mortars and their constituent materials; the mortar’s application technique; the climatic conditions at the time of application and throughout the life period of the cladding or rendering; and the time span after mortar application (Carasek, 1996). Several factors influencing mortar behavior have been studied by different researchers, including: substrate characteristics and substrate preparation (Starinieri; Hughes; Wilk, 2015; Stolz et al., 2016); mortar curing environmental conditions (Tongyuan et al., 2018); number and thickness of mortar layers (Starinieri; Hughes; Wilk, 2015; Zanelatto et al., 2013; Silveira et al., 2021); and mortar application techniques (Válek; Skruzná, 2019; Zanelatto et al., 2013). Although significant progress has been made in the study of the behavior of masonry prisms subjected to compression in recent years, there is a fundamental need for further research to enhance the understanding of the behavior of rendering under this condition. Therefore, the objective of the study presented here is to evaluate the impact of various properties of coating mortar on the compressive behavior of masonry prisms constructed with two structural ceramic blocks, as commonly utilized in rationalized masonry. Materials and methods Masonry prisms, constructed with two ceramic blocks and stabilized laying mortar, were coated with three mortar types (mixed, industrialized, and stabilized). These coatings were selected based on their suitability for rationalized masonry in the Southern region of Brazil. The mortars were characterized before and after application to the prisms, which were then subjected to a compression strength test. Blocks The ceramic blocks utilized in this study were of the EST60 structural type, featuring vertical perforations and nominal dimensions of (140 x 190 x 290) mm (length x thickness x height) (Figure 1a). They were stored in a laboratory environment, maintaining covered, dry, and well-ventilated conditions until use (Figure 1b). The blocks were subjected to geometric (effective dimensions, wall thickness), physical (water absorption), and mechanical characterizations, including characteristic compressive strength (fbk) and average compressive strength (fbm), as specified by NBR 15270-2 (ABNT, 2023). Figure 1 Ceramic blocks Mortars The mortars utilized in this study included laying mortar, plastering mortar, and three types of coating mortars (mixed, industrialized and stabilized). Laying mortar The laying mortar, a stabilized batch type, underwent a curing period of thirty-six hours and was sourced from a reputable company. Transported from the batching plant to the laboratory’s outdoor area using a concrete mixer truck, it was discharged into metal boxes with a 0.5 m³ capacity, ensuring adequate protection against external elements. Plastering mortar The adhesive industrialized mortar used for the rolled rendering was composed of cement, polymers, mineral aggregates, and special additives, according to the manufacturer. The recommended water-to-dry material ratio was 4.5 liters of water per 20 kg bag. It exhibited a coverage of ± 2.80 kg/m², fresh density ranging from 1.6 to 2.0 g/cm³, and laboratory tensile bond strength ≥ 0.4 MPa at 3 days and ≥ 0.6 MPa at 28 days. Coating mortars Three types of mortars were utilized for the coating of the prisms: mixed mortar (MM); industrialized mortar (IM); and stabilized mortar (SM). The mixed mortar had a mix ratio of 1:1:6, by volume, and was commonly used as a coating material in civil construction. It was produced with Portland cement CP II F-32, with a unit weight of 1053.20 kg/m³ (ABNT, 2021a) and density of 3.09 g/cm³ (ABNT, 2017); hydrated lime CH III, with a unit weight of 593.51 kg/m³ (ABNT, 2021a) and density of 2.66 g/cm³ (ABNT, 2017); and natural sand of quartzous origin sourced from the Paraná River, Brazil. The granulometric composition and physical characteristics of the sand are presented in Table 1, and the CP II-F-32 specifications, as provided by the manufacturer, are outlined in Table 2. Table 1 Grains retained percentage in the sieves and physical characteristics of the sand Sieve (mm) Retained mass (g) % retained % retained accumulated 4.75 0.84 0,2 0,2 2.36 2.49 0,5 0,7 1.18 6.84 1,4 2,0 0.6 37.03 7,4 9,4 0.3 277.36 55,5 64,9 0.15 166.27 33,3 98,2 0.075 7.79 1,6 99,7 Fineness modulus (-) 1.75 NBR NM 17054 (ABNT, 2022) Maximum size (mm) 1.18 Classification (-) Fine Unit mass (g/cm³) 1.49 NBR 16972 (ABNT, 2021a) Specific mass (g/cm³) 2.65 NBR 16916 (ABNT, 2021b) Absorption (%) 0.90 Table 2 Cement chemical and physical properties CP II-F-32 Limit – NBR 16697 (ABNT, 2018) Physical properties Initial curing period (min.) 216 ≥ 60 Initial curing period (min.) 270 ≤ 600 Specific surface area (cm²/g) 3404 ≥ 2600 Insoluble residue (%) 1.43 ≤ 7.5 Compressive strength – 1 day (MPa) 15.9 N/A Compressive strength – 3 days (MPa) 30.2 ≥ 10 Compressive strength – 7 days (MPa) 35.5 ≥ 20 Compressive strength – 28 days (MPa) 41.8 ≥ 32 Chemical compositions AI2O3(%) 4.31 - SiO2 (%) 18.10 - Fr2O3(%) 2.95 - CaO (%) 60.25 - MgO (%) 2.59 N/A SO3(%) 2.55 ≤ 4.5 Loss on ignition (%) 6.73 ≤ 12.5 Free calcium oxide (%) 1.73 - The industrialized mortar (IM) used for coating the prisms was a pre-mixed type, composed of Portland cement, silica sand, and calcium carbonate sand in concentration ranges of 5-25%, 10-35%, and 45-74%, respectively, according to the manufacturer. The batched mortar used for coating the prisms was a stabilized type with a curing period of thirty-six hours, supplied by an established company, and the composition details were not provided by the manufacturer. Production and characterization of mortars Mixed and industrialized mortars were prepared using a planetary mortar mixer according to NBR 16541 (ABNT, 2016a). The batched mortar, supplied ready for use, required no additional mixing. Fresh-state characterization included consistency index measurements (ABNT, 2016b) (Figure 2a), bulk density, and air content (ABNT, 2005a). Mortar rheological behavior was assessed via the squeeze-flow method at 1 mm/s (ABNT, 2010) (Figure 2b). Tests were replicated on both the ceramic block and the block with plastering (Figure 2c and 2d), with the lower plate of the testing equipment replaced. Test specimens were molded for evaluating hardened-state properties after 28 days, including water absorption, void index, dry bulk density (ABNT, 2005b), flexural strength (Figure 2e), compressive strength (ABNT, 2005c) (Figure 2f), dynamic modulus of elasticity (ABNT, 2005c) (Figure 2g), and dimensional variation (ABNT, 2005d) (Figure 2h). Figure 2 Tests Ceramic block prisms Prisms were constructed by placing two hollow ceramic blocks in a plumb orientation, with a height/thickness ratio of 2.8 (ASTM, 2022). Full mortar bedding was utilized, maintaining a (10 ± 3) mm joint thickness (ABNT, 2020) (Figure 3a). A 3 mm layer of plastering mortar was applied using a high-texture roller. The coating mortar type varied among mixed, industrialized and stabilized mortars, as detailed in Table 3, and was applied with an approximate thickness of 20 mm, ensuring uniformity with templates (Figure 3b). Prisms were molded by a qualified professional to ensure execution standardization, and the curing process occurred in a laboratory environment for 28 days (Figure 3d). The prisms underwent the compression strength test, with a compression load applied at a rate of (0.05 ± 0.01) MPa/s, on the EMIC universal testing machine, which had a load capacity of up to 300 kN (ABNT, 2023) (Figure 3f). The coating mortars applied to the prisms were evaluated for their tensile bond strength (ABNT, 2021c) (Figures 3c and 3e). Figure 3 Prisms: (a and b) without and with coating mortar, (c) with metal inserts, (d) molded prisms, (e) tensile bond strength test using the Solotest manual hydraulic pull-off tester, (f) compression strength of prisms Table 3 Identification and characterization of prisms and test conditions Prism Coating mortar Condition* Number of specimens PREF - 0.7 f b ≤ f l m ≤ 1.5 f b 5 PMM MM 5 PIM IM 5 PSM SM 5 Note: flm = laying mortar compressive strength (MPa); fb = block gross area compressive strength (MPa); * recommended according to Parsekian et al. (2012). Results and discussions Table 4 presents the geometric, physical and mechanical properties of the ceramic blocks. Table 5 presents the properties of coating mortars in the fresh state. The curves obtained through the squeeze-flow test are shown in Figure 4. Table 4 Average values of different properties of the ceramic blocks Property Values SD CV (%) Width (mm) 137.5 0.3 0.2 Heigth (mm) 188.5 0.6 0.3 Length (mm) 287.9 0.8 0.3 Average thickness of longitudinal shells (mm) 8.5 0.2 1.9 Average thickness of transverse webs (mm) 8.3 0.2 2.5 Gross area (mm²) 39587.0 123.9 0.3 Water absorption (%) 21 0.27 0.28 Gross area compressive strength (MPa) 7.4 0.9 12.5 Characteristic compressive strength (MPa) 6.0 - - Table 5 Average values, standard deviation (SD) and coefficient of variation (CV) of different properties of fresh coating mortars Mortar Flow (mm) Bulk density (g/cm³) Air content (%) Average SD CV (%) Average SD CV (%) Average SD CV (%) MM 253a 1.53 0.60 2.03b 0.01 0.61 4c 0.59 15.81 IM 262a 2.08 0.79 1.93b 0.01 0.45 16c 0.38 2.40 SM 269a 0.58 0.21 1.86b 0.00 0.26 - - - Statistical analysis ap = 5.4075E-05 bp = 2.59011E-09 cp = 4.09008E-08 Note: (-) data was not provided by the manufacturer; analysis of variance (ANOVA) was performed with a confidence level of 95%: a,b,c statistically significant. Figure 4 Squeeze-flow test curves for mortars: (a) mixed, (b) industrialized, and (c) stabilized, at a test velocity of 0.1 mm/s Statistical analysis was conducted (ANOVA) to verify the differences between all parameters evaluated in experiments. The results indicate that the mortars significantly differ from each other concerning fresh properties such flow, bulk density and air content (the p-values are shown in the table 5). The analysis of the curves reveals a similar behavior among the mixed, industrialized, and stabilized mortars when tested on three distinct substrates. The industrialized and stabilized mortars demonstrated increased displacement on all three substrates compared to the mixed mortar. In terms of the mixture composition, this can be attributed to the incorporation of chemical additives in the industrialized and stabilized mortars, enhancing material fluidity. The introduction of these additives likely influenced air incorporation during mixing, resulting in a higher air content in the industrialized and stabilized mortars, consequently leading to lower mass density compared to the mixed mortar. The industrialized mortar showed a 400% increase in the air content compared to the mixed mortar. Commercial mortars displayed diverse compositions, contributing to substantial variability in phase distribution in the fresh state (Grandes et al., 2021). The consistency indices of the industrialized and stabilized mortars increased by 3.6% and 6.3%, respectively, compared to the mixed mortar. In terms of substrate characteristics, notably, there is a greater spreading capacity of the mortars on the metal base compared to the ceramic block, followed by the plastered substrate on the ceramic block, which exhibited more restricted spreading. This phenomenon can be partially attributed to the irregular surface of the plaster hindering the mortar’s flow, while the non-absorbent and smooth metal surface facilitates such behavior. Additionally, potential water percolation through the porous structures of the ceramic block and plaster may have contributed to a reduction in the total water content in the sample. Substrate water absorption enhances resistance to mortar deformation, consequently reducing spreading capacity during the test. Similar results were observed in previous studies involving mortars and cement pastes (Costa et al., 2020; Barbosa; Lourenço; Hanai, 2010). The physical and mechanical properties of coating mortars in the hardened state are presented in Figure 5 and Table 6, respectively. The shrinkage curves of the mortars are illustrated in Figure 6. Figure 5 Average values with standard deviation of the physical properties of hardened mortars Table 6 Average values, standard deviation (SD) and coefficient of variation (CV) of the mechanical properties of hardened mortars Mortar Flexural strength (MPa) Compressive strength (MPa) Tensile bond strength (MPa) Dynamic modulus of elasticity (GPa) Average SD CV (%) Average SD CV (%) Average SD CV (%) Average SD CV (%) MM 1.04a 0.09 8.21 3.32b 0.19 5.65 0.24c 0.04 14.84 4.01d 0.29 7.20 IM 2.77a 0.16 5.94 7.28b 0.30 4.10 0.35c 0.06 16.03 10.88d 0.41 3.78 SM 2.15a 0.18 8.27 5.17b 0.29 5.60 0.30c 0.04 13.10 5.69d 0.36 6.40 Statistical analysis aρ = 1.047E-11 bρ = 5.501E-19 cρ = 8.534E-12 dρ = 1.630E-09 Note: analysis of variance (ANOVA) was performed with a confidence level of 95%: a,b,c,d statistically significant. Figure 6 Shrinkage curves The results indicate that the mortars significantly differ from each other concerning physical properties such as water absorption (ρ = 2.62196E-06), void index (ρ = 9.26177E-08), and dry bulk density (ρ = 1.879E-11). Significant differences were also found among the mortars for the mechanical properties, as indicated by the p-values in Table 6. The results indicate that the industrialized mortar exhibited the highest values for compressive strength, flexural tensile strength, tensile bond strength, and dynamic modulus of elasticity, followed by the stabilized and mixed mortars. Although the calculation of the average potential tensile bond strength excluded values deviating by 30% from the mean, following NBR 15258 (ABNT, 2021c). The coefficient of variation in the tensile pull off results was approximately 13-16%, which is typical for such experiments and were findings from other authors (Carasek et al., 2014; Santos et al., 2020). The highest values of tensile bond strength were observed in industrialized and stabilized mortars. More water facilitated the flow to the substrate, which increased the wetting capacity and consequently the contact area at the interface. Mortars with faster water loss, either to the substrate or the environment, accelerate the approach of mortar particles, reducing the fluid amount to mitigate friction forces between them. Consequently, this limitation in mortar mobility may increase the occurrence of defects at the interface with the substrate, diminishing tensile bond strength (Bernardo et al., 2020). On the other hand, increases in compressive strength do not proportionally impact tensile bond strength. While the increases in the compressive strength of IM and SM were in the order of 120% and 56%, compared to MM, in terms of bond strength, the gains were 45% and 25%, respectively. Other authors did not find a correlation between bond strength and the corresponding average compressive strength of the mortars (Costa et al., 2020). Additionally, shrinkage was more pronounced in the mixed mortar, especially at early ages, compared to the other mortars, which exhibited more similar behaviors. Table 7 presents the average compressive strength results and analysis of the prisms, including the enhancements in compressive strength observed after the application of the coating mortars. Table 7 Average values, standard deviation (SD) and coefficient of variation (CV) of the compressive strength of prisms Prism fb (MPa) fIm(MPa) fIm/fb(%) fp (MPa) Increase after application of coating mortar (%) Average SD CV (%) PREF 7.4 6.25 0.84 3.59a 0.11 19.26 - PMM 4.28a 0.48 13.01 19 PIM 4.76a 0.94 21.89 33 PSM 4.69a 1.50 32.54 31 Statistical analysis ρ = 0.01172   Notes: fp = prism compressive strength (MPa); fIm/fb recommended according to Parsekian et al. (2012) (0.7 fb ≤ fIm ≤ 1.5fb); analysis of variance (ANOVA) was performed with a confidence level of 95%: a statistically significant. The analysis of variance (ANOVA) conducted with a confidence level of 95% showed statistically significant differences in the compressive strength among the prisms produced with different types of mortar coatings. However, it is important to note that the coefficients of variation observed, ranging from 13.01% to 32.54%, indicate that the observed values should be examined with caution. Notably, the mortar with the highest mechanical strengths (IM) exhibited superior performance for the prism, followed by the stabilized mortar (SM), corroborating with Milani et al. (2021). A comparison of the average compressive strength values for prisms coated with mixed, industrialized, and stabilized mortar with the reference prism (uncoated) reveals increases of approximately 19%, 33%, and 31%, respectively. Similar behaviors have been reported in previous studies (Oliveira et al., 2018). The coating of mixed mortar provided the smallest increase in strength for the prisms compared to the other coatings. The individual increases of IM and SM, in relation to MM, were 46% and 25% for tensile bond strength (bs); 166% and 107% for flexural strength (σm); 120% and 56% for compressive strength (fm); and 171% and 42% for dynamic modulus of elasticity (Em), respectively. This resulted in increments of 12% and 10% in prism strength, showing that the mortars with better mechanical performance contributed more significantly to this; however, the increases did not occur proportionally, as shown in Figure 7. Figure 7 Mechanical properties of coating mortar and enhancements in prism strength Notes: fp1 = increase in compressive strength of prisms after the application of coating mortar compared to uncoated prisms; fp2 = increase in compressive strength of prisms with IM and SM coating mortars compared to prisms with MM coating mortar. Response surfaces and contour graphs illustrating the relationships between compressive strength and modulus of elasticity (Figure 8) and flexural strength and tensile bond strength of coating mortars (Figure 9) on the compressive strength of prisms. Figure 8 (a) Response surfaces and (b) contour graphs illustrate the relationships between compressive strength (fm, in MPa) and modulus of elasticity (Em, in GPa) of coating mortars and compressive strength of prisms (fp, in MPa) Figure 9 (a) Response surfaces and (b) contour graphs illustrate the relationships between flexural strength (σm, in MPa) and tensile bond strength (bsm, in MPa) of coating mortars and compressive strength of prisms (fp, in MPa) It is possible to observe a trend of increasing compressive strength in the prisms as the compressive and flexural strength of the mortar rises. However, regarding the modulus of elasticity, there is noticeable variability where an increase in this parameter does not always reflect an increase in prism strength. This may be related to the fact that less deformable mortars may lack the capacity to absorb deformations, leading to their rupture. Figure 8a highlights a better performance of the prism when mortars have higher values of flexural and tensile bond strength; however, it is possible to observe that there are no direct relationships between these properties. In Brazil, a large portion of the buildings is constructed using clay block structural masonry. Advancements in research are necessary to enhance mechanical properties and devise new procedures for evaluating stress and strain in multi-story structures at a smaller scale. Figure 10 illustrates the failure modes observed in the ceramic block prisms, characterized by brittle failures with an immediate loss of the system’s strength capacity shortly after reaching the maximum load. Figure 10 Prisms failure mechanisms: (a) uncoated; with: (b) mixed, (c) industrialized, (d) stabilized mortars; (g) loose coating The relationships between the laying mortar strength and the ceramic block strength were within the recommended parameters for use (Parsekian et al., 2012), therefore, the failure mechanism of the uncoated prism occurred due to lateral tension of the block (Figure 9a). This type of failure, considered most desirable, is characterized by the appearance of a vertical crack in the block, preceded by signs of joint mortar failure through its cracking (Cheema; Klinger, 1986). In this condition, the mortar joint has a greater tendency to expand laterally in relation to the blocks since they have higher rigidity. The mortar is laterally confined at the block/mortar interface by the blocks; therefore, shear stresses at the block/mortar interface result in an internal stress state consisting of triaxial compression in the mortar and bilateral tension and axial compression in the blocks. This stress state initiates vertical cracks in the blocks, leading to the failure of the walls (Fonseca et al., 2019). In the coated prisms, the cracking process initiated in the blocks, and subsequently, the two layers of mortar coating primarily assumed the load. The mixed coating mortar showed signs of deformation under lower compression loads, compared to the others (Figure 9b). This may also be related to the fact that this mortar exhibited the lowest individual values of mechanical strength. The failure mode of industrialized and stabilized mortars occurred through the detachment of the coating layers from the block (Figures 9c and 9d). It should be noted, however, that the mortar coating layer prevented the complete visualization of the block’s behavior. After the rupture and complete detachment of the coating layers from the block, cracks in the blocks preceding the failure became visible (Figure 9e). Moreover, various factors can influence the failure process, including the quality of the workforce used in the construction of specimens, the thickness, and uniformity of the laying mortar joints, among other factors (Oliveira et al., 2018). Conclusions This study aimed to investigate the impact of various coating mortars on ceramic block prisms to anticipate the performance of rationalized masonry walls. The obtained results lead to the following conclusions: the greater spreading capacity on the substrate did not directly result in higher bond strength after the application of the coating on the prism. Prisms produced with coating mortars with the highest mechanical strengths showed superior performance; however, the increments do not occur proportionally. The increased adhesion of the coating to the substrate does not guarantee a delay in the rupture of the prisms, as mechanical properties can also influence the behavior of the assembly. Semi-prepared or factory-produced mortars exhibited favorable behavior when applied as coatings, indicating that technological control and the use of additives lead to performance improvement. The limited technical information on the influence of this layer on the compression load capacity of masonry elements emphasizes the importance of the obtained results. Furthermore, these findings have potential applications in assessing the structural safety of existing buildings and facilitating safety analyses for construction structures. PAULINO, R. S.; COSTA, M. do R. de M. M. da. Investigation of properties of different types of coating mortars and their impact on the behavior of ceramic block prisms. Ambiente Construído, Porto Alegre, v. 25, e138302, jan./dez. 2025. References ABASI, A. et al. Influence of prism geometry on the compressive strength of concrete masonry. Construction and Building Materials, v. 264, 120182, 2020. ABASI A Influence of prism geometry on the compressive strength of concrete masonry Construction and Building Materials 264 120182 120182 2020 ÁLVAREZ-PÉREZ J. et al. Multifactorial behavior of the elastic modulus and compressive strength in masonry prisms of hollow concrete blocks. Construction and Building Materials, v. 241, 118002, 2020. ÁLVAREZ-PÉREZ J. Multifactorial behavior of the elastic modulus and compressive strength in masonry prisms of hollow concrete blocks Construction and Building Materials 241 118002 118002 2020 AMERICAN SOCIETY FOR TESTING AND MATERIALS. C-1314: standard test method for compressive strength of masonry prisms. Pensilvânia, 2022. AMERICAN SOCIETY FOR TESTING AND MATERIALS C-1314: standard test method for compressive strength of masonry prisms Pensilvânia 2022 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15258: argamassa para revestimento de paredes e tetos - determinação da resistência potencial de aderência à tração, Rio de Janeiro, 2021c. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 15258: argamassa para revestimento de paredes e tetos - determinação da resistência potencial de aderência à tração Rio de Janeiro 2021c ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13276: argamassa para assentamento e revestimento de paredes e tetos: preparo da mistura e determinação do índice de consistência. Rio de Janeiro, 2016b. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 13276: argamassa para assentamento e revestimento de paredes e tetos: preparo da mistura e determinação do índice de consistência Rio de Janeiro 2016b ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13278: argamassa para assentamento e revestimento de paredes e tetos: determinação da densidade de massa e do teor de ar incorporado. Rio de Janeiro, 2005a. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 13278: argamassa para assentamento e revestimento de paredes e tetos: determinação da densidade de massa e do teor de ar incorporado Rio de Janeiro 2005a ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 13279: argamassa para assentamento e revestimento de paredes e tetos - determinação da resistência à tração na flexão e à compressão. Rio de Janeiro, 2005c. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 13279: argamassa para assentamento e revestimento de paredes e tetos - determinação da resistência à tração na flexão e à compressão Rio de Janeiro 2005c ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15261: argamassa para assentamento e revestimento de paredes e tetos - determinação da variação dimensional (retratação ou expansão linear). Rio de Janeiro, 2005d. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 15261: argamassa para assentamento e revestimento de paredes e tetos - determinação da variação dimensional (retratação ou expansão linear) Rio de Janeiro 2005d ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15270-2: componentes cerâmicos: blocos e tijolos para alvenaria: parte 2: métodos de ensaios. Rio de Janeiro, 2023. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 15270-2: componentes cerâmicos: blocos e tijolos para alvenaria: parte 2: métodos de ensaios Rio de Janeiro 2023 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 15839: argamassa de assentamento e revestimento de paredes e tetos: caracterização reológica pelo método squeeze-flow. Rio de Janeiro, 2010. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 15839: argamassa de assentamento e revestimento de paredes e tetos: caracterização reológica pelo método squeeze-flow Rio de Janeiro 2010 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16541: argamassa para assentamento e revestimento de paredes e tetos: preparo da mistura para a realização de ensaios. Rio de Janeiro, 2016a. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 16541: argamassa para assentamento e revestimento de paredes e tetos: preparo da mistura para a realização de ensaios Rio de Janeiro 2016a ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16605: cimento Portland e outros materiais em pó: determinação da massa específica. Rio de Janeiro, 2017. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 16605: cimento Portland e outros materiais em pó: determinação da massa específica Rio de Janeiro 2017 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16697: cimento Portland: requisitos. Rio de Janeiro, 2018. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 16697: cimento Portland: requisitos Rio de Janeiro 2018 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16868-2: alvenaria estrutural - parte 2: execução e controle de obras. Rio de Janeiro, 2020. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 16868-2: alvenaria estrutural - parte 2: execução e controle de obras Rio de Janeiro 2020 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16916: agregado miúdo: determinação da densidade e da absorção de água. Rio de Janeiro, 2021b. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 16916: agregado miúdo: determinação da densidade e da absorção de água Rio de Janeiro 2021b ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 16972: agregados: determinação da massa unitária e do índice de vazios. Rio de Janeiro, 2021a. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 16972: agregados: determinação da massa unitária e do índice de vazios Rio de Janeiro 2021a ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 17054: agregados: determinação da composição granulométrica: método de ensaio. Rio de Janeiro, 2022. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 17054: agregados: determinação da composição granulométrica: método de ensaio Rio de Janeiro 2022 ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS. NBR 9778: argamassa e concreto endurecidos - determinação da absorção de água, índice de vazios e massa específica. Rio de Janeiro, 2005b. ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS NBR 9778: argamassa e concreto endurecidos - determinação da absorção de água, índice de vazios e massa específica Rio de Janeiro 2005b AZEVEDO, A. et al. Compression behaviour of clay bricks prisms, wallets and walls: coating influence. Revista de la Construcción, v.18, n.1, Apr. 2019. AZEVEDO A Compression behaviour of clay bricks prisms, wallets and walls: coating influence Revista de la Construcción 18 1 04 2019 BAGHI, H. et al. Behavior of reinforced concrete frame with masonry infill wall subjected to vertical load. Engineering Structures, v.171, p. 476–487, 2018. BAGHI H Behavior of reinforced concrete frame with masonry infill wall subjected to vertical load Engineering Structures 171 476 487 2018 BARBOSA, C. S.; LOURENÇO, P. B.; HANAI, J. B. On the compressive strength prediction for concrete masonry prisms. Materials Structures, v. 43, p. 331–344, 2010. BARBOSA C. S LOURENÇO P. B HANAI J. B On the compressive strength prediction for concrete masonry prisms Materials Structures 43 331 344 2010 BERNARDO, H. M. et al. The effect of water absorption and type of substrate on the performance of rendering mortars in the fresh and hardened state. Ambiente Construído, Porto Alegre, v. 20, n. 3, p. 493-511, 2020. BERNARDO H. M. The effect of water absorption and type of substrate on the performance of rendering mortars in the fresh and hardened state Ambiente Construído Porto Alegre 20 3 493 511 2020 BOTAS, S.; VEIGA, R.; VELOSA, A. Bond strength in mortar/ceramic tile interface: testing procedure and adequacy evaluation. Materials Structures, v. 50, p. 1-13, 2017. BOTAS S VEIGA R VELOSA A Bond strength in mortar/ceramic tile interface: testing procedure and adequacy evaluation Materials Structures 50 1 13 2017 CALDEIRA F. E. et al. Influence of joint thickness and strength of mortars on the compressive behavior of prisms made of normal and high-strength concrete blocks. Construction and Building Materials, v. 234, 117419, 2020. CALDEIRA F. E. Influence of joint thickness and strength of mortars on the compressive behavior of prisms made of normal and high-strength concrete blocks Construction and Building Materials 234 117419 117419 2020 CARASEK, H. et al. Bond between 19th Century lime mortars and glazed ceramic tiles. Construction and Building Materials, v. 59, p 85-98, 2014. CARASEK H Bond between 19th Century lime mortars and glazed ceramic tiles Construction and Building Materials 59 85 98 2014 CARASEK, H. Aderência de argamassas a base de cimento Portland a substratos porosos: avaliação dos fatores intervenientes e contribuição ao estudo do mecanismo da ligação. São Paulo, 1996. 285 f. Tese de doutorado (Doutorado em Engenharia Civil) – Escola Politécnica da Universidade de São Paulo, São Paulo, 1996. CARASEK H Aderência de argamassas a base de cimento Portland a substratos porosos: avaliação dos fatores intervenientes e contribuição ao estudo do mecanismo da ligação São Paulo 1996 285 f Tese de doutorado (Doutorado em Engenharia Civil) – Escola Politécnica da Universidade de São Paulo COSTA, E. B. C. et al. Squeeze-flow of mortars on brick substrate and its relation with bond strength. Construction and Building Materials, v. 265, p. 120298, 2020. COSTA E. B. C. et al. Squeeze-flow of mortars on brick substrate and its relation with bond strength Construction and Building Materials 265 120298 120298 2020 CHEEMA, T. S.; KLINGNER, R. E. Compressive strength of concrete masonry prisms. Journal of American Concrete Institute, p. 88-97, jan./feb. 1986. CHEEMA T. S. KLINGNER R. E. Compressive strength of concrete masonry prisms Journal of American Concrete Institute 88 97 01 1986 EWING, B. D.; KOWALSKY, M. J. Compressive behavior of unconfined and confined clay brick masonry. Journal of Structural Engineering, v. 130, n. 4, p. 650–661, 2004. EWING B. D. KOWALSKY M. J. Compressive behavior of unconfined and confined clay brick masonry Journal of Structural Engineering 130 4 650 661 2004 FONSECA, F. S. et al. Compressive strength of high-strength concrete masonry grouted prisms. Construction and Building Materials, v. 202, p. 861–876, 2019. FONSECA F. S Compressive strength of high-strength concrete masonry grouted prisms Construction and Building Materials 202 861 876 2019 FORTES, E. S. et al. Compressive strength of masonry constructed with high strength concrete blocks. Revista IBRACON de Materiais e Estruturas, v. 10, n. 6, p. 1273–1319, 2017. FORTES E. S. Compressive strength of masonry constructed with high strength concrete blocks Revista IBRACON de Materiais e Estruturas 10 6 1273 1319 2017 GARZÓN-ROCA, J.; MARCO, C. O.; ADAM, J. M. Compressive strength of masonry made of clay bricks and cement mortar: estimation based on neural networks and fuzzy logic. Engineering Structures, v. 48, p. 21–27, 2013. GARZÓN-ROCA J MARCO C. O ADAM J. M Compressive strength of masonry made of clay bricks and cement mortar: estimation based on neural networks and fuzzy logic Engineering Structures 48 21 27 2013 GRANDES F. A. et al. Rheological behavior and flow induced microstructural changes of cement-based mortars assessed by Pressure Mapped Squeeze-flow. Powder Technology, v. 393, p. 519–538, 2021. GRANDES F. A. Rheological behavior and flow induced microstructural changes of cement-based mortars assessed by Pressure Mapped Squeeze-flow Powder Technology 393 519 538 2021 GUMASTE, K. S. et al. Strength and elasticity of brick masonry prisms and wallettes under compression. Materials Structures, v. 40, p. 241–253, 2007. GUMASTE K. S. Strength and elasticity of brick masonry prisms and wallettes under compression Materials Structures 40 241 253 2007 KAUSHIK, H. B.; RAI, D. C.; JAIN, S. K. Stress-strain characteristics of clay brick masonry under uniaxial compression. Journal of Materials in Civil Engineering, v. 19, n. 9, p. 728–739, 2007a. KAUSHIK H. B. RAI D. C. JAIN S. K. Stress-strain characteristics of clay brick masonry under uniaxial compression Journal of Materials in Civil Engineering 19 9 728 739 2007a KAUSHIK, H. B.; RAI, D. C.; JAIN, S. K. Uniaxial compressive stress–strain model for clay brick masonry. Current Science, v. 92, pp. 497–501, 2007b. KAUSHIK H. B. RAI D. C. JAIN S. K. Uniaxial compressive stress–strain model for clay brick masonry Current Science 92 497 501 2007b MILANI, A. S. et al. Case study of prototype and small-scale model behavior of clay blocks masonry under compression. Case Studies in Construction Materials, v. 15, e00684, 2021. MILANI A. S. Case study of prototype and small-scale model behavior of clay blocks masonry under compression Case Studies in Construction Materials 15 e00684 2021 MOHAMAD, G. G.; LOURENÇO, P. B.; ROMAN, H. R. Mechanics of hollow concrete block masonry prisms under compression: review and prospects. Cement and Concrete Composites, v. 29, n. 3, p. 181-192, 2007. MOHAMAD G. G. LOURENÇO P. B. ROMAN H. R. Mechanics of hollow concrete block masonry prisms under compression: review and prospects Cement and Concrete Composites 29 3 181 192 2007 NALON, G. H. et al. Review of recent progress on the compressive behavior of masonry prisms. Construction and Building Materials, v. 320, n. 126181, 2021. NALON G. H Review of recent progress on the compressive behavior of masonry prisms Construction and Building Materials 320 126181 2021 NOGUEIRA, R.; PINTO, A. P. F.; GOMES, A. Design and behavior of traditional lime-based plasters and renders. Cement and Concrete Composites, v. 89, p. 192–204, 2018. NOGUEIRA R PINTO A. P. F GOMES A Design and behavior of traditional lime-based plasters and renders Cement and Concrete Composites 89 192 204 2018 OLIVEIRA, R. A. et al. Structural performance of unreinforced masonry elements made with concrete and horizontally perforated ceramic blocks: laboratory tests. Construction and Building Materials, v. 182, p. 20-34, set., 2018. OLIVEIRA R. A Structural performance of unreinforced masonry elements made with concrete and horizontally perforated ceramic blocks: laboratory tests Construction and Building Materials 182 20 34 09 2018 PADALU, P. K. V. R.; SINGH, Y. Variation in compressive properties of Indian brick masonry and its assessment using empirical models. Structures, v. 33, p. 1734–1753, 2021. PADALU P. K. V. R SINGH Y Variation in compressive properties of Indian brick masonry and its assessment using empirical models Structures 33 1734 1753 2021 PARSEKIAN G. et al. Behavior and dimensioning of structural masonry. São Paulo: EdUFSCar, 2012. PARSEKIAN G Behavior and dimensioning of structural masonry São Paulo EdUFSCar 2012 RAVULA; M. B.; SUBRAMANIAM, K. V. L. Experimental investigation of compressive failure in masonry brick assemblages made with soft brick. Materials Structures, v. 50, n. 19, 2017. RAVULA M. B. SUBRAMANIAM K. V. L. Experimental investigation of compressive failure in masonry brick assemblages made with soft brick Materials Structures 50 19 2017 SANTOS, A. R. L. et al. Tensile bond strength of lime-based mortars: The role of the microstructure on their performance assessed by a new non-standard test method, Journal of Building Engineering, v. 29, n. 101136, 2020. SANTOS A. R. L Tensile bond strength of lime-based mortars: The role of the microstructure on their performance assessed by a new non-standard test method Journal of Building Engineering 29 101136 2020 SILVEIRA D. et al. Evaluation of in-service performance factors of renders based on in-situ testing techniques. Journal of Building Engineering, v. 34, p. 101806, 2021. SILVEIRA D Evaluation of in-service performance factors of renders based on in-situ testing techniques Journal of Building Engineering 34 101806 101806 2021 STARINIERI, V.; HUGHES, D. C.; WILK, D. Influence of substrate and sand characteristics on Roman cement mortar performance. Construction and Building Materials, v. 91, p. 274–287, 2015. STARINIERI V HUGHES D. C WILK D Influence of substrate and sand characteristics on Roman cement mortar performance Construction and Building Materials 91 274 287 2015 STOLZ, C. et al. Influence of substrate texture on the tensile and shear bond strength of rendering mortars. Construction and Building Materials, v. 128, p. 298–307, 2016. STOLZ C Influence of substrate texture on the tensile and shear bond strength of rendering mortars Construction and Building Materials 128 298 307 2016 SUMATHI, A.; MOHAN, K. S. R. Study on the effect of compressive strength of brick masonry with admixed mortar. International Journal of ChemTech Research, v. 6, p. 3437–3450, 2014. SUMATHI A MOHAN K. S. R Study on the effect of compressive strength of brick masonry with admixed mortar International Journal of ChemTech Research 6 3437 3450 2014 TONGYUAN, N. et al. Influences of environmental conditions on the cracking tendency of dry-mixed plastering mortar. Advances in Materials Science and Engineering, p. 9160801, 2018. TONGYUAN N Influences of environmental conditions on the cracking tendency of dry-mixed plastering mortar Advances in Materials Science and Engineering 9160801 9160801 2018 TORRES, I.; VEIGA, M. R.; FREITAS, V. Influence of substrate characteristics on behavior of applied mortar. Journal of Materials in Civil Engineering, v. 30, n. 10, p. 04018254, 2018. TORRES I VEIGA M. R FREITAS V Influence of substrate characteristics on behavior of applied mortar Journal of Materials in Civil Engineering 30 10 04018254 04018254 2018 VÁLEK, J.; SKRUZNÁ, O. Performance assessment of custom-made replications of an original historic render – a study of application influences. Construction and Building Materials, v. 229, n.116822, 2019. VÁLEK J. SKRUZNÁ O. Performance assessment of custom-made replications of an original historic render – a study of application influences Construction and Building Materials 229 116822 2019 ZANELATTO, K. et al. Evaluation of the influence of the execution technique on cement-based render applied by continuous mechanical projection, Ambiente Construído, Porto Alegre, v. 13, n. 2, p. 87–109, abr./jun. 2013. ZANELATTO K Evaluation of the influence of the execution technique on cement-based render applied by continuous mechanical projection Ambiente Construído Porto Alegre 13 2 87 109 abr./jun 2013 ZHOU, Q; WANG, F.; ZHU, F. Estimation of compressive strength of hollow concrete masonry prisms using artificial neural networks and adaptive neuro-fuzzy inference systems. Construction and Building Materials, v. 125, p. 417-426, 2016. ZHOU Q WANG F ZHU F Estimation of compressive strength of hollow concrete masonry prisms using artificial neural networks and adaptive neuro-fuzzy inference systems Construction and Building Materials 125 417 426 2016