Introduction: Concrete sealing blocks are not only used in Brazil but worldwide. T he knowledge of the material properties in the presence of moisture becomes necessary to study the durability of buildings. Methods: An experimental study was carried out in order to analyse the effect of contact area on the capillary absorption coefficient of concrete samples used in sealing blocks, according to several standards: NBR 9779 (2012), EN 1015-18 (2002), ISO 15148 (2002) and ASTM C1794 (2015). Two types of specimens were analysed; monolithic samples and samples with a perfect contact interface. The monolithic samples were also subjected to axial and radial compression in order to enhance the capacity of masonry. Results: The experimental results for the samples with perfect contact interface indicate that the water absorption before the interface presents similar behaviour to the monolithic samples. However, it is possible to observe a reduction of the absorption rate when water reaches the interface due to the hygric resistance. In other words, the moisture transport is significantly retarded by the existence of an interface, i.e., the discontinuity of moisture content across the interface indicated that there was a difference in capillary pressure across the interface. Also, the interface contact area does not greatly influence the water-resistance values. Conclusion: Finally, the Hygric Resistance values (HR), in multilayer building components, with perfect contact interface are calculated using the “knee point” methodology.

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This work aims to study the influence of using construction and demolition waste in the replacement of coarse and fine aggregate to produce recycled aggregate concrete (RAC). A moderate compressive strength concrete made with usual fine and coarse aggregate was used as a benchmark material. Compressive and split tensile tests were performed using 120 cylindrical concrete specimens with 150 mm diameter and 300 mm length. Four-point flexural tests in reinforced beams made with conventional concrete and RAC were performed. The results obtained showed that the use of recycled fine aggregates, in both percentages of substitution investigated—50% and 100%— did not generate any deleterious influence on the values of compressive strength and split tensile strength of the RACs produced. Tin fact, the mechanical strengths of RACs produced with recycled fine aggregate were equal or higher than those from the reference concrete. The same behavior was not observed, however, when the recycled coarse aggregate was used. For this case, decreases in concrete mechanical strengths were observed, especially in compressive strength, with values around 35% lower when compared to the reference concrete. Tensile mechanical tests results confirmed the excellent behavior of all RACs made with replacement of usual fine aggregates by recycled. Bending tests performed in reinforced RAC beams had as objective to evaluate the deformation profile of the beams. The obtained results showed that RAC beams with full replacement of usual fine aggregate by the recycled aggregates have presented little changes in the global behavior, an aspect that encourages its use.

This work describes an experimental study carried out on running bond 195 red clay 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 prisms were subjected to compressive loading and all of them had deformation control on each face with a deflectometer, to obtain information about the structural behaviour of the prisms. 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, not complying with the specifications of conventional structural mortar. The load ratios of prism/wallettes and prisms with two blocks/prisms with three blocks were satisfactory.

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Resumo O trabalho apresenta reflexões acerca das edificações em alvenaria resistente no Estado de Pernambuco. São abordados temas relativos às principais características dessa técnica construtiva bem como as peculiaridades que influenciam diretamente seu desempenho estrutural. Aspectos relacionados aos desabamentos que ocorreram nos últimos anos são igualmente abordados, acompanhados da indicação da causa da ruptura e do ano em que ocorreram. O artigo contempla, adicionalmente, uma extensa caracterização dos materiais e componentes utilizados em construções em alvenaria resistente na região, constituindo-se numa das mais abrangentes investigações sobre essa temática desenvolvida no país. Foi analisado experimentalmente o comportamento compressivo de blocos, prismas e miniparedes confeccionados com esses materiais que integram um sistema de vedação que tem sido utilizado com função estrutural frequentemente na região. Os resultados obtidos permitem identificar a contribuição das camadas de argamassa de revestimento na capacidade de carga dos elementos ensaiados. Diversos fatores que interferem nessa contribuição foram igualmente estudados. Ao final, expõe-se uma súmula dos resultados de todos os ensaios realizados que esclarecem de maneira detalhada as formas de ruptura observadas que se mostraram marcadamente frágeis, a exemplo do que ocorreu na maior parte dos acidentes com esse tipo de edificação na região.

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The work presents the results of an experimental campaign carried out on concrete elements in order to investigate the potential of using artificial neural networks (ANNs) to estimate the compressive strength based on relevant parameters, such as the water–cement ratio, aggregate–cement ratio, age of testing, and percentage cement/metakaolin ratios (5% and 10%). We prepared 162 cylindrical concrete specimens with dimensions of 10 cm in diameter and 20 cm in height and 27 prismatic specimens with cross sections measuring 25 and 50 cm in length, with 9 different concrete mixture proportions. A longitudinal transducer with a frequency of 54 kHz was used to measure the ultrasonic velocities. An ANN model was developed, different ANN configurations were tested and compared to identify the best ANN model. Using this model, it was possible to assess the contribution of each input variable to the compressive strength of the tested concretes. The results indicate an excellent performance of the ANN model developed to predict compressive strength from the input parameters studied, with an average error less than 5%. Together, the water–cement ratio and the percentage of metakaolin were shown to be the most influential factors for the compressive strength value predicted by the developed ANN model.