ResumoThis study was conducted with the aim of evaluating the influence of different methods for end surface preparation of compressive strength test specimens. Four different methods were compared: a mechanical wear method through grinding using a diamond wheel established by NBR 5738; a mechanical wear method using a diamond saw which is established by NM 77; an unbonded system using neoprene pads in metal retainer rings established by C1231 and a bonded capping method with sulfur mortar established by NBR 5738 and by NM 77. To develop this research, 4 concrete mixes were determined with different strength levels, 2 of group 1 and 2 of group 2 strength levels established by NBR 8953. Group 1 consists of classes C20 to C50, 5 in 5MPa, also known as normal strength concrete. Group 2 is comprised of class C55, C60 to C100, 10 in 10 MPa, also known as high strength concrete. Compression tests were carried out at 7 and 28 days for the 4 surface preparation methods. The results of this study indicate that the method established by NBR 5738 is the most effective among the 4 strengths considered, once it presents lower dispersion of values obtained from the tests, measured by the coefficient of variation and, in almost all cases, it demonstrates the highest mean of rupture test. The method described by NBR 5738 achieved the expected strength level in all tests.Keywords: axial compression tests, surface preparation methods of cylindrical specimens.Este estudo foi realizado com o objetivo de avaliar a influência de diferentes métodos de regularização dos topos de corpos de prova cilíndricos de concreto nos ensaios de compressão axial. Foram comparados os métodos de desgaste pela retificação com disco de desbaste estabelecido pela NBR 5738 e equipamento tipo policorte estabelecido pela NM 77, o método da almofada de neoprene confinada C 1231 e o método de capeamento colado com argamassa de enxofre estabelecido pela NBR 5738 e NM 77. Para desenvolvimento desta pesquisa foram determinados 4 traços com níveis de resistências diferentes, sendo 2 do grupo 1 e 2 do grupo 2 de resistência da NBR 8953. O grupo 1 é composto pelas classes C20 até C50, de 5 em 5MPa, também conhecidos como concretos de resistência normal. O grupo 2 é formado pelas classes C55, C60 até C100 de 10 em 10MPa, também conhecidos como concretos de resistência elevada. Os ensaios de compressão foram realizados com 7 e 28 dias para os 4 métodos de regularização. Os resultados deste estudo apontam que o método estabelecido pela NBR 5738 é o mais eficaz entre os 4 níveis de resistência estudados por possuir menor dispersão nos valores obtidos nos ensaios, mensurado por meio do coeficiente de variação e, em quase todos os casos, apresentar maior média das tensões de ruptura. O método da NBR 5738 atingiu o nível de resistência desejado em todos os testes.Palavras-chave: ensaios de compressão axial, métodos de regularização de corpos de prova cílidricos.

Die brasilianische Bauweise für Beton-und Ziegelmauerwerk hat viele Gemeinsamkeiten mit üblichen Konstruktionen, wie man sie auf der ganzen Welt findet: Steine ähnlicher Form werden in Mörtel eingebettet, vertikale und horizontale Bewehrung wird in nachträglich verfüllte Aussparungen gelegt, die Tragwerksplanung und Konstruktion folgt universellen Prinzipien und die lokalen Bemessungsnormen entsprechen denen anderer Länder. Im Vergleich zu herkömmlichen Stahlbetonlösungen hat sich der tragende Mauerwerksbau in Brasilien jedoch aufgrund seiner Wirtschaftlichkeit und Einfachheit zu einer der bevorzugten Bauweisen für den Hochhausbau entwickelt. Dieser Fachbeitrag gibt einen Überblick über die Konstruktion von tragendem Mauerwerk in Brasilien, zeigt Fallbeispiele von bedeutenden Hochhausbauten und zeigt auf, inwiefern sich brasilianische Materialien, Normen und Praktiken von anderen Ländern unterscheiden. Abschließend wird erläutert, wie der Einsatz hochfester Steine der steigenden Nachfrage nach immer höheren Gebäuden gerecht wird und warum Bauherren und Generalunternehmer häufig tragendes Mauerwerk bevorzugen. Stichworte: Mauerwerk; Hochhäuser; Hochbau; Hochhausbau; brasilianische Bauweise 1 Allgemeines Seit den 1960er Jahren werden in Brasilien mehrstöckige Gebäude aus Betonsteinen und Ziegeln errichtet. Die hochwertigen Mauersteine verfügen über eine hohe Druckfestigkeit und sind in Standardformaten erhältlich. Der erste große brasilianische Steinproduzent nahm 1966 seinen Betrieb auf. Zu dieser Zeit verfügten nur sehr wenige Tragwerksplaner über die notwendigen bautechnischen Fachkenntnisse. Deshalb wurden häufig ausländische, insbesondere nordamerikanische, Normen angewandt und sogar externe Berater hinzugezogen, die die Bauvorhaben unterstützten. Da die Bemessungsempfehlungen auf ausländischen Normen beruhten, die die sozialen und ökologischen Besonderheiten der jeweiligen Region berücksichtigten, wurde Mauerwerk durchgängig mit einem hohen Bewehrungsgrad und einer hohen Anzahl von verfüllten Aussparungen eingesetzt. Bis in die 1980er Jahre gab es in den Studiengängen des Bauingenieurwesens nirgends das Fach Mauerwerksbau. Das erste große brasilianische Mauerwerksprojekt war 1966 der Bau mehrerer vierstöckiger Türme in der Stadt Sao Paulo. Später wurden im Rahmen desselben Projekts vier 12-geschossige Türme aus bewehrtem Mauer- High-rise concrete and clay block masonry building in Brazil Hochhäuser aus Mauerwerk in BrasilienBrazilian structural concrete and clay block masonry construction shares many common features with construction all over the world: blocks of a similar shape are bedded in mortar, vertical and horizontal reinforcement is placed in grouted cells, engineering analysis and design follows universal principles and local design codes mimic those adopted elsewhere. However, loadbearing masonry construction in Brazil has become one of the most preferred high-rise building systems due to its cost-effectiveness and ease of construction compared to normal reinforced concrete solutions. This paper pro...

Este trabalho avalia a resistência à tração na flexão para a alvenaria estrutural de blocos de concreto, executada com juntas finas de composto polimérico. Para isso, foram realizados ensaios por meio da NBR 16868-3 (2020) e AS 3700 (2017), para prismas com blocos de concreto de 4, 8 e 16 MPa, considerando argamassa cimentícia e composto polimérico. Os resultados mostram que os valores de resistência a tração na flexão são maiores para compostos poliméricos. Quando foram comparados os dois ensaios, constatou-se que os dados obtidos por meio da norma australiana são maiores que os obtidos com o ensaio da norma brasileira.

This study aims to evaluate the adherence between clay blocks and grouts. For this purpose, push-out and pull-out tests were performed to assess the adherence presented by different combinations of five types of clay blocks and two types of grouts. The results demonstrated that the geometry of the cells of the clay blocks has a preponderant role in their adherence with grout, as the extent of the contact area between grout and block depends on the geometry of the cell. The shrinkage of the grout can cause the formation of cracks at the interface between block and grout, reducing the adherence between the materials. The shrinkage formed inside each type of block can be estimated based on the testing procedure developed in this research and used in conjunction with the geometric characteristics of the cells of the blocks to estimate the maximum load in the push-out tests. The test procedure developed to estimate the percentage of contact area lost due to grouts shrinkage shows to be promising, since its results were used in the equation to estimate the bond strength between blocks and grouts and shown good correlation. However, more study must be done because there are other variables that can affect the results. These results show that it is possible to use different characteristics of blocks and grouts to increase the adherence between these materials and provide a better behavior for reinforced masonry structures. However, it looks like if block types with a grooved hollow cell are used, a bigger contact surface is produced, and a higher bond strength appears to be assured.