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Copyright of Revista de Arquitetura IMED is the property of Revista de Arquitetura IMED and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The use of recyclable materials in the elaboration of hydraulic concrete is currently booming in order to reduce environmental impacts and improve the mechanical properties of concrete, representing optimal adhesion between aggregates, cement and water. The objective of this work was to evaluate the mechanical behavior of hydraulic concrete with the addition of nylon fibers and microparticles of PET plastic bottles. The mortars or specimens had their physical properties evaluated in fresh state and hardened their resistance to compression and flexural tensile, for these 6 dosages were made: a control mixture and others with designed fibers. For the execution of the tests, an Amsler universal testing machine with a nominal capacity of 30,000 kilograms and a resolution of 10 kg, calibrated for analysis in accordance with ISO 376, was used. It was evidenced that the flexural strength improved by 80% (c), 75% (d), 80% (e) and 95% (f) at 28 days, for compression an 80% increase in strength was evidenced in all samples with respect to the control specimen. It was concluded that the performance of hydraulic concrete with the addition of PET fibers was better than conventional concrete, the properties of the studied specimens improve with respect to the control specimen. [ABSTRACT FROM AUTHOR]

Objetivo: Esta investigación tiene como objetivo reducir el contenido de cemento Portland en el concreto mediante el uso de bajas cantidades de aditivos. Esto, como estrategia de la asociación Industria-Universidad hacia la economía circular de hormigón en Medellín, Colombia. Metodología: Utilizando un modelo estadístico factorial y multinivel, se prepararon mezclas de mortero con dos superplastificantes diferentes: el aditivo 1, basado en policarboxilato; y el aditivo 2, basado en naftaleno. Las muestras se evaluaron a los 7, 14, 21 y 28 días de curado mediante pruebas de compresión. El modelo mencionado se implementó para estudiar la influencia de los aditivos en la mezcla de mortero de cemento. La microestructura se analizó con difracción de rayos X y microscopía electrónica de barrido. Resultados: Los resultados revelaron que ambos aditivos mejoraron la trabajabilidad. El aditivo 1 mostró mejores propiedades generales, por lo que esta investigación se enfocó en él. Conclusiones: El aditivo 1 (basado en policarboxilato) reduce la relación agua/cemento de 0,485 a 0,38, lo cual corresponde a una reducción de cemento del 7,3 % y una reducción de agua del 27,3 %.

As estações de tratamento de esgoto são exemplos de estruturas submetidas a ambientes industriais altamente agressivos. Deste modo, o objetivo do estudo foi avaliar o efeito de cristalizantes comerciais e do silicato de sódio (Na2SiO3) no aumento da durabilidade do concreto armado submetido ao ataque sulfúrico de origem biogênica em uma ETE e de origem química em laboratório. Para atingir esse objetivo, foram realizados diversos ensaios, como velocidade de degradação, variação de massa, profundidade de neutralização, velocidade de pulso ultrassônico, resistência à tração na flexão e à compressão. Ao final, pôde-se concluir que a velocidade de degradação e a perda de massa são menores nos concretos com cristalizantes e cinza volante e que esses dois ensaios são os mais confiáveis para avaliar a durabilidade em longo prazo de estruturas de concreto exposto ao ácido sulfúrico.

O concreto autoadensavel representa um avanco na tecnologia do concreto, pois e capaz de reunir desempenho, uniformidade e outros requisitos que nao se podem alcancar com o concreto convencionalmente vibrado. A principal caracteristica deste concreto e sua elevada fluidez, obtida utilizando materiais finos e aditivos modificador de viscosidade e superplastificante, entretanto, o excesso na dosagem deste ultimo torna a mistura suscetivel a segregacao e exsudacao, alterando suas propriedades no estado endurecido. Atualmente, ensaios nao destrutivos (END) sao empregados para avaliar as propriedades fisicas e mecanicas do concreto, sem causar danos ao elemento analisado, dentre os quais, destaca-se a ultrassonografia, que possibilita realizar uma avaliacao da homogeneidade do concreto atraves da velocidade de pulso ultrassonico, e, estudos recentes demostram que o formato de onda pode trazer parametros potencialmente mais eficazes na analise de concretos nao-homogeneos. Neste contexto, o presente estudo avaliou as propriedades de um traco de concreto autoadensavel com duas dosagens distintas de aditivo superplastificante, utilizando parametros advindos do formato de onda ultrassonica para identificar a exsudacao do concreto. Os resultados mostraram que a velocidade de grupo e a propagacao da energia pelo material apresentam-se como parametros sensiveis as variacoes da uniformidade do concreto, demonstrando capacidade na deteccao da exsudacao.

Se evaluó el desempeño de la influencia de la ceniza de bagazo de caña (CBC) como filler en mezclas de concreto autocompactante (CAC), adicionado en un 0%, 5%, 10%, 15%, 20% y 25% con respecto al peso de cemento. La caracterización de la ceniza se realizó mediante FTIR, FRX y DRX. Las propiedades de trabajabilidad del CAC fueron determinadas mediante ensayos de flujo de asentamiento, anillo J, caja en L, embudo V, Índice de Estabilidad Visual y resistencia a la compresión. De acuerdo con los resultados, los porcentajes de 10 al 20% en las mezclas de CAC obtuvieron un desempeño satisfactorio, evidenciando parámetros de trabajabilidad y resistencia a la compresión sobresalientes comparados con trabajos similares a los publicados en la literatura.

O objetivo desse trabalho é estudar a capacidade de transporte de íons cloretos em concretos com adições de metacaulim e cinza volante. Para tanto, foram realizados ensaios de resistividade elétrica superficial e difusão de íons cloreto (NT Build 443). Como resultado, observou-se que o uso das adições empregadas foi eficiente para retardar o ingresso de íons cloreto, reduzindo o coeficiente de difusão de cloretos - Dns e aumento na resistividade elétrica superficial - ρ nos materiais estudados. A relação geral entre Dns e ρ para os concretos estudados pode ser expressa por Dns = 2,7E-7*ρ-0,475 e a relação entre os cloretos acumulados no concreto e a resistividade elétrica superficial pode ser expressa por Clacum = 4,09-0,20945𝜌.

The growing quest to reduce the impacts generated on the environment, the application of materials of alternative origin in civil construction increases and the need for companies to reduce costs through the recycling of materials that would be disposed of in the trash. One of these materials is PET (polyethylene terephthalate), a material with certain resistance and flexibility This study envisages analyzing the tensile strength of concrete when incorporated with fiber or PET bottle powder as an addition, verifying the feasibility of this union. [ABSTRACT FROM AUTHOR]

El ladrillos es uno de los materiales mas requeridos para la construcción de viviendas, los cuales debido a un exceso de compra, o por rotura mediante traslado no se utilizan totalmente. El presente trabajo tiene como objetivo lograr una revisión sistematica sobre el uso de ladrillos triturados en el concreto, con el fin de sintetizar los resultados obtenidos y discutir la posibilidad de poder utilizar en las diferentes áreas de la construcción este material reciclado. Se hizo una revisión de 50 articulos indexados entre los años 2015 al 2021, distribuido de la siguiente manera: 40 articulos son de Scopus y 10 de Sciencedirect, de los cuales muestran como influye el ladrillo triturado en las propiedades del concreto. La revisión de los resultados constataron que los agregados de ladrillos reciclados (RBA) generan una deficiencia en resistencia a la compresión y una mayor porosidad a diferencia del agregado natural (NA).

El objetivo de este trabajo fue evaluar la posible aplicación del sustrato de producción de shiitake como aditivo al concreto, estudiando su constitución química y evaluar las probetas. En el análisis elemental de las muestras de sustrato realizado por fluorescencia de rayos X, la muestra bloques inoculados que no pudieron producir (SSP) mostró una disminución de calcio, silicio, fósforo, manganeso y zinc en comparación con las muestras bloques inoculados que están listos para iniciar la producción (SIP) y bloques inoculados al final de la producción (SFP). Las mezclas de concreto 1:1.5:2.2 y 1:2:3 después de 28 días de moldeado, cuando se fue agregado 5 % del sustrato, causó resistencias mecánicas a la compresión de 0.19 ± 0.02 MPa y 0.30 ± 0.03 MPa, y absorción de agua de 10.17 ± 0.11 % y 9.03 ± 0.22 %, respectivamente. Con la adición de 1 % presentó 18.87 ± 1.16 MPa y 21.57 ± 0.66 MPa, y 5.58 ± 0.31 % y 6.44 ± 0,04 %, respectivamente. Sin aditivo, 28.62 ± 3.45 MPa y 17.28 ± 0.81 MPa, y 6.23 ± 0.11 % y 5.44 ± 0.17 %, respectivamente. La interacción entre los factores, tipo de hormigón y concentraciones de sustrato, fue significativa (p

Las colillas de cigarrillo tardan en degradarse entre 2 y 10 años; tienen sustancias perjudiciales para el medio ambiente pues una sola colilla puede contaminar 8 litros de agua de mar y hasta 50 litros de agua potable, no son residuos biodegradables por lo que tirarlas junto con los residuos orgánicos no es una alternativa. Es un residuo diminuto difícil de reciclar, por estas razones, deben buscarse alternativas innovadoras para su disposición y destino final. En la industria de la construcción el concreto es uno de los materiales más utilizados en el mundo por sus características físicas y mecánicas antes diversas exigencias y su gran disponibilidad local. El objetivo del trabajo consiste en emplear las colillas en el concreto como una alternativa para la disposición final de estos residuos disminuyendo de esta manera el porcentaje de desechos en el ambiente. Se diseñaron mezclas con resistencias a la compresión de 24.5 y 29 MPa a las cuales se les adicionó la colilla de cigarrillo en diferentes porcentajes. Se realizaron ensayos al concreto en estado endurecido de compresión cilíndrica y tracción indirecta. En estado fresco se midió la trabajabilidad del concreto, temperatura, densidad y contenido de aire. Con los resultados obtenidos se obtuvieron resultados favorables, demostrando que la adición de las colillas al concreto como alternativa para la disposición final de dichos residuos es viable.

Este trabalho analisa o impacto da corrosão na estabilidade global de colunas em concreto armado, avaliando a eficácia dos critérios de redução de rigidez propostos pela ABNT NBR 6118:2014. A partir das análises, utilizando-se modelos em elementos finitos que reproduziram o comportamento dos materiais, definiu-se que a corrosão causa a intensificação dos esforços globais de segunda ordem na estrutura. Entretanto, em situações críticas, a perda de equilíbrio na seção transversal conduziu à falha estrutural antes mesmo da perda de estabilidade. O estudo foi realizado tanto por meio de uma análise não-linear geométrica, quanto pela aplicação do coeficiente γz, onde concluiu-se que a posterior adição de efeitos reológicos pode conduzir a uma configuração que ultrapasse os limites propostos pela norma brasileira.

O objetivo desse estudo compreende na utilização de resíduos sólidos industriais quanto à melhoria das propriedades mecânicas dos compósitos cimentícios. Para tanto, foi avaliado a incorporação do pó de “brita” granítica e pó de mármore na confecção de compósitos à base de cimento, substituindo parcialmente o agregado miúdo natural em teores de 50% e 100%. Para isso, foram realizados ensaios de caracterização dos agregados, além da avaliação da resistência à compressão axial dos corpos-de-prova. Os resultados evidenciaram que as misturas contendo 50% de agregado reciclado confere ao material uma resistência à compressão de 29,09 MPa, ou seja, 4% superior quando comparado com as misturas de referência, tornando os resultados satisfatórios, demonstrando a viabilidade dos agregados reciclados em peças de concreto

Lightweight concrete (LWC) has become an outstanding material in the construction sector to conform nonstructural and structural members into buildings. Expanded clay aggregate is a special type of lightweight aggregate formed by heating clay with little lime content, having low unit weight, high durability, and mechanical strength. Despite the massive use of the expanded clay lightweight aggregate worldwide, their use in the Colombian context is still limited. This research reports the characterization of the behavior of lightweight concrete from Colombian expanded clay aggregates. Experimental tests on fresh and hardened state (compressive strength, apparent density, and chloride migration) were carried out on lightweight concrete added Colombian expanded clay aggregate. It was found that the inclusion of up to 50% of the Colombian expanded clay aggregate causes a 15% workability decrease, 36% compressive strength decrease, 22% apparent density decrease as well as 34% decrease in the chloride migration coefficient of the lightweight concrete. In the same way, the lightweight concrete added with 50% of Colombian expanded clay aggregate meets the lightweight concrete requirements prescribed by the ACI 318 building code in terms of compressive strength, and unit weight. From the results, it is concluded that the use of Colombian expanded clay aggregate added up to 50% by weight of conventional aggregate is feasible to manufacture structural lightweight concrete. [ABSTRACT FROM AUTHOR]

This research work shows the contribution of supplementary cementitious materials (SCMs) in reducing the corrosion phenomenon in steel embedded in ternary concrete. Ternary steel-concrete systems were developed, consisting of AISI 1018 (AC) steel embedded in ternary concrete with a water/cement ratio of 0.45. Partial substitutions were made with respect to the mass of ordinary portland cement (OPC) by sugarcane bagasse ash (SCBA) and fly ash (FA) at 10, 20 and 30 %, the value of these percentages corresponds to 50 % CBCA and 50 % CV. The systems were evaluated with the electrochemical polarization resistance (Rp) technique, where corrosion current density (icorr) and corrosion velocity (Vcorr) were analyzed as indicators to evaluate corrosion phenomenon. The steel-concrete system with 20 % substitution (AC-CT20), decreased the Vcorr by 89 % with respect to the reference system (AC-REF). This result was attributed to the AC being in a passive state, which was associated with the passive film formation that was confirmed by the value of the mean icorr of 0.09 µA/cm² . [ABSTRACT FROM AUTHOR]

Concrete in the construction industry is a widely used material, so there has been research on how to innovate the materials that are usually used for the production of concrete, but without altering the mechanical properties, that is to say that they are equal or better than they usually are; so using recycled material is a good option because it would help to reduce pollution, reduce the use of raw materials and improve the environmental situation. The objective of this article is to review different research on a material called tire steel fibers incorporated in concrete, which allows improving the properties of workability, compressive strength, flexural strength and density of concrete. A search of 80 review articles indexed in different databases was performed, in addition to being published research from the last 7 years between 2015 and 2021, which are divided as follows: 14 from ScienceDirect, 21 from EBSCO, 20 from Sopas and 24 from Web Of Scince, documents that point out the importance of sustainable construction and the description of recycled tire steel fibers. The steps, methods and techniques of selection, characteristics and adequate volume that the fiber should have were reviewed, after discussing and analyzing the results, it is concluded that recycled tire steel fibers cause positive effects on the mechanical characteristics of concrete. [ABSTRACT FROM AUTHOR]

The objective here is to determine the influence of the incorporation of recycled rubber in structural concrete and its hypothetical seismic response, developing the investigation under a type of applied investigation, of pure experimental design with a non-probabilistic sample of DBCA method of 84 briquettes that include the standard concrete with a design of 210 kgf/cm2 and concrete with the incorporation of recycled rubber at 2%, 4% and 6%, which were evaluated at 7, 14 and 28 days of age under the technique From direct observation, parameters such as resistance to compression and indirect diametral traction where the results showed that the most optimal incorporation was 4% of both fine and granulated rubber at 28 days in all parameters, surpassing the resistance to compression by 3.76% and 4.14%, as well as the diametral indirect tensile strength by 8.98% and 16.05% with respect to the standard concrete and according to or with the analysis of the hypothetical seismic response with the optimal rubber percentages found, an improvement percentage was determined with the incorporation of 4% rubber, both fine and granulated, in the maximum drifts for the X-X direction 3.44% and 3.87%, as well same for the Y-Y direction of 3.47% and 3.96% respectively compared to the concrete pattern. Thus demonstrating that the use of 4% rubber, both fine and granulated, in concrete is acceptable. [ABSTRACT FROM AUTHOR]

Copyright of Revista Avances: Investigación en Ingeniería is the property of Universidad Libre, Facultad de Ingenieria and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Among the pathological manifestations associated with reinforced concrete, corrosion of the reinforcement is one of the most serious issues since it is related to the durability of the structures and the safety of the users. Although the reinforcement in the structural components is protected by a covering layer, carbonation or the presence of chlorides in the concrete generates necessary conditions for corrosion of the reinforcement. This causes a reduction in the cross section and the generation of products that, due to their volumetric expansion, cause cracks in the interior of the concrete. This work evaluates the effects of corrosion on mechanical properties of corroded reinforcements through accelerated conditions in the laboratory. Steel bars installed inside cylindrical concrete specimens are subjected to accelerated corrosion, immersed in a saline solution with the application of an electric current for periods of 1, 3, 5 and 7 d. After corrosion, the steel bars are removed and their weight loss, degree of corrosion and tensile strength are evaluated. The results demonstrate an increased degree of corrosion with exposure time to the saline solution and the non-uniform reduction of the tensile strength of the bars due to the formation of corrosion pits with varying depth along the bar.

El objetivo de este trabajo fue evaluar el efecto del uso del PET reciclado en la elaboración de concreto para pavimentos, con la finalidad de promover su uso racional en lugar de desecharlo y disminuir la contaminación ambiental que representa el plástico PET. En esta investigación se comparó el concreto con agregado patrón diseñado para una resistencia de f'c=280 kg/cm2 con adiciones al 3%, 4% y 5% de PET en los ensayos de permeabilidad, compresión axial y flexión. Los resultados muestran que el PET en un 0.3% mejora la resistencia a la compresión, mientras que en un 0.4% de PET mejora la flexión y permeabilidad. Se concluye que si se busca la mayor resistencia se utilice menor dosificación de PET y si se busca mayor flexión y permeabilidad se utilice mayor porcentaje de PET. Este estudio demostró que el PET si influye significativamente en las propiedades físico-mecánicas del concreto permeable en pequeñas adiciones.

Currently, one of the methods to improve the properties of materials in construction is the use of nanomaterials. The objective of this paper is to review the technological advances in the application of nanomaterials, which improve mechanical properties when used in concrete, soils, pavements, among others. A total of 82 articles corresponding to the Scopus, Ebsco, Science Direc and IOP Science databases were reviewed. The studies show that with the application of nanomaterials, positive results are obtained in the improvement of the compressive and flexural strength of concrete, improvement in the stabilization of soils and in asphalt, avoiding the formation of grooves and cracks. The studies conclude that the applicability of nanomaterials in the construction industry is a good alternative from a sustainable point of view, in order to reduce the indiscriminate use of non-renewable resources. [ABSTRACT FROM AUTHOR]

Used tires constitute an environmental problem, since they are visually contaminating, they attempt against public health and can be fire generators. The purpose of this work is to evaluate the technical feasibility of incorporating rubber from used tires as a raw material in the elaboration of the wear layer of washed grain two-layer tiles. For the wear layer composed of gray cement and aggregate (granite and crushed rubber), three mixtures were designed with granite substitution by crushed rubber in percentages of 0%, 30%, and 50%. Physical and mechanical properties were evaluated, using as reference document the standard NTC 2849: Tiles with grain surface (terrazzo). The results show that wear resistance is not affected or favored by the addition of rubber and that impact resistance improves with the increase in the percentage of granite replaced by rubber. Also, it was found that density decreases and water absorption increases with the addition of rubber. The present study indicates that the incorporation of crushed rubber into the wear layer of washed grain tiles is feasible and can help in reducing environmental contamination. [ABSTRACT FROM AUTHOR]

Grande parte do lodo presente nas estações de tratamento de efluentes tem como destino o seu descarte em local inadequado ou sem o tratamento correto, podendo afetar significativamente o meio ambiente. Portanto a vigente pesquisa tem por finalidade a análise do lodo seco de uma indústria frigorífica como substituição parcial do agregado miúdo para o concreto não estrutural, sendo necessário optar por traços com menor proporção desta a fim de não extrapolar os custos de consumo. Os corpos de prova subsidiados pela NBR 5738 foram moldados com adição parcial do lodo de frigorífico seco na substituição do agregado miúdo, sendo respectivamente 2%, 5% e 8%, e ensaiadas a compressão axial no laboratório de Engenharia Civil da UNOESTE. Por meio dos resultados obtidos, houve um aumento de resistência comparado ao traço padrão nos corpos de prova com menor adição de lodo, entretanto o resíduo sólido retém grande quantidade de água, sendo necessário optar por traços com menor proporção da mesma.

Este artigo tem por finalidade a determinação da Avaliação do Ciclo de Vida (ACV) e do Custo do Ciclo de Vida (CCV), em concretos através da substituição do cimento Portland (CP) por elevados teores de filer calcário (FC) e cinza volante (CV), em teores de 50% a 80%, com o propósito de diminuir as emanações de CO2 na fabricação do CP. Foi aplicado a ACV e o CCV com a intenção de aferir a sustentabilidade dos concretos estudados com base nos impactos ambientais e no custo. O estudo demonstrou que, por ocasião da elevação da proporção de FC nas misturas, o impacto ambiental é reduzido devido a minoração da utilização de CP. O comportamento foi observado na totalidade dos índices ambientais estudados demonstrando a estreita relação entre a proporção de CP e a poluição do meio ambiente, chancelando, assim, a eficácia na utilização de elevados teores de FC. Os resultados mostraram a exequibilidade de concretos com elevados teores de FC, do ponto de vista técnico-ambiental, considerando que os resultados alcançados apontaram, de maneira inequívoca, para a excelente performance ambiental das misturas.

Este artículo tiene como objetivo hacer una revisión de los trabajos realizados usando polvo de mármol como sustitución de cemento, arena o agregado fino en concreto, mortero y ladrillos. Se revisaron investigaciones realizadas en varias partes del mundo con procedimientos experimentales diferentes. Se concluye que el polvo de mármol se puede usar como sustituto parcial de cemento o agregado fino (hasta por un 15 %, dependiendo del material a sustituir), sin afectar la resistencia a compresión de las muestras o las piezas, y sin importar la forma. Por lo tanto, el polvo de mármol no solo ayuda a aminorar la contaminación que genera, sino que también a la reducción de uso como arena y polvillo, aportando al desarrollo sustentable.

The following work presents, defines and compares different materials used in civil construction over the years, highlighting for this approach adobe, clay, reinforced and prestressed concrete. It is known that each material has very peculiar characteristics and properties and this is what defines the best applicability best suited to meet a specific request. However, over the years, the demand for materials of greater strength, durability, workability, thermal comfort and a concern for aesthetics gradually emerged, which influenced changes in materials and construction techniques. For a better understanding of the topic, a literature review of the contents proposed in articles and books was carried out, comparing the nature and main properties of each contextualized material to its respective temporal reality and cultural predominance. Regarding each material, the following items were addressed: such as resistance, thermal behavior, practice and use in civil construction, also highlighting the improvement of materials and methods developed for each type of application, as engineering and technology have evolved and continue to evolve. [ABSTRACT FROM AUTHOR]

The objective of the research is to determine the effect of the use of recycled PET on the permeability, compressive strength, and flexure of the permeable pavement f'c=280 kg/cm2. The methodology is applied type, experimental design, and quantitative approach. Permeable concrete is a type of porous pavement that seeks to solve the problems of traditional pavements, since traditional pavements, by not having an adequate gutter, tend to accumulate rainwater causing various accidents due to lack of inertia and decrease in pavement life. PET is a material that is found everywhere as waste, this material tends to resist tensile loads. The results show that 0.3% PET improves compressive strength, while 0.4% PET improves flexing and permeability. It is concluded that if the greatest resistance is sought, a lower dosage of PET is used and if greater flexing and permeability is sought, a higher percentage of PET is used. This study showed that PET does have a significant influence on the compressive strength, flexural strength, and permeability of pervious concrete. [ABSTRACT FROM AUTHOR]

Introduction--The large quantities of fly ash obtained as a by-product of coal combustion in thermoelectric power plants have generated concern about its environmental impact; for example, in Colombia this waste represents 6 million tons per year. One of the solution strategies is the use of this residue in industrial processes. The residue has pozzolanic properties useful in industries such as cement and concrete. Objectives--The objective of this research is to evaluate the compressive strength at different ages of concrete by replacing cement with 40% fly ash. Methodology--Alkaline activation with NaOH and activation with sodium sulfate and limestone, in different proportions, were used. Results--The results showed that activation improved the performance of the ash. Conclusions--Better mechanical properties were obtained than without activation. [ABSTRACT FROM AUTHOR]

The fatigue behavior of ultrahigh-performance fiber-reinforced concrete for use as an overlay in the typical rehabilitation of a flexible pavement structure was analyzed in this study. Compression and four-point bending tests were carried out to characterize the concrete mechanical properties. Fatigue tests were performed using the four-point method, and test beams were evaluated without precracking. The specimens were subjected to constant-amplitude sinusoidal loading with a loading frequency of 10 Hz. The magnitude of each stress level was calculated as a percentage of the initial crack stress. The following results were obtained for the concrete: a compressive strength of 127.1 MPa, bending yield strength of 6.23 MPa, maximum bending stress of 9.89 MPa, Young's modulus of 38.1 GPa, and dynamic modulus of 28.6 GPa. The stress and strain at one million cycles were 6.0 MPa and 166 μm/m, respectively. The fatigue test results indicated superior properties of the ultrahighperformance concrete to those of similar materials. [ABSTRACT FROM AUTHOR]

Copyright of Endoxa is the property of Editorial UNED and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research was conducted to determine the effect of the scallop shell lime (SSL) on the compressive strength of concrete made with Portland cement type Ico and natural aggregates from a quarry, where SSL was added at 3%, 4% and 5%. The physical and mechanical characteristics of the aggregates were determined based on the N.T.P. 400.037/ASTM C22 standard, and the mix design was carried out through the ACI method. The SSL was used due to the high calcium content present in the valve. Standard concrete controls were prepared and cured by adding 3%, 4% and 5% SSL (339.0183/ASTM C192M), which were analyzed at 7, 14 and 28 days of curing. The results showed that the compressive strength at 28 days was 242.63 kg/cm² when 3% SSL was added, increasing with respect to the standard control by 16%. With the addition of 4% SSL, the maximum strength reached was 245.25 kg/cm², and with 5%, the compressive strength reached was 261.17 kg/cm², increasing by 24%. In conclusion, the SSL positively affects the increase of concrete strength, and the percentage with the highest incidence is 5%. [ABSTRACT FROM AUTHOR]

Concrete is one of the most studied industrial products with the aim of improving its durability, strength, and workability, as well as developing innovative alternatives in its production to reduce the environmental footprint (Rivera, 2013). This research validates the use of industrial waste generated in the department of Boyacá - Colombia, within the production of concrete for the construction of rigid pavements. The research followed several stages, beginning with the physical, chemical, and mechanical characterization of the materials and the design of the standard mixture following the ACI 211 methodology. Subsequently, the 25%, 50%, 75%, and 100% of the gravel was replaced by electric arc furnace slag (EAFS), and 20, 30 and 40% of the sand by the recycled ground glass (RGG). Finally, the compressive strength of the concrete mixtures was analyzed. [ABSTRACT FROM AUTHOR]

The present research study examined the optimal conditions for using aluminous sludge, from a drinking water treatment system, as a partial substitute for cement to manufacture non-structural construction materials. Standard mixtures consisted of aluminous sludge (5, 10, 15 and 20%) and cement. At 7, 28, and 42 days, mixtures were examined for granulometry, X-ray fluorescence, organic matter content, humidity, compressive resistance, and absorption. The results showed significant differences with variations in compressive strength between 2.60 and 7.70 MPa. The mixtures with 15 and 20% aluminous sludge were the only ones that met the limits established for non-structural building materials by the ASTM-C129 regulation. In conclusion, introducing aluminous sludge (15 and 20%) as a substitute for cement did not deteriorate material mechanical resistance. [ABSTRACT FROM AUTHOR]

Contexto: Este artículo analiza la efectividad de apantallamiento electromagnético de varias estructuras de concreto en función de la variación del grosor y el contenido o nivel de humedad (NH) para un rango de frecuencias definido. Método: El estudio se fundamenta en la implementación de simulaciones en dos dimensiones (2D) usando un software basado en el método de elementos finitos (FEM) y se desarrolló a partir de un conjunto de valores obtenidos de la aplicación de modelos matemáticos para medios dieléctricos. Inicialmente, se caracterizan las propiedades eléctricas complejas de las estructuras (permitividad dieléctrica y conductividad) aplicando el modelo matemático de Jonscher de tres variables. Posteriormente, se evalúan dichas propiedades sobre diferentes estructuras de concreto para un rango de frecuencias determinado. Resultados: Se observó que el blindaje electromagnético ofrecido por el concreto aumenta cuando se incrementa el NH y el grosor de las estructuras. Adicionalmente, las pruebas evidencian que las pérdidas de energía por absorción son mayores en comparación con los demás tipos de pérdidas analizadas en el estudio. Conclusiones: Luego de la investigación se puede afirmar que modelo electromagnético de Jonscher ofrece una buena respuesta al ser aplicado a las propiedades eléctricas complejas del concreto en un rango de frecuencia desde 250 MHz hasta 700 MHz. Asimismo, al variar el grosor y el NH en las estructuras analizadas, se evidenció un aumento en la efectividad de apantallamiento electromagnético total. Debido a que el concreto es un medio dieléctrico imperfecto, las pérdidas de energía por reflexión son bajas comparadas con las pérdidas de absorción y de múltiples reflexiones. Aun así, este material estructural puede ser usado como apantallamiento natural contra perturbaciones electromagnéticas radiadas en la banda de UHF. Agradecimientos: Este trabajo fue posible gracias al soporte y asesoría del Grupo de compatibilidad e interferencia electromagnética (GCEM-UD) de la Universidad Distrital Francisco José de Caldas.

El presente artículo forma parte del proyecto de investigación promovido por la Universidad Nacional de Ingeniería, titulado “Riesgo Urbano: aproximación diagnóstica para la ciudad de Managua” el cual se ha desarrollado desde el 2019 y en el transcurso del 2020. El cemento y la mampostería de bloques huecos son de los materiales más utilizados para la construcción en américa latina, así mismo son de los principales volúmenes de desechos que se generan al acabar la vida útil de un edificio, creando impactos negativos al entorno natural. Pero existen otras alternativas para este tipo de desechos como es la reutilización en sub-base para carreteras y la integración en diseños de mezclas para elementos de concreto, bloques u otro tipo de piezas implementadas en la construcción. En este artículo se exploran tres investigaciones realizadas respecto al tema y se proponen actividades que favorezcan un estudio en la Universidad Nacional de Ingeniería aplicando pruebas básicas al alcance de la tecnología con que se cuenta, a la vez que se sugieren opciones de usos para las diferentes mezclas de concreto reciclado acorde a su capacidad estructural.

O concreto é o material de construção civil mais utilizado no mundo devido à sua versatilidade, propriedades mecânicas, baixo custo e grande disponibilidade de elementos constituintes. Dentre suas propriedades, destaca-se o bom desempenho quando exposto a elevadas temperaturas, garantido por características como a baixa difusividade térmica e incombustibilidade. Apesar de apresentar boa resistência ao fogo, estruturas de concreto nessas situações têm sua resistência mecânica reduzida em situações de incêndio incorrendo em problemas estruturais. Os efeitos do método de resfriamento do concreto após exposto às elevadas temperaturas nas propriedades mecânicas ainda requer estudos. Nesta pesquisa, corpos de prova cilíndricos foram moldados e submetidos a temperaturas de 200 e 400 oC por um período de 7 horas, sendo posteriormente submetidos a dois modos de resfriamento: imersão em água e ao ar ambiente. Após o resfriamento, os corpos de prova foram ensaiados a compressão axial e os resultados comparados aos corpos de prova de referência curados a 23 oC em câmara úmida. Os resultados demonstraram que o aquecimento até 200 oC não resultou em decréscimo de resistência independentemente do tipo de resfriamento aplicado, entretanto para 400 oC ocorreu redução de aproximadamente 30% da resistência, de forma mais acentuada no resfriamento em água.

Abstract Carbonation has been a concern of constructors and researchers because, by lowering the pH of the interstitial solution of the concrete, it can favor the post-deposition and subsequent corrosion of reinforced concrete reinforcement. Among the factors that influence carbonation is the use of pozzolanic materials, such as metakaolin. However, there is no consensus as to the positive or negative contribution of these additions. This work evaluated the influence of metakaolin on the mechanical properties, porosity and in particular on the carbonation of concrete, from the addition of 0%, 5%, 10% and 15% of metakaolin, in relation to the cement mass. From the results, it was observed that the addition of metakaolin, while not significantly influencing the porosity, gave the concrete a greater resistance to axial compression, a decrease in the capillary absorption and delayed the advance of the carbonation front in the concrete.

Esta investigación tiene como objetivo determinar los efectos del uso de productos curadores en el concreto hidráulico mediante condiciones de laboratorio. No obstante que investigaciones y especificaciones técnicas de los productos curadores indican mejoras en el curado del concreto, su utilización y posibles ventajas deben ser experimentalmente verificadas para las condiciones y tipos de concretos fabricados en Costa Rica. Se utilizan tres tipos de productos curadores, el primero corresponde a un producto curador transparente a base de silicatos que no produce membrada (C1), el segundo es un producto curador formador de membrana a base de resinas (C2) y el tercero es un producto curador formador de película a base de solución coloidal (C3). Por medio de ensayos de laboratorio se determina la resistencia a la compresión, módulo de ruptura y cambio de longitud (expansión o contracción) del concreto para diferentes condiciones de curado. En general, los resultados indican que los productos curadores, a cualquier edad de aplicación, no disminuyen la contracción o expansión del concreto. Para que los curadores logren una efectividad adecuada en el desarrollo de la resistencia a la contracción y a la flexión en el concreto, se debe curar con agua por un mínimo de tres días previo a la aplicación del producto. Los resultados sugieren mejores resultados al aplicar el producto curador a los 7 días luego de mantener los especímenes en el cuarto húmedo.

O presente trabalho apresenta uma investigação experimental com objetivo de avaliar a influência da frequência de carregamento, intensidade da carga e resistência à compressão do material, no comportamento à fadiga do concreto. Ensaios foram realizados considerando três frequências de carregamento (0,125, 0,25 e 0,5 Hz), dois níveis de tensão máxima (50% e 70% da resistência à compressão) e concretos com três classes de resistência (30, 50 e 70 MPa). Os resultados encontrados apontam que à medida que a frequência de carregamento é aumentada, a vida útil à fadiga cresce exponencialmente. No entanto, observou-se que a vida útil à fadiga é menor em concretos de alta resistência e que a VUF apresentou uma relação inversa com a resistência à compressão.

In petrochemical industry, the step of abrasive blasting in naphtha storage tanks, in preparation of the surface for application of anti-corrosion coatings generate, by intervention in each tank, approximately 100 tons of waste classified as class II A. Two annual interventions, in average, are carried out in each tank. In this context, the main objective of this paper is to evaluate the use of blasting abrasive wastes as fine aggregate, instead of natural sand, in concrete production. For this research, one water/cement ratio was specified, with subsequent use of the abrasive waste in three different levels, 25%, 50% and 75%, in substitution by natural fine aggregate. The behavior of compressive strength at 7, 28 and 91 days, flexure strength at 28 days, capillary water absorption at 28 days and the pozzolanicity of the waste were analyzed. As a result of the tests realized, it can be seen that for both mechanical strength and water absorption by capillarity, the concrete with up to 50% replacement of fine aggregate by blasting waste, is a technically adequate alternative that adds value to the waste and, mainly, minimizes impacts at the environment.

Conventional concrete presents in its mechanical behavior low tensile and shear strengths when compared to the compressive strength. In order to improve these mechanical properties, several researches have evaluated the combination of concrete matrix with steel fibers, resulting the steel fiber reinforced concrete composite (SFRC), a heterogeneous mixture that aims to adequately unite the characteristics of its components and obtain improvements in the mechanical behavior of the material, especially when applied to structures. This work evaluates the mechanical behavior of SFRC specimens compared to conventional concrete. A reference concrete mixture with axial compressive strength around 40 MPa was produced, in which hooked end steel fibers of 60 mm in length, diameter of 0.75 mm and shape factor of 80 were added, in the volumetric fractions of 0.5 and 1.0%, percentages in relation to the total volume of concrete. Eighteen prismatic specimens (150mmx150mmx500mm) were cast and submitted to the direct shear test until rupture, and the ultimate stress and vertical displacement of the shear plane were evaluated. The results showed a reduction in the axial compressive strength due to the addition of fibers, however, it obtained gains in tensile and shear strength and increased concrete toughness, avoiding its sudden rupture.

Este artículo presenta una síntesis de los resultados experimentales obtenidos al ensayar la evolución de la resistencia a la compresión en concretos hechos con distintos cementos modificados, a diferentes edades. Se incluye la caracterización de dos agregados de procedencias distintas (río y tajo) y tres tipos de cemento modificado. Los cementos ensayados corresponden al MM/C(P-C)-28, MM/C(C-P)-28 y MC/A-AR. El objetivo del estudio fue generar las curvas estándar de desarrollo de resistencia de seis mezclas de concreto usando estos cementos y agregados. Las pruebas de caracterización se llevaron a cabo siguiendo los estándares del Instituto de Normas Técnicas de Costa Rica (INTECO) y la Sociedad Americana de Pruebas y Materiales (ASTM). El curado de especímenes de concreto se realizó en cámara húmeda a 4 edades diferentes (3, 7, 28 y 56 días). La resistencia del concreto se obtuvo por medio de ensayos en la Máquina Universal, posteriormente, se procesó y validó estadísticamente los resultados, utilizando los parámetros de aceptación del informe del Instituto Americano del Concreto (ACI 214-2002). A partir del análisis realizado, se logró generar las curvas de desarrollo estándar de resistencia para todos los cementos en estudio, según dos procedencias de agregados e incluyendo un análisis estadístico inferencial para los resultados de resistencia de los concretos. Se concluyó que, al variar la procedencia del agregado para un mismo cemento, su resistencia es significativamente diferente (en términos estadísticos), al igual que para un mismo agregado, cuando se cambia el tipo de cemento.

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