Comparative study of concrete panels' fire resistance

There is still a concern regarding concrete structures' fire safety, mostly due to the occurrence of concrete spalling. Although many tests have already been carried out, there is no clear definition about the parameters of the factors that influence its occurrence. This paper aimed to compare three different types of concrete panels, with dimensions of 300 x 315 x 10 cm (124.0 x 39.4 x 3.9 in.), composed of reinforced concrete (RC), prestressed concrete, and polypropylene microfiber RC. The panels were exposed to the standard fire curve based on ISO 834, aged 28 days, measuring the temperatures in panels' surfaces. Prestressed concrete panels experienced explosive spalling 18 minutes after the test began. RC panels and the panels with polypropylene microfiber addition maintained their integrity and structural stability for 240 minutes, failing in the thermal insulation criteria at 210 and 140 minutes, respectively. Although polypropylene microfiber concrete panels presented no spalling of concrete, conventional concrete panels attended the standardized criteria for a longer period due to its better thermal insulation

Avaliação da resistência ao fogo de paredes maciças de concreto armado

O desempenho das construções está em evidência no Brasil, principalmente após a aprovação da Norma de Desempenho, a ABNT NBR 15575: 2013. Esta norma remete a necessidade dos sistemas construtivos de atender, dentre outros, a níveis mínimos de segurança contra incêndio. O intento deste artigo é estudar o potencial de aplicação na construção civil de sistemas de vedação vertical de concreto armado em termos de resistência ao fogo. Através de protótipos ensaiados em escala real (3,15 x 3,00 m) em um forno vertical normatizado, foram analisadas duas espessuras de paredes de concreto armado maciço, de 10 e 14 cm, com um mesmo traço, observando o comportamento em termos de isolamento térmico, estanqueidade e estabilidade. Evidenciou-se que as amostras atenderam as condições aplicáveis para até 120 minutos de ensaio, com a de 14 cm mostrando melhores índices de isolamento térmico e estanqueidade

Influence of curing time on the fire performance of solid reinforced concrete plates

When reinforced concrete elements are subjected to high temperatures, such as in a fire, they are susceptible to physical and chemical changes that cause spalling, thereby undermining their performance under such conditions. It is known that the age and the internal moisture content of concrete are factors that contribute to this event, but the intensity of spalling is not yet a consensus. This study aimed to assess the influence of age and internal moisture on the performance of concrete walls at high temperatures. Therefore, 6 real-scale walls were built with dimensions of 3.15 × 3.00 m, with the same composition of concrete, for tests in a vertical furnace under the ISO 834 curve, for ages of 7, 14, 28, 56, 84 and 830 days. Moisture was measured as per the electrical resistivity of concrete. It was noted that walls with ages above 84 days showed no spalling whatsoever, due to the internal moisture of concrete. The most severe spalling took place at 14 days, thus evidencing that pore interconnectivity and hydrated cement crystallization can contribute as well

Analysis of highway trafficability under the pathological manifestations in the concrete plates: A case study

O descomedido incremento da frota nacional de veículos fomenta debates quanto à infraestrutura rodoviária, principalmente na construção, ampliação ou recuperação das estradas existentes. Nesse contexto, observa-se que a Rodovia Mário Quintana (ERS-118) apresenta alarmante estado de conservação e trafegabilidade, proveniente, principalmente, do grau de deterioração elevado das placas de concreto constituintes do pavimento. O objetivo deste trabalho foi determinar a integridade funcional dessa rodovia segundo avaliação e análise das manifestações patológicas das placas de concreto. Fundamentado no método desenvolvido pelo U.S. Corps of Engineers (USACE), através do índice de condição do pavimento (ICP), o trabalho foi estruturado em três partes: (a) método de avaliação das placas, (b) análise dos resultados e (c) conclusão. Os resultados obtidos indicam que a rodovia não apresenta mais funcionalidade e que sua vida útil, por conseguinte, findou-se.Palavras-chave: patologia, pavimentos de concreto, rodovia ERS-118, Método ICP, trafegabilidade.The increase of the Brazilian vehicle fleet highlights the discussion about road infrastructure, especially the construction, expansion or rehabilitation of the existing roads. In this context, it is noted that the Mario Quintana highway (ERS- 118) shows poor conditions of conservation and trafficability, coming mainly from the high degree of deterioration of the constituents of the concrete pavement slabs. The objective of this study was to determine the integrity of this highway, following an evaluation and analysis of pathological manifestations of concrete pavement. Based on the method developed by the U.S. Corps of Engineers (USACE) through the pavement condition index (PCI), the work was divided into three parts: (a) method of evaluation, (b) result analysis and (c) conclusion. The results indicate that the highway has no more functionality and service life, consequently, consummated.Keywords: pathology, concrete pavement, highway ERS-118, ICP method, trafficability

Comparative study of fire resistance and acoustic performance of ceramic brick walls in concern to NBR 15575 in residential buildings in Brazil

After the publication of NBR 15575 (ABNT, 2013) standard, it became necessary that the constructive systems used in residential buildings go through verification processes concerning the performance requirements. Considering the security requirements, it is necessary to evaluate the fire resistance of vertical sealing systems. Within the scope of habitability, the standard specifies that these systems must have an adequate acoustic performance. Regarding this scenario, this study has the purpose of evaluate the performance of two non-structural vertical sealing systems in ceramic bricks by comparing two different layouts of horizontal air gaps. Therefore, laboratory tests were performed, following the prescriptions of NBR 10636 (ABNT, 1989) and ISO 10140-2 (ISO, 2010). It was verified that the system with higher air gaps number had a better performance on fire resistance, and that the acoustic performance was very similar between the two systems.Con la publicación de la norma NBR 15575 (ABNT, 2013), ha sido necesario que los sistemas constructivos utilizados en edificios residenciales se sometiesen a ensayos para el cumplimiento de los requisitos de desempeño. En el ámbito de los requisitos de seguridad solicitados por la norma, existe la necesidad de la evaluación de la resistencia al fuego de los sistemas de aislamiento vertical. Dentro de la habitabilidad, la norma recomienda que estos sistemas tienen un desempeño acústico adecuado. Dentro de este escenario, el objetivo de este trabajo es evaluar el desempeño acústico de dos sistemas de pared compuestos por diferentes tipos de bloques cerámicos con agujeros horizontales. Para este análisis, fueron realizados ensayos de laboratorio de acuerdo con las normas NBR 10636 (ABNT, 1989) y ISO 10140-2 (ISO, 2010). Se verificó que el sistema con mayor densidad presentó desempeño sensiblemente mejor acerca la resistencia al fuego, con desempeño prácticamente idéntico en el análisis del aislamiento acústico

Thermal damage evaluation of full scale concrete columns exposed to high temperatures using scanning electron microscopy and X-ray diffraction

When exposed to elevated temperatures, concrete suffers physicochemical changes, resulting in reduction of mechanical properties, cracking and spalling. These macroscopic changes are related to changes in the microstructure of concrete. In this paper, the microstructure of thermally damaged concrete from real-scale reinforced concrete columns was studied, using scanning electron microscopy (SEM) and x-ray diffraction (XRD). Two real-scale reinforced concrete columns, with different concrete mixtures, were exposed to ISO 834 firestandard curve for 4 hours. After heating, concrete core samples were drilled, sectioned and analyzed in different column section depths.Core samples from reference column not exposed to high temperatures, were also obtained. Macroscopic observations showed a change inthe color of concrete exposed to high temperatures. SEM micrographs presented distinct changes in morphology, like coarsening, and thepresence of cracks and voids. XRD diagrams showed a reduction of portlandite and presence of larnite as depth increasesCuando se expone a temperaturas elevadas, el concreto sufre cambios fisicoquímicos relacionados con cambios en la microestructura del hormigón. En este artículo, se estudió la microestructura del concreto dañado térmicamente en columnas de hormigón armado a escala real, utilizando microscopía electrónica de barrido (SEM) y difracción de rayos X (XRD). Dos columnas de hormigón armado a escala real, con diferentes mezclas de hormigón, se expusieron a la curva estándar de fuego ISO 834 durante 4 horas. Las observaciones macroscópicas mostraron un cambio en el color del concreto expuesto a altas temperaturas. Las micrografías SEM presentaron cambios distintos en la morfología, como el engrosamiento y la presencia de grietas y huecos. Los diagramas de XRD mostraron una reducción de portlandita y la presencia de larnita a medida que aumentó la profundida

Evaluación del daño térmico de columnas de hormigón a gran escala expuestas a altas temperaturas utilizando microscopía electrónica de barrido y difracción de rayos X

When exposed to elevated temperatures, concrete suffers physicochemical changes, resulting in reduction of mechanical properties, cracking and spalling. These macroscopic changes are related to changes in the microstructure of concrete. In this paper, the microstructure of thermally damaged concrete from real-scale reinforced concrete columns was studied, using scanning electron microscopy (SEM) and x-ray diffraction (XRD). Two real-scale reinforced concrete columns, with different concrete mixtures, were exposed to ISO 834 firestandard curve for 4 hours. After heating, concrete core samples were drilled, sectioned and analyzed in different column section depths.Core samples from reference column not exposed to high temperatures, were also obtained. Macroscopic observations showed a change inthe color of concrete exposed to high temperatures. SEM micrographs presented distinct changes in morphology, like coarsening, and thepresence of cracks and voids. XRD diagrams showed a reduction of portlandite and presence of larnite as depth increases.Cuando se expone a temperaturas elevadas, el concreto sufre cambios fisicoquímicos relacionados con cambios en la microestructura del hormigón. En este artículo, se estudió la microestructura del concreto dañado térmicamente en columnas de hormigón armado a escala real, utilizando microscopía electrónica de barrido (SEM) y difracción de rayos X (XRD). Dos columnas de hormigón armado a escala real, con diferentes mezclas de hormigón, se expusieron a la curva estándar de fuego ISO 834 durante 4 horas. Las observaciones macroscópicas mostraron un cambio en el color del concreto expuesto a altas temperaturas. Las micrografías SEM presentaron cambios distintos en la morfología, como el engrosamiento y la presencia de grietas y huecos. Los diagramas de XRD mostraron una reducción de portlandita y la presencia de larnita a medida que aumentó la profundidad

Thermal damage evaluation of full scale concrete columns exposed to high temperatures using scanning electron microscopy and X-ray diffraction

When exposed to elevated temperatures, concrete suffers physicochemical changes, resulting in reduction of mechanical properties, cracking and spalling. These macroscopic changes are related to changes in the microstructure of concrete. In this paper, the microstructure of thermally damaged concrete from real-scale reinforced concrete columns was studied, using scanning electron microscopy (SEM) and x-ray diffraction (XRD). Two real-scale reinforced concrete columns, with different concrete mixtures, were exposed to ISO 834 firestandard curve for 4 hours. After heating, concrete core samples were drilled, sectioned and analyzed in different column section depths.Core samples from reference column not exposed to high temperatures, were also obtained. Macroscopic observations showed a change inthe color of concrete exposed to high temperatures. SEM micrographs presented distinct changes in morphology, like coarsening, and thepresence of cracks and voids. XRD diagrams showed a reduction of portlandite and presence of larnite as depth increases

Análisis experimental de resistencia al fuego de revestimientos de mortero en muros de mampostería estructural

The discussion on fire safety is necessary in Brazilian buildings. Current legislation requires construction with compartmentalized areas separated by walls with structural ceramic blocks capable of resisting fire for an amount of time pre-determined in norm NBR 14432 (ABNT, 2001). However, a lack of building standards requires experimental tests according to NBR 5628 (ABNT, 2001) to determine the necessary configuration to achieve fire resistance. For this purpose, this study analyzed the effect of fire on structural walls covered with a mortar coating. Experiments were conducted in real scale in a standardized vertical oven and the fire growth curve of ISO 834 (ISO, 1999). Three types of walls were tested, each with a different mortar coating: (a) lime; (b) 0.6 kg/m3 polypropylene fiber and 1.2 kg/m3 polypropylene fiber. The mortar coatings were 1.5 cm thick on the side facing the fire and 2.5 cm thick in the outside. The wall was composed of structural blocks measuring 14 cm x 19 cm x 29 cm. Fire experiments evaluated the structure stability, impermeability to hot gases and smoke and thermal insulation of each sample. Results showed that the structural system with 1.2 kg/m3 polypropylene fiber mortar coating obtained the best thermal insulation effect with the longest fire resistance time of 176 min.La discusión sobre seguridad contra incendios es necesaria en los edificios brasileños. La legislación actual exige la construcción con áreas compartimentadas separadas por muros con bloques cerámicos estructurales capaces de resistir el fuego por un tiempo predeterminado en la norma NBR 14432 (ABNT, 2001). Sin embargo, la falta de estándares de construcción requiere pruebas experimentales según NBR 5628 (ABNT, 2001) para determinar la configuración necesaria para lograr la resistencia al fuego. Para ello, este estudio analizó el efecto del fuego en los muros estructurales revestidos con un revestimiento de mortero. Los experimentos se realizaron a escala real en un horno vertical estandarizado y la curva de crecimiento del fuego de ISO 834 (ISO, 1999). Se ensayaron tres tipos de muros, cada uno con un revestimiento de mortero diferente: (a) cal; b) 0,6 kg / m3 de fibra de polipropileno y 1,2 kg / m3 de fibra de polipropileno. Los revestimientos de mortero tenían 1,5 cm de espesor en el lado de cara al fuego y 2,5 cm de espesor en el exterior. El muro estaba compuesto por bloques estructurales de 14 cm x 19 cm x 29 cm. Los experimentos de fuego evaluaron la estabilidad de la estructura, la impermeabilidad a los gases calientes y el humo y el aislamiento térmico de cada muestra. Los resultados mostraron que el sistema estructural con revestimiento de mortero de fibra de polipropileno de 1,2 kg / m3 obtuvo el mejor efecto de aislamiento térmico con el tiempo de resistencia al fuego más largo de 176 min

Avaliação da resistência ao fogo de paredes maciças de concreto armado

ResumoO desempenho das construções está em evidência no Brasil, principalmente após a aprovação da Norma de Desempenho, a ABNT NBR 15575: 2013. Esta norma remete a necessidade dos sistemas construtivos de atender, dentre outros, a níveis mínimos de segurança contra incêndio. O intento deste artigo é estudar o potencial de aplicação na construção civil de sistemas de vedação vertical de concreto armado em termos de resistência ao fogo. Através de protótipos ensaiados em escala real (3,15 x 3,00 m) em um forno vertical normatizado, foram analisadas duas espessuras de paredes de concreto armado maciço, de 10 e 14 cm, com um mesmo traço, observando o comportamento em termos de isolamento térmico, estanqueidade e estabilidade. Evidenciou-se que as amostras atenderam as condições aplicáveis para até 120 minutos de ensaio, com a de 14 cm mostrando melhores índices de isolamento térmico e estanqueidade