Determination of volume and distribution of pores of concretes according to different exposure classes through 3D microtomography and mercury intrusion porosimetry

Pacheco, Fernanda; Souza, Rodrigo Périco de; Christ, Roberto; Rocha, Clarissa Argenti; Silva, Luis; Tutikian, Bernardo Fonseca

doi:10.1002/suco.201800075

Cited by 16 publications

(13 citation statements)

References 24 publications

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“…The porosity of mortar with two different mix ratios is given in Table 5 . According to the literature [ 49 , 50 , 51 , 52 , 53 ], pores less than 50 nm, 50–500 nm, and greater than 500 nm are defined as harmless pores, less harmful pores, and harmful pores, respectively.…”

Section: Resultsmentioning

confidence: 99%

Effects of MgO Expansive Agent and Steel Fiber on Crack Resistance of a Bridge Deck

Jiang

Deng

et al. 2020

Materials

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To prevent cracks caused by shrinkage of the deck of the Xiaoqing River Bridge, MgO concrete (MC) and steel fiber reinforced MgO concrete (SMC) were used. The deformation and strength of the deck were measured in the field, the resistance to chloride penetration of the concrete was measured in the laboratory, and the pore structure of the concrete was analyzed by a mercury intrusion porosimeter (MIP). The results showed that the expansion caused by the hydration of MgO could suppress the shrinkage of the bridge deck, and the deformation of the deck changed from −88.3 × 10−6 to 24.9 × 10−6, effectively preventing shrinkage cracks. At the same time, due to the restriction of the expansion of MgO by the steel bars, the expansion of the bridge deck in the later stage gradually stabilized, and no harmful expansion was produced. When steel fiber and MgO were used at the same time, the three-dimensional distribution of steel fiber further limited the expansion of MgO. The hydration expansion of MgO in confined space reduced the porosity of concrete, optimized the pore structure, and improved the strength and durability of concrete. The research on the performance of concrete in the in-situ test section showed that MgO and steel fiber were safe for the bridge deck, which not only solved the problem of shrinkage cracking of the bridge deck but also further improved the mechanical properties of the bridge deck.

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Section: Resultsmentioning

confidence: 99%

Effects of MgO Expansive Agent and Steel Fiber on Crack Resistance of a Bridge Deck

Jiang

Deng

et al. 2020

Materials

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“…Há uma relação inversa entre espessura de cobrimento e temperatura média das armaduras (KODUR; YU; DWAIKAT, 2013;PACHECO et al, 2018). Quanto maior a espessura do cobrimento das armaduras, mais protegidos estão os reforços, devido ao isolamento térmico do concreto, segundo Mehta e Monteiro (2014).…”

Section: Introductionunclassified

Análise das resistências ao escoamento (fy) e de ruptura (fu) residual das armaduras de pilares de concreto em altas temperaturas

et al. 2021

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Resumo Neste artigo, foi avaliada experimentalmente a influência do diâmetro de barras no grau de redução da resistência ao escoamento (fy) e de ruptura (fu) de armaduras extraídas de quatro pilares expostos à ação térmica em um forno vertical, pela curva padrão de aquecimento da ISO 834-1:1999, por 240 min. Os pilares tinham seção transversal de 25 cm x 25 cm e altura de 300 cm. Os diâmetros analisados foram de 10 mm e 16 mm, e a espessura de cobrimento, de 25 mm a 50 mm. Os resultados mostraram que, independentemente da espessura de cobrimento, as barras com 16 mm de diâmetro sofreram maior redução na resistência de escoamento (fy) e na resistência última (fu) em relação às barras de 10 mm de diâmetro, devido ao maior volume de desplacamento do concreto dos pilares, com exposição direta às temperaturas elevadas. Os maiores volumes de desplacamento foram identificados nos elementos com maior espessura de cobrimento (50 mm), atingindo valores até 52 vezes maiores que os desplacamentos identificados nos elementos com espessura de 25 mm no cobrimento. As tensões fy das armaduras obtiveram redução entre 29% e 56%. Assim, com base neste estudo, mostra-se relevante prever a redução do fy e do fu das armaduras no dimensionamento das estruturas de concreto armado em situação de incêndio.

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“…It is important to assure the quality of building materials, so the facility to run the compressive strength test and its low cost make it the most usedformaterial quality control (Moreno, Solís-Carcaño, Varela-Rivera, & López, 2016). According to Tunç (2018) and Pacheco et al (2018), compressive strength is the most important and applied analysis, considering concrete specimens. Gupta (2018) considers the advantage of the destructive test commonly applied is its cost of execution.…”

Section: Introductionmentioning

confidence: 99%

Influence of the molding process and different surface regularization methods on the compressive strength of concrete specimens

Lerner

Ott

Führ

et al. 2020

rdlc

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Concrete is one of the most important material for civil construction, given its high applicability. C Compressive strength (fc) is one of the main parameters to evaluate the concrete quality. Concrete of the same mixing volume may vary even with the same materials preparation. Concrete specimens molding, and its surface regularization contribute to these variations that are often hard to measure. Therefore, this paper aims to determine the variations in compressive strength of concrete, simulating different processes for casting, initial curing and surface treatment. In stage 1, the specimens were subjected to five surface treatment types, resulting in variations of 30% for concrete fc, whereas grinding specimens reached the highest 28-day compressive strength, so they were carried over to the next stage. In stage 2, specimens were produced as per ABNT NBR 5738 (2015) and with induced errors in casting and initial curing. The specimen produced according to the standard achieved the second-best result, whose 28-day fc was3% lower than that of the similar method, despite leaving the specimen uncovered for the first 24 hours after casting. Specimens produced in metal cylinder form works shows higher results than those produced in polyvinyl chloride molds (PVC).

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Determination of volume and distribution of pores of concretes according to different exposure classes through 3D microtomography and mercury intrusion porosimetry

Cited by 16 publications

References 24 publications

Effects of MgO Expansive Agent and Steel Fiber on Crack Resistance of a Bridge Deck

Effects of MgO Expansive Agent and Steel Fiber on Crack Resistance of a Bridge Deck

Análise das resistências ao escoamento (fy) e de ruptura (fu) residual das armaduras de pilares de concreto em altas temperaturas

Influence of the molding process and different surface regularization methods on the compressive strength of concrete specimens

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