3D investigation of steel fiber distribution in reinforced concrete by X-ray microtomography

Abstract

ResumoThe effects of the inclusion of steel fibers in concrete have been widely studied in order to investigate possible changes in mechanical properties, such as the increase in tensile strength, ductility, stiffness, toughness (energy absorption capacity), and durability. An immediate consequence of this addition is the mitigation of concrete's brittle behavior, so that the material meets new quality requirements. In this context, it is important to study the spatial distribution of the entire internal structure of these materials. Three-dimensional computed microtomography is a non-destructive inspection technique used to characterize the internal structures of various materials based on X-ray interaction with the inspected object. Topological and morphological properties can be obtained directly in three dimensions by means of mathematical reconstruction of the radiographs, which allows analyzing, for example, porosity and distribution of objects. In this context, the aim of this study is to investigate the spatial distribution of steel fibers, as well as of porosity in reinforced concrete samples. To this end, we used a microtomography system calibrated to operate at a voltage of 80 kV, electric current of 100 μA and a pixel size equal to 24 µm. The results showed low porosity and that the steel fibers were not uniformly distributed throughout the sample.Os efeitos da inserção de fibras de aço em concretos têm sido amplamente estudados com o objetivo de investigar possíveis modificações nas propriedades mecânicas, tais como, o aumento da resistência à tração, ductilidade, rigidez, tenacidade (capacidade de absorção de energia), e durabilidade. Uma das consequências imediatas dessa adição é a mitigação do comportamento frágil do concreto, de forma que o material passe a ter novas exigências de qualidade. Nesse contexto, é de grande importância o conhecimento espacial da distribuição de toda estrutura interna desses materiais. A microtomografia computadorizada tridimensional é uma técnica utilizada na caracterização de estruturas internas de diversos materiais, baseada na interação dos raios X com o objeto inspecionado, sendo considerado um ensaio não destrutivo. Propriedades morfológicas e topológicas podem ser obtidas diretamente em três dimensões através da reconstrução matemática das radiografias, o que possibilita analisar, por exemplo, a porosidade e a distribuição de diversos objetos. Nesse contexto, o objetivo desse trabalho é a investigação da distribuição espacial das fibras de aço, assim como da porosidade em amostras de concreto. Para tal, foi utilizado um sistema de microtomografia calibrado para operar com uma tensão de 80 KV, corrente elétrica de 100 µA e um tamanho de pixel igual a 24 µm. Os resultados mostraram uma porosidade baixa e que as fibras de aço não estão distribuídas uniformemente ao longo da amostra.Palavras-chave: raios X, fibras de aço, microtomografia, porosidade, concreto.

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

“…The procedure turned out to be appropriate for analyzing the transitioning zone between paste and fiber, pointing towards an adequate adherence with no void agglomerations. Finally, this procedure was put into use for measuring and analyzing the distribution of voids with respect to pore size of a fiber‐reinforced concrete, resulting in a void diameter preponderantly between 0.39 and 0.77 mm …”

“…Finally, this procedure was put into use for measuring and analyzing the distribution of voids with respect to pore size of a fiber-reinforced concrete, resulting in a void diameter preponderantly between 0.39 and 0.77 mm. 28 The technique can be applied for evaluating pore connectivity, thus allowing the understanding of its relation with characteristics such as water absorption and durability of the material. 29 An experimental procedure was then carried out comprising diagnostic tests on concretes specified in accordance with EN 1992-1 and EN 206 to validate conclusions drawn by other studies.…”

Snakes as a model for measuring skull preparation errors in geometric morphometrics

“…For these reasons, curators of zoological collections may be restrictive about the use of such techniques, especially in the case of type material or rare taxa. In such cases, the use of microCT scan may be the best alternative, as this is a non‐destructive and relatively fast technique (Machado et al ., ), besides allowing the visualization of internal structures and different cuts (e.g. sagittal, transversal, frontal).…”

“…For these reasons, curators of zoological collections may be restrictive about the use of such techniques, especially in the case of type material or rare taxa. In such cases, the use of microCT scan may be the best alternative, as this is a non-destructive and relatively fast technique (Machado et al, 2015), besides allowing the visualization of Figure 5 Mean shape of the asymmetric component of the dorsal view of the skulls of Liophis miliaris merremi for different preparation methods (dry and CT scan). (a, c) The real differences between the means for dry and scanned skulls respectively; (b, d) The differences increased by 10 times, for dry and scanned skulls respectively.…”

Análise experimental da adição de fibras poliméricas nas propriedades mecânicas do concreto

“…Recentemente diversos estudos sobre a influência das fibras de aço no comportamento concreto foram publicados [3,4,5,6].…”