Theoretical Calculation of ITZ Volume Fraction and Morphological Characterization of Crushed Stone in Concrete

Abstract

According to the morphological characteristics of crushed stone, the sphericity was introduced to establish the theoretical calculation model of volume fraction of interfacial transition zone (ITZ) around crushed stone. The sphericity of crushed stone was obtained by image processing technology and numerical statistics. The experimental results show that when the maximum particle size of coarse aggregate is less than 31.5 mm, the practical sphericity is generally around 0.75, while the sphericity of sand is generally above 0.85. And the closer to 1 the practical sphericity is, the smaller the ITZ volume fraction (V _ITZ) is, that is, the closer to spherical shape the aggregate is, the lower the ITZ content in concrete is. The V _ITZ and ITZ thickness in concrete and mortar have a linear relationship, and the ITZ content in concrete is lower than that in mortar at the same aggregate volume fraction.

Keywords

crushed stone / sphericity / interfacial transition zone / image processing / concrete

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