Study on the effect of aggregate distribution on mechanical properties and damage cracks of concrete based on multifractal theory

Abstract

The mechanical properties and damage cracks of concrete, especially the former in non-elastic phase, are obviously discrete and random. One important influencing factor is the aggregate distribution, but its quantitative characterization is a tricky issue. At mesoscale, the numerical specimen of concrete is established by assuming the concrete as three-phase composite material, which is composed of aggregate, mortar matrix, and the interfacial transition zone (ITZ) between them. The uniaxial tensile mechanical behaviors of 36 groups of concrete specimens with different aggregate distribution are performed numerically to gain the mesoscopic damage crack paths. Successively, the box dimension and multifractal spectrum are employed to quantitatively characterize the aggregate and crack distribution. It is found that the multifractal spectrum shows a better performance for the local detail features characterization than that of box dimension, which thus is turned out to be a new method for quantitative study of aggregate distribution. Furthermore, the correlations among multifractal spectrum width of aggregate distribution, peak stress, brittleness, and box dimension of crack distribution are analyzed statistically. The results show a negative relation of multifractal spectrum width of aggregate distribution and box dimension of crack distribution with peak stress and brittleness, but positive relation of multifractal spectrum width of aggregate distribution with box dimension of crack distribution. This implies that lower multifractal spectrum width of aggregate distribution, indicator of more uniform of aggregate distribution, will result in higher tensile strength and brittleness, and lower box dimension of crack distribution, representative of more regular of crack propagation. These results provide valuable information for in-depth understanding of the mechanical properties and damage cracking of concrete.