Fractal Characteristics of the Pore Structure of Coral Powder–Cement Slurry under Different Fractal Models

Qingshan Meng,Kai Wu,Qinglong Qin,Haoran Zhou,Lei Wang,Huamei Yang

doi:10.3390/fractalfract6030145

Abstract

In this study, coral powder with different contents and levels of fineness were incorporated into cement; then, the pore structure of a coral powder–cement slurry was measured using the MIP test at days 3 days and 28, respectively. Neimark’s model, Ji’s model, and Pfeifer and Avnir’s model were also used to analyze the fractal characteristics of the coral powder–cement slurry. The results show that the coral powder–cement slurry has multifractal characteristics when using Neimark’s model, and the entire pore size range of the cement slurry can be divided into three parts: Region I (1–200 μm), Region II (70 nm–4 μm), and Region III (5–500 nm). The pore surface fractal dimension of both Regions I and III is less than 3, while that of Region II is greater than 3. This indicates that Regions I and III have obvious fractal characteristics, which Region II does not. Meanwhile, the pore surface fractal dimension of Region I is positively correlated with hydration age, while the pore surface fractal dimension of Region III is less affected by hydration age and coral powder contents. Ji’s model reveals that coral powder–cement slurry also has multifractal characteristics, but the entire pore size range of the cement slurry can be divided into two parts: Region I (5.482 nm–500 m) and Region II (120 nm–370 μm). The pore volume fractal dimension of Region I is greater than 2 and less than 2.5, while that of Region II is greater than 2.9 and less than 3. Therefore, both Regions I and II have fractal characteristics. In addition, the coral powder admixture, fineness, and age have large effects on the pore volume fractal dimension and pore size range of Region II. Pfeifer and Avnir’s model reveals that the entire pore size range of cement slurry can also be divided into Region I (5.482–600 nm), Region II (120 nm–10 μm), and Region III (5–365 μm), and that the pore surface fractal dimension of both Regions I and III is less than 3, while that of Region II is greater than 3. This indicates that Regions I and III have fractal characteristics, while Region II does not have fractal characteristics.

Highlights

Zhang’s model to study the pore surface fractal dimension of fly ash–cement slurry, and the results showed that fly ash–cement paste had obvious multifractal characteristics
The pore surface fractal dimensions of Region I, Region II, and Region III of FCP30 at 3 days are 2.9970, 4.6613, and 2.7639, respectively, which correspond to the pore size zones of 179.835–4.527 μm, 1.046–151.072 nm, and 120.845–5.482 nm, respectively
The results showed that the fractal dimension calculated by Neimark’s model was basically larger than that of Zhang’s model, which may be because Neimark’s model is based on the assumption of cylindrical tube pores

Summary

Introduction

Classical Euclidean geometry can only describe some geometries with regularity, and it is difficult to describe and characterize complex nonlinear things such as complicated coastlines, mountain scenery, and rock structures [1]. Pore structure parameters such as porosity [2,3], pore size distribution [2,3], and pore surface area [4] can only reflect the overall characteristics of pore structure and not the spatial distribution or tortuous degree of pore structure [5,6]. Fractal theory provides theoretical support and a basis for describing fragmented, irregular, and fractional objects. Fractal geometry is a new nonlinear science with the two characteristics of local and global self-similarity and non-integer dimensions, providing a method for describing irregular, complex, and Fractal Fract.

Methods

Results

Conclusion