Abstract
Just as it is regarding ordinary cement-based materials, the pore structure and microstructure of alkali-activated materials are disordered. It is essential to predict the macroscopic properties by studying the pore and microstructure fractal characteristics of materials. In this paper, the effects of slag content and alkali activator modulus on compressive strength, porosity, and microstructure of alkali-activated coal gangue-slag (AACGS) mortar were studied. Further, with the help of mercury intrusion porosimetry (MIP) data and the MATLAB programming, the pore and SEM photos fractal dimensions of AACGS mortar specimens were obtained, respectively, and the relationship between the microscopic fractal dimensions and the macroscopic strength and the structural characteristics of pores was established. The results show that the pore fractal dimension has a good linear relationship with the compressive strength and pore characteristic parameters (porosity, total pore area, and average pore diameter, etc.). With the increase of slag content, the SEM photos fractal dimension of AACGS mortar specimens increases, and the fractal dimension and compressive strength also show a significant positive linear relationship. The two fractal characterization methods can be used in the alkali-activated material system and have important guiding significance for predicting the macroscopic strength and pore characteristic parameters of the material.
Highlights
In recent years, research on alkali-activated materials has shown a rapid growth trend
The effects of slag content and alkali activator modulus on the compressive strength and microstructure of alkali-activated coal gangue-slag (AACGS) mortar will be investigated, and the surface morphology and microstructure of mortar specimens will be observed by means of mercury intrusion porosimetry (MIP) method and scanning electron microscope (SEM)
The binarization image of the SEM image can be obtained based on computer image processing and uses the box dimension method to calculate the fractal dimension of the binary image
Summary
Research on alkali-activated materials has shown a rapid growth trend. The microstructural properties of alkali-activated materials depend on their microscopic structural characteristics. Liu et al [16] applied the fractal theory to metakaolin concrete and found that the fractal method can quantitatively analyze the characteristics of the internal microstructure changes in metakaolin concrete. In the study of concrete subjects, the fractal theory has been applied successfully to cementitious materials, pores, and fracture properties, etc., showing its fractal characteristics [17,18]. The effects of slag content and alkali activator modulus on the compressive strength and microstructure of alkali-activated coal gangue-slag (AACGS) mortar will be investigated, and the surface morphology and microstructure of mortar specimens will be observed by means of MIP method and SEM. This paper provides an analytical method to study the internal laws between microstructure and macroscopic physical and mechanical properties of advanced concrete materials
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