Micro-Mechanism of Strength for Cement-Treated Soil Based on the SEM Experiment: Qualitative and Quantitative Analysis

Abstract

The strength of cement-treated soil (CTS) is influenced by a range of complex factors. Investigating the microstructure of cement-treated soil provides a fundamental understanding of its strength evolution. This study explores the micro-mechanism of strength in cement-treated soil through qualitative and quantitative analyses. Unconfined compressive strength (UCS) tests were conducted on two types of cement-treated soils with different curing ages. Microstructural images were obtained via Scanning Electron Microscopy (SEM), from which micro-parameters—including image porosity ((Formula presented.)), mean shape factor ((Formula presented.)), particle grading entropy ((Formula presented.)), and directional probability entropy ((Formula presented.))—were obtained. Finally, the Grey Relation Analysis (GRA) method was employed to evaluate the relative importance of these micro-parameters in influencing strength. And the micro-mechanism of strength was discussed. Results show that these variations of cement-treated soil strength are primarily governed by porosity, particle shape, size, and arrangement. GRA results indicate that particle grading entropy ((Formula presented.)) has the greatest impact on CTS strength, followed by image porosity ((Formula presented.)). In contrast, mean shape factor ((Formula presented.)) and directional probability entropy ((Formula presented.)) have relatively lower impacts. The order of influence is (Formula presented.), suggesting that changing particle grading entropy ((Formula presented.)) is recommended to achieve higher CTS strength more efficiently. Finally, a polynomial relation between (Formula presented.) and strength is proposed and the sensitivity analysis indicates that the best value of (Formula presented.) for Hangzhou CTS is 0.3125 and for Taizhou CTS is 0.5. The corresponding UCSs are 56.96 kPa and 425.8704 kPa, respectively. These findings contribute to optimizing the strength of cement-treated soils and provide insights into the micro-mechanisms underlying macro-scale material properties.