Damage evolution, brittleness and solidification mechanism of cement soil and alkali-activated slag soil

Abstract

Alkali-activated materials are environmentally friendly gelling agents that have been intensively studied in soil solidification over a long period of time. Currently, there is little research on the deformation and damage laws of solidified soils during compression failure. This study investigates the energy dissipation mechanism and plastic damage model of Weibull distribution to explore solidified soil under different curing ages, moduli, and cement, ground granulated blast furnace slag (GGBS), and alkali-activator contents to further explore the damage evolution law and elastic-plastic state of alkali-activated slag soil. The destruction of solidified soil is accompanied by energy dissipation, and the damage to a specimen under load can be expressed as the amount of dissipated energy. In this paper, the change rules of the damage variable (D), total dissipation energy (U), elastic strain energy (Ue), and dissipation energy (Ud) of solidified soil during compression are described in detail, and the damage to the solidified soil is characterized using the dissipation energy ratio (Ud/U) and damage variable. Based on the energy dissipation mechanism, a brittleness index (BI) is established considering the pre-peak elastic-plastic state and post-peak load-bearing capacity loss states. The U, Ue, and BI increase with a decrease in the modulus and increase in the curing age and cement, GGBS, and alkali-activator contents, whereas Ud/U and D decrease. D is linearly proportional to Ud/U. The BI and Ud/U demonstrated an exponential correlation. Finally, the influence of the cement, GGBS, and alkali-activator contents are shown to increase through X-ray diffraction (XRD), thermogravimetry (TG/DTG) and nuclear magnetic resonance (NMR) tests. Additionally, the effects of the cement, GGBS, and alkali-activator contents and alkali-activator modulus on the damage variable and brittleness index are explained from a microscopic point of view. The relationships between porosity and Ud/U, D, and BI are established. This study provides a reference value for the characterization of mechanical properties of solidified soil and the relationship between the pore structure and mechanical indexes.

Keywords

• Alkali-activated materials
• Soil solidification
• Pore structure
• Energy dissipation mechanism
• Damage model
• Brittleness index