Multi-objective optimal control and application of solid waste synergistically excited fluidized solidified soil

Area of Science:

• Materials Science
• Geotechnical Engineering
• Environmental Engineering

Background:

• Traditional backfilling materials in Northwest China's loess areas suffer from settlement and poor durability.
• Special backfilling conditions require materials with enhanced mechanical properties and economic viability.

Purpose of the Study:

• To prepare controllable low-strength ready-mixed flow solidified soil (CLSM) utilizing solid waste and alkali activators.
• To optimize the CLSM mix ratio for enhanced performance and cost-effectiveness.
• To investigate the durability mechanisms of CLSM under extreme environmental conditions.

Main Methods:

• Utilized loess from Lanzhou as the matrix.
• Employed an L16(4^5) orthogonal test design for mix ratio optimization.
• Applied the entropy weight method to establish a double-objective optimization model (28d compressive strength-cost).
• Conducted multi-dimensional tests and micro-mechanism analysis for durability assessment.

Main Results:

• The optimal mix ratio (15% coal gangue, 3% carbide slag, 15% blast furnace slag, 60% alkali activator) achieved 4.44 MPa compressive strength at 73.23 yuan/ton.
• CLSM exhibited significantly improved durability: 44.83% less mass loss and 34.89% higher strength after 25 freeze-thaw cycles compared to cement soil.
• Sulfate dry-wet cycle tests showed a 55.56% decrease in mass loss and a 40.01% increase in strength, indicating superior resistance.
• Micro-mechanism analysis revealed a five-stage strength formation process, with synergistic effects of solid waste and alkali activators promoting C-S-H gel and ettringite formation.

Conclusions:

• The developed CLSM, using a 'waste treatment by waste' approach, offers a sustainable and durable solution for backfilling in arid and cold regions.
• The multi-objective optimization method provided a scientifically sound approach to determining the optimal mix ratio.
• The study provides theoretical support and engineering guidance for the application of solidified soil in challenging environments.