GMCs stabilized/solidified Pb/Zn contaminated soil under different curing temperature: Physical and microstructural...

Area of Science:

• Geotechnical Engineering
• Environmental Science
• Materials Science

Background:

• Soil contamination with heavy metals like lead (Pb) and zinc (Zn) poses significant environmental risks.
• Stabilization/Solidification (S/S) is a common technique for soil remediation, improving physical properties and immobilizing contaminants.
• Granulated ground blast furnace slag (GGBS)-MgO-CaO (GMCs) offers a potential solution for treating Pb/Zn contaminated soils.

Purpose of the Study:

• To investigate the physical and microstructural characteristics of Pb/Zn contaminated soil treated with GMCs.
• To evaluate the effectiveness of GMCs in improving the unconfined compressive strength (UCS) and leachability of contaminated soil.
• To understand the immobilization mechanisms of Pb and Zn within the S/S matrix.

Main Methods:

• Treatment of Pb/Zn contaminated soil using varying proportions of GMCs (5%-15%).
• Curing of treated soil samples at different temperatures (5°C, 21°C, 45°C) and times (7 and 28 days).
• Analysis of physical properties (UCS) and microstructural characteristics (XRD, SEM) of the stabilized soil.

Main Results:

• The primary hydration products were calcium silicate hydrate (C-S-H) and hydrotalcite-like gels (Ht), crucial for soil strength.
• Increased GMC proportion, curing time, and temperature generally enhanced UCS and reduced leachability.
• Most mixes met the US EPA criterion for compressive strength (0.35 MPa).
• Pb and Zn were immobilized through precipitation and adsorption onto C-S-H, with Zn also incorporated into C-S-H and Ht structures.
• Higher Pb/Zn concentrations negatively impacted soil strength, with Pb generally causing a greater reduction than Zn/Pb mixtures.

Conclusions:

• GMCs are effective in stabilizing Pb/Zn contaminated soil, improving mechanical properties and contaminant immobilization.
• The hydration process, influenced by GMC proportion, curing time, and temperature, is key to the S/S performance.
• The study demonstrates the potential of GMCs for environmentally sound remediation of heavy metal-polluted soils.