Expanded Perlite Reinforced Magnesium Phosphate Cement-Based Fireproof Coating: Composition Optimization, Fire...

Area of Science:

• Materials Science
• Civil Engineering
• Fire Safety Engineering

Background:

• Steel structures require effective fire protection to prevent catastrophic failures.
• Inorganic fireproof coatings offer a durable solution, but often lack lightweight properties.
• Magnesium phosphate cement (MPC) and expanded perlite (EP) present potential for high-performance, lightweight coatings.

Purpose of the Study:

• To develop a high-performance inorganic fireproof coating for steel structures.
• To investigate the impact of expanded perlite (EP) content and magnesium-to-phosphorus ratio (M/P) on coating properties.
• To determine the optimal formulation for a balance of lightweight, mechanical, and fire resistance characteristics.

Main Methods:

• Systematic variation of EP content (40-55%) and M/P ratio (4:1-7:1).
• Evaluation of dry density, compressive strength, bond strength, and fire resistance.
• Microstructural analysis using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA).

Main Results:

• Increased EP content reduced density and thermal conductivity, improving insulation but decreasing mechanical strength.
• Optimal EP content was found to be 45% for a balance of properties.
• M/P ratio influenced hydration products (K-struvite, MgO) affecting interfacial strength and high-temperature stability; optimal M/P was 5:1 for bond strength and fire resistance.

Conclusions:

• The optimal coating formulation (45% EP, M/P = 5:1) achieved a dry density of 560 kg/m³, compressive strength of 0.53 MPa, bond strength of 0.097 MPa, and limited back-side temperature rise to 180.4 °C.
• High-temperature transformation of K-struvite and interaction with MgO and SiO₂ formed a stable ceramic skeleton.
• The developed coating offers a favorable combination of lightweight, mechanical integrity, and thermal insulation for steel structure fire protection.