Comparative Analysis of Three Expansion Agents

Expansion agents are specialized additives used in concrete to counteract shrinkage during hydration and curing. By generating controlled expansion, they compensate for thermal contraction, drying shrinkage, and autogenous shrinkage, thereby enhancing crack resistance, impermeability, and structural durability.

Composition:

1.Magnesium Oxide (MgO) Expansion Agent

Primary Component: ≥80% MgO (light-burned MgO with adjustable reactivity).

Additives: Minor impurities (burn loss ≤4%, moisture ≤0.3%).

Mechanism:Hydration of MgO generates M

g(OH)₂, inducing controlled expansion.Expansion timing and magnitude are tailored to match concrete’s shrinkage phases (thermal and drying).

2.Calcium-Magnesium Composite Expansion Agent

Dual Components: Calcium-based (early expansion) + magnesium-based (late expansion).

Standards: Complies with T/CECS 10082-2020.

Mechanism:Calcium component compensates early autogenous shrinkage.

Magnesium component addresses thermal and drying shrinkage in later stages.

3.T60 Polymer Anti-Crack Expander

High-Performance Polymer: Low-alkali (≤0.75%), low dosage (6–8%).

Standards: Complies with GB/T 23439-2017.

Mechanism:Polymer particles absorb water, creating micro-expansion to offset shrinkage.

Enhances self-waterproofing and enables seamless construction (100–150m pours).

Pros:

1.Magnesium Oxide (MgO) Expansion Agent

Adjustable reactivity (R/M/S types for seasonal/temperature adaptability).

High compatibility with diverse structures (underground, waterproof, large-span).

Complies with CBMF 19-2017; proven effectiveness in massive projects.

2.Calcium-Magnesium Composite Expansion Agent

Phased compensation for full-cycle shrinkage control.

Higher dosage flexibility (6–10% of cementitious materials).

Ideal for thick/massive structures (≥500mm).

3.T60 Polymer Anti-Crack Expander

Low alkali content reduces ASR risk.

Seamless integration with standard mixing processes.

Superior for structural self-waterproofing.

Cons:

1.Magnesium Oxide (MgO) Expansion Agent

Limited dosage (≤8% of cementitious materials).

2.Calcium-Magnesium Composite Expansion Agent

Complex formulation requires precise mix design.

3.T60 Polymer Anti-Crack Expander

Strict curing protocols (14-day wet curing).

Temperature-sensitive (unsuitable for >80°C environments).

Applications:

1.Magnesium Oxide (MgO) Expansion Agent

Underground structures: Parking lots, basements.

Waterproof projects: Dams, tunnels, reservoirs.

Large-span buildings: Airports, stadiums.

2.Calcium-Magnesium Composite Expansion Agent

Massive concrete: Hydropower dams, thick foundations.

Ultra-long structures: Tunnels, metro systems.

Marine environments: Ports, coastal structures.

3.T60 Polymer Anti-Crack Expander

Self-waterproofing structures: Bridges, basements.

High-rise buildings: Continuous slabs, cores.

Rapid construction: Precast elements, industrial floors.

Recommended Application Scenarios:

1.Magnesium Oxide (MgO) Expansion Agent

Projects requiring long-term shrinkage compensation (e.g., dams, underground parking).

2.Calcium-Magnesium Composite Expansion Agent

Thick/massive structures with phased shrinkage demands (e.g., hydropower plants).

3.T60 Polymer Anti-Crack Expander

High-durability, self-waterproofing applications (e.g., metros, high-rises).