How to Determine the Compounding Ratio of PCE

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How to Determine the Compounding Ratio of PCE

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The compounding ratio of polycarboxylate superplasticizers is determined primarily by concrete performance requirements and raw material compatibility. There is no fixed universal ratio—it must be calibrated through laboratory trial mixes.

The fundamental approach is: First determine the baseline dosage of PCE mother liquor, then incorporate functional components (retarder, slump retention agent, air-entraining agent, defoamer, antifreeze, etc.) according to project requirements.

The practical procedure is as follows:

I. Establish the Baseline Dosage of PCE Mother Liquor (Core Step)

The solid-based dosage of PCE mother liquor is selected according to required water reduction and workability:

Ordinary pumped concrete: 0.15%-0.25%
High-flow/ self-compacting concrete: 0.25%-0.40%
High-strength concrete: 0.30%-0.50%

Note:

20% or 40%

Actual dosage = Solid-based dosage ÷ Mother liquor solid content

II. Define Functional Components and Their Ratios(Percentages are based on mother liquor mass)

A compounded PCE system consists of mother liquor + functional additives (retarder, slump retention agent, air-entraining agent, defoamer, antifreeze, etc.). Compatible components may be combined as required.
Typical ranges:

1. Retarding / Slump Retention (most commonly used)

Sodium citrate: 0.5%-2%, Sodium gluconate: 0.5%-3%, Polyols: 1%-4% (For high-temperature conditions or long transportation distances, this may be increased to 2%-5%.)

2. Air-Entraining

Air-entraining agent: 0.01%-0.05% (Improves workability and freeze-thaw resistance; use cautiously in high-strength concrete.)

3. Defoaming

Defoamer: 0.05%-0.20% (To counter excessive entrapped air and reduce bleeding or surface laitance.)

4. Antifreeze/ Early Strength (for subzero construction)

Early-strength agent: 2%-5%, Antifreeze agent: 5%-10% (Must match minimum construction temperature.)

5. Dilution Adjustment

Water is added to reach the target solid content of the compounded solution, typically 20%-30%, balancing pumpability and storage stability.

III. Trial Mix Calibration (Mandatory)

Laboratory validation is essential to avoid discrepancies between theoretical ratios and field performance:

1. Prepare 3-5 compounded formulations using the above ranges. Keep cement content, sand ratio, and water-binder ratio constant; adjust only admixture dosage.

2. Test key concrete parameters: Initial slump/ spread,Slump retention at 1 h and 2 h, Setting time, Compressive strength.

3. Adjustment principles:

Insufficient flow → increase mother liquor dosage
Poor slump retention → increase retarding/slump retention components
Excessive air → increase defoamer
Setting too fast or too slow → fine-tune retarder dosage

IV. Key Factors Affecting Ratio Optimization

1. Raw materials: High C₃A cement or fly ash with high water demand typically requires increased mother liquor and slump retention components.

2. Construction environment: High temperature (≥35 °C) or strong wind → increase retarder/slump retention; Low temperature (≤5 °C) → reduce retarder and add early-strength agents

3. Construction process: For pumping distances >500 m or waiting times >2 h, strengthen slump retention by increasing retarding components by 1-2×.

4. Typical Reference Formula (Ordinary pumped C30/C40 concrete, 40% solid PCE mother liquor)