19/03/2026
Method for Determining Compounding Ratios of Polycarboxylate Superplasticizers and Compounding Schemes for Concrete of Various Grades
The compounding ratio of polycarboxylate superplasticizers is mainly determined by the performance requirements of engineering concrete and the compatibility of raw materials. There is no fixed value, and calibration through trial mixing is required. The core idea is to first determine the base dosage of the mother liquor, then compound retarders, slump-retaining agents, air-entraining agents and other components according to functional requirements. The following are practical determination methods and general schemes for concrete of various grades.
I. Method for Determining Compounding Ratios of Polycarboxylate Superplasticizers
（I）First Determine the Base Dosage of Polycarboxylate Mother Liquor (Core Basis)
The mother liquor dosage (on solid basis) is determined by the water reduction rate / fluidity required by concrete design, with conventional ranges (percentage of total cementitious materials):
1. Ordinary pumped concrete: 0.15%~0.25%
2. High-flowability / self-compacting concrete: 0.25%~0.40%
3. High-strength concrete: 0.30%~0.50%
Note: The solid content of mother liquor is generally 20% / 40%, and the actual dosage shall be converted (Actual dosage = Solid-based dosage ÷ Solid content of mother liquor).
（II）Determine Compounding Components and Ratios According to Engineering Requirements
(Individual component as percentage of mother liquor mass)
The core compounding system consists of mother liquor + functional additives (retarding / slump-retaining / air-entraining / defoaming / anti-freezing). Ratios of individual components are superimposed as needed, and non-conflicting components can be compounded. Conventional ratios:
1. Retarding & slump-retaining (most commonly used): Sodium citrate 0.5%~2%, sodium gluconate 0.5%~3%, polyols 1%~4%; can be increased to 2%~5% under high temperature or long-distance transportation
2. Air entrainment: Air-entraining agent 0.01%~0.05% (improves workability and frost resistance; use with caution in high-strength concrete)
3. Defoaming: Defoamer 0.05%~0.2% (counteracts air entrainment from raw materials, resolves bleeding and laitance)
4. Anti-freezing (construction at sub-zero temperature): Early-strength agent 2%~5%, anti-freezing agent 5%~10% (shall match the minimum construction temperature)
5. Concentration adjustment: Water (adjust to target solid content of compound solution, generally 20%~30%, balancing fluidity and storage stability)
（III）Key Trial Mixing and Calibration Steps (Mandatory)
1. Prepare 3~5 groups of compound solutions per the above theoretical ratios; fix cementitious materials, sand ratio and water-binder ratio, and only adjust the dosage of compound solution;
2. Test core concrete indicators: Initial fluidity / spread, slump retention at 1h / 2h, setting time, compressive strength;
3. Calibration principles: Increase mother liquor dosage if fluidity is insufficient; increase retarder ratio if slump retention is poor; add defoamer if air content is too high; fine-tune retarder dosage if setting is too fast or too slow;
4. Finalize the optimal ratio meeting design and construction adaptability, and verify compatibility with cement and admixtures (fly ash / ground granulated blast-furnace slag).
（IV）Core Influencing Factors (Basis for Ratio Adjustment)
1. Raw materials: High C₃A content in cement and high water demand ratio of fly ash require appropriately increased mother liquor / slump-retaining component ratios;
2. Construction environment: Increase retarding & slump-retaining ratios at high temperature (≥35℃) or strong wind; reduce retarder and add early-strength agent at low temperature (≤5℃);
3. Construction technology: For pumping distance >500m or waiting time >2h, enhance slump retention and increase retarder ratio by 1~2 times.
（V）General Reference Compounding Formula
For ordinary pumped C30/C40 concrete (mother liquor solid content 40%):
40% polycarboxylate mother liquor (20%) + sodium gluconate (1%) + sodium citrate (0.5%) + water (78.5%)
Total dosage of compound solution: 0.8%~1.2% of cementitious materials (direct pumping applicable, slump retention ≥200mm in 2h).
II. General Compounding Schemes of Polycarboxylate Superplasticizers for Concrete of Various Grades
Core Principles: Low-grade concrete focuses on workability / pumpability; medium-high grade focuses on water reduction / strength; ultra-high grade emphasizes water reduction / compactness. All schemes shall be fine-tuned according to cement type, admixtures (fly ash / slag powder) and construction environment. For high temperature or long-distance transportation, retarder components can be increased by 0.5~1 times.
(Mother liquor solid content 40%, target solid content of compound solution 20~25%, dosage based on total cementitious materials)
（I）Low-grade (C15/C20): Ordinary Pumping / Cushion / Foundation
Application scenarios: Mass concrete cushions, foundation backfilling; low water reduction, high workability, compatible with low-quality aggregates
1. Compounding components (percentage of total compound solution mass): 40% mother liquor 18% + sodium gluconate 0.3% + sodium citrate 0.2% + air-entraining agent 0.01~0.02% + water 81.48~81.49%
2. Dosage of compound solution: 1.0%~1.3%
3. Core performance: Water reduction rate 15~20%, initial spread ≥450mm, slump retention ≥350mm in 1h, suitable for pumping distance ≤300m
（II）Medium-low Grade (C25/C30): Civil Main Structures / Beams, Slabs, Columns / Ordinary Pumping
Application scenarios: Residential main structures, municipal roads; mainstream general grades balancing pumpability, slump retention and strength development
1. Compounding components: 40% mother liquor 20% + sodium gluconate 0.8% + sodium citrate 0.4% + defoamer 0.05% + water 78.75%
2. Dosage: 0.8%~1.2%
3. Core performance: Water reduction rate 20~25%, initial spread ≥500mm, slump retention ≥400mm in 2h, suitable for pumping distance ≤500m
（III）Medium-high Grade (C35/C40): High-rise Main Structures / Bridge Substructures / Ready-mixed Concrete Mainstream
Application scenarios: High-rise beams, slabs, columns, bridge foundations; high water reduction, good slump retention, compatible with Class II fly ash / slag powder
1. Compounding components: 40% mother liquor 22% + sodium gluconate 1.0% + sodium citrate 0.5% + polyol slump-retaining agent 0.3% + defoamer 0.05~0.1% + water 76.1~76.15%
2. Dosage: 0.7%~1.0%
3. Core performance: Water reduction rate 25~30%, initial spread ≥550mm, slump retention ≥450mm in 2h, suitable for pumping distance ≤800m
（IV）High-grade (C45/C50): Super High-rises / Bridge Superstructures / Prestressed Components
Application scenarios: Super high-rise core tubes, bridge box girders, prestressed beams and slabs; high water reduction, low water-binder ratio, stable strength
1. Compounding components: 40% mother liquor 25% + sodium gluconate 1.2% + sodium citrate 0.6% + polyether slump-retaining agent 0.5% + defoamer 0.1~0.15% + water 72.55~72.6%
2. Dosage: 0.6%~0.9%
3. Core performance: Water reduction rate 30~35%, water-binder ratio ≤0.35, initial spread ≥600mm, slump retention ≥500mm in 3h, compatible with manufactured sand / high-grade cement
（V）Ultra-high Grade (C55/C60): Super High-rise Core Tubes / Main Bridge Spans / Precast Components
Application scenarios: Super high-rise core tubes, long-span bridges, precast PC components; ultra-high water reduction, low air content, high strength
1. Compounding components: 40% mother liquor 30% + sodium gluconate 1.5% + sodium citrate 0.8% + high-efficiency slump-retaining agent 0.8% + defoamer 0.2% + water 66.7%
2. Dosage: 0.5%~0.8%
3. Core performance: Water reduction rate 35~40%, water-binder ratio ≤0.30, air content ≤2.0%, initial spread ≥650mm, slump retention ≥550mm in 3h; requires Class I fly ash / S95+ slag powder
（VI）Extra-high Grade (Above C60): Super High-rises / Long-span Bridges / Nuclear Power Engineering
Application scenarios: Top floors of super high-rises, steel-concrete joints of long-span bridges, nuclear power projects; extreme water reduction, high compactness, low shrinkage
1. Compounding components: 40% mother liquor 35~40% + sodium gluconate 1.8~2.0% + high-efficiency slump-retaining agent 1.0~1.2% + defoamer 0.2~0.3% + water 56.5~59.0%
2. Dosage: 0.4%~0.6%
3. Core performance: Water reduction rate ≥40%, water-binder ratio ≤0.28, air content ≤1.5%, initial spread ≥700mm; requires low water-demand cement / high-quality manufactured sand / silica fume
III. General Fine-tuning Rules
1. Cement C₃A content >8% / fly ash water demand ratio >105%: Increase mother liquor ratio by 2~3% and slump-retaining components by 0.3~0.5%
2. Low-temperature construction (≤5℃): Reduce retarder components by 50%; add 2~3% early-strength agent (sodium sulfate / calcium formate) (based on compound solution)
3. Manufactured sand mud content >3%: Increase mother liquor ratio by 3% and defoamer by 0.05% to prevent bleeding and laitance
4. Precast components / self-compacting: Reduce or eliminate air-entraining agent; increase slump-retaining components by 0.5% to ensure compact forming
