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Synthesis and Performance of Workability Polycarboxylate Superplasticizer

Concrete workability (consisting of fluidity, cohesiveness and water retention) is the core indicator that determines on-site pumping, pouring efficiency and final structural durability. With the expansion of modern infrastructure projects, ready-mix concrete is often produced with unstable raw materials, such as high-mud manufactured sand, variable aggregate gradation and temperature fluctuations, which can easily lead to segregation, excessive bleeding and rapid slump loss. Ordinary commercial polycarboxylate superplasticizers often fail to balance water reduction, slump retention and water retention performance under complex raw material conditions.

This article uses EPEG macromonomer as the main raw material, to synthesize a novel high-workability polycarboxylate superplasticizers via low-temperature free-radical copolymerization.

Raw Materials & Experimental Procedures

Synthesis Raw Materials

Main macromonomer: EPEG polyether (molecular weight = 3000 g/mol)

Monomers & reagents: Acrylic acid (AA), hydrogen peroxide initiator, sodium hypophosphite (SHP), mercaptoethanol (ME), reducing agent E51, ferrous sulfate heptahydrate, N,N-dimethylacrylamide (DMAM), cross-linked functional monomer Y, and sodium hydroxide for pH adjustment.

Concrete Test Raw Materials

Binder: P·O 42.5R cement, S95 blast furnace slag powder, Class II fly ash

Aggregates: Washed fine sand (fineness modulus 2.8), manufactured sand (6.5 mud content), 5–20 mm crushed stone (10% flaky particles)

Reference admixture: Commercial general polycarboxylate

Mixing water: Tap water

Synthesis Process

oad EPEG, AA, DMAM, functional monomer Y and deionized water into a four-neck flask and fully dissolve under water bath temperature control.

Prepare drop solution A (acrylic acid aqueous solution) and drop solution B (reducing agent E51 + ME mixed liquid).

Add ferrous sulfate and hydrogen peroxide initiator, stir evenly, then simultaneously drip A over 50 min and B over 60 min.

Maintain a constant temperature for 60 min after dripping is complete, then supplement water and neutralize with sodium hydroxide to adjust the pH to 5–7, obtaining finished PCE-KZJ mother liquor.

est Standards

Fresh concrete performance: GB/T 50080-2016 (spread, T500, pressure bleeding rate Bv)

Compressive strength: GB/T 50081-2019

Single-Factor Optimization Test Results

Effect of Initial Polymerization Temperature

Temperature directly controls the rate of free radical generation and the molecular weight distribution of the polymer.

Temp (℃)	T500 (s)	0h Spread (mm)	2h Spread (mm)
15	6.1	580	500
20	6.4	585	510
25	7.8	560	450
30	9.5	535	400
35	11.8	515	360

As the temperature rises, the initiator decomposes rapidly, producing excessive free radicals that disrupt molecular chain control, leading to slower flow (longer T500) and serious slump loss at 2 h. A comprehensive performance and energy consumption balance indicates that 20 ℃ is the optimal initial reaction temperature.

Influence of Acid-Ether Ratio

The acid-ether ratio determines the side-chain density and the steric hindrance effect of PCE molecules.

Acid-Ether Ratio	T500 (s)	0h Spread (mm)	2h Spread (mm)
2.85	13.5	530	470
3.15	10.8	545	480
3.45	6.3	585	500
3.75	6.7	590	485
4.05	9.2	550	400

A too-low ratio leads to insufficient carboxyl groups for cement adsorption; an excessive ratio reduces side chains and weakens steric repulsion. The optimal acid-ether ratio is 3.45, delivering balanced initial dispersion and long-term slump retention.

Compound Chain Transfer Agent

Sodium hypophosphite and mercaptoethanol jointly regulate molecular weight to improve cohesiveness and reduce bleeding.

n(SHP):n(ME)	T500 (s)	0h Spread (mm)	2h Spread (mm)	Bv (%)
4:0	4.5	605	480 40
3:1	5.1	600	500 33
2:2	6.2	590	525 27
1:3	8.3	570	500 29
0:4	10.5	540	470 30

The 2:2 proportion introduces moderate phosphate groups for rapid cement adsorption, minimizing pressure bleeding (Bv = 27%) while maintaining excellent 2-hour slump retention.

DMAM & Functional Monomer Compound Ratio

DMAM provides hydrophilic amide groups to reduce bleeding; functional Y monomer brings cross-linking structures to boost slump retention.

Total Monomer Dosage	DMAM:Y Ratio	T500 (s)	0h Spread	2h Spread	Bv (%)
0.8%	1.1:1	4.2	600	510	5
0.8%	1.3:1	4.2	605	495	6
1.2%	1.1:1	5.1	590	450	8
1.2%	1.3:1	5.6	595	430	10

Lower total monomer dosage (0.8%) with DMAM:Y = 1.1:1 achieves the lowest pressure bleeding rate of 5% and outstanding water retention performance.

Core Research Conclusions

Increasing the polymerization temperature, the acid-ether ratio, or the total dosage of functional monomers weakens long-term slump retention; reducing the SHP proportion improves slump retention but increases the risk of concrete bleeding.
Optimal low-temperature copolymer synthesis parameters: initial temperature 20 ℃, acid-ether ratio 3.45, chain transfer agent molar ratio n(SHP):n(ME) = 2:2, functional monomer mass ratio DMAM:Y = 1.1 with total addition 0.8%.
The customized high-workability PCE-KZJ superplasticizer offers greater water-reduction capacity, excellent slump retention and superior anti-bleeding performance compared to conventional commercial polycarboxylate admixtures.

Engineering Application Guidance

Ready-mix plants with high-mud manufactured sand: Adopt EPEG-based PCE-KZJ to reduce pumping segregation and slump loss during long-distance transportation.
Mass cast-in-place and self-compacting concrete: This admixture’s low-pressure bleeding rate avoids surface honeycombing and poor surface finish.
Seasonal construction: The low-temperature synthesis formula exhibits its stable performance across a range ofge of ambient temperatures and is less sensitive to raw material fluctuations than traditional polycarboxylate superplasticizer.
Admixture manufacturers: Reference this EPEG copolymer process to upgrade high-workability polycarboxylate superplasticizer products for complex aggregate conditions.

Conclusion-Synthesis and Performance of Workability Polycarboxylate Superplasticizer

Traditional commercial polycarboxylate superplasticizers struggle with poor cohesiveness and rapid slump loss when using high-mud local aggregates. This study develops an optimized EPEG-copolymerized PCE via single-factor parameter tuning during low-temperature synthesis. The novel admixture balances water reduction, long-term slump retention and anti-segregation water retention. For ready-mix, precast and large-scale infrastructure projects with variable raw material quality, this high-workability PCE serves as a reliable admixture solution to stabilize fresh concrete performance and upgrade finished structural strength.