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study on the influence of low acid ether ratio PCE mother liquor on concrete properties

Polycarboxylate superplasticizers (PCE) are essential chemical admixtures for modern ready-mixed concrete, precast components and infrastructure construction. Traditional commercial PCE products rely on high acrylic acid dosage to achieve water-reduction capacity, which leads to high sensitivity, unstable dosage response and poor slump retention during transportation. Therefore, developing low-acid, ether-ratio PCE mother liquor has become a hot research focus for admixture manufacturers seeking to improve construction adaptability.

This laboratory research synthesizes two low-acid-ether PCE products using HPEG and VPEG as main raw materials under room-temperature polymerization. A full series of paste and concrete tests compares their initial fluidity, time-dependent slump loss, air content and compressive strength with those of conventional commercial PCE. The paper also discusses performance improvements achieved by compounding with SR-1, a slump-retaining mother liquor, and provides practical guidance on optimizing concrete admixture formulations.

Raw Materials & Laboratory Synthesis Process

Synthesis Raw Materials

Two polyether macromonomers are adopted as core backbones:

HPEG: Methallyl polyoxyethylene ether, molecular weight 2400
VPEG: 4-hydroxybutyl vinyl oxyethylene ether, molecular weight 2400
Auxiliary synthesis materials: industrial acrylic acid (AA), hydrogen peroxide, vitamin C reducing agent, 3-mercaptopropionic acid chain transfer agent, and HEMA.

Test Raw Materials for Paste & Concrete

Binder: P·O 42.5 ordinary Portland cement, 28d compressive strength 48 MPa
Fine aggregate: Manufactured sand with a fineness modulus of 2.69, stone powder content 10%
Coarse aggregate: 5–20 mm continuous graded crushed stone, crushing value 6%

Room-Temperature Synthesis Steps

Dissolve the solid HPEG/VPEG macromonomer in water in a 20 ℃ water bath; stop heating once fully dissolved.
Add hydrogen peroxide and acrylic acid sequentially with high-speed stirring to avoid excessive temperature rise.
Prepare a vitamin C aqueous solution mixed with MPA, then slowly add the mixture while continuously stirring.
Stop stirring naturally once the reaction temperature drops back to ambient, to obtain a low-acid, ether-PCE mother liquor.

Tested PCE Samples

Commercial C6 PCE (solid content 49.5%)
Self-made low acid-ether C6 PCE (solid content 38%)
Self-made low acid-ether C4 PCE (solid content 38%)
Conventional HC100C4 PCE (solid content 39%)
SR-1 slump-retaining mother liquor (solid content 49.5%)

All paste tests follow GB/T 8077-2012; concrete performance tests comply with GB/T 50080-2011. Water-cement ratio for paste tests is fixed at 0.29. The standard C30 concrete mix design is adopted for mixing proportion verification.

Test Results & Performance Analysis

Cement Paste Fluidity & Slump Retention

Paste fluidity data at initial, 1h, 2h and 3h indicate the following advantages of low acid-ether ratio PCE:

Initial fluidity: Self-made C6 (250 mm) and C4 (245 mm) far outperform commercial C6 (210 mm) and HC100C4 (210 mm), delivering superior initial dispersion capacity for fresh paste.
Long-term retention: Self-made low-acid-ether PCE maintains fluidity above 230 mm after 3 hours, while HC100C4 suffers severe flow loss, dropping to 140 mm.
Solid content comparison: Commercial C6 has a high solid content (49.5%) but weak retention, while self-made C4/C6 with only 38% solid content achieves much better stability, verifying that a low-acid, ether-based-acid, and ether-based molecular structure optimizes sustained dispersion.

Single PCE Performance in C30 Concrete

Four PCE liquids are blended to a uniform 1% total admixture dosage for concrete testing:

Slump & spread: Self-made C4 and C6 deliver the highest fresh slump (240 mm). However, all single PCE groups exhibit a significant slump loss after 30 minutes, with HC100C4 reaching only 90 mm residual slump.
Air entrainment characteristic: Low acid-ether C4 and C6 bring an obvious air-entraining effect (3.0%–3.8% air content), while conventional PCE keeps air content at 2.8%. Extra tiny air voids can enhance freeze-thaw durability. Bulk density & compressive strength: Higher air content reduces concrete compactness. As a result, HC100C4 and commercial C6 produce denser mixtures with higher 28d strength (48.5 MPa and 46.1 MPa), whereas self-made C4/C6 only reach 40.4 MPa and 41.0 MPa.a.

Performance After Compounding with SR-1 Slump-Retaining Mother Liquor

To solve severe slump loss of single low acid ether PCE, 8% SR-1 slump-retaining liquid is added to each formula. Slump retention greatly improved: All groups maintain slump above 140 mm after 30 min mixing, indicating that SR-1 effectively offsets early slump loss. Commercial C6 achieves optimal initial flow (250 mm), while self-made C4/C6 keep balanced workability.y.

Air content adjustment: Self-made C4/C6 still maintain high air content (4.9%–5.0%), suitable for road, bridge and outdoor structures requiring freeze resistance.Balanced strength performance: After compound modification, all four PCE systems reach stable 28d compressive strength around 47–49 MPa, showing that SR-1 eliminates the early strength deficit of pure low acid-ether PCE.

Core Research Conclusions

low acid ether ratio PCE mother liquor synthesized from HPEG and VPEG monomers significantly boosts concrete initial fluidity and possesses natural slump-retaining capacity compared to traditional high-acid PCE mother liquor.
Low acid-ether C4 and C6 have moderate air-entraining properties. They are suitable for projects with high freeze-thaw durability requirements, but their higher air volume reduces concrete compactness and early compressive strength if used alone.
Conventional HC100C4 and commercial high-solid C6 PCE produce denser concrete with higher mechanical strength, making them better suited for high-strength structural concrete without strict anti-freeze requirements.
Compounding low-acid-ether PCE with SR-1 slump-retaining mother liquor effectively eliminates slump-loss defects, balancing long-term construction workability and long-term compressive strength.
Formulators should adjust acid-ether proportion and air content modifier according to project demands: prioritize low acid-ether PCE for long-distance transported concrete; reduce air entrainment for high-strength cast-in-place components.

Practical Engineering Application Guidance

Ready-mix concrete with long transit time (60–180 min transport): Adopt low acid-ether C4 or C6 PCE compounded with a slump-retaining liquid to avoid severe slump loss.
Highway, pavement and outdoor hydraulic structures: Choose self-made C4/C6 low acid-ether PCE for its natural air-entraining performance to improve freeze-thaw cycle resistance in service.
High-strength precast concrete, high-rise structural members: Select commercial C6 or HC100C4 high-density PCE to guarantee compactness and early strength development for structural performance.
Admixture factory optimization: Reduce acrylic acid dosage during PCE synthesis to lower the acid-ether ratio, cutting raw material costs while improving concrete construction adaptability.

Conclusion-study on the influence of low acid ether ratio PCE mother liquor on concrete properties

A low acid ether ratio PCE mother liquor, using HPEG and VPEG macromonomers, addresses the major drawback of traditional PCE: insufficient slump retention during long-distance delivery. Although its inherent air-entraining effect slightly lowers early compressive strength, simple compounding with commercial slump-retaining admixtures achieves a perfect balance between construction workability and mechanical performance.

Admixture manufacturers and concrete batching plants can select HPEG or VPEG low-acid-ether PCE formulas based on structural durability requirements, greatly improving the stability and construction efficiency of commercial concrete in various infrastructure projects.