Oxidized Starch as Concrete Admixture: Research Progress and Application Prospects (2018–2026)

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Oxidized Starch as Concrete Admixture: Research Progress and Application Prospects (2018–2026)

Abstract
This review systematically summarizes the research progress of oxidized starch as a concrete admixture from 2018 to 2026. Oxidized starch introduces carboxyl and carbonyl groups, effectively reducing the peak cement hydration heat, achieving a water reduction rate of up to 25%, and improving water retention and anti‑segregation properties. Starch‑based superplasticizers have been successfully applied in major national projects such as the Shenbai Railway and the Sichuan‑Tibet Railway, reducing construction costs by approximately 10–25% and lowering dependence on petroleum‑based admixtures. Challenges remain including high sensitivity to process parameters, insufficient long‑term durability data, and significant retarding side effects. Future research should focus on long‑term performance evaluation, process standardization, multifunctional compounding, and cost optimization.

1. Introduction
Concrete is one of the most widely used construction materials, and its performance directly affects project quality and service life. Concrete admixtures have become an indispensable “fifth component” to improve workability and hardened properties. With global “dual carbon” goals, the concrete industry faces an urgent need to reduce carbon emissions and achieve sustainable development. Traditional petroleum‑based superplasticizers (e.g., polycarboxylate ethers) perform well but rely on fossil resources and carry environmental burdens.
Oxidized starch derived from renewable biomass offers a promising alternative. Starch – an abundant plant carbohydrate – can be chemically oxidized to introduce carboxyl, carbonyl, and other polar groups, significantly altering its physicochemical properties and making it a potential concrete admixture. Oxidized starch concrete admixtures offer outstanding advantages: renewable raw materials, low cost, and environmental friendliness, representing an important direction for the green transformation of the concrete industry.

2. Preparation Methods and Chemical Characteristics

2.1 Main Preparation Processes
Sodium hypochlorite (NaOCl) oxidation

Most traditional and widely used method.
Oxidation occurs at C2, C3, C6 positions; breaks glycosidic bonds; converts hydroxyls to carboxyl and carbonyl.
Typical conditions: pH ~9.5, 40°C, 2–5% NaOCl (on dry starch).
Advantages: mature process, high carboxyl content (0.5–1.1%).
Disadvantages: severe chain degradation, chloride residue (0.1–0.5% Cl⁻).

Ozone oxidation

Emerging green technology, no residues.
Involves free radical mechanisms; simultaneously causes depolymerization and cross‑linking.
Process parameters (ozone dose, reaction time, pH) significantly affect product properties – main challenge for industrial application.

Hydroxypropyl oxidized starch

Combined modification: first hydroxypropylation with propylene oxide, then oxidation.
Hydroxypropylation improves hydrophilicity and solubility; oxidation reduces molecular weight.
At dosages of 0.05–0.3% (by cement or mortar), improves water retention and adhesion.

2.2 Chemical Characteristics and Structural Changes
FT‑IR, XPS, and NMR analyses show:

Carboxyl absorption peaks at 1733 cm⁻¹ and 1714 cm⁻¹.
C‑O‑C stretching at ~1150 cm⁻¹.

Key structural parameters:

Parameter	NaOCl oxidation	Ozone oxidation	Hydroxypropyl oxidized
Carboxyl content	0.5–1.1%	Lower, variable	Low
Molecular weight	Strongly decreased	Depolymerization + cross‑linking	Reduced
Hydroxypropyl DS	–	–	0.3–1.3%

A two‑step oxidation method (patent CN115010819B) increases carboxyl content to >2%, significantly enhancing water‑reducing performance. Electrochemical oxidation is also being explored as a greener alternative.

2.3 Working Mechanisms
Electrostatic repulsion
Carboxyl and hydroxyl groups dissociate in water, creating negatively charged adsorption on cement particles. The resulting electric double layer prevents particle agglomeration, improving workability.
Adsorption‑dispersion
Polar groups undergo ion exchange with Ca²⁺ from cement hydration products, forming a protective film that slows hydration rate, reduces peak hydration heat, and improves flowability.
Cross‑linked network (especially for ozone‑oxidized starch)
Inter‑chain cross‑linking forms a weak gel network that enhances water retention and film‑forming ability, reducing bleeding and increasing concrete density.
Thermodynamic stability
Oxidized starch increases paste viscosity and stability, delaying particle sedimentation and improving anti‑segregation properties.

3. Performance and Engineering Applications
3.1 Hydration Heat Control and Workability
Adding 0.6% starch‑based admixture:

Reduces heat flow rate of cement paste by 43%.
Lowers maximum mortar temperature from 36°C to 25°C (an 11°C drop).

Performance indicator	Value
Water reduction rate	20–25%
Water retention	Significantly improved
Anti‑segregation	Enhanced (beneficial for self‑compacting concrete)
Setting time	Retarded (advantage for mass concrete)

3.2 Major Engineering Projects
Shenbai Railway
Starch‑based superplasticizer used in tunnel shotcrete, effectively reducing hydration heat peak and temperature crack risk, improving durability.
Sichuan‑Tibet Railway
Applied in high‑altitude, cold environments, controlling cement hydration rate and solving early strength development issues.
Lin‑Ning Expressway
Used across bridges, tunnels, and subgrade concrete:

50% substitution of petroleum‑based monomers.
Water reduction >25%.
Improved anti‑segregation and water retention.
Reduced construction cost by ~25 RMB/m³.

Other products

PT‑1‑ZN rebound inhibitor: reduces shotcrete rebound rate from 15–20% to <5%.
DF‑1‑FS starch‑based superplasticizer: enhances anti‑segregation, water retention, cohesion.
FZ‑1‑TY demolding & curing integrated agent: solves difficult curing in cold, dry areas and ultra‑high structures.

3.3 Advantages and Limitations
Advantages

Renewable raw materials, lower carbon footprint.
10–25% lower cost than polycarboxylate superplasticizers.
Multifunctional (water‑reducing, retarding, slump‑retaining).
Easy to use, wide adaptability for mass concrete, especially in high‑temperature environments.

Limitations

High sensitivity to process parameters (especially ozone oxidation).
Water reduction rate 10–20 percentage points lower than PCE.
Significant retarding side effect.
Lack of long‑term durability data (freeze‑thaw, chloride penetration, carbonation).
Narrow optimal dosage range (0.5–2.0%); excessive dosage reduces strength.

3.4 Compressive Strength
At 0.5–1.0% dosage, oxidized starch improves density and thus compressive strength. For example, cassava or corn starch increased 1‑year strength by 2.7% and 3.8% respectively. However, dosage >2.0% may cause strength loss up to 3%.

4. Research Gaps and Controversies
4.1 Preparation Process

Oxidant choice: NaOCl gives high carboxyl content but leaves chloride residues (potential rebar corrosion). Ozone is residue‑free but process‑sensitive and equipment‑intensive.
Two‑step oxidation: Claimed to increase carboxyl content >2%, but lacks systematic comparison with traditional processes.
Synergy of hydroxypropylation and oxidation: Mechanism still unclear; hydroxypropyl groups may react with Ca²⁺, causing viscosity changes and strength loss.

4.2 Long‑Term Durability – Missing Data

Durability aspect	Current status
Freeze‑thaw cycles (>300)	No data available
Chloride penetration (RCPT, CPT)	Systematic experimental evidence lacking
Carbonation depth	Almost no research
Strength development (90–365 days)	Scarce (most studies focus on 28 days)

4.3 Economic and Standardization Challenges

Cost: Lin‑Ning Expressway case suggests 10–25% lower cost than PCE, but systematic analysis is missing.
Scale‑up stability: Lab performance often not replicated in industrial production. A pilot line exists, but cost control and standardized processes need further optimization.
Standards: The group standard “Starch‑Based Superplasticizer” was selected as a 2024 MIIT “100 Group Standards Application Promotion Typical Case”, but it lacks specific provisions for oxidized starch properties.

5. Future Research Directions
5.1 Process Optimization and Standardization

Optimize ozone oxidation parameters (dose, time, pH) to achieve reproducible results.
Industrial validation of two‑step oxidation.
Establish standard dosage systems based on starch source, oxidation degree, and concrete type.
Improve quality evaluation indicators (carboxyl content, molecular weight distribution, etc.).

5.2 Long‑Term Performance Evaluation

300 freeze‑thaw cycles per GB/T 50082‑2009.
Rapid chloride permeability test (RCPT) and electrochemical chloride migration test (CPT).
Carbonation depth and sulfate resistance studies.
Strength development from 7 to 365 days, establish prediction models.

5.3 Multifunctional Compounding

Synergy with air‑entraining agents to improve freeze‑thaw resistance.
Compatibility with traditional retarders (sugars, hydroxycarboxylic acids) to mitigate excessive retardation.
Synergy with anti‑crack agents (e.g., polypropylene fibers).
Composite application with water repellents (e.g., silane impregnation).

5.4 Cost Optimization and Green Manufacturing

Raw material diversification: use agricultural residues (straw, rice husks).
Greener oxidation processes: electrochemical oxidation, ultrasound‑assisted oxidation.
Intelligent production: AI and IoT for precise control, reducing energy consumption.
Circular economy: valorize by‑products from oxidized starch production.

5.5 International Standards and Market Expansion

Participate in RILEM, ACI standard development.
Promote application in Belt & Road countries.
Explore use in extreme environments (high temperature, high humidity, radiation).
Interdisciplinary innovation (chemistry, materials science, civil engineering).

6. Conclusion
Oxidized starch has made significant progress as a concrete admixture between 2018 and 2026, especially in hydration heat control, water reduction, and environmental friendliness. By introducing carboxyl and carbonyl groups, oxidized starch effectively disperses cement particles, delays hydration, reduces peak hydration heat, and improves concrete workability. Its raw material is renewable biomass, offering outstanding environmental advantages.
Starch‑based superplasticizers have been successfully used in major national projects such as the Shenbai Railway, Sichuan‑Tibet Railway, and Lin‑Ning Expressway, reducing construction costs by 10–25% and decreasing dependence on petroleum‑based admixtures. Challenges remain, including high sensitivity to process parameters, insufficient long‑term durability data, and significant retarding side effects.
Future research should focus on process optimization and standardization, long‑term performance evaluation, multifunctional compounding technologies, cost optimization and green manufacturing, and international standard development. Through these efforts, oxidized starch concrete admixtures are expected to contribute to the green transformation and sustainable development of the concrete industry.

References (selected)

Aled D. Roberts & Nigel S. Scrutton (2023). StarCrete. Open Engineering.
Zhang, H. et al. (2018). A starch‑based admixture for reduction of hydration heat. Construction and Building Materials, 173, 317–322.
MIIT “2024 Group Standards Application Promotion Typical Case No. 7” – Starch‑Based Superplasticizer.
China Construction Eighth Engineering Bureau technical releases (2025).
Luo Faxing et al. Properties and cross‑linking mechanism of starches oxidized by sodium hypochlorite at low level. Journal of South China University of Technology.
Liu Qingfeng et al. (2019–2026). Various studies on concrete durability and ion transport.

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