Surfactants have extensive applications in asphalt pavement construction, mainly including the following aspects:
1. As Warm Mix Additives
(1) Mechanism of Action
Warm mix additives are a type of surfactant (e.g., APTL-type warm mix additives) composed of lipophilic and hydrophilic groups in their molecular structure. During the mixing of asphalt mixtures, warm mix additives are sprayed into the mixing pot synchronously with asphalt. Under mechanical agitation, the lipophilic groups bond with asphalt, while residual water molecules combine with hydrophilic groups to form a structural water film between asphalt-coated aggregates. This water film acts as a lubricant, enhancing the workability of the mixture during mixing. During paving and compaction, the structural water film continues to provide lubrication, increasing paving speed and facilitating compaction of the mixture. After compaction is completed, water molecules gradually evaporate, and the surfactant migrates to the interface between asphalt and aggregates, strengthening the bonding performance between aggregates and asphalt binder.
(2) Advantages
Warm mix additives can reduce mixing, paving, and compaction temperatures by 30–60°C, extending the construction season to environments above 0°C. They reduce CO₂ emissions by approximately 50% and toxic gas emissions (e.g., asphalt fumes) by over 80%. Additionally, they prevent asphalt aging, ensure compaction quality and construction performance, and prolong the service life of asphalt pavements. Furthermore, the use of warm mix additives can increase the output of mixing plants by 20–25% and raise paving/compaction speeds by 10–20%, thereby improving construction efficiency and shortening construction time.
2. As Asphalt Emulsifiers
(1) Classification and Characteristics
Asphalt emulsifiers are surfactants classified by ionic properties into cationic, anionic, non-ionic, and amphoteric types. Cationic asphalt emulsifiers adsorb onto negatively charged aggregates via positive charges, offering strong adhesion—making them particularly suitable for humid and rainy regions. Anionic emulsifiers, while low-cost, have poor water resistance and are gradually being replaced. Non-ionic and amphoteric emulsifiers meet the requirements of special environmental conditions. Classified by demulsification speed, they include slow-setting (used for slurry seal and cold recycling), medium-setting (balancing opening time and curing speed), and fast-setting (used for surface treatment to enable rapid curing and traffic opening) types.
(2) Application Scenarios
Asphalt emulsifiers enable cold mixing and cold paving processes that eliminate the need for asphalt heating, reducing energy consumption by over 30%—a significant advantage in remote mountainous areas or rapid urban road repairs. They are also used for preventive maintenance (e.g., slurry seal) to repair aged pavements and extend service life by 5–8 years. Additionally, they support in-situ cold recycling, achieving 100% recycling of old asphalt pavement materials and reducing costs by 20%.
3. Improving the Workability of Cutback Asphalt and Its Mixtures
(1) Effect
Surfactants formulated by compounding heavy oil viscosity reducers (AMS) with Span80, when added to cutback asphalt, significantly reduce the surface tension at the asphalt-aggregate interface and lower the viscosity of cutback asphalt. This ensures optimal mixing performance of the mixture while reducing diesel dosage. The incorporation of compound surfactants enhances the spreadability of asphalt on aggregate surfaces, reduces resistance during paving, and increases the final compaction degree of cutback asphalt mixtures—improving mixing uniformity and paving/compaction performance.
(2) Mechanism
Compound surfactants alter the liquid-solid interfacial tension between asphalt and aggregates, enabling asphalt mixtures to maintain favorable construction performance even with reduced diluent dosage. At a surfactant dosage of 1.0–1.5%, the improvement in paving and compaction characteristics of cutback asphalt mixtures is equivalent to adding 4–6% diesel diluent, allowing the mixture to achieve the same mixing uniformity and compaction workability.
4. For Cold Recycling of Asphalt Pavements
(1) Recycling Mechanism
Cold recycling asphalt emulsifiers are surfactants that disperse asphalt into micro-particles via chemical action and stabilize them in water, with their core function enabling ambient-temperature construction of asphalt. Emulsifier molecules form an oriented adsorption layer at the asphalt-aggregate interface, resisting water erosion—especially effective for acidic aggregates. Meanwhile, light oil components in emulsified asphalt penetrate aged asphalt, partially restoring its flexibility and increasing the recycling rate of reclaimed materials.
(2) Advantages
Cold recycling technology enables ambient-temperature mixing and construction, reducing energy consumption by 50–70% compared to hot recycling and lowering greenhouse gas emissions. It aligns with the demands of resource recycling and sustainable development.
Post time: Dec-09-2025