In road maintenance and asphalt construction, asphalt emulsifier is the core additive to realize normal temperature asphalt construction, widely used in slurry seal layer, micro-surface, viscous oil, priming oil, cold regeneration construction and other scenes, effectively solving the pain point of traditional hot asphalt high temperature construction with high energy consumption and limited by seasonal weather. This paper explains the core definition, category characteristics and standardized use method of asphalt emulsifier. 

1. What is asphalt emulsifier? 

Asphalt emulsifier is a kind of surface-active chemical additive, whose core function is to break the immiscible property of asphalt and water. Through mechanical shearing and emulsifier adsorption, high temperature molten asphalt is dispersed into micron-sized fine particles, which are uniformly suspended in aqueous solution to form stable aqueous emulsion liquid, namely emulsified asphalt. 
Simply put: Emulsifier is the "fusion medium" of asphalt and water, which makes the asphalt that cannot be melted stably combine with water to produce emulsified asphalt that can be stored at normal temperature, sprayed at normal temperature and constructed at normal temperature. 

1. Core operating principle 

Emulsifier molecules have hydrophilic and lipophilic dual characteristics, lipophilic end adsorption asphalt particles, hydrophilic end wrapped water molecules, asphalt particles on the surface of the formation of protective film. It can not only make asphalt disperse evenly in water without agglomeration and precipitation, but also quickly precipitate asphalt after construction demulsification, firmly adhere aggregate and pavement base, and realize pavement bonding, waterproof and wear-resistant effects. 

2. Common categories and applicable scenarios 

According to ionic properties, emulsifiers commonly used in engineering are divided into three categories to adapt to different construction processes and road conditions: 
- Anionic asphalt emulsifier: high cost performance, good stability, mostly used in ordinary road transparent layer, sticky layer, conventional maintenance engineering, wide range of application. 
- Cationic asphalt emulsifier: fast demulsification speed, strong adhesion, excellent combination effect with stone, mainly in micro-surface, slurry seal, cold pavement regeneration, disease repair and other high-viscosity requirements scenarios, is the mainstream selection category of high-grade roads. 
- Non-ionic asphalt emulsifier: strong stability, good anti-interference, suitable for complex water quality, low temperature, high humidity and other special conditions, mostly used for special pavement and fine maintenance construction. 

Two, the correct use of asphalt emulsifier 

Asphalt emulsifier can not be directly used in pavement construction alone, but should be matched with equipment to produce emulsified asphalt, and then used in road engineering. The whole process is divided into five steps: preliminary preparation, soap preparation, emulsion production, storage and use, and post-maintenance. Standardized operation can ensure emulsion stability and construction effect up to standard. 

1. preliminary construction preparation 

Check the working conditions of emulsifying equipment, colloid mill, storage tank and spraying equipment in advance to ensure that the equipment is clean and free of oil and impurities; determine the emulsifier content according to the construction temperature, water quality and asphalt model (the conventional content is 0.6%-1.2% of the asphalt quality); give priority to clean tap water to avoid hard water and sewage affecting the emulsion stability. At the same time, clean the construction pavement to ensure that the base is dry, free of floating dust and debris. 

2. Preparation of emulsion soap (core step) 

It is forbidden to pour emulsifier directly into asphalt. Soap solution must be prepared by dissolving in water first. Heat water to 55 - 65℃, pour asphalt emulsifier according to the proportion, add appropriate amount of acid and alkali regulator to adjust pH value according to demand, stir fully for 3 - 5 minutes, until the emulsifier is completely dissolved, forming a uniform transparent soap solution without caking and layering. 

3. Production and preparation of emulsified asphalt 

The molten asphalt heated to 120 - 140℃ and the prepared soap solution are simultaneously fed into the colloid mill according to the predetermined oil-water ratio, and the asphalt is fully dispersed by high-speed shear grinding to produce uniform and stable emulsified asphalt. After the production is finished, standing and cooling are carried out, the emulsion state is observed, and the qualified finished product is obtained without layering, floating asphalt and precipitation. 

4. Site construction use according to construction scenarios 

Corresponding construction methods shall be adopted: uniform spraying shall be adopted for sticky layer and permeable layer construction to ensure uniform spraying thickness, no leakage and no accumulation; emulsified asphalt shall be evenly mixed with aggregate, water and filler for micro-surface and slurry sealing layer, and paved and leveled; accurate proportion shall be adopted for cold recycling construction to ensure uniform bonding of mixture. Construction can be carried out at normal temperature, not limited by low temperature and light wind weather. 

5. Demulsification molding and post-curing 

After construction, it enters emulsion breaking and solidification stage. With water evaporation, asphalt particles aggregate and precipitate, and gradually form dense asphalt bonding layer. Allow to stand for 2 - 6 hours at room temperature. After the road surface is completely dry, molded and firmly bonded, it can be opened to traffic. During the maintenance period, it is forbidden to roll vehicles and soak them in accumulated water to avoid peeling, peeling and loosening. 

III. Precautions for use 

- Emulsifiers should be stored in a sealed environment, avoiding exposure and freezing at low temperatures, and the storage environment temperature should be controlled at 5 - 35℃; 
- Strictly control the proportion of oil and water temperature, water temperature is too low easy emulsification incomplete, too high easy to cause emulsion failure; 
- Emulsifiers of different ionic types should not be mixed, which is easy to cause emulsion demulsification and delamination. 
- The finished emulsified asphalt should be used within the shelf life, and it is easy to cause stability decline and precipitation stratification after long-term storage. 

IV. Summary 

Asphalt emulsifier is the core additive of asphalt curing at room temperature. Its core value is to realize asphalt construction at room temperature, reduce energy consumption and break through seasonal construction restrictions. The core key to its use is "preparing soap solution first, accurately proportioning, standardizing emulsification and reasonable maintenance". According to different construction scenarios, corresponding types of emulsifiers are selected, and standardized processes are strictly followed, which can effectively improve pavement bond strength and construction quality, and widely adapt to various road maintenance and new supporting projects.