Emulsified asphalt is the core raw material of synchronous macadam seal, slurry seal, micro-surfacing, pavement adhesive layer and waterproof adhesive layer in highway maintenance and road construction engineering.The quality of emulsified asphalt products lies not in the mixing ratio, but in the grinding and emulsifying effect of colloid mill.Colloidal mill, as the core component of emulsified asphalt production equipment, directly determines the fineness of asphalt particles, emulsion stability, bond strength and pavement construction quality.The structure, working principle, emulsification process and core technical advantages of asphalt colloid mill are analyzed deeply in this paper.

Core positioning of colloid mill: "ultra-micronization processor" of emulsified asphalt 

Asphalt and water are immiscible with each other. Ordinary mixing can only achieve simple mixing. After standing, it will quickly delaminate, demulsify, and precipitate, which cannot meet road construction standards. Colloid mill is a special equipment for high speed shearing, ultra-micro grinding and dynamic emulsification. It breaks high temperature matrix asphalt into micron particles by pure physical and mechanical force, and forms uniform, fine and stable oil-in-water emulsified asphalt emulsion with the aid of emulsifier. It is the key equipment to realize permanent emulsification of asphalt. 

Core structure of colloid mill 

The colloid mill for emulsified asphalt has precise structure, and the core working unit consists of rotor, stator, grinding cavity, speed regulating drive system and feeding and discharging channel. The overall structure is compact, wear-resistant and can be continuously operated: 
- High-speed rotor: core moving parts, made of high wear-resistant alloy material, can achieve high-speed operation of more than 2900 rpm, is the core power source to produce shear, impact and centrifugal force. 
- Fixed stator: static grinding body precisely matched with rotor, multi-layer staggered tooth structure is designed inside, forming narrow precision grinding gap. 
- Precision grinding gap: rotor and stator gap can be accurately adjusted, the normal range is 0.1mm-0.5mm, gap size directly determines the fineness of asphalt particles. 
- Sealing and temperature control system: suitable for high temperature asphalt operation, anti-leakage, anti-high temperature deformation, ensure long-term continuous and stable operation of equipment. 

Complete working principle and emulsification process of colloid mill 

The core of colloid mill is negative pressure feeding + multi-force composite shearing + ultra-micro grinding + homogeneous emulsification. The whole process is continuously automated, uninterrupted and without secondary pollution. It is divided into four stages: 

Negative pressure suction, material mixing and convergence 

After the equipment is started, the high-speed rotating rotor creates an instantaneous negative pressure inside the grinding chamber. The liquid matrix asphalt preheated to the standard temperature and the emulsifier aqueous solution evenly mixed in advance are simultaneously sucked into the grinding cavity according to the precise proportion. The two materials are initially merged before entering the grinding area to prepare for fine emulsification. 

High pressure shear breaks asphalt macromolecules 

After entering the tiny gap between rotor and stator, mixed materials are subjected to four-fold mechanical forces of high frequency shear, strong extrusion, high speed friction and instantaneous impact. The asphalt micelles with large volume, high viscosity and molecular agglomeration were repeatedly cut and torn by multi-layer gullets, and the macromolecular structure was completely scattered and broken, and disassembled into fine particles from blocks and flocculent particles. 

Ultrafine grinding, particle homogenization and refinement 

The material flows with the rotor at high speed, continuously grinding and refining in the precision gap, and finally grinding the asphalt particles to a uniform particle size of 1 - 5 microns. Compared with the uneven particles produced by ordinary stirring equipment, the asphalt particles treated by colloid mill have uniform size and strong dispersibility, which completely solves the problems of coarse particle precipitation and stratification. 

Homogenization of coating to form stable emulsion 

At the moment of ultrafine asphalt particles, emulsifier molecules are fully adsorbed and wrapped on the surface of asphalt particles, greatly reducing the interfacial tension between oil and water, so that the originally mutually exclusive asphalt and water are closely fused to form uniform and stable oil-in-water emulsified asphalt. The emulsified material is quickly thrown out of the grinding cavity under the action of centrifugal force, and the discharged material is the finished emulsion, which can be directly used for road construction.

Core technical advantages of colloid mill emulsification 

Emulsion stability is very strong, not easy to break emulsion 

The emulsified asphalt finely ground by colloid mill has uniform particles and complete package. It is not easy to separate, precipitate and crust when stored at rest, effectively prolonging the storage time and meeting the requirements of batch construction and long-term operation. 

Excellent bonding performance, higher construction quality 

Ultra-fine asphalt particles have stronger permeability and adhesion. After paving, they form uniform film and bond firmly. They can perfectly fit macadam, water-stabilized base course, old asphalt pavement and cement pavement, greatly improve the bonding strength of synchronous macadam seal layer, sticky layer and waterproof layer, and effectively avoid pavement diseases such as particle loss, loosening, water seepage and delamination. 

Adapt to multi-category asphalt, versatility 

By adjusting the grinding gap and rotating speed, the colloid mill can produce various kinds of materials such as ordinary emulsified asphalt, modified emulsified asphalt, cationic emulsified asphalt, etc., which are fully suitable for the construction and maintenance of highways, national and provincial roads, municipal roads and rural roads. 

Continuous operation, high construction efficiency 

The equipment has high degree of automation, can continuously and stably produce for 24 hours, has fast discharge speed, and the qualified rate of finished products is 100%. It completely matches the rhythm of large-scale road mechanization construction and effectively improves the construction progress of the project. 

Distinguishing common mistakes in the industry 

Many construction companies tend to equate "mixing" with "emulsification". Ordinary stirring can only achieve simple mixing of oil and water, belonging to physical patchwork, and will break emulsion failure in a short time; while colloid mill is to complete ultrafine and coated emulsification from the molecular level, which is stable emulsification in the true sense, and is also an essential core process for the production of national standard emulsified asphalt. 

SUMMARY 

In short, the working principle of emulsified asphalt colloid mill is to use high-speed mechanical shearing and ultra-micro grinding to break the macromolecular structure of asphalt, and to achieve stable integration of oil and water with emulsifiers. As the core of emulsified asphalt equipment, the working state of colloid mill directly determines the finished quality of emulsified asphalt, and then affects the waterproof, bonding and wear-resistant effects of road construction such as synchronous gravel seal. It is an indispensable core equipment for road refinement and high quality construction and maintenance.