I. Technical definition and core advantages
Micro-surfacing project is a preventive maintenance method based on the upgrade of slurry seal technology. Its core lies in the use of polymer-modified emulsified asphalt, mixed with stone chips, fillers (such as cement, lime), water and additives of specific grading, to form a fluid slurry mixture, which is spread on the original road surface through special equipment to form a thin layer of seal. This technology has the following significant advantages:

Fast construction and open traffic
Construction at room temperature, no need to heat materials, traffic can be opened within 2 hours, significantly reducing traffic interruption time.
It is suitable for highways with large traffic volume, and 500 tons of mixture can be spread per day, with construction efficiency far exceeding traditional hot-mix asphalt process.
Fully improved performance
Anti-skid: The macro-structure depth is improved, the friction coefficient is increased, and the problem of slippery road surface is effectively improved.
Waterproof: The porosity is as low as 5% or less, forming a dense anti-seepage layer to prevent surface water from seeping into the road surface.
Durability: The service life is 5-8 years, and the ruts with a depth of ≤38mm can be repaired, delaying the overhaul cycle of the road surface.
Environmental protection and economy
Normal temperature construction, no toxic smoke and dust emissions, energy consumption is reduced by more than 50%.
The cost is 30%-40% lower than that of hot-mix asphalt, and it can be directly used in the wear layer of new roads to reduce the use of expensive stones.

2. Construction technology and key control points
Pretreatment of the original road surface
Rut treatment: ≤5mm ruts are directly paved with 1cm micro-surfacing; 5-20mm ruts are filled in two layers; >20mm ruts need to be milled and paved in multiple layers.
Crack treatment: >5mm cracks need to be sealed with grouting; loose and potholes need to be dug and filled before paving.
Defect repair:
Cleaning requirements: Use a sweeper or high-pressure water to wash to ensure that there is no debris or water accumulation, and construction after drying.
Material and mix design
Aggregate: Use alkaline stones such as basalt and diabase, with sand equivalent ≥65% to ensure adhesion with asphalt.
Emulsified asphalt: must be polymer modified (such as SBR, SBS), and the softening point of the residue is ≥57℃.
Filler: Cement is preferred, and the dosage is determined by test, which can adjust the mixing time and strength development of the mixture.
Gradation design: Use ISSA III gradation to ensure the workability of the mixture and the uniformity of paving.
Paving and forming control
Paving thickness: Select according to traffic volume (heavy traffic 10mm, medium 7mm, light 3-4mm).
Driving speed: 1.5-3.0km/h, maintain a uniform speed to avoid uneven paving.
Joint treatment: The horizontal joints overlap 4-5m, and the longitudinal joints are located at the marking line to ensure flatness.
Equipment requirements: Use a continuous slurry seal paver equipped with a V-shaped paving trough to achieve normal distribution of aggregates.
Construction parameters:
Care and traffic opening
Initial maintenance: Avoid sudden braking and turning after paving. When the 12.7mm thick seal layer is above 24℃ and the humidity is below 50%, it can withstand vehicle rolling within 1 hour.
Fully open: Depending on the temperature and the curing of the mixture, traffic is usually fully opened after 24 hours.

III. Application effect and typical cases
Performance improvement data
The anti-skid performance (friction coefficient) is improved by 30%-50%, and the accident rate is reduced by more than 20%.
The pavement water permeability coefficient drops to below 50ml/min, effectively delaying water damage.
After rutting is filled, the flatness IRI value is reduced to below 1.5m/km, and the driving comfort is significantly improved.
Economic benefit analysis
After micro-surfacing was applied to a highway project, the maintenance cost was reduced by 40% within 5 years, and the overhaul cycle was extended by 3-5 years.
Compared with hot-mix asphalt, the maintenance cost per kilometer was reduced by about 200,000 yuan, and carbon emissions were reduced by 60%.
Applicable scenarios
Road sections with large traffic volume and a high proportion of heavy-loaded vehicles.
Non-structural defects such as minor cracks, rutting, and aging appear on the road surface.
Emergency maintenance projects that require rapid restoration of traffic.
IV. Technical standards and specification requirements
Climate conditions
The temperature during the construction and curing period is >10℃. Construction is prohibited on rainy days. The road surface must be dry after rain.
Avoid construction in seasons with a maximum daily temperature below 15℃ to ensure the quality of the mixture solidification.
Original road surface requirements
The structural strength meets the design requirements, and local strength is insufficient and needs to be reinforced.
Crack width >5mm requires grouting, and loose defects need to be dug and patched to the stable layer.
Quality control indicators
Mixture performance: wet wheel wear value ≤500g/m2, load wheel sand adhesion ≤450g/m2.
Paving thickness: design value ±0.5mm, flatness standard deviation ≤1.2mm.
Open traffic conditions: cohesion test ≥1.2N·m to ensure interlayer bonding strength.
5. Technology Development Trends
Low-noise micro-surfacing
By optimizing grading and adding fiber materials, the driving noise can be reduced by 5-8dB, and the applicability of urban roads can be improved.
Fiber-reinforced micro-surfacing
Polyester fiber is added to improve high-temperature stability and crack resistance, and the service life can be extended to more than 8 years.
Intelligent construction equipment
Develop a 3D paving control system to achieve millimeter-level thickness control and reduce material waste by 10%-15%.
Conclusion
The preventive maintenance micro-surfacing project of highways has become the core technology for extending the service life of the road and improving driving safety with its characteristics of "fast, efficient, environmentally friendly and economical". By strictly controlling the quality of materials, construction technology and quality inspection, its technical advantages can be fully utilized to provide sustainable solutions for highway maintenance.