Quasi-asphalt is a temperature-sensitive material. If the temperature is too high, it will accelerate aging and performance attenuation; if the temperature is too low, the viscosity will increase, the fluidity will deteriorate, and it will be easy to have problems such as wall hanging, precipitation, and discharge difficulties.Temperature control of asphalt storage tank is the basic guarantee for road construction links such as asphalt mixing, emulsification and slurry sealing. There are clear differences in storage temperature control standards corresponding to different types of asphalt, so the temperature in the tank shall be controlled strictly according to the specifications, giving consideration to material performance and safety production.

Standard for temperature control of different types of asphalt storage tanks

Road asphalt (base asphalt)

The storage temperature of matrix asphalt is generally controlled at 130℃~150℃.
- Lower limit: should not be lower than 130℃, lower than the temperature asphalt viscosity significantly increased, transfer pumps, pipelines easy to block, discharge difficult.
- Upper limit: maximum temperature not exceeding 150℃.If the temperature exceeds 150℃ for a long time, asphalt will undergo thermal oxidation aging, penetration will decrease, brittleness will increase, and pavement durability will be reduced.
Note: Short-term heating to the mixing discharge temperature (150~160℃) can be done, but it is not possible to maintain high temperature in the storage tank for a long time.

SBS modified asphalt

Modified asphalt contains polymer modifier, more sensitive to temperature, storage temperature range is narrower: 160℃~170℃.
- Below 160℃: the compatibility between modifier and asphalt decreases, segregation easily occurs, modified asphalt is layered, and the upper and lower properties are inconsistent.
- Above 170℃: the modifier is easy to degrade, and the modification effect is greatly lost; high temperature will also increase safety risks.
Matching requirements: modified asphalt storage tank must be equipped with stirring device, constant temperature stirring, to prevent static storage segregation.

Emulsified asphalt (special for slurry seal coat)

Emulsified asphalt and hot asphalt are completely different. It is forbidden to heat at high temperature. The temperature of storage tank shall be controlled at 5℃~40℃, and the best normal temperature shall be 20~30℃.
- Temperature>40℃: emulsifier failure, asphalt emulsion demulsification, coagulation, direct scrap.
- Temperature <5℃: easy to freeze at low temperature, emulsion structure damage, can not be used for slurry seal construction.
Key points: storage tank only do insulation, do not configure heating system; avoid direct sunlight, summer do a good job of tank shading.

warm mix asphalt

Storage temperature of warm asphalt: 110℃~130℃.Rely on warm mix additives to reduce viscosity, lower storage temperature than base asphalt, reduce heat aging and energy consumption.

Key points of temperature control technology for asphalt storage tank

Temperature measuring device requirements

Storage tanks shall be equipped with multi-point temperature sensors (tank top, tank middle and tank bottom). It is not possible to rely only on single-point temperature measurement. The stratified temperature in the tank shall be monitored in real time. The temperature instrument shall be calibrated regularly.

Insulation and heating system

Rock wool and other thermal insulation layer shall be made outside the tank to reduce heat loss; heating with thermal oil is the preferred scheme, and direct heating of tank wall by open fire is strictly prohibited.Gradient heating is adopted, and the heating speed should not be too fast to prevent local overheating and aging.

Storage duration linkage control

Even if the temperature reaches the standard, asphalt should not be stored indefinitely.The storage of matrix asphalt is generally not more than 15 days; the storage of modified asphalt shall be controlled within 7 days as far as possible, and it will slowly separate and age even if stored at constant temperature for a long time.

safety management and control

The temperature in the tank shall not exceed the flash point temperature; the breather valve on the top of the tank shall be kept unobstructed to prevent oil and gas accumulation during storage of high temperature asphalt and prevent fire risk.

Common temperature control errors

1. In order to facilitate pumping, the storage temperature of base asphalt is raised to more than 160℃ for a long time, resulting in asphalt aging;
2. Modified asphalt only temperature control without stirring, static storage produces segregation;
3. Misheating emulsified asphalt resulted in emulsion breaking failure and could not be used for slurry seal.

epilogue

Core principles of temperature control of asphalt storage tank: ** Base asphalt anti-high temperature aging, modified asphalt anti-segregation degradation, emulsified asphalt is strictly prohibited from heating **.In engineering application, it is necessary to strictly implement temperature range in combination with asphalt brand and construction technology (slurry sealing layer, mixture mixing, etc.), and at the same time cooperate with stirring, multi-point temperature measurement and heat preservation measures to ensure the stability of asphalt raw materials and finally ensure the construction quality of road engineering.