Differences between cold and hot asphalt pavements and their engineering applications
Under the action of long-term driving load, rain erosion and alternating freezing and thawing of high and low temperature, asphalt pavement is easy to appear pit, crack, looseness, subsidence and other diseases, which not only affect the traffic comfort of road, but also greatly reduce the overall service life of road, and seriously cause traffic safety hidden danger.Pavement repair is the core work of road maintenance engineering, and asphalt cold repair material and asphalt hot repair material are the two most commonly used core materials for pavement repair.
The production technology, construction conditions, forming mechanism, road performance and application scene of the two materials are significantly different. If the type is not selected properly in actual engineering, it is easy to fall off after repair, seepage, secondary damage and other problems.In this paper, the differences between asphalt cold repair material and hot repair material will be comprehensively compared from the core definition, construction technology, performance characteristics, application scenarios, economy and other dimensions, providing professional reference for material selection and process application of road maintenance construction.
Differences between core definition and molding principle
asphalt hot mix
Hot asphalt mixture is the traditional hot mix asphalt mixture, which is consistent with the materials used in new road pavement. It is a conventional repair material produced by hot mix asphalt equipment at high temperature. The core of production and construction depends on high temperature conditions. Raw material aggregate and asphalt need to be dried and mixed at 150-180℃. Asphalt has good fluidity and cohesiveness at high temperature, and aggregate and asphalt can be tightly wrapped and adhered.
The forming principle is high temperature bonding, cooling and solidification: after high temperature mixing and paving, the mixture is in a soft and dense state. After rolling and compaction, as the temperature naturally decreases, the asphalt viscosity increases rapidly, and the mixture is cured and formed as a whole, forming a high strength., high stability of the pavement structure, and finally form a complete pavement layer that is integrated with the original pavement.
asphalt cold mix
Asphalt cold repair material is a kind of modified normal temperature asphalt mixture, belonging to a new road maintenance material, without high temperature heating production and construction. The material is prepared by special modified asphalt, solvent and auxiliary agent. It can keep loose and constructable state for a long time at normal temperature, and is not limited by temperature environment.
Its molding principle is solvent volatilization, pressure curing, and later strength increase: after construction paving and compaction, the light solvent in the material gradually volatilizes, and at the same time, the bonding reaction is triggered by the pressure of driving compaction, the asphalt bonding performance is gradually released, and the mixture strength is steadily improved with time. Finally, stable road performance is achieved without high temperature curing conditions.
Difference between construction technology and operation conditions
Construction temperature requirements
Hot patching material has strict temperature requirements and is only suitable for construction at normal temperature and high temperature season. When the ambient temperature is lower than 5 ℃, it is basically impossible to construct. If the temperature of hot material is too fast in low temperature environment, problems such as compaction failure, bonding failure and joint cracking will occur. Therefore, hot material repair operation is prohibited in winter and rainy and snowy weather.
Cold repair material has no temperature limit, can realize all-weather, all-season construction, no matter summer high temperature, winter low temperature, or light rain, frost weather, can carry out normal road repair operation, is the core material of winter emergency maintenance, rainy day emergency rescue.
Construction process and equipment requirements
The construction of hot patching materials depends on complete sets of professional equipment, with complicated flow and complicated procedures. Before construction, hot mix asphalt equipment shall be started in advance to produce hot materials. During transportation, heat preservation transportation vehicles shall be required. Large equipment such as pavers and road rollers shall be equipped on the construction site. Hot materials shall be used up in a short time after production, and shall be discarded directly after cooling, so that they cannot be used again. The overall construction depends on mechanized teams, and the operation threshold is high.
Cold patching construction is extremely simple, no large equipment, no on-site heating. Finished materials can be directly opened for use, only manual paving, small compaction equipment can complete the operation, single person or small team can be constructed, the operation efficiency is extremely high, and the remaining materials can be sealed and reused, without material waste.
Open traffic hours
After the hot supplement construction, it needs to be completely cooled and solidified before it can be opened to traffic. It usually takes 2 - 4 hours under normal temperature environment. In winter, the cooling time at low temperature is longer, which seriously affects the road traffic efficiency and easily causes traffic congestion.
Cold repair materials support immediate repair and opening to traffic. Traffic can be opened immediately after compaction without long-term maintenance waiting. It is perfectly suitable for emergency repair scenarios of roads with large traffic volume such as urban trunk roads and expressway networks, which are not allowed to be closed for a long time.
Difference between road performance and service life
structural strength and stability
The hot patching material is evenly mixed at high temperature, the aggregate is tightly packed, the asphalt is fully bonded, the structure after molding is high in compactness, the overall strength is large, the compression resistance is excellent, it can withstand repeated rolling by heavy vehicles, the structure stability is extremely strong, and the deformation and loosening problems are not easy to occur. The overall performance is completely consistent with that of the newly built pavement.
Cold mending material initial strength is low, rely on later solvent volatilization and rolling gradually shaped, early anti-heavy load, anti-deformation ability is weak. After molding, the overall compactness and bond strength are slightly lower than those of hot patching materials. Under long-term heavy load conditions, it is easy to have slight loose, seepage and other problems, and the structural stability is relatively weak.
Waterproof, weather resistant and durable
After forming, the hot patch material has good integrity, dense gaps, excellent waterproof, anti-aging, high and low temperature resistance, high temperature resistance, no oil flooding, low temperature cracking, adaptability to various complex climatic environments, long-term use is not easy to damage, and excellent durability.
Cold patching material has good low temperature crack resistance and waterproof performance, suitable for rain, snow, low temperature harsh environment, but long-term high temperature exposure, heavy repeated rolling, aging speed is faster, durability is not as good as hot patching material, long-term use is easy to occur local disease recurrence.
service life
The pavement repaired by hot patching material has strong integrity and stable performance, and its service life can reach 3-5 years. It belongs to permanent repair technology and is suitable for long-term repair engineering.
Cold repair materials are mostly used as emergency and temporary repair materials, with a normal service life of 1-2 years, and regular maintenance is required in the later period, which belongs to temporary and transitional repair technology.
Accurate differentiation of applicable scenes
Application scenarios of asphalt hot mix
It is mainly suitable for long-term, high-standard and large-scale pavement repair projects. Including large-area pit repair, pavement renovation, partial disease complete repair of heavy traffic roads such as expressways, national highways and urban trunk roads; routine maintenance construction in high temperature season, finishing repair of new pavements, and key section projects that need to ensure long-term use effect.
Application scenarios of asphalt cold mix
Mainly suitable for emergency, temporary, small-scale repair works. It includes emergency repair of roads in low temperature and rainy and snowy weather in winter; daily repair of light load roads such as urban branch roads, community roads and parking lots; rapid repair of scattered small pits and grooves, emergency construction of sections with large traffic flow that cannot be closed for a long time; small-scale disease repair of remote sections.
Comparison between economy and operation and maintenance cost
single construction cost
The unit price of raw materials for hot patching is low, but the construction cost is high. It needs supporting hot mixing equipment, heat preservation transportation vehicles, large compaction machinery and professional construction teams. The equipment start-up and shutdown, fuel consumption, labor cost are high, and the residual materials cannot be stored. The cost performance of single large-scale construction is high, and the repair cost of small scope is extremely high.
The unit price of cold patching material is slightly higher than that of hot patching material, but the comprehensive construction cost is extremely low. No large-scale equipment, no heating, no waste of residual materials, small area repair time and effort, sporadic disease repair comprehensive economy is far better than hot repair.
Long-term operational costs
Hot patch material one-time repair, long-term durability, low maintenance frequency in later period, lower total cost of long-term operation and maintenance, suitable for long-term maintenance of key road sections.
Cold patching materials have limited service life, need regular inspection, secondary repair, long-term maintenance frequency is higher, suitable for emergency transition, not suitable for long-term long-term repair.
Comparison table of core differences
| Compare Dimensions |
asphalt hot mix |
asphalt cold mix |
| forming principle |
High temperature bonding, cooling curing molding |
Solvent volatilisation, pressure compaction, later strength increase |
| construction temperature |
Only in normal temperature, high temperature season, low temperature rain and snow can not be constructed |
All-weather, all-season construction, regardless of temperature and humidity restrictions |
| construction plant |
Hot mixing equipment, insulated transportation, and large rolling equipment are required |
No heating, only small tamping tools |
| opening time |
It can be opened to traffic after cooling for 2-4 hours |
Compaction complete immediately open traffic |
| structural strength |
High strength, good compactness, strong stability |
Low intensity in the early stage, steadily increasing in the late stage, weak overall |
| service life |
3-5 years, long-lasting permanent repair |
1-2 year, temporary transitional repair |
| applicable scenarios |
Large-area, high-standard, long-term heavy-duty pavement repair |
Small-scale, emergency, all-weather rapid repair |
| comprehensive cost |
Large area construction cost-effective, small area high cost |
Small-area piecemeal repair comprehensive cost is lower |
Suggestions and Conclusion on Project Selection
In road maintenance engineering, there is no absolute difference between cold repair material and hot repair material, only the difference of applicable scenarios. In engineering application, reasonable selection should be made according to disease scale, road grade, traffic flow and construction environment. For large-area diseases of heavy-duty and high-standard roads such as expressways and trunk roads, hot repair materials shall be preferred to ensure long-term stability and durability of pavement; for emergency rescue in winter, rain and snow emergency, sporadic small pits and grooves, and rapid repair of busy traffic sections, cold repair materials shall be preferred to give consideration to construction efficiency and traffic demand.
In the actual maintenance operation, the combination process of "cold repair emergency, hot repair radical cure" can be adopted: cold repair material can be used to quickly treat diseases under severe weather and emergency conditions to ensure road traffic safety; when the weather warms up and the construction conditions are suitable, hot repair material can be used for thorough renovation and repair, which not only ensures traffic efficiency, but also considers the long-term service life of roads, realizing the optimal balance between economy and practicality of road maintenance.
