What is the danger of temperature segregation?
The segregation of grading reduces the paving quality of pavement, and has attracted people's attention, but the harm of temperature segregation has not been paid attention to. In fact, the harm of temperature segregation is much more serious than that of pure grading segregation, and it is also the main cause of poor paving quality.
Study on J.Don Astec Dr. Brock pointed out that because of the asphalt mixture in the transport and unloading of heat loss of material in the process of uneven temperature difference, paving the road, local area and even lower than the temperature of materials of asphalt mixture for paving temperature. The low temperature mixture will not be compacted, causing the screed to rise and fall, resulting in irregularities in the paving surface, and some mixtures in colder areas may also cool and agglomerate. When rolling, the caking material may bear all the weight of the roller, and cause overloading and cracking, resulting in the mixture can not roll forming, destroy the pavement structure, and affect the road speed. Compaction modified asphalt mixture needs higher paving temperature than traditional mixture. The possibility of temperature segregation is greater, and the quality of pavement after paving is more difficult to guarantee.
The cold spots of the paving will also lead to uneven density of the pavement, resulting in higher air gap rate and roughness. The results show that the air gap rate is only 6.8% when the mixture temperature is 149 degrees centigrade. When the temperature is reduced to 93 degrees centigrade, the air gap rate increases to 9.3%. The air gap is easy to let the water penetration into the asphalt concrete, freeze in the winter after the asphalt concrete rupture, formation of potholes, affecting the surface quality, to shorten the life of highway.
Some people abroad have made a comparative fatigue fracture test in the laboratory, and the data have proved the correctness of the above conclusions. When the air gap rate in the paver increases, the number of wheel tests required for the specimen breaking is significantly reduced. The specimens pressed at 104 DEG C, whose life span is approximately equivalent to the 10%~20% of the specimens pressed at 149 DEG C. Study on the Department of transportation of a state in the United States pointed out that due to temperature segregation, life expectancy may only pavement design life (12~15) of the half, the actual service life of highway is shortened by 50%, lead to a huge waste of highway construction investment.
Temperature segregation will also greatly increase the cost of road maintenance, fuel consumption and tire wear increase, driving safety and driving effects are also greatly reduced.
