Why does asphalt concrete pavement produce temperature segregation?

The transportation and unloading process of dump truck is the main reason for the segregation of asphalt mixture.

As everyone knows, the construction of highways, but very close to the asphalt concrete mixing section, paving the other sections of the road transport distance required for asphalt mixture with a certain length, need certain transportation time. Even in the hot summer, with temperatures higher than the temperature of asphalt mixture is much lower, is bound by the wall for heat exchange, and three ways of heat exchange exist at the same time, heat loss caused by mixture, causing the decrease of the temperature. There is no doubt that the loss of heat and the decrease in temperature occur mainly in the mixture near the wall of the car. If the car is not covered, the asphalt mixture at the top of the car will be in direct contact with the relative movement of the air, and the heat loss and temperature drop of the top material will be much more serious. As transportation distance increases, the heat loss caused by the transportation process increases correspondingly. The higher the temperature of the mixture, the lower the thermal conductivity of the asphalt and aggregate in the air temperature mixture. In the course of traveling, the temperature of the mixture around the truck is greatly reduced, but because of the low thermal conductivity, the heat travels slowly from the center of the mixing pile to the four sides. When the truck arrives at the paving site, the temperature of the material around the truck will be much lower than the temperature in the middle of the material, and the temperature difference will appear.

The truck arrives at the paving site to the paver when unloading, the central compartment of the material due to high temperature, low viscosity first is discharged into the hopper of paver, and near the wall material for the opposite reason is always the last fall on the sides and top of the hopper. Therefore, the high temperature material is firstly transported to the rear of the paver by the scraper conveyor, and is spread to the base by the spiral spreader, while the low temperature mixture is delayed until the last is paved. This process further intensifies the inhomogeneity of asphalt mixture temperature, that is, the segregation of temperature is more serious. As this phenomenon occurs in the course of transportation and discharge of each vehicle, segregation occurs periodically.