Generation and control of segregation of asphalt pavement

First, the process of segregation in the paving process

The separation of the mixture includes gradation segregation and temperature segregation. Graded segregation is the phenomenon that aggregates are aggregated with large particle size and small particle size under external force. When the mixture is subjected to external force (mechanical), the moving rate of the large-size aggregates is necessarily larger than that of the small-grain aggregates, and then the motion of the aggregates is different. Size separation of the size of the material to form a separation. Temperature analysis refers to the paving concrete surface layer, the full mixing, the temperature uniformity of the asphalt mixture, after a certain process, the temperature appears a big difference between the phenomenon.
(1) the generation of longitudinal segregation of gradation segregation
A large number of tests and paving practices have shown that longitudinal segregation is caused by a spiral feeder structure. As the material laid by the paver is from the middle to both sides of the conveyor, in the spiral feed slot in this open space, due to the needs of the structure, there must be an intermediate drive chain box, at both ends must also have multiple Lengthened support, these support caused a spiral of the discontinuity, while the flow of materials increased resistance, the flow of material in this space to form a large particle material and small particle size material separation, resulting in a number of segregation.
(2) the generation of horizontal segregation of gradation segregation
The occurrence of lateral segregation is not related to the paver itself, which is mainly caused by the operating method. In a working cycle of the paver, the mixture mixes the stockpile to form a conical stack, which for the first time causes the segregation in the silo and the unloader of the mixing station to unload the truck Also formed a conical pile, the second time caused a large truck hopper in the segregation, when the truck to the paver hopper in the discharge, once again the formation of cone-like material, in the paver hopper in the formation of re-segregation. After a work cycle is completed, the unloading truck leaves and the paver stops the hopper. At this time, the material of the final large particle size is sent to the screw feeder, forming a later and one of the transverse segregation zones.
(3) the generation of temperature segregation
The transportation and unloading process of the dump truck is the main reason for the temperature separation of the asphalt mixture. Dump truck in the transport to the paver, the asphalt mixture through the car and the air for heat exchange, near the car wall and the top of the mixture temperature decreases, due to low thermal conductivity, heat from the center of the mixture to the four The speed is quite slow, so the truck arrived at the paving scene, the car inside the material temperature will be lower than the middle of the material temperature, the temperature difference. During the discharge process, the material in the middle of the compartment is high and the viscosity is low. First, it is unloaded into the paver hopper, and the material near the car wall always falls on both sides and the top of the hopper. The high temperature material is the first And the low temperature mixture is delayed to the final paving, this process further exacerbates the unevenness of the asphalt mixture temperature, the temperature is more serious segregation, and the transport and discharge of each car will appear this separation phenomenon.

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