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Segregation of Asphalt Pavement
[Abstract] This paper describes the Weiwu highway construction, the analysis of asphalt pavement segregation. From raw materials to finished products into the plant's appearance transport asphalt and paving mixture during the various factors that affect quality, and to all aspects of the various segregation of solutions put forward
[Key words] segregation segregation Segregation of control
1. Project Overview
Shandong Wei (Shanghai) to Ukraine (sea) highway segment second contract start and end mileage K11 +300 ~ K22 +700, full 11.4KM, according to two-way four-lane design.
Mainline pavement structure:
Upper layer: the top layer of asphalt Horseshoe fat (SMA-13A) 4CM
In the surface layer: surface layer of asphalt concrete (AC-20B) 6CM
The following layers: Asphalt Concrete (AC-25B) 8CM
2. Segregation
Asphalt road surface segregation is a major area of asphalt mixture uneven nature, such as asphalt content, aggregate composition, additive content and the porosity and other surface.
3. Segregation of the hazard
Segregation of the event, they changed the original design of the pavement with, the quality of asphalt pavement segregation great harm. In particular in:
○ 1 rolling process, easily crushed coarse aggregate
○ 2 aggregate surface area increases, resulting in rolling after molding loose, damaged road pavement structural strength of influence
○ 3 concentration of coarse aggregate to pavement deterioration of local density, high porosity, easily formed in the surface water, causing water damage to the road early
○ 4 disease have a lot of asphalt mixture segregation and closely related, such as: loose, net crack, holes, local severe Track Channel, local weeping, newly paved asphalt pavement structure of the depth of inequality.
○ 5 Segregation of Asphalt Pavement Compaction will produce differences in degree of compaction, smoothness impact damaged the car's comfort
4. Segregation of species
Segregation will affect the road surface appearance, asphalt mixture segregation can be broadly classified into two types: level and temperature segregation with segregation. Gradation segregation occurs, asphalt road coarse material concentrated in some regions, while others focus on regional fine materials, making become uneven mixture gradation and asphalt content and design are inconsistent, leading to poor road showing the structure and texture characteristics . Concentration of fine material in some regions, the porosity is small, there may be weeping, rutting; other coarse material concentrated in some regions, high porosity, surface water may cause damage. Temperature segregation is the mixture in the storage, transportation and spreading in the weather, construction machinery impact, because the temperature difference between heat loss and the situation there. Mixture temperature of segregation, will lead to uneven road surface compaction, low temperature region, the road porosity greater texture depth of greater road in these areas prone to early damage. Temperature of the consequences of segregation and isolation graded as severe, can lead to premature failure of asphalt pavement, greatly shorten the life of asphalt pavement. Research shows that serious segregation of the road life may be reduced by 50% or more. Present some early Asphalt Pavement damage, such as loose, net crack, holes, local severe Track Channel, local weeping, newly paved asphalt pavement structure of the depth of inequality, with the asphalt mixture segregation are closely related.
5. Segregation generation
Asphalt Mixture Segregation affect the characteristics of the pavement, and segregation issue has been throughout the construction process, it is the construction unit has long been one of the urgent solution of the problem.
5.1 Segregation of raw materials
In the raw materials transported from the quarry to the mixing station piling up, because a high degree of reason, a large aggregate rolled off the bottom of the heap in the material to form a coarse aggregate material the first focus, which will Segregation material mixing machine feeding in the cold difficult to control when different silos of the material ratio;
5.2 Segregation of mixing station mixing machine
When using the scraper conveyor to unload mixture into the finished product hopper, the hopper must be located in the central discharge hopper, or the body in a barrel of vertical segregation, that crude is expected to roll it toward the side of hopper.
When using the scraper conveyor to unload into the ingredient mixture into the bucket and then finished unloading hopper, the ingredients should be kept as part of each discharge mixture, so that all the material emptied, the scraper conveyor of the mixture directly into the hopper caused segregation within
Product discharge from the hopper, the discharge should be quickly opened the door, do not allow mixture to flow slowly, so as to avoid segregation
5.3 Material Segregation
Asphalt dump truck from the finished product warehouse discharge to the transport process, the same as drop-off, large aggregate will be rolling in the car on both sides to form a coarse aggregate of the second concentration;
5.4 Discharge segregation
Transportation dump truck unloading in the mixture to the paver, the large aggregate in paver and a half car rolled near the formation of coarse aggregate the third concentration;
5.5 Segregation Feed
Paver feeders in the feed process, the first intermediate aggregate device to send the cloth, the remaining coarse aggregate retained in the hopper, the paver hopper collection, the formation of coarse aggregate of the fourth concentration; construction process The temperature segregation.
5.6 The joint segregation
Joint segregation in the upper layer construction is more common, especially in the section of pavement widening, the small number of paver or mixing plant capacity is low, thanks to two Paver, Road, the central vertical heat joints are often the weakest link. Seams paving mixture too much or too little will produce Segregation in the seams, will form a bridge over the effects of compaction on both sides of affected joints, seams less inadequate compaction. If the two are inconsistent paver paving thickness, the small thickness of the side seams are not easily compacted. Behind the paver two different rolling temperatures also cause excessive joint segregation. In addition, isolation joints are often the end of segregation in conjunction with trucks or other forms of segregation in the formation of combination effects. As the vertical seams in the lane, the number of multi-wheel loads, which often produces greater harm.
6. Segregation of control
6.1 Control of materials piling up approach
Layered aggregates (especially coarse aggregate) can reduce the random segregation problem. Loader stacking up piles of material, the material on the particle size should be large changes in the slope layer by piling, slope less than 1:3. In the yard space to allow the case to minimize the height of the heap material. If the coarse aggregate in the stockpile segregation occurred in the bottom, front-end loader will be used to re-mixing material, the hopper can be sent to the cold. Unloading and loading to enhance stockpile management, the key is to reduce the random segregation.
6.2 Temperature Control Mixing Station
Temperature to determine the factory by the paving temperature. Mixture temperature losses influenced by the weather, according to the distance of the mixture of time and storage, construction of the asphalt test section of the process to determine the temperature loss, to determine the temperature of asphalt factory. Aggregate level of the heating temperature is mainly affected by fluctuations in raw material moisture content, and thus affect the quality of asphalt and asphalt mixing plant productivity. Fine aggregate rain shelter structures can effectively control the water content and reduce the volatility of aggregate temperature, and can save heating oil and reduce costs.
6.3 Loading and Unloading vehicles
Prevent the formation of vehicle loading and segregation, in the loading process, should be at least three times a load, the first near the front of the car, the second near the rear, the third time in the middle of the car by this method can basically eliminate the formation of the segregation load. If mixed with a material for each load, the top of the car by sliding movement of the vehicles can even load, it loads the effect of the score three times even better. In addition, when a car when the mixture into the paver, the first time from the top to fill the hopper once and should be so that the mixture as a whole into the paver hopper, so to avoid car unloading caused by segregation.
6.4 paver paving operation
Paver paving process to maintain stable and continuous spiral fabric uniform rotation device, spreader feeders on both sides to maintain a high degree of not less than 2 / 3 of mixture to prevent the formation of the outer spiral fabric mixture accumulation device segregation. After each discharge as dump truck paver hopper scraper conveyor on both sides there will always be less than scraping the mixture, which is often coarse material after segregation. If every time close to the paver hopper mixture paving, road laws of segregation phenomena occur. Resolve this problem, close the hopper should be minimized, artificial accumulation not affect the leveling hopper dump truck dumping mainly to minimize the mixture segregation, and the paver in a car expected to be finished, close the feeder, so get off after the material uniformly into the feed and cloth. Unloading the car when the paver, uninstall the fast speed as far as possible, as far as possible to ensure continuous paver operation, do not stop. Adjust the speed of paver paving and mixing station to the feed rate is the same.
6.5 Joint Treatment
In Weiwu highway paving, in the normal section, using two ABG-423-type paver simultaneously, paver to ensure two before six cars waiting for unloading transport material, and between pavers spacing not greater than 20 meters.
The paving of the widened section to the Highway Bureau of Dongying City, the introduction of a Suge Le paver, three forward together in a section of paving. To avoid cold joints, to avoid temperature segregation.
6.6 Rolling
Compaction is to ensure that an important part of the quality of road construction. To ensure compactness and flatness, rolling should follow the "high-frequency, low amplitude, followed, less water, slow pressure" principle, from low to high, full-rolling. Roller should be rolled slow even pace, according to initial pressure roller rolling speed, complex pressure, final pressure and the corresponding roller type.
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