Application of the hottest small milling machine i

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Application of small milling machine in the reconstruction of box girder bridge deck of high-speed railway on December 26, Wuhan Guangzhou high-speed railway, the longest high-speed railway in the world, will be opened to traffic

394 km/h! On December 9, after the test vehicle of Wuhan Guangzhou Passenger Dedicated Line departed from Guangzhou north railway station, it ran out of the highest speed per hour since the test in Shaoguan section, creating the highest operating speed of the world's high-speed railway under the condition of double connection of two vehicles. The Wuhan Guangzhou passenger dedicated line has a total length of 1068 kilometers and a design speed of 350 kilometers per hour. After opening to traffic, the travel time from Wuhan to Guangzhou will be shortened from the current 10.5 hours to less than 4 hours. As a landmark event in the history of China's railway construction, this event caused a sensation across the country and set off a "high-speed rail fever" across the country

let's leave Wuhan Guangzhou high-speed railway and turn to another high-speed railway "Beijing Shanghai high-speed railway". There are few high-speed railways with a length of more than onethousand kilometers in the world, and the 1318 kilometer long Beijing Shanghai high-speed railway is likely to become the longest high-speed railway in the world. After this line is opened, Beijing and Shanghai will come to see the performance of the universal wood-based panel testing machine, which will be accessible in five hours

in the future, China will build more than 10000 kilometers of high-speed railways and passenger dedicated lines, including Shanghai Nanjing intercity railway, Beijing Shanghai high-speed railway, Guangzhou Shenzhen Hong Kong passenger dedicated line, Beijing Harbin passenger dedicated line, Harbin Dalian passenger dedicated line, Beijing Shijiazhuang Wuhan passenger dedicated line and so on. These lines cover most parts of China from north to South and from east to west, serving the most promising urban circles in China. The next 20 years will be the golden stage of railway development in China, and China will usher in a new era of high-speed railway

next, the technicians of Changsha Zhubang Construction Machinery Co., Ltd. will discuss two specific problems in the construction of high-speed rail. The first is the reconstruction of the beam surface of the high-speed railway box girder, and the second is the waterproof treatment of the bridge deck of the high-speed railway

I. box girder surface reconstruction

in the prefabrication process of high-speed railway box girders, many problems have occurred in the beam surface of many box girders due to the differences in construction experience, formwork installation quality, concrete ratio and concrete pouring technology. The main problems are large elevation error of the beam surface, poor flatness, hollowing, looseness, honeycomb and pitted surface, floating ballast, floating soil and oil stain on the concrete surface. After these problems occur, we will face a construction treatment of beam surface reconstruction. At present, the common treatment methods used by the high-speed railway construction units in each beam making field are as follows:

1. Grinding the beam surface with a terrazzo machine; 2. Roughening the surface with a roughening machine; 3. Milling the surface with a small milling machine

the leveling and grinding treatment of the beam surface with a terrazzo machine is the most original construction method. Because of the low purchase cost, many high-speed railway beam making fields often purchase fiveorsix or more such equipment, However, the grinding efficiency of the terrazzo machine is very low. The thickness of each grinding is only mm. The strength of some box girder surface concrete exceeds C50, and the terrazzo machine cannot grind at all. Therefore, it is time-consuming and laborious to level the beam surface with a terrazzo machine with poor flatness

product drawing of terrazzo machine (left) grinding effect drawing of terrazzo machine (right)

it has been nearly two years since the use of roughing machine for beam surface treatment. The standards first adopted by government departments have become increasingly stringent. Some dealers in Dalian, Liaoning have introduced such products from abroad. Because roughing machine is much more efficient than terrazzo machine, even if the price (about 20000) is much more expensive than grinder, but on Harbin Dalian high-speed railway, Many beam fabrication yards and construction teams still choose roughening machines for beam surface treatment

the working principle of the roughening machine is to use the compressed air generated by the air compressor to drive an alloy chisel head. Driven by the air cylinder, the chisel head impacts the bridge deck in a rapid reciprocating motion, playing the role of stripping and breaking the concrete surface. The deepest chiseling can be about 5mm

however, due to the need for external power supply, external air compressor, connecting air pipe and other auxiliary components, the chisel head has some disadvantages, such as time-consuming and expensive replacement, inconvenient construction transfer, inflexible operation and so on

product drawing of roughing machine (left) effect drawing of roughing machine (right)

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and the more advanced construction party at present d: check whether the power switch can operate normally. The method is to use a small milling machine or shot blasting machine to transform the beam surface. Shot blasting is a good construction process, but as far as shot blasting machine equipment is concerned, Imported shot blasting machines are very expensive (the price of shot blasting machines with a power of more than 20kW suitable for beam surface treatment is about 10000), while domestic shot blasting machines and domestic manufacturers imitating imported shot blasting machines are not many at present, which started late, and the products are still in the stage of experimental exploration, so I won't go into details here

the manufacturing of small milling machines has been relatively mature in China. The use effect of small milling machines is the same as that of roughening machines, but because they have their own power (gasoline engine) and do not need external air compressors, gas pipes and other auxiliary devices, they have convenient transition and flexible operation

advantages of fast blade replacement. The small milling machine was first used in the beam surface treatment of high-speed railway in Xianning section of Wuhan Guangzhou high-speed railway. At that time, the construction unit raised the elevation of the box girder base by several centimeters due to measurement reasons. Because the base concrete grade was close to C80, it could not be ground by the grinder at all. Considering the huge cost of blasting rework, it finally tried the small milling machine of Changsha Zhubang construction machinery company to solve the problem

site construction drawing of small milling machine (left) effect drawing of milling machine (right)

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there are many models and configurations of small milling machine, and the model is basically determined according to the milling width. At present, the widths of small milling machines on the market are 200mm, 250mm, 300mm and 350mm. The price ranges from 10000 to 130000. The power is equipped with a gasoline engine, an electric motor, and an electric motor is cheaper. At the same time, the speed of the motor is low (2-pole motor up to 2800 RPM) and the speed of the gasoline engine is high (up to 3600 RPM), so the effect of the electric milling machine is not as ideal as that of the gasoline engine

of course, due to the quality of the operator, if the gasoline milling machine is not operated and maintained well, the failure rate is also many. The key lies in whether the operation technical disclosure to the operators is in place. The maintenance of electric milling machine is simpler. As for the problem of dust collection, small milling machines have reserved the interface of dust collector, and users can configure industrial dust collector additionally

the small milling machine equipped with gasoline engine has the power of 5.5 HP, 9 HP, 13 HP, 20 hp, etc. if it is only used to deal with the old floor, renovate paint, resin, use the milling width of 200mm, equipped with 5.5 HP gasoline engine, 4 cutter shafts, more than 70 blades, and the weight of the machine is about 80 kg. The price is only a little over 10000

such small milling machine products are shown in the following figure:

small milling machine

but if it is a high-grade (above C50) cement bridge deck surface or box girder milling chiseling, elevation leveling, at least 250mm milling width, gasoline engine power horsepower or motor power above 7.5kW, 6 cutter shafts, 100 blades, 6-star-8-star cemented carbide blades, and the body weight is about 130 kg, otherwise the milling effect is very poor

this kind of small milling machine is shown in the following figure:

zp250b small milling machine (left) zp250e small milling machine (right)

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if you want to milling deeper and faster, you need to be equipped with power of more than 20 horsepower. Of course, this high-power milling machine is not a hand push type, its forward and backward are driven by hydraulic motor, and the blade is a star blade. The maximum depth of milling asphalt pavement can reach 20mm/time, and milling C50 cement concrete pavement can reach 10mm/time. Small hydraulic milling machine is shown in the following figure:

zp250h small hydraulic milling machine (left) zp350h small hydraulic milling machine (right)

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II. Waterproof treatment of high-speed railway deck

the design service life of high-speed railway is generally 50 years, and most of the high-speed railway roads are cast-in-place girder bridges or prefabricated reinforced concrete box girders, How to ensure that the reinforcement framework and prestressed steel tendons in the box girder are not eroded by seepage rainwater has become the focus of quality assurance. The bridge deck waterproof treatment technology started late in China and has only been applied in recent ten years

the waterproof layer of concrete bridge deck of high-speed railway is an important technical means to improve the durability of bridge structure. There are many cases of bridge deck water seepage and reinforcement corrosion caused by the waterproof failure of the existing bridge deck, which directly affect the service life of the structure. At present, the technical conditions for the treatment of waterproof layer of high-speed railway in China are based on the requirements of the domestic passenger dedicated lines for the durability of bridge structures, the structural characteristics of ballastless track bridges and the experience of spraying polyurea waterproof layer, which are still being improved

the construction of cement concrete waterproof layer is roughly divided into two links. The first is the rough treatment and cleaning of the surface of the base, but the spraying of waterproof materials. The cement concrete surface is roughened by mechanical milling, which eliminates the defects such as honeycomb and pitted surface, hollowing and loosening, laitance, oil stain, etc., and effectively solves the affinity problem between the cement concrete surface and asphalt mixture, spraying materials, or twice paved cement concrete. At the same time, before the waterproof layer of high-speed railway bridge is sprayed, the roughness of the base course is very high, and the flatness of the bridge deck base course should meet the design requirements, Its roughness should meet SP3 ~ SP4. As mentioned above, in order to meet such technical requirements, the better equipment options are small milling machine and shot blasting machine. The surface after milling:

1, the surface roughness is uniform; It will not damage the original pavement structure and flatness

2. Completely remove laitance and sanding; 100% of "wound"

3, exposed, but will not cause loosening and microcracks of aggregate at the same time

4. One time construction without cleaning; No environmental pollution (industrial vacuum cleaner is required)

5. Expose concrete defects in advance; 3. Stable fertilizer and expansion have improved the industrial grade

6, and meet the requirements of macro texture and micro texture at the same time; Suitable for various waterproof coating and paving processes

7, and increase the adhesion of waterproof materials on the surface and provide a certain penetration effect

any construction scheme or mechanical equipment has its advantages and disadvantages. How to choose, we need to have a clear understanding and understanding of all kinds of equipment, and seek the best match for different construction environment and technical requirements

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