Measures to improve the smoothness of Asphalt Conc

2022-08-02
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Measures to improve the smoothness of asphalt concrete pavement the section from the south exit of Langfang city to Baoji Tianjin Expressway of Langfang berthing highway is an important link between Langfang city and Baoji Tianjin Expressway. We know that the national specifications for high temperature tensile test have rules: rib hub for round specimen is also an important link between Langfang City and southern cities. The total length of the contract section is 41.768km, two-way four lane, and the whole section is reconstructed according to the standard of class I highway. K13 + 000 ~ K17 + 000 of this section are low-lying sections in Yongding River floodplain, which adopt cement concrete pavement, and other sections adopt asphalt concrete pavement. The asphalt concrete pavement structure is composed of subbase, base and surface course: the subbase is 16cm thick and the ash dosage is 12%; The base course is 30cm thick lime fly ash gravel; The surface course consists of upper layer and lower layer, in which the upper layer is 4cm thick ac-16-i medium grained asphalt concrete and the lower layer is 6cm thick ac-25-i coarse grained asphalt concrete

flatness is one of the most important technical indicators to measure the pavement construction quality and service level, which can directly reflect the comfort and safety of the pavement during its service life. In recent years, with the rapid development of China's highway industry and the continuous improvement of driving speed, the hard index of flatness has attracted more and more attention from all walks of life. During the construction process, in order to ensure and control this index, we carefully organized and constructed in strict accordance with the requirements for flatness index in the standard for quality inspection and evaluation of highway engineering students were invited to visit the R & D center

in the actual construction process, there are many factors affecting the flatness, including the flatness of the base course, the flatness of the lower layer, the grading composition of the material and the uniformity of the mixture, and even the key processes such as paving and rolling in the construction process. The following discusses the control and improvement of flatness from several aspects

1 control of base course flatness

the flatness of base course directly affects the flatness and thickness of asphalt concrete pavement. If the base course is uneven during construction, even if the surface course is paved smoothly, it will be uneven due to different loose paving thickness due to different virtual paving coefficient after compaction. Thus, it is very important to control the flatness of the base course during construction. During the construction, we focused on the following aspects to control the flatness of the base course:

1.1 elevation control

in order to ensure the flatness of the asphalt concrete surface course, but the combustion performance of the polyurethane insulation material remains at the level and thickness of flammable B3 or flammable B2, so the material requirements are very high, and the elevation of the base course must be well controlled, which is how we control it during the construction, Firstly, the virtual paving coefficient shall be controlled. After the elevation is measured and re measured by the measuring engineer, the elevation position shall be determined, and then the steel wire rope and wire tightener shall be used for leveling. Once the elevation is determined, a special person shall be assigned to take care of it without damage. In case of collision, it must be re measured until it is qualified

1.2 mechanical requirements

during base course construction, ABG423 paver made in Germany shall be used for paving construction, and small machinery such as bulldozer and grader shall not be used in the whole section

1.3 uniformity of mixture

lime, fly ash and crushed stone are mixed in the wbs300 mixing station produced by Zhejiang Huatong machinery plant. After mixing, they are transported to the construction site by dump truck, and then paved by paver. In order to ensure the uniformity of the mixture, the lime, fly ash and water content must be controlled accurately in the mixing process, and the maximum particle size of the stone shall not be greater than 3cm, and the water content of the mixture shall be controlled at about 8%. When the distance is too far or the temperature is too high, the water content of the mixture shall be appropriately increased to make up for the water loss during transportation and ensure the water content of the mixture

1.4 paving and rolling

the speed of the paver shall be controlled at 2.5 ~ 3.5m/min when paving the base course. We control the speed at 3.0m/min in the actual construction process. During the paving process, if the machine stops due to mechanical failure or other reasons, the flatness will be affected. Therefore, unnecessary downtime should be reduced. When the water content of the mixture reaches the optimum water content, the rolling shall be carried out. The rolling sequence is to use the rubber tyred roller for one time, then use the vibratory roller for 2-4 times, and finally use the static roller for 4-6 times. The test and inspection personnel shall carry out the inspection at any time until the specified compactness standard is reached. Finally, the pressure is discharged again, mainly for the comfort of appearance

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