Quality control of asphalt concrete pavement construction?

Asphalt commercial concrete pavement is the main type of high-grade highway pavement in China, which has the characteristics of rutting resistance at high temperature, cracking resistance at low temperature, fatigue resistance, aging resistance and good water stability. In order to improve the engineering quality of asphalt pavement, it is necessary to control several processes such as asphalt pavement base treatment, mixing, paving, rolling and joint treatment of raw materials and asphalt mixture. The following is the main content of asphalt concrete pavement construction quality control brought by Zhong Da Consulting Company for reference.

1 raw material control

First of all, the cement grade should be selected according to the Code for Construction and Acceptance of Cement Commercial Concrete Pavement. Cement produced by large factories should be used as much as possible. Due to the relatively sound quality assurance system and perfect inspection methods in large factories, the cement produced is of good quality and stable performance. Before use, the cement product test report of the manufacturer must be strictly checked to see if it meets the road use index. The fineness of cement, water consumption of standard consistency, setting time, volume safety and strength shall be sampled on site, and they can be used only after they are qualified. The grade of cement directly affects the strength of commercial concrete, especially for cement with higher grade. The quality of cement is the prerequisite for commercial concrete to meet the design strength requirements.

Mixtures with different quality and gradation have great influence on the flexural and compressive strength of commercial concrete, so the flexural and compressive strength of mixtures with different mix proportions have no fixed regularity. The main mechanical index of cement commercial concrete pavement is flexural strength, which must meet the design requirements. Fine aggregate should be hard and clean, with grade I and grade II grading areas, and the fineness modulus is 2.5-3.3. Coarse aggregate is made of hard, high-strength, wear-resistant and clean crushed stone, with the maximum particle size of 40 mm and continuous grading. It is required that the small-size aggregate must be used in sufficient amount, but the large-size aggregate should not be too much, so as to meet the requirements of various technical and economic indexes of cement commercial concrete pavement.

2. Basic processing

The smoothness of pavement base has a great influence on the quality of asphalt commercial concrete, so it must be checked and accepted in strict accordance with the construction specifications, and problems should be dealt with seriously. Remove floating soil, floating ash and floating sand from the pavement base; If it is found that there are loose, potholes and other damage with poor stability and low strength at the grass-roots level, it should be handled in time. Otherwise, uneven settlement will occur, which will affect the smoothness of the pavement and even cause early damage to the asphalt pavement. When the smoothness of the base surface is poor, asphalt mixture should be used to repair it before pavement construction.

3. Mix proportion design of mixed materials

The design unit of commercial concrete mixture ratio must be a road and bridge inspection station with more than two qualifications in the province. After the mixture ratio design of commercial concrete, the appropriate construction mixture ratio must be converted according to the actual situation on site. Appropriate mix ratio plays an important role in the strength and shrinkage of commercial concrete. The dosage of small-particle aggregate should be increased as much as possible in the construction mixture ratio to improve the flexural strength of commercial concrete. In the case of certain cement, the water-cement ratio should be reduced to reduce the adverse effects of shrinkage of commercial concrete.

The mix design of asphalt mixture is divided into three stages: target mix design, production mix design and production mix verification. The synthetic gradation of the mixture is made up of coarse, fine and filler. The optimum oil-stone ratio is determined by Marshall test. Design the production mixture ratio according to the target mixture ratio. Debug each cooler to determine the rotation speed of each aggregate, and select the aggregate that enters each hot bin after secondary screening to determine the aggregate ratio of each hot bin for use in the mixer control room. The 200m test section is selected, and all the data from the processes of mixing, transportation, paving and rolling are recorded to determine the loose paving coefficient of pavement paving thickness. After rolling, the core sample is taken for Marshall test to verify the rationality and practicability of production mixture ratio, and the construction technology and mixture ratio are adjusted in time to ensure the pavement construction quality to reach the best state.

4. Joint processing

The treatment of joints directly affects the smoothness index, and the quality of joints reflects the construction and management level of the construction unit to a certain extent.

4. 1 transverse joint treatment technology

(1) joint cutting: check the smoothness of the paving layer in the front section with a 3m ruler, draw lines where it meets the requirements, and cut off the asphalt mixture that does not meet the requirements with a joint cutting machine. The cut part should be flat and vertical, and emulsified asphalt should be applied to the joint edge.

(2) Paver in place: Paver in place on the cut construction joints, adjust the reserved height, cross slope and initial working angle. At the same time, the flat plate is heated to above 100℃.

(3) Start the paver: pour the newly delivered asphalt mixture into the machine hopper, and start the scraper conveyor belt and the spiral distributor to make the asphalt mixture fill the spiral distributor. Pause 10- 15 minutes, and start paving after the joint pressing and screed are further warmed up.

(4) Joint treatment: the coarse aggregate in the hot material is picked up manually, and fine asphalt is added to make the fine material at the joint uniform and the loose paving coefficient meets the requirements.

(5) Rolling at the joint: firstly, horizontally roll the joint, with the purpose of making the newly paved asphalt surface layer the same as the previously paved asphalt surface layer. When rolling, drive the roller onto the compacted mixture layer and extend it into the new pavement layer with a width of about15 ~ 20cm, and then move it to the new pavement layer by 20cm at a time until it reaches 2/3 of the wheel width. After transverse rolling, normal longitudinal rolling will be carried out. Because the local displacement of asphalt mixture caused by transverse rolling and longitudinal rolling will affect the smoothness, a 3mg ruler will be used to check the smoothness, and 1 15t vibratory roller will be used to roll the unqualified parts, and then DDll0 or CC42 will be used to finally roll the whole width.

4.2 longitudinal joint treatment process

(1) Because the project is a semi-finished product, it is necessary to treat the cold joint to improve the flatness.

(2) Seam cutting: Cut off the edge of the paved asphalt commercial concrete pavement 10 ~ 15 cm with a seam cutting machine, and the cutting surface shall be flat and vertical.

(3) Clean the joint edge and spray a small amount of emulsified asphalt.

(4) When paving, each layer should overlap 5 ~ 10 cm, manually pick up the coarse aggregate in the hot material, then level it with fine asphalt, and then use manual shovel to roll the paved mixture in the first half.

(5) Longitudinal seam rolling: the roller first walks on the compacted pavement and extends into the newly paved pavement 10 ~ 15 cm. Then extend it 20 cm at a time until it reaches 1/2 of the wheel width, and the joint is compacted by the well.

5, quality inspection and construction management

After construction, inspection is a very important link. The test contents include: compactness, thickness elevation, flatness, deflection value and structural depth, which are the most important factors to determine the quality of asphalt commercial concrete pavement. Through the test, the problems existing in seed preparation construction can be reflected in time, such as poor grading, improper oil consumption, insufficient rolling times and so on. As long as the asphalt commercial concrete pavement is constructed according to the reasonable construction technology and under the standard quality control, it will certainly achieve the ideal effect of waterproof, anti-slip and wear resistance. This not only greatly saves the maintenance cost, but also prolongs the service life of asphalt commercial concrete pavement.

In construction management, improve the quality management awareness of all staff and establish and improve the quality assurance system. Strengthen the contact between the front and back, and solve the unexpected situation in the project in time. Implement detailed process management, and assign special personnel to be responsible.

Strengthen the test, and timely feedback the test results, timely adjust and solve problems.

With the continuous development of economic construction, the requirements for highways are getting higher and higher. Construction quality is related to whether the expected purpose can be achieved. Only by establishing a firm sense of quality, perfecting and implementing the engineering supervision system, strengthening quality supervision, and carrying out construction in strict accordance with design drawings and relevant construction specifications, can the diseases of commercial concrete pavement be prevented. The quality of the project can be guaranteed. Only by constantly learning and summing up experience and lessons in time can we continuously improve our technical level.

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