Analysis on quality control of cement concrete pav

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Analysis on the quality control of cement concrete pavement constructed by slip form paver

due to the backward construction technology and the fact that the cement concrete pavement paved in the traditional way is prone to many diseases such as pavement breaking and fragmentation, it is urgent to apply the advanced technology of cement concrete pavement construction. The slip form paving technology is such a new highway pavement construction technology. The construction experience of cement concrete pavement at home and abroad has proved that the slip form paving technology is a cement concrete pavement construction technology with the highest construction quality, the strongest overload resistance, the best panel homogeneity, the fastest construction speed and the longest service time. Compared with asphalt concrete pavement, cement concrete has the advantages of large bearing capacity, long service life (the design service life of cement concrete pavement is 20-30 years), and low daily maintenance cost. Using this technology on the cement pavement of expressway can not only enhance the continuity and integrity of the pavement and ensure the smooth driving of vehicles, but also basically solve the problems of high friction noise on the cement concrete pavement and poor visual smoothness on the surface. The cement pavement can even be comparable to the asphalt pavement to a certain extent. It can be predicted that the slipform paving technology will make the cement concrete pavement more and more used in the future development of highway construction industry. Slip form paving cement concrete pavement is a new technology of modern large-scale rapid mechanical construction of concrete pavement, and its construction quality and efficiency are very high. The general process of slipform paving construction is: construction preparation → mixture mixing → mixture transportation → installation of dowel bar and reinforcement → Slipform Paver paving → anti sliding structure construction → panel curing → joint cutting construction → joint filling construction → expansion joint and construction joint construction. How to ensure that the newly paved road reaches and exceeds the specified service life and ensure the comfort and safety of driving, the key is to do a good job in quality control during construction. The quality control method in the construction of this technology is discussed from two aspects

1 operate in strict accordance with the key operating points of the slip form paver

the slip form paver is the most critical equipment in the construction of slip form paving. Its models are many, and it should be selected according to the specific situation of the site during construction. Taking wirtgensp8500 as an example, concrete slabs with a thickness of 10~50cm and a width of 2.5~9m can be paved (which can be combined and adjusted according to needs). The concrete slump is required to be 2~4cm, and 120~200m3 can be paved every hour. The components of wirtgensp8500 that are directly related to the paving quality are mainly organic distributor, vibrating bin, high-frequency vibrator, guide sensor, leveling beam and super trowel. The key points of paving operation are as follows:

(1) spreader: control the amount of cloth when distributing, not too much or too little, especially pay attention to the balance of both sides, and the material at the corners must be sufficient

(2) feeding door: control the height of the material level in the vibrating silo. Too high will cause large resistance of the paver, poor vibration and exhaust effect, and poor pavement density; Too low will lead to insufficient material supply for the extrusion base plate, which will not form an extrusion effect, resulting in a lack of material on the road and a lack of material pit. The normal material level is controlled at about 10cm above the vibrator

(3) traveling speed: the paver must work slowly, evenly and continuously, and it should be selected between 1~2m/min according to the mixing capacity. Vibration frequency 1 × About 104 times/min, and the frequency of tamping plate is about 167 times

(4) high frequency vibrator: the vibrator should be turned on before the paver moves to prevent leakage of vibration. The vibration frequency shall be controlled within 6000~10000r/min, which shall be controlled according to the consistency and slump of the concrete, the walking speed of the paver and the downtime, so as to achieve dense vibration and sufficient exhaust. When the fresh concrete is thin, reduce the vibration frequency appropriately and speed up the operation; On the contrary, the vibration frequency should be appropriately increased to reduce the operation speed. It is not allowed to cause pitting or cracking due to under vibration and missing vibration, nor is it allowed to cause edge collapse, edge sliding and non wear resistance of concrete surface due to over vibration and thick slurry lifting

(5) forming density: the forming formwork can be adjusted to an elevation angle according to the construction requirements, so that the concrete entering the forming formwork can be squeezed to increase the compactness of the concrete. The elevation angle shall be controlled between 2 ° ~5 ° depending on the situation

(6) curve operation: the manipulator should control the material level and left and right height of the silo. First adjust the metering plate so that the superelevation side is raised and the other side is lowered; The second is to increase the rotation speed of the small stirring cage to speed up the lifting of slurry to the high side, so as to ensure that the material level of the silo is consistent

(7) ramp operation: when paving high or low, the metering plate should also be controlled to ensure that the material level entering the silo is moderate; In addition, when paving from low to high, try to avoid large mixing cage. In terms of 5g characteristics, there is too much stacking in front to prevent the paver from slipping, which will affect the excess capacity of raw material industry, and there will be a long-term impact on flatness

(8) surface smoothing and trimming: after smoothing the beam, trim the concrete surface with small deformation, fine flatten the formed concrete surface, and eliminate the bubbles on the surface. The mortar roll rubbed out by the leveling beam can also repair the pits left after the central pull rod is driven, and then it is troweled by the super

trowel. Since the super trowel cannot completely wipe the edge, in order to ensure the flatness of the edge, skilled workers must manually trowel it

(9) longitudinal roughening: after the concrete surface is smoothed with a trowel, the concrete surface is roughened longitudinally with a linen cloth with the same width as the paver hung after the lengthened formwork, so as to eliminate bubbles on the concrete surface, form the roughness of the road surface, and increase the driving safety factor. The mop should not be too long, and the effect of the contact surface between

and concrete is the best within 1m. The rag should be moistened every time and replaced and cleaned every 4~5h to prevent the condensed cement particles from damaging the flatness of the road surface

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