——Cement concrete pavement construction technology
1. After a long time of strong engineering and freezing, the water and gas are mixed with mud
The mix ratio design of concrete should meet the requirements of flexural tensile strength, workability and durability while taking into account economy, and conform to the relevant provisions of CJJ1-2008 of the Code for Quality Acceptance of Urban Road Engineering.
The 28d flexural tensile strength value of concrete should conform to the provisions of JTGD40-2011 of the Code for Design of Highway Cement Concrete Pavement, and the coefficient of variation, standard deviation and guarantee rate coefficient of test samples obtained according to statistical data. The optimal working range and maximum water consumption, concrete air content, maximum water-cement ratio and minimum unit cement consumption of concrete with different paving methods should meet the requirements of the specification, and the frost resistance level of concrete in severe cold areas should not be less than F250, and should not be less than F200 in cold areas.
The use of concrete admixtures should be in accordance with: when the high temperature construction, the initial setting time of the concrete mixture shall not be less than 3h, and the final setting time shall not be greater than 10h during low temperature construction; the amount of admixture should be determined by the concrete trial matching; when the air-entraining agent and the water reducer or high-efficiency superplasticizer and other admixtures are compounded in the same aqueous solution, the flocculation phenomenon shall not occur.
The calculation of the relevant parameters of the concrete mix ratio should be carried out in accordance with the "Design Code for Ordinary Concrete Mix Ratio" JGJ55-2011.
2. Intermittent calibration mixing, viscosity is strong and stable
The mixing equipment should give priority to the batch mixing equipment, and the calibration and test mixing should be carried out before putting into production, and the batching measurement deviation of the mixer should meet the specifications. According to the cohesion, homogeneity and strength stability of the mixture, the optimal mixing time was determined by test mixing. The total mixing time of the single vertical shaft mixer should be 80~120s, and the shortest pure mixing time should not be shorter than 40s after the feeding is complete; the total mixing time of the planetary vertical shaft and twin-shaft mixer should be 60~90s, and the shortest pure mixing time should not be shorter than 35s after the feeding is complete; and the shortest pure mixing time of the continuous double-shaft mixer should not be shorter than 40s after the feeding is complete.
3. Dampness and secretion of dampness than collapse
(2) During the mixing process, the water-glue ratio and stability, slump and uniformity, slump loss rate, vibration viscosity coefficient, gas content, water secretion rate, wet density, segregation and other items of the mixture should be inspected and controlled, which should meet the requirements of quality standards.
(3) The mixing of steel fiber reinforced concrete shall comply with the relevant provisions of the Code for Construction and Quality Acceptance of Urban Road Engineering CJJ1-200.
4. The feed distance is 2.5
(1) The total number of models and vehicles should be selected according to the construction progress, volume, distance and road conditions. The maximum allowable time from the discharge of the mixer to the completion of the paving of concrete mixtures for different paving processes shall comply with the regulations. For example, when the construction temperature is 10~19 °C, the construction of sliding form and track machinery is 2.0h, and the construction of three-roller unit and small machine tools is 1.5h; when the construction temperature is 10~29 °C, the former is 1.5h, the latter is 1.25h; when 30~35 °C, the former is 1.25h, and the latter is 1.0h.
(2) The maximum allowable time from the discharge of the concrete mixture to the completion of transportation and paving (h) is shown in Table 1K411043.
The maximum allowable time from the discharge of the concrete mixture to the completion of transportation and paving (h) Table 1K411043
| Construction Temperature*(°C) | The maximum time allowed until the completion of transportation | The maximum time allowed until the completion of paving | ||
| Sliding form, track | Three-roller shaft, small machine tools | Sliding form, track | Three-roller shaft, small machine tools | |
| 5~9 | 2.0 | 1.5 | 2.5 | 2.0 |
| 10~19 | 1.5 | 1.0 | 2.0 | 1.5 |
| 20~29 | 1.0 | 0.75 | 1.5 | 1.25 |
| 30~35 | 0.75 | 0.50 | 1.25 | 1.0 |
Note: The * in the table refers to the average daytime temperature of the construction time, and the value of this table can be increased by 0.25~0.5h after the use of retarder to extend the setting time.
5. Support the prohibition of 185, check the high quartile, and inspect and seal the coating after installation.
(1) It is advisable to use steel formwork, which should be straight and smooth, and set up 1 support device every 1m. If the wood formwork is used, the texture should be solid, the deformation is small, there is no decay, distortion, cracks, and it must be soaked before use, the thickness of the straight part of the wood formwork should not be less than 50mm, and 1 support device should be set up every 0.8~1m; the thickness of the curved part of the plate should be 15~30mm, and 1 support device should be set up every 0.5~0.8m, and the contact surface between the template and the concrete and the top surface of the template should be planed. The deviation of template production should meet the requirements of the specification.
(2) The formwork installation should conform to: the pavement elevation, panel blocking, expansion joints and the position of the structure should be checked before formwork; the formwork should be installed firmly, straight, flat, without distortion, and the adjacent formwork connection should be tight and smooth, and should not be dislocated; it is strictly forbidden to dig grooves on the base layer and embed the formwork; special steel rail formwork should be used when using the track paver; after the formwork is installed, it should be inspected and can be used only after it is qualified; the surface should be coated with a separator after the formwork installation inspection is qualified, and the joints should be sealed with tape or plastic film.
6. Seed gauge retention
Before the installation of the steel bar, the raw material variety, specification and processing quality should be checked to confirm that it meets the design requirements and specifications, and the installation of the steel mesh and corner steel bar should be firm and accurate. After the steel bar is installed, it should be inspected and can be used only after it is qualified; The force transmission rod should be installed firmly and accurately. The expansion joint force transmission rod should be installed together with the expansion joint plate and the lifting seam plate. When the width of a paving is less than the width of the surface layer, a longitudinal construction joint should be arranged, and the longitudinal construction joint should be a flat joint plus tie rod type.
7. Static rolling after front vibration, and the interval is inserted for a long time
When the three-roller unit paves the concrete surface course, the diameter of the roller shaft should match the thickness of the paving layer, and must be equipped with a row type vibrator machine that installs the plug-in vibrator group at the same time; when the pavement thickness of the surface course is less than 150mm, the vibrating beam can be used; when the two-lane surface course is paved at one time, it should be equipped with a longitudinal seam tie rod insertion machine, and is equipped with insertion depth control and tie rod spacing adjustment device.
The unloading should be uniform during the paving operation, and the distribution should be adapted to the paving speed; the concrete surface layer with longitudinal joints and shrinkage joints should be installed in time during the surface layer construction; the length of the operation unit of the three-roller shaft leveling machine should be 20~30m, and the time interval between the vibrator and the three-roller shaft leveling process should not exceed 15min; within the length of an operating unit, the forward vibration and backward static rolling mode should be adopted, and the optimal rolling times should be determined by the test section.
8. Spread the width and collapse of the loose paving height, vibrate and vibrate the leveling table
When using rail paver paving, the minimum paving width should not be less than 3.75m, and the appropriate paving model should be selected, and the slump should be controlled at 20~40mm, according to the loose coefficient of different slump to calculate the height of the loose paving; the track paver should be equipped with a vibrator group, when the panel thickness exceeds 150mm, the slump is less than 30mm, the vibrating must be inserted; the track paver should be equipped with a vibrating beam or a vibrating plate to vibrate and trim the concrete surface, when using the vibrating plate to lift the grout finish, the slurry thickness should be controlled at (4±1) mm; when the surface of the surface layer is leveled, the remaining material should be removed in time, and the surface repair should be completed with a trowel.
9. Wiring Qingrunji high-frequency walking distance
When using slipform paver paving, the baseline should be laid, the wet base layer should be cleaned, and the expansion joint support should be firmly installed at the expansion joint to be set, and the spacing of the support points should be 40~60cm.
Adjust the working parameters of the slipform paver to achieve the best state, rotate the distributor in time according to the front discharge position, and evenly distribute the materials on both sides laterally. The height of the material level in the vibrating bin should generally be 10cm higher than the road surface. The concrete slump is small, and high-frequency vibration and low-speed paving are applied, and the concrete slump is large, and low-frequency vibration and high-speed paving are applied.
In the paving process, it is necessary to do: slow start, stable mechanical operation, uniform speed, tacit understanding of the crew, paver walking speed of 1~3m/min, vibration frequency of 8000~9000r/min.
10. Loose paving, before the initial setting, once poured and vibrate.
When using small machinery to pave concrete, the loosening coefficient should be controlled at 1.10~1.25; when the paving thickness reaches 2/3 of the thickness of the concrete slab, the steel brazing in the mold should be pulled out, and the drill hole should be filled; when the concrete surface layer is paved twice, the paving of the upper layer of concrete should be completed before the initial setting of the lower layer of concrete, and the thickness of the lower layer should be 3/5 of the total thickness; concrete paving should be matched with the placement of steel mesh, force transmission rod and edge corner steel bar; a concrete slab should be poured continuously at one time, and vibrate according to the requirements.
11. The end of the wooden mold is connected to the bracket
There are two ways to install the force transfer rod. One is the end wood mold fixed force transmission rod installation method, which is suitable for the expansion joint set when the concrete slab is discontinuous pouring - half of the length of the force transmission rod should pass through the end baffle and be fixed in the outer positioning template. Before pouring the concrete mixture, the position of the force transmission rod should be checked, and when pouring, the lower concrete mixture should be paved and compacted with a plug-in vibrator, and the position of the force transmission rod should be corrected before pouring the upper concrete mixture.
The other is the installation method of the bracket fixed force transmission rod, which is suitable for the expansion joint that is set when the concrete slab is continuously poured - half of the length of the force transmission rod should pass through the expansion joint plate and the end baffle, and should be fixed in place with a steel bar support. When pouring, the position of the force transmission rod should be checked first, and then the concrete mixture should be paved to the plate surface in front of both sides of the expansion joint, and after vibrating and compacting, the end baffle should be withdrawn, and the void part should be filled with the concrete mixture, and the plug-in vibrator should be used to vibrate. The expansion joint plate should be continuously connected to the entire width of the pavement slab.
12. Vertical width and deep cutting
(1) The expansion joint should be provided with an expansion joint reinforcing steel support, an expansion joint plate and a force transmission rod. The expansion joint should be perpendicular to the center line of the pavement, the joint wall must be vertical, the joint width must be consistent, and the slurry shall not be connected in the joint. The upper part of the seam is filled with caulk, and the lower part is installed with the expansion joint plate and the force transmission rod. When the width of the pavement is less than the total width of the hardened shoulder of the surface layer, the longitudinal construction joint should be set according to the design requirements.
(3) The shrinkage joint should be vertical, and the cutting and sewing machine should be used for construction, and the width should be 4-6mm. Cutting depth: when the force transmission rod is set, it should not be less than 1/3 of the thickness of the surface layer and not less than 70mm, and when the force transmission rod is not set, it should not be less than 1/4 of the thickness of the surface layer, and should not be less than 60mm. When the concrete reaches 25%-30% of the design strength, the cutting machine is used to cut. When the cutting water is cooled, the cutting water should be prevented from seeping into the base layer and soil layer.
13、平企涂沥青， 凹榫与槽缝
Longitudinal seam construction seams are available in the form of flat seams, tongue seams and other forms. Flat longitudinal joints, apply asphalt to the gaps of the poured concrete slabs to avoid coating on the stalks. When pouring adjacent plates, the upper part of the seam is pressed into a groove of the specified depth. For the longitudinal joints of the tongue and groove joints, it is advisable to pour one side of the concrete slab concave tenon first, the joint wall is coated with asphalt, and the adjacent plate is poured by the joint wall. When the tie rod is set in the longitudinal seam, the tie rod should be arranged in the middle of the plate thickness, the longitudinal seam template of the tie rod should be arranged, and the hole should be lofted and drilled according to the design position of the tie rod in advance.
14. Clean and sticky seams, low and normal temperature in winter
After the expiration of the curing period of the concrete slab, the joint groove should be filled in time. Before filling the joint, remove the sand, condensed mud, and debris in the joint. Select the caulk according to the design requirements, and formulate process technical measures according to the variety of caulk. When pouring caulk, the groove must be dry and clean. The fullness of the caulk is determined according to the construction season, the construction at room temperature is flat with the road surface, and the construction in winter should be slightly lower than the board surface. The caulk should adhere tightly to the concrete joint wall and not seep water. Before the tensile strength of the surface layer concrete reaches the design strength and the caulking is completed, it shall not be opened to traffic.
15. Wet cultivation should not be enclosed, and low temperature curing
After the concrete pouring is completed, it should be cured in time, and the method of spraying curing agent or moisturizing cover can be adopted; in the case of rainy days or sufficient water for maintenance, the moisturizing film, geofelt, sack, straw bag, straw curtain and other covering can be used to sprinkle water and wet curing methods, and it is not suitable to use surrounding water curing; the temperature difference between day and night is greater than 10 °C or the area where the average daily temperature is lower than 5 °C The concrete slab should adopt thermal insulation and maintenance measures. The curing time should be determined according to the growth of the flexural tensile strength of the concrete, which should not be less than 80% of the design tensile strength, and generally should be 14~21d. Special attention should be paid to the moisturizing (warm) maintenance of the first 7 days.
16, 40 pedestrian complete and caulking
Pedestrians can be allowed to pass through the concrete after it has reached 40% of the design tensile strength. The concrete in the surface layer shall not be open to traffic until the design flexural tensile strength has been fully reached and the caulking is completed.
Yesterday 速记口诀
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