Cement Concrete Pavement Construction Technology

(1) Preparation
1, construction retest: the crossing, toll Station Road center pile position, level point base pile and other measurement data for retest, to strengthen the control pile.
2. Preparation of raw materials
(1) Aggregate: hard texture, clean, no weathering, needle flake particles, mud content, organic matter content in line with the requirements of the code, aggregate grading in line with the design and code requirements.
(2) Cement: stability, fineness modulus, initial and final setting time and other indicators meet the design and specification requirements.
(3) Stone: hard texture, clean, dense, no weathering, the ultimate compressive strength and other physical and mechanical indicators meet the design requirements, geometric size and other appearance indicators meet the requirements of the code.
(2) Concrete mix ratio
1. The concrete pavement cement, crushed (gravel) stone, sand, admixture and other materials planned for each mechanized construction and small supporting machinery and tools construction shall be commissioned by the central laboratory to conduct raw material test and mix ratio design according to the relevant standard method requirements 5 days before being used in the project. Mix ratio design should include concrete bending and compressive strength, aggregate grading requirements, water-cement ratio, consistency, cement amount, quality control and other details.
2. Timely submit the mix ratio design report and general description to the supervision engineer for approval. After the concrete mix design is approved, the test mix is carried out immediately.
(3) Sampling inspection
According to the frequency required by the relevant specifications, two groups of compressive and flexural specimens were made, and the compressive and flexural tensile strength tests were carried out for 7 days and 28 days respectively.
Fourth, concrete placement
1. Basic preparation:
(1) Before laying the cement concrete surface layer, all the pumice stone, debris, dust and so on on the base should be removed, keep the surface clean, and organize the drainage facilities.
(2) If there are ruts, soft and other parts that do not meet the requirements of the regulations. All should be dug, removed, and filled with the same kind of mixture, the compaction thickness shall not be less than 8cm, re-shaping, rolling, and meet the requirements of compactness.
2. Preparation of construction machinery:
According to the project scale, construction quality and schedule requirements, the appropriate construction machinery should be configured, and its technical performance should meet the requirements of concrete pavement construction. The names, models, specifications, quantities, etc. of various construction machinery configured on the site shall be listed and reported to the supervision engineer for approval.
3. Template:
(1) The formwork is made of steel plate material, and is equipped with suitable devices to ensure that the formwork connection is firm and reliable, so that it can withstand the impact and vibration of the ramming and finishing equipment when pouring concrete.
(2) Template installation should be straight, without distortion; The adjacent steel dies shall be closely connected by flat head locking, and shall not leak pulp; Formwork joints should not move in any direction. The height of the formwork should be the same as the thickness of the concrete pavement, with an error of +0,-5mm.
(3) The template for expansion joints and construction joints shall be lofted and drilled according to the design position of the force transfer rod and the pull rod.
(4) The formwork is fully pressed against the base for the entire length and is properly placed at the required slope and longitudinal position of the finished road edge.
(5) The formwork should be thoroughly cleaned and applied with a spacer before each concrete pouring.
4. Steel bar setting:
The installation of steel mesh, corner reinforcement and edge reinforcement shall comply with the provisions of relevant codes.
5. Concrete mixing and transportation:
(1) The mixing and transportation of concrete meet the requirements of the code.
(2) The maximum allowable time from the discharge of the concrete mixture from the mixer to the completion of pouring shall be determined by the laboratory according to the initial setting time of the cement and the construction temperature, and shall be reported to the supervision engineer for approval.
6, concrete paving:
(1) Before the concrete mixture is spread, the spacing, height, lubrication, support stability of the formwork, as well as the installation position of the steel bar, force transmission rod and tie rod are comprehensively inspected.
(2) The concrete shall be paved with approved pavers, pavers shall be carried out continuously. If the stoppage occurs for any reason, construction joints shall be set up according to the instructions of the supervision engineer.
(3) The mixed concrete shall be vibrated fully along the surface of the formwork within the entire length of the formwork and on both sides of all expansion joints with a plug-in vibrator. Vibrator shall not contact the joint device and the side die, and shall not touch the steel mesh, the force transfer rod and the pull rod, at any position, the vibration time should not be less than the specification requirements, and then use the plate vibrator to vibrate. Then use vibration leveling beam vibration leveling, vibration beam should move parallel, round trip vibration leveling 2-3 times.
7, surface dressing:
(1) After the concrete paving, ramming and scraping operations are completed, the approved finishing equipment is used to further smooth the concrete surface to achieve the required transverse slope and flatness.
(2) During the dressing operation, water shall not be sprayed on the surface of the concrete.
(3) Manual trimming of joints and irregularities on the surface of the concrete shall be carried out on a work bridge approved by the supervision engineer, and the work bridge shall not be supported on concrete that has not reached the required strength.
(4) Finishing operations are carried out while the concrete remains plastic and workable to ensure the removal of moisture and float from the surface of the concrete. In low-lying areas on the surface, it is strictly prohibited to sprinkle water and dry cement, and must be filled and trimmed with newly mixed concrete.
8. Seam:
(1) Longitudinal seam:
Set longitudinal construction joint according to the drawing. The longitudinal construction joint adopts the flat seam type, and the pull rod is set according to the requirements of the drawing. The pull rod is made of rebar, which is set in the middle of the plate thickness, parallel to the plate surface, and perpendicular to the seam wall. After the half panel is completed, paint asphalt on the joint wall, but do not contaminate the tie rod.
(2) Transverse expansion joint:
1, according to the requirements of the drawing set the expansion joint, the expansion joint is perpendicular to the center line of the road, the seam wall must be vertical, the expansion joint of the adjacent lane is located on the same cross-section, the width of the gap should be consistent. The lower part of the expansion joint is arranged with the expansion joint plate, and the upper part is poured with the joint filler. No concrete or other debris is allowed anywhere in the gap.
(2) The active end of the expansion joint transmission rod can be located at one end of the joint or staggered. The sleeve of the active end of the power transmission rod is made of metal or plastic, and the maximum gap between the inner diameter of the sleeve and the power transmission rod is 1.5mm, which can make the power transmission rod move freely. The sliding end of the power transmission rod should be coated with grease or lubricant to prevent the power transmission rod from sticking with the concrete.
③. The gap between the end of the transmission rod and the sleeve is filled with asphalt oakum.
(4) The installation method of the fixed device of the force transmission rod shall be submitted to the supervision engineer for approval. The fixed force transmission rod must be parallel to the center line of the road surface, and the displacement of the assembled parts is strictly prohibited when the concrete is poured.
(3) Transverse shrinkage joint:
①, the form, size and spacing of the joint should be set according to the requirements of the drawing.
2, sawing with concrete sawing machine cutting, sawing time according to the use of cement type, climate conditions to determine, generally in the concrete strength of 1 ~ 1.5MPa sawing seam is appropriate, each sawing operation must be completed at a time. The powder and debris in the seam are thoroughly removed.
(3) When the curb and concrete pavement are constructed as a whole, the joint should be extended to 5cm above the curb.
(4) Transverse construction joint:
(1) When the end of the work every day or when the pouring process is interrupted for more than 30 minutes, the flat construction joint perpendicular to the middle line of the road should be set.
(2) The position of the construction joint is consistent with the expansion joint or the contraction joint as far as possible, and the construction is located at the expansion joint according to the expansion joint form.
(3) According to the design requirements, the force transfer rod or pull rod must be parallel to the center line of the road and vertical seam wall.
(4) When using the form of flat seam plus force transfer rod. Half of the length of the transmission rod is anchored in concrete, and the other half is coated with grease or lubricant to allow movement; When the flat seam rod is used, both ends are anchored.
(5) When laying adjacent plates, asphalt should be applied to the joint wall of the poured concrete panel, but it should not pollute the tie rod or the force transfer rod.
9, mold removal, health and sealing:
(1) Mold removal:
(1) When the strength of concrete reaches the relevant specification requirements of the design strength, the mold is removed, and the consent of the supervision engineer is obtained.
(2) After removing the mold, any honeycomb, hemp surface and plate edge damage should be repaired, and the transverse expansion joint along the edge of the concrete panel should be opened to the full depth in time.
(2) Health care:
Cement concrete pavement can be heat preservation and maintenance after the completion of the slit, the geotextile is soaked and covered with watering and maintenance, the number of daily sprinkling depends on the climate, the general maintenance period of cement concrete surface layer is 14 ~ 21 days, and the temperature is low. During the maintenance period, vehicles are prohibited from running, and traffic can be opened after reaching the design strength.
(3) Sealing:
①, all the joint slots in the concrete panel are sealed with caulking materials according to the requirements and positions of the design drawings.
2. The joint slot should be dry, free of dust, concrete debris or other debris.
③, the caulk should be heated and filled in accordance with the method recommended by the manufacturer; The joint filler adheres closely to the concrete joint wall without water seepage.
(4) The caulk should be filled from the bottom of the groove to the road surface, and the seam with a depth greater than 2.5cm should be divided into at least two layers of caulk, and the thickness of each layer is roughly equal.
⑤, in the high temperature season, the filling material is poured to the road surface, and in the low temperature season, it is slightly lower than the road surface.
(6) Caulking with the progress of the project, so that before opening to traffic, the caulking material should have sufficient time to harden.
10. Quality control:
1, the construction process of concrete mixture according to the requirements of the code to check the compressive and flexural tensile strength of concrete, as well as the allowable deviation of the amount of various components in the mixture. And according to the relevant provisions of the code, the qualified strength of concrete is assessed.
(2) The appearance of the road side stone is straight, the curve is smooth, and the joint filling is full and dense.