1. Install steel formwork
The installation of steel formwork is an important link to ensure various technical indexes such as straightness, flatness, camber, longitudinal seam straightness, plate thickness and plate width. Adhere to the requirements of "solid and accurate" in the operation process.
"Solid" means that the steel formwork is made of standard channel steel, and the height of channel steel is consistent with the thickness of concrete slab. Joints shall be firmly fixed with special fittings, and the joints shall be tight without separation, staggered stubble and unevenness. After the template is in place, fix it with T-shaped spikes embedded in the base. Fill the bottom of the template with mortar and fix it tightly to ensure the stability of the steel mold.
"Accurate" means to keep the accuracy of the top elevation of the steel formwork, and check the flatness error of the top elevation with a level meter to control it within millimeters. After inspection, evenly coat a thin layer of engine oil on the inside of the steel mold.
2, concrete mixing
The pavement concrete of this project is mixed by forced mixer. Before construction, prepare enough sand, gravel, cement and other materials that meet the requirements in the mixing station in advance.
Before mixing the first plate of concrete mixture, mix it with an appropriate amount of concrete mixture or mortar, discard it after mixing, and then mix it according to the specified mixture ratio. The loading sequence in the mixer is sand, cement, crushed stone or crushed stone, cement and sand. After feeding, add water while stirring. The shortest time of concrete mixture conforms to Technical Specification for Construction of Highway Cement Concrete Pavement (JTG F30-2003), and the longest mixing time shall not exceed three times of the shortest time.
3, transportation, unloading, paving concrete
The concrete mixture is transported to the paving site by the concrete tanker for paving, vibrating and mixing.
Before laying concrete mixture, the interval, height, lubrication, support stability, smoothness and wettability of the base, as well as the location of steel bars and dowel bar devices should be thoroughly checked.
After the concrete tanker arrives at the paving site, the concrete mixture is directly discharged into the road groove where the side formwork is installed. The discharging should be as uniform as possible. If individual segregation is found, it should be stirred evenly immediately.
After the concrete paving is completed, first start the vibrator to vibrate the pavement concrete evenly. Then start the three-axis paver and roll it repeatedly along the template. Three-axis machine rolls once per roll, and someone needs to scrape the laitance along the transverse direction with a 4 m ruler. At the same time, it is necessary to clean up the scattered concrete at the top of the formwork in time to ensure the smooth rolling of the triaxial machine. The rolling times of triaxial machine depend on the vibrating of concrete. If the vibrated concrete is dense and there is not too much laitance, the triaxial machine can be stopped for rolling. In any case, the rolling times of the three-axis paver shall not be less than 3 times.
The vibrating of concrete is mainly completed by a row of vibrators, which are mainly composed of a row of vibrators with a spacing of 40cm and a power of 1. 1.5 kW, which can be mechanically lifted and moved forward automatically (walking speed 1.2 ~ 1.5 m/min). When vibrating, the residual materials should be manually treated or supplemented according to the situation to ensure that the concrete surface after vibrating is basically flat, slightly higher than the top of the template. When the vibrator travels, bury the longitudinal pull rod. In the specific operation of the three-axis paver, the three-axis leveler will roll back and forth for 3 ~ 4 times, during which the original pulp will be leveled manually, and then the three-axis leveler will pass. After straightening with three-axis straightener, the flatness requirement specified in the specification can not be reached. After the shrinkage and hardening of the concrete surface, it should be plastered manually.
Step 4 slot
Slotting construction can only be carried out after the concrete slab is finally solidified. The slotting machine is self-propelled. Slotting machine with 7.5KW, 16 blade. When grooving adjacent panels, the grooves should be continuous and straight. During construction, mark lines should be drawn or hung before construction. Mechanical operators must control and adjust the machinery at any time to ensure the quality of straight line intersection and groove. The groove depth is 3 ~ 5 mm, the groove width is 3 ~ 5 mm, and the groove spacing is 20 ~ 25 mm, and the groove should be gradually advanced from high to low. In the process of operation, the cooling water consumption of the cutter head is relatively large, and it is necessary to have someone to supply water for the slotting machine. In order to shorten the operation time as much as possible, multiple slotting machines are used to speed up the construction. During the construction operation, one section shall be chiseled and the other section shall be cleaned.
5. Health
After the anti-sliding structure of concrete slab is made, it should be cured immediately after the concrete is solidified, and it is proposed to adopt the method of watering and wetting curing such as covering geotextile. Generally, water is sprayed 4-6 times a day, but it must be ensured that the bottom of the plastic film is always wet during the curing period under any climatic conditions, so as to determine the number of times of watering every day. Curing time depends on the increase of concrete strength, and should generally be 14 ~ 2 1 day.
After the curing period, the covering can be removed without leaving any traces on the surface of the plate.
6, split
Grasping the timing of joint cutting is an important measure to prevent the initial plate breaking. According to our experience, when the concrete strength reaches 6.0 ~ 12.0 MPa, it is the best time to crack. However, when the temperature changes suddenly, we will cut the joints early to prevent irregular cracks in the concrete slab. The kerf is constructed by pavement kerf-cutting machine. The kerf depth is (1/4 ~ 1/5), the longitudinal kerf is (1/4 ~ 1/5), the expansion joint is 3 ~ 4 cm, and the joint width is 0.3. When the seam cutting stops, first turn off the knob, lift the blade above the surface of the concrete slab, and then stop running. After slitting, we will pour the joint filler as soon as possible.
7, caulking
Asphalt is used for joint filling. Before joint filling, use compressed water and compressed air to thoroughly remove sand, stone and other pollutants in the joint, and ensure that the joint wall and interior are clean and dry. Pouring should be carried out in a dry and clean state in the tank, and the inspection of the tank wall should be based on the fact that dust can not be wiped off. The pouring height should be lower than 1-2mm, because it is winter construction. Joint filling should be full, uniform and continuous. After the completion of the construction, carefully check the bonding between the joint filler and the joint wall, and bake it on a small fire with a blowtorch where it falls off to make it bond closely.