⛳ Two methods of concrete pavement leveling
♬●●♬Traditional manual leveling method
◑◐Construction method: Use a 3-4m light ruler to scrape the concrete surface, remove excess water and slurry, fill the low-lying areas with concrete, vibrate and re-trim, remove and trim the high parts, and then smooth them appropriately. The vibrator rod will also be used to "quickly insert and slowly pull out" to fully vibrate the concrete. The moving distance of each rod is generally not more than 1.5 times its effective radius (can be controlled as 30cm), and the distance from the template is less than 0.5 times the effective radius of the vibration. Vibrate until the slurry overflows on the surface of the concrete mixture, no longer sinks significantly, and no obvious bubbles overflow; then use the vibration beam to walk back and forth 2-3 times to level and raise the slurry to make the surface flat and uniform.
◑◐Applicable scenarios: Applicable to small projects, rural roads with narrow construction sites or relatively low requirements for flatness. For example, some self-built roads in rural areas, internal roads in small factory areas, etc.
◑◐Advantages: The equipment is simple and easy to obtain, the cost is low, the operation is relatively easy, and the technical requirements for operators are relatively low.
◑◐Disadvantages: The construction efficiency is low, the labor intensity of manual operation is high, the flatness control accuracy is limited, and it is difficult to meet the requirements of large-area, high-precision road projects.
♬●●♬Concrete laser leveling machine leveling method
◑◐Construction method: The laser emitted by the transmitter is used as the reference plane, and the leveling head is controlled in real time through the laser receiver on the laser leveling machine. Just like the laser leveling machine equipped with a HONDA GX690 engine (power 18.4kW/25HP, fuel tank capacity 19L), the steel bar is tied after the formwork of the civil engineering project. Before pouring concrete, the elevation is set on the column reinforcement and led to the laser leveling control system. When the pouring personnel scrape the elevation, the elevation is controlled to be 5-10mm higher than the design elevation, and then the machine operator uses the equipment to accurately level the concrete surface. The leveling width is 3m (9.84ft), and it adopts hydraulic screw conveying paving mode. The vibration system is hydraulic vibration, with a maximum excitation force of 2000N, which can be automatically calibrated and controlled at a certain frequency. After the water seepage of the concrete pouring surface is completed, the laser leveling instrument is used for re-measurement, the water accumulation is filled, and the 3-meter scraper is used to rotate and level it, and then the single-disc trowel is used to level the slurry.
◑◐Applicable scenarios: It is widely used in large-scale industrial plants, large shopping malls, warehouses, underground garages, airport runways, docks and other large-scale concrete floor projects with high requirements for ground flatness, horizontality and strength. For example, the workshop floor of a large automobile manufacturing plant, the floor of a large logistics storage center, etc.
◑◐Advantages: It can achieve high-precision and fast leveling of concrete, and the flatness and levelness of the ground are more than 3 times higher than conventional methods, and the density and strength are increased by more than 20%; it can improve work efficiency by more than 50% and save about 35% of labor; it can lay high-strength concrete, low-slump concrete and fiber concrete; and it can also automatically control the longitudinal and transverse slopes. The equipment has an all-aluminum body and is light in weight (net weight 835kgs / 1841lbs), which is convenient for operation under various working conditions. It is also equipped with an anti-skid system, a hydraulic brake system and a trailer system, a more precise height adjustment rod, a standard soft landing system for the working head, and switch detection and valve port calibration functions to ensure stable machine performance after long-term use. It is also equipped with two types of tires (inflated narrow tires and inflated wide tires) to adapt to different working conditions.
◑◐Disadvantages: The equipment has high purchase costs, high professional and technical requirements for operators, and requires professional training; the site requirements are relatively high, and it is inconvenient to operate in narrow and complex terrain sites.
⛳ Concrete pavement leveling skills
◑◐Pre-construction preparation skills: Before construction, ensure that the roadbed is stable, the formwork is strong and installed straight and flat, and set up a support device every 1m. Accurately measure and lay out the construction site to determine the road elevation and slope. At the same time, clean the construction site to ensure that the ground is clean, dust-free, and oil-free. If there are cracks or unevenness on the ground, it needs to be repaired first. In addition, the quality control of raw materials and mechanical debugging must be done well to ensure the quality of concrete and the normal operation of equipment (such as the laser leveling machine equipped with the HONDA engine mentioned above).
◑◐Concrete spreading skills: Spread the material during pouring. When unloading with a dump truck or a mixer truck, it is strictly forbidden to concentrate the material on a few points to prevent concrete accumulation and ensure that the concrete mixture is evenly distributed.
◑◐Vibration operation skills: Use the vibrator to "insert quickly and pull out slowly" to avoid missing vibration and over-vibration. Control the moving distance of the vibrator and the distance from the formwork. For equipment using a hydraulic vibration system (such as the relevant laser leveling machine), the exciting force should be reasonably adjusted according to the characteristics of the concrete and construction requirements.
◑◐Surface treatment skills: Correct minor defects in the leveling process in time; rub the surface with a grinding disc to compact the slurry before the initial setting to eliminate water seepage channels and tiny cracks; complete the finishing and embossing processes before the final setting, and finish 3-4 times. Moisturize in time during hot and windy weather in summer to prevent the surface from evaporating too quickly and forming a hard shell.
⛳ Measures to improve leveling efficiency and quality
♬●●♬Improve efficiency
◑◐Equipment upgrade and reasonable configuration: When conditions permit, give priority to equipment such as advanced laser leveling machines with the above parameters. Its hydraulic screw conveying paving mode and larger leveling width can improve construction efficiency. At the same time, according to the scale of the project and the conditions of the construction site, reasonably match other auxiliary equipment, such as concrete mixers, pump trucks, etc., to ensure smooth connection between concrete supply and construction.
◑◐Construction process optimization: Scientifically plan the construction sequence and operation area, adopt a segmented flow operation method, and reduce the waiting time between each process. For example, reasonably arrange the connection between concrete pouring, vibration, and leveling with a laser leveler (operated according to its performance parameters) to avoid idle work.
◑◐Personnel training and management: Strengthen the skills training of operators to enable them to master the operation of construction equipment (especially laser levelers) and construction processes, and improve their operating proficiency and accuracy. At the same time, optimize the division of labor, clarify the responsibilities of each position, and improve the efficiency of teamwork.
♬●●♬Improve quality
◑◐Strictly control the quality of raw materials: Select raw materials such as cement, aggregates, and admixtures of qualified quality, control the mix ratio, and ensure that the strength and workability of concrete meet the design requirements. For example, cement should be selected from brands with stable strength and reliable quality, and the particle size and mud content of aggregates should meet the standards.
◑◐Strengthen process quality inspection: During the construction process, use measuring instruments such as levels and theodolites to monitor road elevation, flatness, slope and other indicators in real time, and make timely adjustments when deviations are found. At the same time, do a good job in testing the slump of concrete and the compaction density. For laser leveling machine construction, it is necessary to regularly check whether the laser system and hydraulic system of the equipment (such as checking the accuracy of its height adjustment rod, the performance of the hydraulic brake system, etc.) are normal.
◑◐Protect the finished product: After the concrete pavement construction is completed, timely take maintenance measures such as covering and sprinkling water, and the maintenance time is not less than 14 days. Set up warning signs to restrict the passage of vehicles and pedestrians before the concrete strength reaches the design requirements to prevent damage to the road surface.
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