What is the working principle of concrete laser leveling machine?

    Objective: To prevent safety accidents such as collapse, falls from heights, mechanical injuries, and electric shock during concrete pouring construction, ensure the safety of construction workers' lives and equipment and property, and standardize operation procedures, this special measure is formulated in accordance with regulations and standards such as the "Code for Safety Inspection of Construction Sites" (JGJ59) and the "Code for Construction of Concrete Structures" (GB50666). ​ Scope of application: This measure is applicable to various concrete pouring operations in building construction, municipal engineering, Bridges, tunnels, etc., including the pouring construction of different parts such as foundations, main structures, and secondary structures. ​ Before construction, a special construction plan should be prepared, clearly specifying the pouring sequence, material distribution method, machinery selection and safety protection requirements. It should be implemented after approval by the technical supervisor. ​ Conduct three-level safety briefings for all personnel involved in the operation: project-level briefing on the overall safety risks of the construction, team-level briefing on the operation norms of the positions, and on-site briefing on the potential hazards of specific operation points (such as edges, openings, and high-voltage line locations). The briefings must be signed for confirmation and archived. ​ Inspect the surrounding environment of the pouring area: Clear the debris on the work surface, and confirm that 1.2-meter-high guardrails have been set up at the edges (such as foundation pits, floor slab edges) and openings (with 20cm high toe boards at the bottom of the guardrails and an additional horizontal bar in the middle). The guardrails should be painted with red and white warning paint and hung with close-mesh safety nets. ​ Check the load on the working surface: Verify the bearing capacity of the formwork support system to ensure that the concrete stacking height does not exceed the specification requirements (the stacking height during floor slab pouring is ≤100mm), and prevent the support from collapsing due to overloading. ​ Check for electrical safety: Confirm that the distribution box meets the requirements of "one machine, one switch, one leakage protection, and one protection". The cables in the pouring area should be overhead or run through pipes for protection to prevent damage from being crushed. When working in a humid environment, the lighting voltage should be 36V or lower, which is a safe voltage. ​ Concrete conveying equipment (pump trucks, ground pumps, placing machines) : Check whether the braking system, hydraulic system and pipe joints of the equipment are in good condition. The outriggers of the pump truck need to be supported on a solid ground (with steel plates or square timbers as pads), and confirm that the outriggers are fully extended and the ground bearing capacity meets the requirements. ​ Protective supplies: Personal protective equipment such as safety helmets, anti-slip shoes, insulating gloves, and dust masks should be provided. When working at heights, safety belts (high hanging and low use) and operation platforms (fully covered with scaffolding boards and surrounded by guardrails) should be prepared. Backup emergency supplies (such as first aid kits, fire extinguishing equipment, and warning tapes). ​   High-altitude work protection: When the pouring height is ≥2 meters, an operation platform or scaffolding must be used. It is strictly prohibited to stand on formwork or steel bars for work. Workers should fasten their safety belts, and the hooks of the safety belts should be hung on solid structural components. It is strictly prohibited to walk on unfixed components. ​ Edge operation protection: When pouring foundation pits, slopes and other edge parts, set up warning areas and prohibit non-operation personnel from entering. Workers should maintain a safety distance of no less than 1 meter from the edge of the edge. Anti-slip scaffolding boards should be laid if necessary. ​ Dust-proof and heat-proof protection: During summer pouring, shading measures should be taken to prevent personnel from suffering from heatstroke. When pouring in winter, when hot water is used to mix concrete, it is necessary to prevent steam scalding. Workers should wear anti-scalding gloves. When there is a lot of cement dust, wear dust masks and set up spray dust suppression equipment on site. ​ Operation precautions for pump trucks and material distribution machines: No one is allowed to stand within the rotation radius of the material distribution rod of the pump truck. Before operation, make sure there are no high-voltage lines or obstacles within the rotation range. The placing machine should be firmly fixed. Before use, check whether the outriggers and the rotating mechanism are locked. It is strictly forbidden to carry out pouring operations when the placing machine is in motion. ​ Vibrator usage protection: The operator of the vibrator should wear insulating shoes and insulating gloves. The cable of the vibrating rod should be protected from damage. It is strictly forbidden to drag the cable. When vibrating, avoid touching the steel bars and formwork to prevent the vibration rods from bouncing and injuring people. When the vibrator is not in use, cut off the power supply and place it in a dry area. ​ Concrete transportation protection: When transporting concrete by tanker, the driver must abide by traffic rules. No one is allowed to stand under the unloading port of the tanker. The ground pump conveying pipeline is firmly fixed. Check the sealing condition of the pipeline joints to prevent concrete leakage and spraying from injuring people. When replacing the pipeline, first turn off the power of the ground pump, release the pressure, and then disassemble it. ​ During the pouring process, dedicated personnel should be assigned to monitor the formwork support system, with a focus on checking the verticality of the vertical rods, the spacing of the horizontal rods, and the setting of the sweeping rods. If any deformation of the vertical rods or loosening of the horizontal rods is found, the pouring should be immediately halted, and personnel should be organized to evacuate. Work can resume only after the reinforcement and rectification are completed. ​ The pouring sequence follows the principle of "symmetrical pouring and layered pouring" to avoid instability of the support system due to excessive local loads. The thickness of the layered pouring shall be carried out in accordance with the specifications (generally ≤500mm), and it is strictly prohibited to pour the formwork in a centralized manner at one time to avoid deformation. ​   Regular maintenance and servicing of concrete conveying equipment, vibrators and other machinery should be carried out. The operating status of the equipment should be recorded. If any fault is found, the machine should be stopped immediately for repair. It is strictly prohibited to operate with faults. Mechanical operators must be certified and familiar with the equipment operation procedures. Unlicensed personnel are strictly prohibited from operating. ​ When the pump truck is in operation, a dedicated person should be assigned for command. The command personnel should use standard signals (flag language or walkie-talkies) to avoid communication errors with the driver. When the fabricating machine is moving, it should proceed slowly to prevent collision with structural components or personnel. ​ On-site electricity usage should be operated by professional electricians. It is strictly prohibited for non-electricians to connect or disconnect wires. The distribution box in the pouring area is locked and a warning sign saying "Beware of Electric Shock" is posted. There are no debris within 1.5 meters around the distribution box. ​ When working in rainy weather, cover the distribution box and electrical equipment, and check the grounding resistance (grounding resistance ≤4Ω) to prevent leakage accidents. After the operation is completed, cut off the power supply of all equipment, organize the cables, and avoid crushing or soaking them. ​   Collapse accident handling: In the event of a collapse of the formwork support, immediately stop the operation, organize personnel to evacuate to a safe area, and prohibit blind rescue. Call the 120 emergency number and at the same time use excavators, jacks and other equipment to clear the collapsed objects and rescue the trapped people to prevent secondary collapse. ​ Handling of falls from heights and mechanical injuries: In the event of a person's fall or mechanical injury, immediately stop the operation, transfer the injured person to a safe area, check the injured person's consciousness and breathing. If fractures or bleeding occur, take temporary immobilization and hemostasis measures, and call 120 for medical treatment. In the event of an electric shock accident, cut off the power supply first, then rescue the injured person to prevent the rescuers from getting electrocuted. ​ Fire accident handling: In case of fire caused by electrical faults or flammable materials burning, immediately cut off the power supply, use on-site fire extinguishing equipment to put out the fire, evacuate people to a safe area, call 119 to report the fire, and at the same time clear flammable materials around to prevent the fire from spreading. ​   Daily inspection: Before each day's work, the team conducts a pre-shift safety inspection, with a focus on personal protective equipment, equipment status, and protective facilities. The project organizes safety inspections every week to identify potential hazards and issue rectification notices, and follows up on the rectification progress. ​ Special acceptance: Before pouring, a special acceptance shall be conducted on the formwork support system, operation platform and electrical equipment. Only after the acceptance is qualified and signed for confirmation can the pouring operation begin. If the acceptance is not qualified, construction is strictly prohibited until the rectification meets the standards. ​ Safety education and training should be provided to newly arrived workers. Only after passing the assessment can they take up their posts. Regularly organize special training on concrete pouring safety, explaining accident cases, operation norms, and emergency skills to enhance personnel's safety awareness. ​ Special operation personnel (such as pump truck drivers, electricians, and scaffolders) must hold relevant certificates to work. Those with expired certificates or those that have not undergone annual review are prohibited from engaging in related operations. Regularly organize refresher training for special operation personnel to update their safety knowledge. Instructions for Use: This plan is a general template. Before the specific implementation of each project, it should be refined and supplemented according to the characteristics of the project (such as super-high, super-heavy, large-span structures, etc.), especially the control measures for major hazard sources.    

Slump: 120~180mm (about 150mm is appropriate) Applicable scenarios: Applicable to laser leveling machine or paver construction to ensure that the fluidity of concrete meets the requirements of mechanical paving and vibration. High slump: 180~220mm (when adding water reducer) Applicable scenarios: Complex reinforcement structure or high temperature dry environment, it is necessary to improve the fluidity of concrete to avoid segregation. Low slump: 80~120mm (dry hard concrete) Applicable scenarios: Construction with slipform paver, or projects with high early strength requirements.   Laser leveling machine: requires a higher slump (120~180mm) to facilitate mechanical vibration and leveling. Slipform paver: The slump should be strictly controlled at 80~120mm to avoid deformation of the structure due to excessive fluidity. Hot and dry weather: The slump can be appropriately increased (+20~30mm) to reduce the slump loss caused by water evaporation. Low temperature or rainy season: The slump can be appropriately reduced (-10~20mm) to prevent concrete segregation. When the coarse aggregate particle size is large and the grading is poor, the slump needs to be increased to ensure workability. Adding water reducer can reduce the water-cement ratio and improve strength while maintaining the slump.   Each truck of concrete needs to be tested for slump before unloading. If the deviation exceeds ±20mm, it needs to be adjusted (such as adding admixtures or secondary mixing). The mixing and pouring of concrete must be completed before the initial setting (usually ≤2 hours) to avoid slump loss due to too long time. Slump is too large: it is easy to cause bleeding and segregation, which can be improved by adding fly ash or reducing the water-cement ratio. Slump is too small: poor fluidity, it is necessary to add water reducer or increase the water consumption appropriately (need to be verified by the laboratory).   "Technical Specifications for Construction of Highway Cement Concrete Pavement" (JTG/T 3650-2020): The recommended slump is 100~180mm, which is adjusted according to the construction machinery. "Concrete Structure Engineering Construction Quality Acceptance Code" (GB 50204-2015): The slump detection frequency is required to be no less than once every 100m³. Reasonable control of slump can ensure the construction quality, durability and appearance smoothness of concrete pavement. The specific parameters need to be determined in combination with design requirements, construction technology and environmental conditions.

  – Importance of smooth start: Good controllability of the trowel means smooth start. If the start process is too hasty, such as the motor or engine reaching a high speed instantly, the trowel blade will suddenly accelerate and have a large impact force with the ground. This may cause scratches on the concrete surface, damage to the local mortar layer, and affect the flatness and finish of the ground. A trowel with good controllability allows the operator to start the machine slowly, allowing the trowel blade to gradually reach the working speed, thereby avoiding these problems and ensuring that the foundation for a good trowel effect is laid from the beginning. – Precise stop protects the machine and the ground: Precise control is essential when stopping the trowel. If the power is suddenly cut off, the trowel may continue to slide due to inertia, causing the trowel blade to drag irregularly on the ground and damage the already troweled ground. Good controllability allows the operator to control the trowel to gradually slow down until it stops, avoiding additional damage to the ground, while also reducing wear on the machine itself and extending the service life of the trowel. – Speed ​​control and trowel quality: A trowel with good controllability allows the operator to control the travel speed conveniently and accurately. Too fast speed will cause the trowel blade to stay too short at each position, unable to fully compact and smooth the concrete surface, resulting in rough and uneven ground. Although too slow speed may make the trowel effect more refined, it will reduce work efficiency. With good control, the operator can flexibly adjust the travel speed of the trowel according to the state of the concrete (such as slump, initial setting time, etc.) and construction requirements (such as coarse grinding or fine grinding), so as to achieve the best balance between trowel quality and work efficiency. – Steering flexibility and corner processing: During the construction process, the trowel machine often needs to be turned, especially when dealing with corners, edges and other areas. If the trowel machine has poor controllability and inflexible steering, it is difficult to effectively smooth these corners. A trowel with good controllability can turn easily and accurately, so that the trowel blade can better fit the corners and ensure uniform and consistent troweling effect on the entire floor. For example, in the construction of indoor room floors, good steering control allows the trowel to operate smoothly in the corners of the wall, avoiding "dead corners" where the trowel is not in place. – Uniform pressure to improve trowel effect: Maneuverability affects the control of the trowel pressure. During the troweling process, it is necessary to apply appropriate pressure according to different stages (such as coarse grinding and fine grinding) and the condition of the concrete. A trowel with good maneuverability allows the operator to control the pressure evenly so that the force of the trowel on the ground is evenly distributed. This can avoid problems such as local unevenness and inconsistent glossiness on the ground due to uneven pressure, and improve the overall troweling quality of the ground. – Flexibility and adaptability of pressure adjustment: Different concrete materials and construction scenarios have different requirements for pressure. For example, for concrete with a large slump, a smaller pressure may be required in the early stage of troweling; while for harder concrete or situations where deep compaction is required, a larger pressure is required. A trowel with good maneuverability allows the operator to easily and flexibly adjust the pressure according to the actual situation, so that the trowel can adapt to various construction conditions, thereby exerting better overall performance.