Technical Knowledge
The standardized construction process of coarse grinding followed by fine grinding, and the timing for switching between the trowel disc and the trowel on the power trowel.
Let's take a detailed look at the standardized construction process of concrete plastering, especially the technique of "rough grinding first and then fine grinding", as well as the key switching timing between the grinding plate and the power trowel. This is the core link to ensure that the concrete floor (especially the industrial floor) achieves a dense, flat and high-strength surface.
Standardized construction process for concrete smoothing: "Rough grinding first, then fine grinding"
This process is a dynamic one that advances based on the setting state of the concrete. The entire process can be summarized into the following stages:
Phase Zero: Preparatory work and grassroots handling
Concrete pouring: Ensure that the concrete pouring is smooth and slightly higher than the designed elevation.
Vibration and leveling: Use a vibration rod to compact it tightly, and then perform an initial leveling with a long straightedge or a laser screed.
Natural settlement and bleeding: Let the concrete settle naturally and bleed out. No mechanical operations are allowed before the bleeding water has completely evaporated.
Phase One: Rough grinding – Slurry lifting and leveling (using a power trowel disc/power trowel disc)
Core objective
Slurry lifting: Bringing the slurry rich in cement and fine aggregates on the surface to the surface layer.
Preliminary leveling: Eliminate the large undulations left by the straightedge, and slightly press the aggregate down to make the large area basically flat.
Seal the pores: Compact the surface layer to lay a solid foundation for subsequent fine grinding.
Entry timing (first disc operation) :
Concrete condition: When a person stands on it, it sinks by 3 to 5 millimeters, with clear footprints but no obvious overflow of slurry water. This is the critical point of "initial condensation".
Test method: The same as the finger pressure method and scratch method mentioned above. This is the signal for the first entry of the power trowel machine.
Key points of operation
Installation disc: Ensure that the power trowel machine is equipped with a plastic or magnesium alloy power trowel disc.
Blade Angle: Adjust the power trowel blade (even if not in use) or keep the chassis parallel to the ground.
Operation mode
Start the machine and slowly cut into the concrete area at an Angle.
Operate along an overlapping route to ensure that each path overlaps with the previous one by one-third.
Maintain a slow and steady moving speed to allow the disc sufficient time to knead and lift the slurry.
When encountering uneven areas, you can appropriately increase the rotational speed or stay in the local area for a while longer.
Effect inspection: After rough grinding is completed, the surface should be a uniform and moist layer of cement slurry, without obvious exposed stones, and the large area should be smooth.
Phase Two: Fine grinding – Compaction, Polishing (using a power trowel/blade)
Core objective
Compact the surface layer: Further enhance the surface density and strength.
Final leveling and smoothing: Eliminate the fine scratches left by the disc to achieve the designed flatness and smoothness.
Surface sealing: Seal the surface capillary pores to enhance wear resistance, impermeability and dust resistance.
Entry timing (first blade operation) :
Concrete condition: This is the most crucial judgment throughout the entire process. After completing the first disc operation, it is necessary to wait for the concrete to continue hardening. When the following phenomena occur, it can be switched to blade:
Surface moisture disappearance: The previously moist and reflective surface layer has become dull and lackluster.
When people walk on it, they leave only very shallow marks or no footprints at all.
When touched by hand, there is a distinct sense of resistance (roughness), but it does not stick to the slurry.
In simple terms: When the surface of the concrete changes from "wet bright" to "dry dark" and has a certain load-bearing capacity.
Key points of operation
Switch the power trowel: Remove the disc and install the metal power trowel (blade). Make sure the blade is installed flat.
Adjust the Angle: For the final finishing, you can slightly lift the tail of the power trowel to form a small Angle (about 5°) between the front edge of the blade and the ground. This will achieve a better shearing and calendering effect.
Operation mode
Cross-operation methods (for example, one horizontal pass and one vertical pass) can be adopted to ensure flatness.
Increase the machine's rotational speed appropriately and speed up the lateral movement.
Perform multiple rounds of polishing, each lighter and faster than the previous one, with the aim of "flattening" the surface.
Final polishing: Before the concrete is about to set, a final fine polishing is carried out. At this time, the best bright effect can be achieved.
Summary of the switching timing between the grinding disc and the power trowel of a power trowel machine
For a more intuitive understanding, we can summarize the switching timing as follows:
| Component | Homework stage | Core role | Judgment of switching timing (Key signal) | Description of concrete state |
| Grinding plate/disc | Rough grinding | Slurry extraction and initial leveling | First entry: The concrete reaches initial setting. | "Wet soft and malleable" |
| Subsequent disc operation: When the surface is damaged due to operation and slurry needs to be lifted again. | • The footprint depth is 3 to 5mm | |||
| • Scratches can be maintained | ||||
| • No free bleeding | ||||
| Spatula/blade | Fine grinding | Compact and finally smooth | The first switch: After rough grinding, the moisture on the surface of the concrete evaporates and its hardness increases. | "Dry, dark, tough and astringent" |
| • The surface water luster disappears | ||||
| • The footprints are extremely shallow or non-existent | ||||
| • It feels rough when touched and is not sticky to the hand |
Important Notes:
Dynamic adjustment: This process is not static. If, after the first blade operation, it is found that the surface is not hard enough and "waves" or "blade marks" appear, it indicates that the switch was made too early. The disc should be switched back or wait further. If the switch is too late and the surface has hardened, it will not be able to effectively collect light and is prone to surface cracking.
Environmental sensitivity: Temperature, wind speed and humidity can greatly affect the time Windows of each stage. In summer, on sunny days, the window period is very short and needs to be closely connected. In winter or humid environments, a long wait is required.
The "Better late than early" principle: When it comes to the timing of switching blades, it is better to do it a little later (as long as it can still produce luster) than too early. Switching too early will tear the surface, causing irreparable damage.
Summarize the process chain
Pouring → Leveling → standing (waiting for initial setting) → Rough grinding of [disc] (lifting slurry) → Waiting (surface dries and darkens) → Fine grinding of [blade] (finishing) → curing
Mastering this process and timing judgment proficiently is an essential skill for producing high-quality concrete floors.
Note: The parameters provided in this document are for reference only and are not mandatory. Due to differences in technical characteristics between different brands and models of laser levelers, please consult the manufacturer for a suitable solution before actual operation. This reference document assumes no responsibility for any issues arising from failure to follow the manufacturer's instructions.
Thanks to All the Friends Who Support and Trust Shandong Vanse Machinery Technology Co., Ltd.
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About the Author: Shandong Vanse Machinery Technology Co., Ltd.
Shandong Vanse Machinery Technology Co., Ltd. is a high-tech manufacturer specializing in concrete construction machinery, including laser screeds and related equipment. The company integrates R&D, production, and global sales, with products exported to over 60 countries and widely used in infrastructure projects worldwide.
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