In cement concrete pavement construction, except for some high-grade highways that use large paver machines, most general roads, municipal streets, and various types of plazas are constructed with roller-type leveling machines or vibrating beam systems combined with insert vibrators and floor power trowels. These systems are compact, cost-effective, and flexible for construction, especially given the constraints of project scale, construction site conditions, and economic factors. The initial investment in mechanical equipment is low, and operational costs are minimized, making it an efficient choice.
These tools provide flexibility in construction while ensuring that the quality of the pavement meets the standards of different road grades. Using power trowels instead of manual smoothing significantly improves work efficiency, often increasing the speed of construction by 8 to 10 times. As a result, power trowels have become essential equipment in most cement concrete projects.
1. Functions and Types of Power Trowels
Power trowels are primarily used for leveling, smoothing, and polishing the surface of cement concrete. They can be classified into two main types based on their working mechanism: disc-type power trowels and blade-type power trowels. The blade-type power trowels can further be divided into single-head and double-head models. Additionally, these machines are available in two power types: electric and internal combustion.
- Disc-type power trowels are mainly used for leveling the concrete surface, while blade-type power trowels are typically employed in the later stages of construction to smooth the surface. Blade-type power trowels offer better construction quality and higher efficiency.
2. Blade-type Power Trowels: A Global Perspective
In developed countries, blade-type power trowels have been widely used, while in China, their application is still in the early stages. Most construction units in China still rely on electric disc-type power trowels for initial leveling, followed by manual polishing. This method limits both efficiency and the quality of the surface.
Some of the most recognized manufacturers of blade-type power trowels globally include:
- Canada: Betta
- USA: MBW
- Germany: Wacker
- Japan: Daikyo, Mikasa
These companies offer a variety of power trowel models, including hand-push, single-head power trowels, and riding, double-head power trowels. The blade angle is adjustable, with the blade diameter generally ranging from 600mm to 1200mm. These machines are powered by either two-stroke or four-stroke gasoline engines.
In contrast, most domestic power trowels in China are powered by electric motors and are disc-type, meaning they are only suitable for leveling and not for polishing. Only a few manufacturers produce small, double-head, blade-type power trowels, but these have non-adjustable blades and are generally limited to small-scale applications.
As a result, most cement concrete pavements in China are still finished manually, which leads to lower efficiency, reduced strength, and poorer surface flatness. Furthermore, since blade-type power trowels are still not widely produced domestically, some companies have to import them, which is costly and can lead to difficulties in sourcing spare parts. This, in turn, has hindered the broader adoption of blade-type power trowels in China.
3. Internal Combustion Blade-type Power Trowels
Internal combustion blade-type power trowels are typically powered by gasoline engines and are more commonly used than electric models in larger construction projects. These machines are particularly beneficial for smoothing and finishing cement concrete surfaces.
3.1 Structure of the Internal Combustion Blade-type Power Trowel
The internal combustion blade-type power trowel consists of several key components, as shown in the diagram below:
- Engine: Powers the machine.
- Base Frame: Supports the components.
- Transmission System: Includes a single-stage belt drive and a worm gear reducer.
- Work Mechanism: Contains the blades, linkage system, and adjustment mechanisms.
- Blade Angle Adjustment Mechanism: Allows the angle of the blades to be adjusted between 0° and 10°.
The transmission system typically uses a simple, reliable worm gear reducer, and the casing is equipped with heat dissipation fins to improve cooling performance. A centrifugal clutch is mounted on the engine output shaft to automatically engage when the engine reaches a certain speed, enabling the power trowel to begin operation.
The blade mechanism consists of four blades arranged in a radial pattern, and these blades can be adjusted for optimal performance during leveling and polishing. The angle of the blades is adjusted using a handwheel at the top of the handle, which controls a screw mechanism that adjusts the blade’s angle via a cable and lever system.
3.2 Technical Specifications of Blade-type Power Trowels
Let’s take the Model 800 Blade-type Power Trowel, which is one of the most commonly used models globally, as an example. Its key technical specifications are as follows:
- Number of Blades: 4
- Blade Diameter: 800mm
- Blade Rotation Speed: 50-70 RPM
- Blade Angle Adjustment: 0° ~ 10°
- Engine Power: 4 hp (2.9 kW)
- Weight: 70 kg (154 lbs)
These specifications highlight the machine’s versatility and efficiency, making it suitable for a wide range of cement concrete paving applications.