A concrete trowel is a tool used to smooth and finish the surface of concrete slabs, creating a flat, dense, and durable finish. There are different types, including manual hand trowels and power trowels, but their fundamental purpose is the same: to refine the concrete surface after it has been placed and screeded.
The Finishing Process: Floating and Finishing
The process performed by concrete trowels, particularly power trowels, involves distinct steps to achieve the desired surface quality. Based on how power trowels work, the process can be described through two key stages:
1. Floating
Floating is the initial stage of the troweling process. This step is crucial for preparing the surface for final finishing.
- Purpose: The primary goals of floating are to remove any humps or high spots left after screeding, fill in any low spots or valleys, and further embed aggregate particles beneath the surface.
- Action: During the floating process, the trowel blades or floats essentially "float" over the semi-wet concrete, leveling imperfections and bringing "fat" (cement paste and fine sand) to the surface. This action also helps to compact the concrete slightly near the surface.
- Result: This stage leaves the concrete surface relatively flat but still with a slightly rough texture.
2. Finishing (Burnishing)
Finishing, sometimes referred to as burnishing, is the subsequent step that refines the surface texture.
- Purpose: The aim of finishing is to create a smooth, hard, and dense "skin" on the top of the concrete slab.
- Action: For power trowels, this involves adjusting the angle of the rotating blades to apply pressure and smooth the surface. The action polishes or "burnishes" the concrete, closing up pores and creating a durable finish. Manual trowels achieve this through repeated passes with a smooth, flat blade.
- Result: This step results in the characteristic smooth, finished look of concrete floors and slabs. The degree of smoothness depends on the number of passes and the timing relative to the concrete's setting.
In summary, power trowels flatten concrete through a floating and finishing process. The first step is to "float" wet concrete by removing humps and filling valleys while compacting the material at the same time. The second step is to create a smooth, hard skin by burnishing the top of the slab.
Manual hand trowels perform similar actions but are smaller and require significant manual effort, typically used for edges, corners, or smaller areas where a power trowel cannot reach. Both types of tools are essential for producing high-quality concrete finishes.
