Understand the key construction points of concrete placement and their effect on the concrete surface. This will improve the quality control of concrete projects. The 3 topics are described in the order of finish - curing - proportioning, and their effects on concrete placement.
Finishing
Spatula finishing point
Nowadays, most of the concrete ground finish with a smoothing machine to deal with, the corner part of the trowel by workers to take light. Broadly speaking, the smear machine is mainly divided into 2 kinds.
1. Hand-held wipers
2. Ride-on wipers
A hand-held smoothing machine is the most commonly used. The blades of the smear machine are slightly tilted and rotate in a clockwise direction, like a ceiling fan.
The ride-on smear consists of two reverse-rotating blade heads, surrounded by a steel cage. The engine and the driver's seat are also included. The counter-rotating force allows the operator to control the direction. As one head accelerates, the wipers rotate in the corresponding direction. A skilled operator can take full advantage of this rotational force by approaching pipes, corners and wall edges and treating the concrete surface around these areas.
Concrete harvesting is a very important step and usually requires specialized equipment to carry out this process. If you want to learn about these specialized equipment, check out: Hiking power trowel introduce
The tilted blade, as the blade head rotates, presses the sandy aggregate on the concrete surface downward, while lifting the mortar located between the aggregates upward. When this process is completed, the surface mortar thickness is approximately 1/8 inch (0.3 cm). Initially, the surface of the concrete is open and porous. As the concrete sets, it is necessary to resurface the surface to compact the mortar and encourage it to form a dense surface layer.
The open pores of the concrete are nicknamed "furry" concrete by people in the industry. This finish is not good for polished or other decorative concrete. Moisture can enter the concrete through the pores and affect the staining or tinting process later. The edges of the concrete pores can be damaged during the grinding process and the concrete is not grindable if left unrepaired. After the concrete has been compacted and hardened, it requires additional light harvesting to increase friction. The heat generated during the light harvesting process melts the small particles in the surface grit, making it a glassy material. In addition, the Portland cement particles in the concrete are scorched and turn from dark grey to black. This process is called "burning" of the surface. The result is a tight surface that has a glass-like sheen to it. However, don't be fooled by this shine, as the concrete surface quickly begins to wear away after a period of time.
Find the best spot to finish!
Concrete used for polishing or decorative effects has an optimum finish point between the "shaggy" and "burnt" states. This is when the concrete is sufficiently tight, but the surface has not yet formed a glassy deposit. The concrete can only be compacted by troweling, and the tighter the surface, the better it is for polishing.
For example, it is much easier to polish solid, tight granite than it is to grind porous, rough limestone or pumice. So the tighter the concrete surface, the better the polish and the better the function of the surface. In other words, burnished surfaces are highly unsuitable for polished concrete floors. The glassy finish is unsuitable for grinding because its smooth texture prevents the blade from cutting the concrete surface. Generally, it is necessary to treat the surface with a low number of abrasive pads before cutting into the already burnished surface. This extra step adds time and material costs to the contractor, which is more than worth it in the long run. When talking to the team, I told them, "The ideal finish should be controlled to make the surface as tight as possible, but before the scorch marks appear. But that's only ideal, so I'd rather the crew tighten the surface a bit to avoid leaving too many holes. By discussing the above issues with the concrete pouring contractor, you can effectively lay the groundwork for a later interior decorative concrete floor (polished/stained/acid tinted/self leveling). It is risky to lack communication and leave it entirely up to the builder to handle the project based on their own understanding.
That's why I recommend careful attention and treatment of the above issues as early as possible. If you wait until you are ready to pour the concrete to put the problem on the table, it will be too late, as the contractor will usually have already made his own construction plans based on the requirements of the specifications.