SCREEDING

SIMILAR AND NOTEWORTHY FORMING EARLY FINISHING VIBRATION

Role of Screeding also known as "STRIKE OFF"

Screeding is a crucial step in the process of pouring concrete that ensures the surface is level, smooth, and at the correct elevation. It's performed right after the concrete is poured and before it starts to set. Here's a breakdown of its role, common methods, tools used, and some practical tips:

Purpose:

• Leveling the surface: Screeding removes excess concrete and fills in low spots.
• Setting the grade/elevation: It ensures the slab is poured to the correct thickness and slope.
• Prepares for finishing: A properly screeded surface allows for easier and more effective troweling and finishing.

Methods of Screeding

1. Manual Screeding (Straightedge Screeding)

• A long, straight board (often a 2x4 or aluminum bar) is dragged across the surface.
• Usually requires two people – one on each end.
• Ideal for small to medium slabs (e.g., patios, sidewalks).

2. Roller Screeding

• Uses a large, rotating tube that spins as it is pulled across the surface.
• Provides a flatter surface with less effort.
• Great for large slabs and projects requiring high flatness.

3. Vibratory Screeding

• A motorized screed board that vibrates to help consolidate and level the concrete.
• Improves compaction and reduces air pockets.
• Common in commercial or industrial applications.

4. Laser Screeding

• Uses lasers and automated machinery to achieve ultra-flat and level surfaces.
• Best for large-scale, high-precision jobs like warehouses or commercial floors.
• Very efficient but expensive and requires trained operators.

Tools Used in Screeding

1. Screed board or straightedge Used to manually level concrete across the formwork. Typically a long, straight 2x4 or aluminum bar.
2. Magnesium float Used after screeding to further smooth and level the surface. Helps push down aggregate and bring cream (fine cement paste) to the top.
3. Bull float A wider float with a long handle that allows you to smooth the surface further out from the edge. Useful for larger slabs.
4. Vibratory screed A motorized tool that vibrates while being pulled across the concrete. Helps compact and level the concrete more efficiently.
5. Laser screed An advanced machine that uses laser-guided systems for precise, automated screeding. Common in large-scale commercial or industrial projects.
6. Knee boards (for hand work) Flat boards worn or used under the knees to allow workers to move across the concrete without damaging the surface.

Tricks and Tips

• Use guide rails or screed pipes set to the desired height for consistent leveling.
• Work in sections and always pull from one end to the other in a steady, sawing motion.
• Don’t overwork the concrete — it brings too much water to the surface, weakening the slab.
• Screed immediately after pouring, before the concrete begins to stiffen.
• Keep tools clean and free of concrete buildup during the job.