When evaluating a floor leveling machine, amateurs look at the engine; veterans look at the blade. The board itself is the only part of the machine that actually touches the concrete, and its material science dictates the quality of your floor. The two dominant materials in the industry are extruded aluminum and extruded magnesium.
Aluminum is cheaper and widely available, but in my field testing, it has distinct drawbacks. Wet concrete is highly alkaline and has a chemical reaction with raw aluminum, causing it to oxidize rapidly and stick to the concrete. It can drag the surface, pulling up small aggregates and leaving a rough, torn finish.
This is why professional-grade screed blades are crafted from magnesium alloys. Magnesium is lighter than aluminum, incredibly rigid, and crucially, it does not chemically react with the cement paste. When I run a magnesium blade across a slab, it glides smoothly, almost self-lubricating on the bleed water and cream. The profile of the blade is also critical. Look closely at a high-end blade, and you'll see it’s not just a flat piece of metal. It usually has a rounded leading edge to knock down the rock, a flat bottom to smooth the surface, and an angled trailing edge to slice off the excess. Understanding the metallurgy of your blade is the secret to a tear-free strike-off.
