12-27-2025, 02:40 AM
I’m trying to build a large, permanent outdoor chessboard in my backyard using poured concrete slabs for the squares, but I’m running into a major issue with the finish. The scale is 8x8 feet total, with each two-foot square being a separate pour. My budget is tight, around $800 for materials, and I’m doing all the work myself over the next three weekends. The problem is that even using a magnesium float and careful timing, my last two test slabs have a slightly gritty, exposed aggregate texture that catches dirt, while the ones I did earlier came out almost glass-smooth. I’m using the same quick-set concrete mix, a consistent wooden form, and it’s been about 65 degrees and cloudy for all pours. I can’t figure out why the finish is so inconsistent, and I need a perfectly flat, cleanable surface for the playing squares before I even think about sealing or painting them.