Why does my concrete not look smooth
The back and forth motion of the screed or float shakes the aggregates and makes the fine ones rise and the big ones sink, which gives a smooth surface. But the concrete has to be more liquid than what you did for that to happen. Then after screeding, before it hardens completely, spray some water on it and finish it with a float.
However if you put too much water in it, you'll have problems, like cracks. So you have to either get the water content &quot;just right&quot; or add some plasticizer which makes it fluid without extra water. You can also vibrate it, but that requires a special tool.
If you intend to tile this, then the rough surface is not a problem. It looks pretty good actually, since if the concrete will be covered, no need to bother with the extra work of making it smooth, all you need is to not have bumps. Tiles will cover roughness and holes just fine. If some aggregates stick out and the tiles stand on them, just smash the aggregates out of the concrete with a hammer.
If you intend to leave it visible, then you can spread a bit of mortar made with fine sand, or self-leveling, to make it smooth if you want.