Sanding back some high spots - Self levelling cement

[powerbuff]

Hi there - I poured this the other day but I was short by 1 bag. So it started setting before I got the other bag in.

When I added the rest it has set higher in one area by abut 3mm. Could I sand the build up slightly to get it relatively level.

I am going to be putting down floating floors.

I there any quick way besides concrete grinding? Id on't have to take too much off..it is reasonably ok.

Thanks

[powerbuff]

Could I use an angle grinder on it to just knock off some of the higher areas?

Thanks