Good morning Mr. Rahman, I would not recommend the use of the SDS paint mixer paddle for your application. The stones in the ballast are like to get caught in the blade, but more importantly you would mix too much air into your concrete mix that could result in voids. For small amounts such as trug loads, I would use a small shovel such as our lightweight 28 inch U1860 with a fibreglass handle to mix the concrete or alternatively consider buying small bags of pre-mixed concrete with smaller sized aggregate [stones] and just add water or even tubs of quick setting patching concrete that you mix in the tub. I trust that this helps?