Hi Can any help me . I want to put a trench in and fill it with concrete/cement but unsure how much . Measurement are as follows. Length roughly 9 m by 30/40 cm wide by 30/40 cm deep. Have used a ready mix mix site for concrete and they only do 1 cubic metres. I want o know how many bags of concrete and sand would I need and also what would be better Ballast or sand. Hope some one can help me.