Hehe, the French sentence is slightly ambiguous here. (de la matière à broyer could mean some stuff which you use to grind something else).
But basically I guess the second translation (to be ground) is correct.
Not being a native, I can't be dead cert, though.
EDIT : I've found 707 google hits for "material to be ground" which is a fairly good result for such a precise wording.
Sentence #1 : here, I think to grind and to be ground would be interchangeable
Sentence #2 : Very different as you can see and of course, you couldn't use "to be ground" there. (the first "hard material" obvioulsy has an active function)
I agree with Benjy that 'to be ground' is better, although both are possible. I think with 'to grind' the emphasis is on the grinding, as if that is the objective in itself, whereas 'to be ground' suggests that the grinding is just a means to an end.
1 ton of material to be ground
1 ton of material to grind (but with the distinction mentioned above)
The ton of material is to be ground
The ton of material is to grind (because the material is not doing the grinding)