In Civil Engineering works, For compaction of free-draining sands or gravels, what is the optimum moisture content to achieve maximum density?

for the free drainage sand and gravel no need for the compaction test. standard proctor test for the soil testing not for the gravel.

I agree with MR WOLF KLAAS & MOHMED.

for answer this question using   standard proctor test ,modified proctor test .

That depends on the type of sand , as stated above you need to do a so called Proctor test to deteremine this

Great answer from Mr. Wolf and all Experts. Thanks for participation.