[spikels]

Don't forget the sand, which is technically an aggregate[1]. Using the wrong sand is a classic mistake being rediscovered in China:

http://www.wired.com/2013/03/poor-quality-chinese-concrete-c...

[1]-The concrete recipes I remember always had sand and rocks, gravel and/or pebbles (depending on local availability)

[jacquesm]

Yes, you want coarsely crushed ('sharp') sand, not sand that has better decorative qualities.