I am currently working with a recruiter who has successfully got me to the next level with a perspective construction employer. My question is - Who negotiates salary? Can I negotiate on my own behalf or does the recruiter handle that?

It depends upon a couple of things. The best way to answer this question is to simply ask the recruiter. If you feel comfortable negotiating, let him/her know and take it from there. If you do not and want to get the recruiter to do this- that is fine also.
Make sure that you are clear on what it is that you are wanting so there is no miscommunication. Sometimes it is better to keep the middle man out and do it yourself.