Expert: Bruce E. Johnson - 9/8/2009

Question
QUESTION: Bruce I am getting ready to pour a concrete driveway at my house.
I have removed the old drive way, and placed 4" of # 57 crushed limestone down (3/4 inch stone).

do you think that amount of stone is too much.
I had planned on using fiber reinforced concrete, and NO mesh.
does this sound OK to you ?


ANSWER: Hi Tom, as long as your base is compacted well you should be okay using the fiber mesh concrete.  If you haven't done it already, rent a plate compactor and beat the base good and solid prior to pouring your concrete.  I can't think of any reason why this base would be too thick.  I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION: Bruce
is the compaction absolutely neccesary ?
the ground under the stone is pretty heavy clay, and has been run over numerous times with the skid loader we were using.
the stone will will probably be spread out for more than 2 weeks prior to the pour.
thnaks
Tom

Answer
Hi again Tom, four inches of rock can develop a lot of voids in it.  By compacting the base you eliminate a good majority of those voids.  Is it necessary?  It's just the way I've always done it.  To be honest, I don't always use base rock under my concrete as long as I have a good compacted base.  Of course most of my concrete work is large commercial slabs and driveways that require compaction tests done by engineer testing companies and even my concrete is tested for uniformity, quality and compression.  Getting back to your question, if the base rock was walked in with the skid loader that will probably suffice for a residential driveway.  Depending on where you live and how convenient it is to rent a plate compactor for a couple of hours I'll let you be the judge as to whether compacting your base is worth the trouble.  I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com