Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Gravel Driveway - Natural 21AA or Crushed Concrete

Gravel Driveway - Natural 21AA or Crushed Concrete

Gravel Driveway - Natural 21AA or Crushed Concrete

I have a gravel drive which has been compacted for 70+ years.  I am going to grade it with a skid steer loader then I want to put down about an additional 4" of 21AA (or 1-1/2" down, Crush and run or whatever they call it in your respective areas).

Is there any issues with using 21AA made from cleaned 1-1/2" concrete.  Crushed concrete 21AA costs about $8/yd and natural costs about $24/yd in my area.  I have heard that the crushed concrete will not be as dusty as natural but less dusty than 21AA made from limestone.

Any thoughts on the material.  Will the crushed concrete absorb moisture and heave when it freezes.  I want to use the concrete 21AA under some brick pavers as well.

Thanks for your help.

Tim Daniel
Electrical Engineer
Dearborn, MI

RE: Gravel Driveway - Natural 21AA or Crushed Concrete

Crushed recycled concrete is not as strong, structuraly, as natural stone.  as a surface for a drive that will see little to no 'heavy' traffic it is suitable.  It will deteriorate over time, and the decrepitation will be faster that the crushed stone product you have mentioned.  The interesting thing I have found is that there is some (slight) cementation action that occures when CRC is compacted with the required water content for good compaction.

RE: Gravel Driveway - Natural 21AA or Crushed Concrete

I'm suprised you are allowed to have a gravel drive in Dearborn.  The CRC will be slightly more permiable than the road rock.  It will make an good base for the pavers.  It should also work well for the drive if compacted properly.  Be sure to grade & compact for cross slope and profile drainage before placing the CRC.  Well compacted road rock will be fine for the drive.  Be sure road rock coarse agg is crushed.  You don't want rounded agg as found in the local morains.  If you use the CRC, be sure to check it closely for rebar and wire mesh shards that will eat your tires

RE: Gravel Driveway - Natural 21AA or Crushed Concrete

I got a variance from the city for the gravel drive.  The house has had a gravel drive for 70 years and is part of the character of the house.  

Since I posted the original question I have completed the grading and CRC placement.  I removed all the topsoil and there was good compacting sand underneath.  The sand was smoothed and graded before placing the CRC.  I put down 4" of 1-1/2" crushed concrete followed by 2" of 21AA Crushed concrete.  We compacted the 1-1/2" CRC as good as possible until the plate compacter shreded a belt.  The bobcat had to go so we placed the 21AA on top of some uncompacted CRC.  I am going to rent another plate compacter this weekend to finish the job.  

When I add pavers, I am going to add 2" of sharp sand and then the pavers.  I heard sharp sand is now recommended under pavers as the slag sand used in the past is pourous and holds water.  In the winter it freezes and heaves. Anyway that's what Unilock told me.  

There was a few pieces of steel but nothing major.  Got the material from Michigan Crushed Concrete and was pretty impressed with the quality of the material.

Time will tell how the driveway holds up.  I put down 32 yds of the CRC and 16 yds of the 21AA.  Glad I didn't have to do that by hand!!!!!


Tim Daniel

RE: Gravel Driveway - Natural 21AA or Crushed Concrete

Provided that you do not disturb the original grade (the 70 + years) too much the CRC will work fine for a driveway.  At $8.00/yard, as with the previous post ensure the metal has been removed and inspect it closely.  If possible, observe the crushing process to ensure the supplier completely removes the steel.

The rubber tire is like a magnet and if there is residual steel in the crush, you will eventually find it in your tire.  

KRS Services

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close