How to pebble concrete sidewalk

Reply

  #1  
Old 11-22-13, 10:56 PM
Member
Thread Starter
Join Date: Jun 2013
Posts: 32
Received 0 Votes on 0 Posts
How to pebble concrete sidewalk

I need to add a section of concrete on the existing side of a walk and the existing concrete is pebbled. I already tried this once and after the stones wouldn't stick real well I think I did it wrong. Before I take a sledge to the stuff I just poured can someone help me on the finer points of adding the pebbles? its about 2' by 8' FWIW
 
Sponsored Links
  #2  
Old 11-23-13, 08:37 AM
czizzi's Avatar
Member
Join Date: Jul 2007
Location: USA
Posts: 7,376
Received 9 Votes on 7 Posts
I don't do concrete, but have a buddy that owns a concrete/driveway business. You don't get exposed aggregate by sprinkling stone on the wet cement. Instead, concrete is spread as normal and a substance is sprayed onto the wet concrete that prevents the top most layer of concrete from curing. The next day, you take a hose and wash away the uncured top layer exposing the stone aggregate.
 
  #3  
Old 11-23-13, 08:46 AM
Banned. Rule And/Or Policy Violation
Join Date: Apr 2013
Location: USA
Posts: 4,297
Received 0 Votes on 0 Posts
I think you missed the part about how the stone comes mixed into the concrete, not just laid on top of it.
 
  #4  
Old 11-23-13, 10:25 AM
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 46,181
Received 132 Votes on 118 Posts
Besides the exposed washed stone method that Z described, there is Chattahoochee rock [at least that was what is was called in fla] While I've sealed a mile or two of it, I've never laid any. I think it's laid on top of the concrete, maybe with some type of epoxy.
 
  #5  
Old 11-23-13, 03:40 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 0 Votes on 0 Posts
I've poured a bit of exposed aggregate concrete in the last 40+ years, and inspected a lot more of it being placed by commercial/government contractors. Sam, as I explained in your other post on what to do with your loose pebbles, I've never used a retarder on the surface to delay initial set from taking place there, but rather have simply waited an appropriate length of time for the concrete to take its initial set before starting the brooming/hosing operation. Timing is everything, and your mistake was probably not waiting long enough for the matrix in the mix to be "grabbed" by the hydrating cement particles. It also helps to use just a light, fan-like spray of water before street-brooming with firm pressure to pull the surface mortar away from around the visible aggregate. Follow the brooming with more lightly-sprayed water, to move the now creamy mortar off of the surface. You should be able to stand on the fresh concrete before starting the process; sooner than that, and you stand a good chance of breaking loose the stones. Surface retarders are often specified and used on larger, commercial operations, but rarely are they needed (or practical) for small residential placements like yours. Several days after placement, a thorough hosing/washing with a very dilute muriatic acid solution removes any remaining cement and mortar from the exposed rocks, followed by application of a good sealer.

Contrary to what others have said, one can easily surface broadcast colored aggregate into the freshly struck-off concrete, then float the rocks into the mix to get them embedded. They are usually a manufactured product, available in 50 or 60-lb. bags. I've used several different colors and sizes of aggregate for same, usually various earth-tones but also including turquoise-colored stones for jobs where a popular theme is SW Native American culture.
 
  #6  
Old 11-24-13, 08:32 PM
Member
Thread Starter
Join Date: Jun 2013
Posts: 32
Received 0 Votes on 0 Posts
Thanks everyone for the replies - this is one of those things that seems to be hard to find information on so it helps a rookie out like me.

BridgeMan45 - I think your method seems the most appropriate for what I'm trying to do. I used bags of Pea Gravel the first time around and the color and size seem to match up really well with what's there already. I think I went wrong in not using the sweep method you describe - I just thought if I got them a bit in there they would stick but I think that was not so bright...

Any other tips that you can think of? I plan on using a 2x4 form and pouring the concrete to the same level as the existing concrete, adding the pea gravel and then following your method of waiting until its firm enough to step on and 'wet sweeping' the surface away to show the stones. I am adding a expansion strip in between the two slabs and I am using the fiber-added concrete. Any other pro tips would be amazing...
 
  #7  
Old 11-24-13, 08:37 PM
Member
Thread Starter
Join Date: Jun 2013
Posts: 32
Received 0 Votes on 0 Posts
One other thing

Would you recommend adding the aggregate to the surface after pouring or adding it to the mixer as I go. I ran across an article just now about something called the monolithic technique that instructs to add the pea gravel to the mix as I go...

Not sure how much to add just yet...
 
  #8  
Old 11-24-13, 11:15 PM
BridgeMan45's Avatar
Member
Join Date: Oct 2011
Location: USA
Posts: 3,196
Received 0 Votes on 0 Posts
If the existing slab that you're trying to match has lots of closely-spaced, exposed stones, you would do best by broadcasting the pea gravel right after you've struck off the placement. Then float all the stones in until they're no longer visible. Then walk away from it, and go in the house and read a book or something. Don't touch anything until well after the bleed water is all gone, especially with the current cooler temperatures (increasing initial set time considerably)--sooner than that and you'll run the risk of stones breaking loose again. Conversely, if the existing slab that you're trying to match has just a moderate amount of exposed pea gravel visible, with a lot of mortar in between the rocks, then you probably wouldn't have to do any surface broadcasting, but rather could just rely on the normal distribution of pea gravel that you add to the mix while you're batching it. You might want to set your forms just a tad higher than the adjacent slab (no more than 1/4"), to compensate for the amount of material you'll be brooming off. I'd skip the fibers in the mix, as they aren't really necessary for your small slab, and could become more visible than you want when exposing the aggregate.

Overloading a mix with pea gravel will tend to weaken it, for several reasons. Typical pea gravel doesn't have enough fractured faces in the aggregate particles to lock in with each other and coarser sand particles, but rather the stones are mostly round and smooth. Also, the rock itself is often considerably softer and less durable than conventional quarried limestone or other aggregates are. Harder gradations are available, at extra cost, if durability of an exposed aggregate surface is a requirement--such as most commercial applications, as opposed to typical light-traffic residential uses.
 
  #9  
Old 12-05-13, 09:16 AM
Member
Join Date: Dec 2013
Location: usa
Posts: 1,334
Received 0 Votes on 0 Posts
well-said - set retarders are a pita to accomplish & unnecessary $$ for a diy'er,,, however, IF you must, 5# of sugar in 5gal of wtr will do the same,,, iirc, ' chattahoochie ' is pebbles embedded in epoxy coating - usually water-based epoxy, its not worth the effort or expense imo as wtr-bas'd epoxies are a larger pita - no longevity & very thin apps
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
 
Ask a Question
Question Title:
Description: