Conference 7.286::home_work

    I'm interested in replacing my existing 20' flagstone front walk with 
    a concrete walk. In particular, I want to use a type of concrete I've 
    seen used at a local playground, where the surface includes small,
    smooth exposed stones. However, I've got some questions:
    	
    	- what's the common name for this type of concrete?
    	- can it be mixed DIY, or should I call the local concrete company?
    	- what's the technique for installation? Any special tools needed?
    	- any idea of what the cost/yd would be? 
    
    The past few winters have taken their toll on the existing walk, and the 
    mortar between the stones has crumbled to the point where the stones are 
    loose and (some) have cracked. I had considered re-laying them in another 
    bed of mortar and have begin removing them completely in order to begin 
    prep work. What I've found underneath them, however, is a concrete slab 
    in relatively good condition, which I think would provide an excellent
    base for the type of walk I want to install. Any comments/gotchas for
    installing a different type of concrete over a pre-existing slab?
    
    Thanks in advance for the advice. 
    
    PS...I still don't understand why the string of "sidewalk" notes is
    in the "Shed" topic. Since the last 100+ replies have dealt with
    various types of sidewalks, isn't that sufficient volume to move them
    into their own topic? 
        

    
    628.353 describes the only process I've seen used to do this. 
    
    							- Mac

    re:last
    
    	The note refered to in the last reply is now .108 of this topic.
    
    	Ray

    Hi All,
    
    I am going to put in a poured cement walk finally and need a little
    advice.  I have roughly a 30' stretch to do and what I was think of
    doing is 4 foot sections, 3 inches of cement over a 1 inch bed of stone.
    
    Does this sound like a plan or should I make changes.  ie: Is 3" of
    cement enough????...
    
    Thanks in advance for all advice....
    
    Kevin

    
    the following are the minimums (only my opinion);
    
    1) make sure you excavate all top soil and sub soil; this may be 12" or
       more down.  If less than 14", then dig down 14" anyway unless you
       have a nice sandy/gravelly base below soil level.  If you think so,
       take a jar add a cup of soil, two cups of water, mix and observe --
       if thick and cloudy or it doesn't quickly settle out then you might 
       want to think about doing #2 anyways.
    2) backfill with minimum of 6" clean gravel but leave 7-8" below nominal grade.
       this might not be necessary if your soil is a good sand or gravel
       base already, but where I am there tends to be a bit of clay too)
    3) add 4" of crusher run, rice stone, or one of the stone dust mixtures
       and tamp. (might want to wet - but not soak - the mixture if hand 
       tamping to help it settle .  if so let dry overnight before
       continuing).  Skree level, add more, tamp again until smooth and
       level.  Path grade should now be about 2-3" below surrounding grade.
    4) add 1x skee boards with 1x1 stakes attached to sides of path, drive
       until side to side is level except for desired pitch.  You can either 
       slightly crown the walk or pitch it to one side to aid water
       runoff - 1/8" per foot should be enough.  The walkway should also pitch
       away from house for the first 8-12 feet - again a 1/8" per foot
       should be sufficient.  The top of the 1x should be 1-2" proud of the
       original grade and should result in about a 4" thick pad.  Pour the
       pad in 4' sections with expansion joints between pads.  If poured separately 
       as opposed to using a tool to make the expansion joint groove
       (really a built in stress reliever which is used only if necessary) 
       then fill in expansion joint with flexible grout.  
    
       The results should be a walkway that is just slightly proud of the 
       surrounding grade so that water runs off rather than into the walk.
       I find it easier to add dirt surrounding a walk and grading out an 
       additional inch or two if the walkway is a little high than it is
       to remove grade so that water doesn't collect.
    
    In my opinion, you'll want a good compressed based just below the pads,
    otherwise water will collect in the air gaps and freeze/expand in the
    winter.  The key here is that it will be freezing/expanding unevenly
    and more than the surrounding grade which will result in trouble.  All
    pathways are subject to freeze/expand/thaw effects unless you're
    pouring all the way down below frost level (4' around here in NH).  You'll 
    want to minimize the air gaps available to collect water so that the 
    walkway aborbs the same or less water than the surrounding grade.  This way 
    any expansion due to freezing will be uniform.  Using a uniform stone, 
    such as 3/4" crushed stone, won't compact as well as a mix like crusher 
    run (which has everything from stone dust to roughly 1" aggregate).
    

    Kevin....
    
    	I'd put down about 2-3 inches of crushed stone for drainage, then I'd
    put rebar(1/2 inch steel rods) in a 12 inch grid pattern elevated an
    inch above the stone.  Tie the rebar together where it crosses using 
    bailing wire and then cover everything with 3-4 inches of concrete.  
	This is a lot of work, put it's worth it.  The rebar will add alot
    of strength to a long thin slab of concrete.  Over time, frost heaves
    and settling will cause the concrete to try to buckle.  Unfortunately,
    concrete doesn't bend, it cracks.  The rebar and thicker concrete will
    add the necessary strength to help your concrete walkway last for many 
    years without cracking.
    	Also, wait at least 1 full year for the concrete to cure before
    applying a sealer to the concrete(Thompson water seal works for me) and
    DO NOT use any kind of ice melter until after you seal the concrete or
    the ice melter will cause discoloration and spalling of the concrete.
    
    		regards
    		Bob 
    

>    	Also, wait at least 1 full year for the concrete to cure before
>    applying a sealer to the concrete(Thompson water seal works for me) and

    Many of the concrete experts (and the sealers themselves)
    recommend sealing the slab right away. The sealer bonds into the
    surface of the concrete and also slows the curing time so that you
    end up with a stronger slab.

    BTW... "right away" means as soon as you can gently walk on the
    surface without leaving any marks. This is usually within hours of
    the final finishing of the slab.

    Charly