# Concrete sidewalk question



## kennyp2339 (May 8, 2016)

I'm pouring a new sidewalk from the driveway to my front porch, total length is about 50ft, I'm basically following the old sidewalks path (replacing because it was narrow at 30" wide, plus the grade has changed since I built my retaining wall and the sidewalk is below the height of my top step.
So my question is, since I'm pouring a new one considerably wider at 48" should I add rebar for strength to prevent cracking? or will the concrete with fibers be enough strength.


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## gzecc (May 8, 2016)

How thick will your pour be?


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## kennyp2339 (May 8, 2016)

Majority is 4" some a little thicker, w/ 3/4 crushed tamped base


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## kennyp2339 (May 8, 2016)

That's what I'm working with, when I do the pour I want about 3/4" to an inch above existing grade


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## NateB (May 8, 2016)

Here is a great discussion on Frost heave with Professor Dick Hill.  Wish I would have watched it before I poured.


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## kennyp2339 (May 8, 2016)

I have seen other videos with dick hill, he is an awesome and extremely intelligent man, I think things are worse in Maine though, I'm south in the northern NJ, is I have a good stone bed I shouldn't have any problems with heaving, the old sidewalk was 3.5 inches depth with what I would call a crap base and it stayed true with no cracks, I'm just worried about going with a larger surface area, but bow not so much, the concrete I'm going to get will be 3500psi with fibers mixed in for strength


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## kennyp2339 (May 8, 2016)

I'll post better pics after I frame my forms out, I'm picking up plywood and stakes tomorrow after work


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## claydogg84 (May 8, 2016)

You could use the wire instead of rebar.


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## Buzz Saw (May 8, 2016)

4" with fiber is all you need.  I poured a 85' long, 60" wide, 4" thick sidewalk 9 years ago and it hasn't cracker or heaved.  I've driven my 7500# truck over it numerous times and no problems.  I do think we used 4,000psi(that's standard here) concrete with fiber.


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## peakbagger (May 8, 2016)

It pretty rare to see concrete get poured in Northern New England for sidewalks or roads. Frost raises havoc and deicing salt eats it up. Maine had an interstate highway that was paved in concrete and several years ago, they shut it down, ripped out all the concrete and repaved it with asphalt paving.  Wire mesh keeps the chunks together when it inevitably cracks somewhat better than fiber reinforcement.


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## gzecc (May 8, 2016)

For a sidewalk don't waste your time with wire or steel. Not necessary..


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## greg13 (May 8, 2016)

For the extra money, it's too easy to to add it now and have peace of mind. I have never heard anyone say "I wish I hadn't over built this"


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## Buzz Saw (May 8, 2016)

greg13 said:


> For the extra money, it's too easy to to add it now and have peace of mind. I have never heard anyone say "I wish I hadn't over built this"


Until you(or more likely your wife ) decide to change thingd around and you have rip out your over built project. [emoji12]


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## jeffesonm (May 8, 2016)

I need to do one of these soon... looking forward to seeing your progress.


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## aussiedog3 (May 9, 2016)

Fibers don't add strength but will hold it together when it cracks.  Keep the slump low and use limestone aggregate if available.

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## iron (May 9, 2016)

i am not familiar with sidewalk design, but i am a structural engineer and i know for 60ksi rebar (or mesh), you need a ratio of steel:concrete area of 0.0018
http://www.engineersdaily.com/2011/04/shrinkage-and-temperature-reinforcement.html

so, if your concrete cross section is 1000 square inches, you would need 1.8 square inches of steel. 

this is called temperature steel. it prevents cracking that occurs from normal temperature swings. using a mesh would be your better bet IMO since you'll likely get more, small bars to better distribute over the area of your sidewalk. you'll also, as a byproduct, get crack protection in the short direction of the sidewalk using mesh.


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## greg13 (May 9, 2016)

Buzz Saw said:


> Until you(or more likely your wife ) decide to change thingd around and you have rip out your over built project. [emoji12]



I can honestly say that I have never had that problem with my wife.


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## firefighterjake (May 9, 2016)

Buzz Saw said:


> Until you(or more likely your wife ) decide to change thingd around and you have rip out your over built project. [emoji12]



Hehheh ... usually it's me and I end up cursing myself for over building.


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## Tracks74 (May 10, 2016)

If you will be driving vehicles across any portion of the sidewalk, increase the depth and add wire or rebar. If it will only serve foot traffic, no wire or rebar is needed.
The fiber mesh reinforcement comes in numerous styles and strengths, so that is difficult to say if it will add much reinforcement.
Of note, the fibers make the finish work more difficult and can make the end result look "fuzzy". Some people don't like that look, especially for interior floor work, like a Costco or Home Depot construction.


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## sportbikerider78 (May 10, 2016)

greg13 said:


> I can honestly say that I have never had that problem with my wife.


Same here.  Mine is just happy that i'm always making things 'better' around the house.  Perfection is something psychos can pursue.  I have a life.


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## peakbagger (May 10, 2016)

I used fiber on my garage years ago, I wouldn't do it again as the area under where my car parks is really deteriorating. I looks like the fibers allow the road salt and other nasties to wick into the concrete.


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## Buzz Saw (May 10, 2016)

peakbagger said:


> I used fiber on my garage years ago, I wouldn't do it again as the area under where my car parks is really deteriorating. I looks like the fibers allow the road salt and other nasties to wick into the concrete.


Did you seal the concrete originally?  Any periodic maintenance sealing?  Road salt will eat up any concrete given enough time.  At my old place the garage floor was pitted from salty cars parking there for 25 years.  No fiber in the concrete either.


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## peakbagger (May 10, 2016)

I did seal the floor originally and am quite familiar with damage from salt, the fiber just seemed to accelerate it.

On the long term list is reslope  the floor as it was originally built with no slope (despite my request to do so). I will probably end up using an epoxy system and that should stop the deterioration.


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## Tracks74 (May 10, 2016)

Fiber for concrete reinforcement is made of different materials. Propex is the largest manufacturer in the U.S. Fibers can be polypropylene, fiberglass, or even crimped steel.
The right mix of fibers can fully replace the need for rebar, but it has to be engineered correctly. 
For this application, fibers are not necessary, but would help. A solid stone base and added depth of 8" where any vehicles may drive is more important than fibers or mesh / rebar.


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## Seasoned Oak (May 10, 2016)

Make sure you cut expansion lines about every 4 to 6 ft, because no matter what you do,that sidewalk will crack.every so many feet.  The idea is to have it crack below the expansion cuts so you will never notice it. I caulk those expansion cuts to keep water out that can freeze and push the sections apart. 4" may be OK if you will  never drive across it. if you do id make it 6 and at least use wire mesh if not rebar.
Make those cuts within 48 hours of the pour,you can use an old skil saw with a diamond blade. Make it about 20 to 25% of the thickness of the slab 1"deep or so.


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## Seasoned Oak (May 10, 2016)

ALso i Never, never, never use any kind of salt or ice melt. There are alternatives sand is one, or sawdust, keeping the ice and snow cleaned off. 
Any kind of ice melt is damaging to concrete,no matter what is says on the bag.


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