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#2466422 - 03/14/18 01:43 PM Questions for the Concrete guys - concrete hardener
Dixie Offline
top fuel

Registered: 06/24/08
Posts: 2271
Loc: Ball Ground, Georgia
Hey Guys,

I had a new driveway and parking pad installed approximately 3 yrs. ago. 4,000 PSI with mesh mixed in. I have noticed some hairline cracks in it in the last year. As these cracks seem to multiply, I'm wondering if there is any type of hardener out there that could possibly harden the concrete to reduce this cracking? Or any other option that might reduce the cracking?

On a secondary note, the contractor cut in relief joints with a concrete saw. Those joints collect dirt, water, and seeds! Which yields plants! I was wondering if there was some type of silicon product that could be put in the cracks that would allow for expansion, but keep the dirt/water/plants out?

Just wondering what my options are from you guys that are in this industry.

Thanks!
Randy


Edited by Dixie (03/14/18 01:46 PM)
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#2466454 - 03/14/18 02:18 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
srt Offline


Registered: 01/19/03
Posts: 8902
Loc: Fire and Fury
I remember when you were planning the project and asked questions.
Are the cracks random, how far apart are they. "mesh" iiare you referring to fiberglass?
What did you do about the areas with water?
what structural section did you put in below the concrete (i.e. clear and grub organic soils, compact to 95%)?
did you place and compact base rock (not sand))?
did you incorporate steel (rebar or reinf mesh)?
thickness of slab?
answers to these questions will determine what is failing: base, soil heaving (wet/dry season), concrete mix, seasonal temperature expansion fluctuations.
Driveways can fail in any of those areas.
De-watering sub soils is key, properly sizing "floating" slabs are important, as are proper layout and sizing of expansion joints (not saw kerfs).

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#2466464 - 03/14/18 02:36 PM Re: Questions for the Concrete guys - concrete hardener [Re: srt]
oldjonny Offline
top fuel

Registered: 02/12/07
Posts: 2028
Loc: Michigan
Yea....NO. What you gots is what you gots at this point. 95% of the project is preparation before (i.e. what is under the concrete). You are now going to live with what you have. Me personally never saw any value in the shredded fiberglass stuff. Big fan of wire (legit wire, not the chicken wire junk from Home Depot). Highway mat and 5-1/2" of concrete for me.


Edited by oldjonny (03/14/18 02:38 PM)
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#2466616 - 03/14/18 07:48 PM Re: Questions for the Concrete guys - concrete hardener [Re: oldjonny]
srt Offline


Registered: 01/19/03
Posts: 8902
Loc: Fire and Fury
I agree, but want to mention that some actions will help prolong the concrete.
1) improve surface drainage by grading and installing edge drains.
2) review and improve saw cutting pattern
3) sealants for control joints are a specialty material called elastomers. To use correctly the cracks need to be opened up by routing and the elastomer placed per recommendations. Generally not the full depth of concrete, usually 1/2 to 1" deep x 1/4 to 1/2" wide. The elastomer can expand and contract without breaking contact with the concrete.
I understand your plight and have been involved with projects dealing with all sorts of concrete issues (failures) generally attributed to inadequate prep.
Think of concrete as an ice sheet on top of a pond. at this point the ice sheet has fractured and the pieces will move about.
The goal of "a perfect slab" is to keep it as a monolithic sheet that moves independent of adjoining sheets (but can be doweled to keep them in basic alignment).
fwiw, I own a home that the prev owner was a concrete mason. he poured some very nice patios finished off as natural slate. Spalling due to freeze thaw is the major issue, he did not use entrained air. There are no cracks to speak of due to our very hard and stable soils and proper control joint placement.
I'd try the above drainage improvements and monitor it for a couple years. I might consider a type of epoxy overlay that incorporates pebbles of various types that can be used in freezing climates, but should be chosen wisely as nothing can cover underling issues. So many variables without visual inspection.

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#2466635 - 03/14/18 08:25 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
Stanton Offline
master

Registered: 10/13/05
Posts: 6622
Loc: Ontario, Canada
When they cut the relief joints in my shop floor I first inserted 1/4" foam rope seal (Home Depot) just below the surface. I then put in a bead of concrete crack filler (Home depot) using a caulking gun and then scraped off and wiped up the excess. Been there 12 years !!

I would definitely recommend this on any concrete driveway. Its the moisture freezing underneath that causes the heaving and cracking. The more moisture you can prevent from getting under it the better.

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#2468433 - 03/18/18 11:44 PM Re: Questions for the Concrete guys - concrete hardener [Re: srt]
Dixie Offline
top fuel

Registered: 06/24/08
Posts: 2271
Loc: Ball Ground, Georgia
Originally Posted By srt
I remember when you were planning the project and asked questions.
Are the cracks random, how far apart are they. "mesh" iiare you referring to fiberglass?
What did you do about the areas with water?
what structural section did you put in below the concrete (i.e. clear and grub organic soils, compact to 95%)?
did you place and compact base rock (not sand))?
did you incorporate steel (rebar or reinf mesh)?
thickness of slab?
answers to these questions will determine what is failing: base, soil heaving (wet/dry season), concrete mix, seasonal temperature expansion fluctuations.
Driveways can fail in any of those areas.
De-watering sub soils is key, properly sizing "floating" slabs are important, as are proper layout and sizing of expansion joints (not saw kerfs).


Yes, the cracks are random, different areas in the parking pad and driveway. The mesh is fiberglass mixed in with the concrete.

The area is slanted, so 99% of the water runs off of it. They ripped up the previous concrete and said the Georgia clay was hard packed enough, although they did bring in some gravel and spread it while other work was being done. They didn't add anything else prior to pouring.

No rebar, slab is 4" thick.
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Dixie Restoration Parts
Phone -(770) 975-9898
Phone Hours: M-F 10am-5pm EST
website: www.dixierestorationparts.com
email: mail@dixierestorationparts.com
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#2468436 - 03/18/18 11:54 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
Dixie Offline
top fuel

Registered: 06/24/08
Posts: 2271
Loc: Ball Ground, Georgia
Here is a pic of one of the cracks.


Attachments
cracked concrete.jpg


_________________________
Dixie Restoration Parts
Phone -(770) 975-9898
Phone Hours: M-F 10am-5pm EST
website: www.dixierestorationparts.com
email: mail@dixierestorationparts.com
Veteran owned small business

The Best Parts at a Fair Price.

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#2468449 - 03/19/18 12:38 AM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
srt Offline


Registered: 01/19/03
Posts: 8902
Loc: Fire and Fury
My gut feeling is the clay is expansive. If the cracks are random and not isolated to where wheel loads normally occur it indicates sub-soil (basement) issues. As expansive clay gets wet it swells and anything above, or along side gets pushed around. This is not equal for the entire slab, or season and random cracks appear.
It's a expensive proposition constructing slabs on expansive soils. Dewatering and liberal use of full depth expansion joints can help.
At this point it's possible de-watering the area with french drains along edges may help. Perhaps cut the slab into many smaller segments or let it break into whatever it will and keep vegetation out of the cracks. If the clay is deep seated it's possible french drains will not help.
I'm really surprised a local(?) contractor did not forewarn you of potential issues of constructing concrete slab on clay.

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#2468456 - 03/19/18 01:54 AM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
4mayhemi Offline
enthusiast

Registered: 11/28/16
Posts: 212
Loc: between the coasts
It looks like they forgot to continue the sawcut in your picture. Nothing can be done except powerwashing, backer if needed, then "self-levelling polyurethane sealant" (about $6 per tube) does pretty good. If you replace the slab next time use welded wire and a good 4" gravel base.

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#2468459 - 03/19/18 02:40 AM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
slantzilla Offline
I Live Here

Registered: 01/24/03
Posts: 18211
Loc: Park Forest, IL
Originally Posted By Dixie
No rebar, slab is 4" thick.


No wire either?

2 things concrete are guaranteed to do, get hard, and crack.
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#2468701 - 03/19/18 04:47 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
Superfreak Offline
master

Registered: 11/08/08
Posts: 3615
Loc: the great wet north
Putting concrete on top of clay is just asking for trouble. The fiberglass strands in the mix is absolute garbage and a waste of money. Your contractor should have laid min 6" of 3/4" roadbase, possibly more depending on the clay base. A min of wire welded mesh should have been used. I put 8" of roadbase down and compacted with a thousand pounder, 6ml poly, then 10m rebar 16" either way. I also did an exposed agg finish using 14mm agg, then saw cut the control joints 1" deep. I still have two little cracks on either side of the garage corners because I did not cut any joints diagonally from the corner, just 90° out both ways. Concrete will always crack at corners because these are stress points. The rest of my driveway and sidewalks and stairs are fine. My neighbours thought I was doing over kill, but after 38yrs in construction I don't like to Micky Mouse things.


Edited by Superfreak (03/19/18 07:28 PM)
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#2468712 - 03/19/18 05:21 PM Re: Questions for the Concrete guys - concrete hardener [Re: Superfreak]
oldjonny Offline
top fuel

Registered: 02/12/07
Posts: 2028
Loc: Michigan
Originally Posted By Superfreak
Putting concrete on top of clay is just asking for trouble. The fiberglass strands in the mix is absolute garbage and a waste of money. Your contractor should have laid min 6' of 3/4" roadbase, possibly more depending on the clay base. A min of wire welded mesh should have been used. I put 8" of roadbase down and compacted with a thousand pounder, 6ml poly, then 10m rebar 16" either way. I also did an exposed agg finish using 14mm agg, then saw cut the control joints 1" deep. I still have two little cracks on either side of the garage corners because I did not cut any joints diagonally from the corner, just 90° out both ways. Concrete will always crack at corners because these are stress points. The rest of my driveway and sidewalks and stairs are fine. My neighbours thought I was doing over kill, but after 38yrs in construction I don't like to Micky Mouse things.


Someone after my own heart. Nothing worse than paying twice for something done wrong. I did Peastone, 6mm poly, 2" foam (in-floor heat), highway mat and 5-1/2" of concrete.
_________________________
Never, ever argue with an IDIOT. They will drag you to their level and then beat you with their years of experience

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#2468831 - 03/19/18 09:01 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
srt Offline


Registered: 01/19/03
Posts: 8902
Loc: Fire and Fury
superfreak, have you used grade reinforcing/separation fabric?
Over the years I spec'ed it in clay areas and it works great. After constructing edge drains woven fabric is laid down on compacted clay (or clay with 3/4 washed rock added), then the base rock (6" cl2 base) compacted. Poly and a #3 bar mat 18" o.c each way with # 4 bars on the perimeter, and wherever a exp jt will be add a #4bar each side (2 bars 5" apart joint @ 2 1/2").
I hesitate saying what "should have been done" without visual of the issue. I recall this project and am sorry to hear only conc, with mesh was placed.

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#2468833 - 03/19/18 09:07 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
Challenger 1 Offline
Too Many Posts

Registered: 02/05/05
Posts: 28167
Loc: Cincinnati, Ohio
Originally Posted By Dixie
Originally Posted By srt
I remember when you were planning the project and asked questions.
Are the cracks random, how far apart are they. "mesh" iiare you referring to fiberglass?
What did you do about the areas with water?
what structural section did you put in below the concrete (i.e. clear and grub organic soils, compact to 95%)?
did you place and compact base rock (not sand))?
did you incorporate steel (rebar or reinf mesh)?
thickness of slab?
answers to these questions will determine what is failing: base, soil heaving (wet/dry season), concrete mix, seasonal temperature expansion fluctuations.
Driveways can fail in any of those areas.
De-watering sub soils is key, properly sizing "floating" slabs are important, as are proper layout and sizing of expansion joints (not saw kerfs).


Yes, the cracks are random, different areas in the parking pad and driveway. The mesh is fiberglass mixed in with the concrete.

The area is slanted, so 99% of the water runs off of it. They ripped up the previous concrete and said the Georgia clay was hard packed enough, although they did bring in some gravel and spread it while other work was being done. They didn't add anything else prior to pouring.

No rebar, slab is 4" thick.


Sorry to pile on.

I have to agree with everyone above...4" is sidewalk thickness around here and driveways are 5.5" thick(2X6) minimum. Mine are 7" thick at home and work. Fiber in the concrete is worthless for strength, got to have at least wire in the concrete. Durability is 80% prep and 20% finish imo.

Just had $10959.00 worth of flat concrete work done at my business 10 days ago, the 15-20th something job I have had done in 30 years of business. It was only a 12' wide driveway about 30' long with a drain running through the middle of it that we drive fully loaded tanker trucks across.

From looking at your relief cuts made in the concrete tells me that the contractor cut corners verses finishing those expansion joints. Yes there are plenty of places that just plain cuts are in order, but not like that above where they meet in the middle.

I am pretty sure I put my 2 cents into one of your posts about concrete flat work.


Edited by Challenger 1 (03/19/18 09:51 PM)

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#2468860 - 03/19/18 10:03 PM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
Dixie Offline
top fuel

Registered: 06/24/08
Posts: 2271
Loc: Ball Ground, Georgia
Thanks for the input guys. I realize it wasn't done properly and wish there was some retribution I could get from the contractor, but I'm sure there isn't.

So, is there anything I can do now, to help mitigate this? Slow down the cracking? I read about some densifiers, but I'm not sure how they would work in a this type of application.
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Dixie Restoration Parts
Phone -(770) 975-9898
Phone Hours: M-F 10am-5pm EST
website: www.dixierestorationparts.com
email: mail@dixierestorationparts.com
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#2468900 - 03/20/18 12:01 AM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
srt Offline


Registered: 01/19/03
Posts: 8902
Loc: Fire and Fury
1) keep surface water draining away
2) install edge drains (shallow french drains (I'd aim for 30" deep, 24" deep drape filter fabric across trench lay in 3" perf pipe fill to 6" below grade, fold over and lap top of filter fabri and cap 6" with original soil (clay). But it might work 24" deep, 3" perf pipe, gravet to within 6" fold over fabric and cap 6" with original material).

The edge drains can be simple.
Rent a trencher, run it all around the concrete, outlet the drains making sure the french drain maintains grade falling toward outlet.

I will say it's expensive to construct concrete slabs on clay soils.
Often ac (flexible) ends up cheaper.
The trick with slabs on clay is to essentially create a drained "foundation" under a slab and allow the slab to "float". Deep seated clay can be dozensof feet in depth. I can imagine homes in the area may often have foundation problems that may be referred to as settlement.

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#2468992 - 03/20/18 08:37 AM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
Dixie Offline
top fuel

Registered: 06/24/08
Posts: 2271
Loc: Ball Ground, Georgia
Thanks SRT !
_________________________
Dixie Restoration Parts
Phone -(770) 975-9898
Phone Hours: M-F 10am-5pm EST
website: www.dixierestorationparts.com
email: mail@dixierestorationparts.com
Veteran owned small business

The Best Parts at a Fair Price.

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#2469090 - 03/20/18 11:07 AM Re: Questions for the Concrete guys - concrete hardener [Re: Dixie]
srt Offline


Registered: 01/19/03
Posts: 8902
Loc: Fire and Fury
hope something good can be done.
Keep in mind, it's only concrete.

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#2469299 - 03/20/18 04:51 PM Re: Questions for the Concrete guys - concrete hardener [Re: srt]
Superfreak Offline
master

Registered: 11/08/08
Posts: 3615
Loc: the great wet north
Originally Posted By srt
superfreak, have you used grade reinforcing/separation fabric?
Over the years I spec'ed it in clay areas and it works great. After constructing edge drains woven fabric is laid down on compacted clay (or clay with 3/4 washed rock added), then the base rock (6" cl2 base) compacted. Poly and a #3 bar mat 18" o.c each way with # 4 bars on the perimeter, and wherever a exp jt will be add a #4bar each side (2 bars 5" apart joint @ 2 1/2").
I hesitate saying what "should have been done" without visual of the issue. I recall this project and am sorry to hear only conc, with mesh was placed.


We use the fabric all the time on jobs, even under city sidewalks where we install structural soils. It is a very heavy fabric and works very well. I did a hanger at the south terminals at Vancouver airport for Esso and due to the ground we used this fabric under the entire slab on grade. Ground consisting of clay, can and does heave especially when ground water levels fluctuate. All our work is inspected for compaction and prep work by professional consultants as well as my inspection prior to placing concrete.
_________________________
"Too much to do and not enough time to do it"

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#2469412 - 03/20/18 08:26 PM Re: Questions for the Concrete guys - concrete hardener [Re: Superfreak]
ahy Offline
master

Registered: 01/22/07
Posts: 7625
Loc: IN
I had (bought) a driveway like that and lived with it. 4", mostly clay base, little re-enforcement. Basically "run it until it drops" was my plan. Or as mentioned, "it is only concrete". Suggestions on drainage can only help. If some sections get really bad, may be worth saw cutting them out and replace with good concrete and steel mesh. Mine had not reached that point.

I sold that house and I am currently putting in a new driveway at a new house. Good packed limestone base 6+", 6" of concrete with steel forms and welded steel mesh and done by a pro who will put joints in where needed. I do not expect this one to crack. We will see.

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