cracking concrete pad 1

[Rich49]

I had a 12x25 concrete floating pad poured late october 2002. Also had floor poured in my pole barn at the same time.
I live in the buffalo ny area.
The pad butted up against an existing pad.
The contractor I had do it has been doing concrete jobs for 30 years, in business for himself.
Well, it is now February and the pad is full of cracks, and the garage floor has a couple of long, front to back ones.
The contractor said he wouldn't be using re-bar or mesh because he would use a fibre glass(I think) substance that held the concrete together just as well. There was at least 10-12 inches of stone base used, and it was power tamped nicely. I am just sick about this, and wonder what my options are. Any help you could give me would be greatly appreciated.
P.S. There was no expansion joint material placed between the existing pad or the new pad and garage.

Thank you for your time......Richard L. Jex

 

[Rjeffery]

Rich,

Concrete cracks. Are there Crack Control Joints cut into the 12 x 25 slab? What is the thickness of the slabs that were poured. Were any test cylinders (for strength) taken? (I guess, probably not. ) Was water added to the concrete during the placement? What was the low temerature for the week after the pour? Were the slabs covered with poly or blankets? Was water or curing compound used?

Fiber mesh greatly improves the tensile strength of the concrete but will not prevent it from cracking. Steel fiber is better that poly and poly is better than fiber glass.

The thicker the slab the lower the chances of through cracking, within limits.

The more water added to the concrete the weaker it is.

If the temperature is too low the concrete could have its set and cure retarded to the point that it is weak and with this cold weather it contracted and had to crack. Because it is longer than it is wide by 2:1 it should have had control joints which induce a weak area that will allow the crack to form 'undetected' and could be filled with flexable caulk.

If the slab has cracks that resemble snake or lizard skin, that could be an indication of water used to hard trowel the surface or poor curing and is only about 1/8 in (3mm) deep.

Portland Cement Institute (Association?) has a great (thin) book about slabs on grade that you can get from your local technical book store that will give you an understasnding of what is going on, so you won't be sick about it any more.

 

[Rich49]

CONTROL CRACK JOINTS WERE PUT IN, BUT NO CRACKS AT THOSE POINTS......NO TEST CYLINDERS TAKEN YET.....WE PROBABLY HAD A LIGHT FROST ONE DAY AFTER THE POUR WAS COMPLETED. SLAB IS 4" THICK. NO WATER WAS ADDED WHILE TROWELING. I HAVE NOTICED THAT THE GARAGE FLOOR HAS THE LIZARD SKIN LOOK, WHICH I THOUGHT WAS THE SEALER I PUT ON. THE CONCRETE NEVER REALLY TURNED WHITE....STILL GREENISH. NO POLY WAS PUT DOWN, IN FACT CONTRACTOR SAID TEMP WAS GREAT IN THAT IT WOULD CURE SLOWLY. EVERYTHING WAS FINE UNTIL LAST WEEK, THAT WHEN THE CRACKS CAME, AND WHEN IT THAWS, I FEEL THIS PAD WILL DISINTEGRATE! SHOULDN'T WIRE MESH HAVE BEEN USED?
AGAIN THANK YOU FOR YOUR TIME AND QUICK RESPNSE. TRICHARD JEX

 

[Rjeffery]

If it is still 'green' then the concrete probably has not cured.

6 x 6 WWF probably would not have prevented the cracking to the extent that you discribe. that is, IF the concrete was frozen of cold. the aligator cracking could be caused by moisture being drawn out by the wind but if the local temperature was cool but not freezing that may not be likly. Still you say that the slabs were not covered. ACI states (paraphrazeing) that the surface of the concrete should be kept moist while curing. this is usualy 7 days. The sealer you used could have been applied too late.


I think, although I don't have the reference handy, that 4" is not quire thick enough for poly or fiber glass. Most of the slabs that use 'fibermesh' are 6 to 8 inches.

It sounds like you have more of a problem than the lack of WWF. You may want to engage a local civil engineer to formally evaluate and document the condition of the slab(s).

concrete is tough stuff but that is only true when it is allowed to cure properly.

Keep up posted, please.

 

[Rjeffery]

Also, was flyash or Newcem (tm) used as a cement replacement?

 

[Rich49]

THANKS FOR THE REPLY,
1) THE GARAGE WAS PUT UP BEFORE THE CONCRETE CONCRETE WAS POURED TO I DON'T KNOW HOW MUCH WATER WOULD HAVE BEEN DRAWN OUT.....I THOUGHT MAYBE THE SEALER CRACKED...THE FLOOR IS COVERED WITH TINY HAIRLINE SURFACE CRACKS.
2) THE CONTRACTOR TOLD ME THE SEALER TO BY AND I BOUGHT IT AND APPLIED IT WITHIN THE NEXT DAY OR TWO.
3) HUMIDITY WAS GREAT FOR CONCRETE AS THE CONTRACTOR STATED..IT WOULD CURE SLOWER WHICH IS A GOOD THING.
4) I AM LOOKING UP A CIVIL ENGINEERING FIRM TO TRY TO ESTABLISH WHAT WENT WRONG.
5) I DON'T HAVE A CLUE IF THE CONCRETE COMPANY USED A SUBSTITUTE FOR CEMENT. BUT THERE IS ONE BIG COAL FIRED POWER PLANT WITHIN 20 MILES OF THE CEMENT PLANT.
THANKS AGAIN FOR YOU INFORMATION.

 

[Rjeffery]

Rich,

Newcem (tm) and fly ash are acceptable replacements for up to 50% of the portland cement. YOU just have to be given the option to use it or not because it does not 'set-up' as quickly as portland does.

I have no connections to Professional Services Industries (PSI) but I think they have an office in upper state NY. This is not a recommendation but a starting point.

You should also contact the company that placed the slab for you and perhaps they (he) will offer to cast it again in the spring.

I know it is frustrating to have something like this happen. It has been my experience that most of us want to do the best job we can. As Forrest Gump said, "S**t happens."

Keep us posted, please.

 

[supercreel]

Rich,

Maybe your problem is just the sealant...

We once poured a slab at Lockheed Martin Meridian. The specs called for the slab to be 6" with fiber reinforced with #4 bars at 12" on centers. The surface to be sealed with a polyureathane sealant from Euclid immediately after troweling. The temperature was approximately 95 degrees.
So, after troweling we sealed then covered with poly and kept wet for seven days. After removing the poly and exposing the surface to the extreme sunlight the surface began to alligator everywhere.
Conclusion:
The sealant shouldn't have be exposed to the extreme temp. A Euclid rep visited site and suggested resealing with the same product...the problems was resolved.

 

[Rich49]

THANK YOU FOR YOUR REPLY....OUR TEMP WAS AROUND 40, TRUE FALL DAY IN BUFFALO AREA. SHOULD HAVE CURED NICE AND SLOW......I THINK IT CURED TOOOOOOOOOOO SLOW! THANKS AGAIN

 

[deven1]

Hi...The main reason for these cracks is large area of soil underneath is loose/weak...so firbreglass reinforcement can not hold only REBARS can hold as whole slab has to act as a stronger plate to resist any differncial settlement.
The cure can be...only remove concrete,make rubble soling with full compaction atlest 18" thick & then lay Rebars of #5 at around 9" o.c bothways& make thickness of concrete atlest 6" then it will hold the whole plate intact.
See this is more of a subject of soil engineer who can stabilise soil in the existing conditions on site.
Contractors have always a limited knowledge & they are not at fault.

 

[bigfoote]

Always educate yourself and set specifications when having concrete poured. Most concrete contractors in this area do a substandard job because they are competing on price with no specifications. Also in many places there are few codes that require them to do the work in a certain manner. Very few of the contractors in this area use any rebar perpendicular to the footing run, standard is 2 #4 running with the footing, they're easy to put in. I just saw a home addition poured with no horizontal bar. They had a #4 sticking up 2' on 3' centers, this work was done by a guy who's been doing concrete for 30 years. You will find that many do things the way they do simply because thats the way the original contractor they started with did it. There was a 3 1/2" thick garage floor poured here over uncompacted dirt & sand, no vapor barier, no rebar, no wire, 3 1/2 bag mix, no code violation, no recourse for the customer. The contractor said sorry concrete cracks. Its always worth the money to obtain specifications as it's very expensive to replace a bad job.