How to thicken an Existing Concrete Slab on Grade
How to thicken an Existing Concrete Slab on Grade
(OP)
I am looking for help on how to effectively and efficiently thicken an existing slab on grade that was poured too thin.
A little background: This is an industrial facility that we specified on our drawings a slab on grade thickness of 6". The facility has forklift traffic. The slab started cracking very soon after installation. After the slab started cracking, a testing firm came in and tested the slab. In their report, they found that the slab had evidence of curling. After taking core drilled samples, it was found that the slab was poured at more like 4.75" rather than 6" and thus deflection and cracking was occuring.
I am now in the process of coming up with a solution to fix the cracks and the curling, but I am stumped on how to make the deflection issue go away, if the slab is too thin, how do I make it thicker?
The owner would prefer not to go on top with more concrete or completely rip out the slab entirely, is there another option out there?
Thanks for your help!
A little background: This is an industrial facility that we specified on our drawings a slab on grade thickness of 6". The facility has forklift traffic. The slab started cracking very soon after installation. After the slab started cracking, a testing firm came in and tested the slab. In their report, they found that the slab had evidence of curling. After taking core drilled samples, it was found that the slab was poured at more like 4.75" rather than 6" and thus deflection and cracking was occuring.
I am now in the process of coming up with a solution to fix the cracks and the curling, but I am stumped on how to make the deflection issue go away, if the slab is too thin, how do I make it thicker?
The owner would prefer not to go on top with more concrete or completely rip out the slab entirely, is there another option out there?
Thanks for your help!






RE: How to thicken an Existing Concrete Slab on Grade
The best way to test something is to squeeze it, slowly, until it breaks!
RE: How to thicken an Existing Concrete Slab on Grade
RE: How to thicken an Existing Concrete Slab on Grade
RE: How to thicken an Existing Concrete Slab on Grade
RE: How to thicken an Existing Concrete Slab on Grade
RE: How to thicken an Existing Concrete Slab on Grade
RE: How to thicken an Existing Concrete Slab on Grade
Intrusion Prepakt /marineconcrete.com
RE: How to thicken an Existing Concrete Slab on Grade
I attended a presentation on concrete pavements not so long ago which dealt with curling. Basically bearing can be restored by injecting grout into the voids that are developed between to the slab and the subgrade.
Another approach could be to wet the slab so it hogs up level so new control joints can be cut around the curled regions of the slab.
It shouldn't take long for this to occur. I have heard of a professor who was study the deflections of reinforced concrete slabs under long-term load conditions when the roof of his laboratory was taken away in a violent storm and flooded the labs.
He noticed with his recordings that after being exposed to water for about two days, the deflections of his slab actually reduced.
RE: How to thicken an Existing Concrete Slab on Grade
To much water in the concrete mix or to high W/C ratio in mix
Inadequate slab reinforcement (hopefully you did not specify a light mesh)
Improper placement of the slab reinforcement.
Improper curing of the concrete. Did they cover and use a curing agent on the slab to prevent curling?
Poor joint detail. For a slab having forklift traffic, the slab should have been placed in alternate pours in a checkerboard fashion with keyed and/or doweled joints.
If you specified saw cut control joints, did they cut them within 24 hours of placing the slab.
Poor subgrade
A little more information regarding the location and type of cracks as well as the slab design would required to help you out here.
RE: How to thicken an Existing Concrete Slab on Grade