Thick Concrete Slab Crack Control Joint
Thick Concrete Slab Crack Control Joint
(OP)
The footing slab of the 40-ft underground concrete tank I am working on will need to withstand uplift pressure (almost 35'). It does act as a ballast. Can I do 90' x60' x 12' thick slab in one pour with no joints assuming the contractor can do it..?
ACI 224 talks about 24 to 36 times the slab thickness for control joints but does not address thick slabs beyond 10". Any recommendations to reduce the heat during placement or just use ice..?
Thank you.
ACI 224 talks about 24 to 36 times the slab thickness for control joints but does not address thick slabs beyond 10". Any recommendations to reduce the heat during placement or just use ice..?
Thank you.






RE: Thick Concrete Slab Crack Control Joint
RE: Thick Concrete Slab Crack Control Joint
Also, talk to your concrete supplier. There are many ways to adjust the concrete mix to reduce the heat during placement for thick concrete sections. Use of fly ash to replace cement content is one.
The important thing is to limit the differential tempatures between different areas in a mass concrete structure. If the exterior surface(s) is(are) allowed to cool too quickly, the tempature gradient between a hot core and cool exterior surface can lead to proplems. Consider use of insulated forms and insulation at any exposed surface to allow the placement to cool uniformly.
JMHO.
RE: Thick Concrete Slab Crack Control Joint
RE: Thick Concrete Slab Crack Control Joint
It isn't a "slab-on-grade". It is a foundation mat.
RE: Thick Concrete Slab Crack Control Joint
RE: Thick Concrete Slab Crack Control Joint
DaveAtkins
RE: Thick Concrete Slab Crack Control Joint
RE: Thick Concrete Slab Crack Control Joint
RE: Thick Concrete Slab Crack Control Joint
RE: Thick Concrete Slab Crack Control Joint
lkjh345 and DaveMinter are correct with regards to concrete temperature. A thermal analysis should be done as DaveMinter pointed out. Significant thermal stresses can develop resulting in cracks which affect the structural capacity of the mat. Thermal cracking is one of the primary concerns for placing mass concrete and should not be taken lightly.
The soil freezing method you mention will further complicate this issue. I'm assuming LIN will be used to freeze the ground. With LIN temps around -385 degrees F, a significant temperature gradient will occur between the interior and exterior of the mat.
RE: Thick Concrete Slab Crack Control Joint