ACI Crack Repair Requirements 2

[KirkGH]

I've been told by my supervisor to "keep looking" for ACI requirements and guidance regarding crack repair vs. crack width (i.e. what width or circumstances require repair?) when I've found none. I've look in ACI 318-08 and the closest guidance I can find is 20.5.3 and 20.5.4. that would indicate repair of existing structures is necessary when cracks indicate shear failure or shear cracks with a projection longer than the depth of the memeber (this is a stretch of interpretation).

ACI 301 provides some guidance on investigating cracks and crack repair but falls shurt on recommendations on crack repair based on crack width.

ACI 360R-92 provided no guidance on crack evaluation.

My questions are:
For a slab on grade cracks can get quite large without compromising the structural integrity (bearing capacity) of the slab. Doe ACI broach the subject?
Grade beams in a similar manner can crack and be ok structurally. Does ACI specify a crack width anywhere that draws a line between acceptable and structural failure?

My job entails a lot of foundation inspections in an area with a lot of clay soil. Cracks are everywhere and I like to know the offical Code position on cracks.

Thanks.

Kirk

 

[BAretired]

It is a subjective judgment. See attached.

BA

 

[Ingenuity]

ACI committee 224 has offered the following crack width guidelines:

Exposure condition Tolerable crack width
(in.) (mm)
Dry air or protective membrane 0.016 0.41
Humidity, moist air, soil 0.012 0.30
De-icing chemcals 0.007 0.18
Seawater and seawater spray: Wetting and drying 0.006 0.15
Water retaining structures(excluding pressure pipes) 0.004 0.10

ACI suggests that a condition survey and evaluation be conducted to determine the cause of cracking as well as whether the crack is static or active. This study is best suited to a professional civil or structural engineer who will consider chemical contamination, on-going corrosion activity and the marginal physical properties of the existing concrete.

For SOG where the cracks are deemed necessary to be repaired by the EoR, and if the crack is of significant width, epoxy injection using a liquid resin may not be the best solution - gravity feed with a higher viscosity resin is probably more appropriate.

For SOG cracks that do do require structural depth repair, it is common to rout-&-seal with a paste resin to the top surface - assuming the cracks are not active.

 

[Ingenuity]

Sorry, formatting of the crack width got all screwed up.

Also, Last sentence should be as follows:

"For SOG cracks that do NOT require FULL structural depth repair, it is common to rout-&-seal with a paste resin to the top surface - assuming the cracks are not active."

 

[BigH]

ACI has a series of Field Guides to Concrete Repair Application Procedures "RAP" Bulletins. RAP #1 is on epoxy injection, RAP #2 is on gravity feed with resin, RAP #4 is on surface repair with form and pour techniques, etc. SBD Limited out of UK has a very nice Concrete Repair Guide; USBR also has a a very good manual on Concrete Repair.