Acceptable crack width in structural concrete

[ATSE]

My firm designs environmental structural concrete (ACI 350) and "building" concrete (ACI 318), and we also specify pre-cast - like box culverts and utility trenches.

Acceptable crack width for pre-cast and cast-in-place structures has been problem (with the exception of fluid-retaining structure, which get leak-tested).

ACI 318 does not give specifics, and there are a multitude of ACI guides (not codes) that discuss and describe cracks. However, when a resident engineer rejects a pre-cast utility trench cover - large cost and schedule impacts - it's important to have a strict, definable standard.

We state: 1/64" (0.4mm) wide or wider x 2" (51mm) long (or longer) is cause for rejection or repair.

Is this reasonable? My only backing is 15 years experience and inferences from various ACI guides.

 

[Ron]

As a comparison, the crack rejection criteria for reinforced concrete pipe is 0.01" width and a length greater than 12 inches.

Your criterion is a bit tight, but if you are the engineer of record and doing the design and specification, then you can make it anything you want...though enforcing it without adequate foundation is a bit tough.