Max aggregate size in cast concrete pier

[marinaman]

I have a series of concrete piers that are 6' x 6' in plan size and 12' tall. The piers support steel columns. The piers are that big, not due to load, but to a series of geometric masonry support requirements above the concrete pier (the pier supports the steel column and a giant masonry wrap around the column).

That said, the size dictates this is a mass concrete pour.

The concrete mix is under design. My drawings require a course aggregate size of no more than 3/4". The concrete designer is asking if he can use up to 1 1/2" aggregate.

While that may be ok per ACI 211.1 (Table A5.2), I'm reluctant to allow it because I typically have not used aggregate this large over the last 30+ years.

What would be the negatives of using aggregate this big?

 

[DaveAtkins]

I see no drawback so long as you are satisfying ACI recommendations.

 

[ChorasDen]

There might be really cool crystals or valuable minerals hidden within the aggregates, and you'll miss out on seeing them.

 

[dik]

Is there a limit on the size of the aggregate. On one project I'm aware of (nuclear facility) they use 18" aggregate using a process called 'intrusion prepact' (sp?).

 

[JAE]

Just make sure your reinforcement is spaced accordingly - otherwise 1 1/2" is OK for a placement that large.

 

[bugbus]

40 mm (~1.5") is generally the largest allowed for in the Australian standards (AS 2758.1) without specific testing