Cylinders or cubes

[kdxbob]

I've a feeling this will fall into the "studid" question category but ....

I'm an owner's rep watching a small construction project. Reinforced CMU with concrete tie beams at the top of the walls. Footing and slab-on-grade concrete was tested with 4 X 8 cylinders; fill cell grout with cubes.

The tec made cubes of the pea-rock concrete used for the tie-beams. When I asked the tech about it he said they "always make cubes for pea-rock concrete".

I'm thinking it's concrete so it should have cylinders for testing. When should cylinders be used and when should cubes be used?

Thanks

 

[concretemasonry]

Were the beams formed or were they filling conventional CMN bondbeams/lintels?

Grout is alawys used to fill CMUs and the "cubes" should be formed with CMUs to allow the excess water to be absorbed since the specified slump is in the range of 8" - 11", as compared to the much lower slump specified for concrete. Since grout strength is not critical, is more important for it to be at or slightly above the strength of the CMU. The purpose of the grout is to tranfer the loads between the steel and the masonry units.

Grout in non-abdorptive molds give very misleading results.

If the "tie beam" is really a masonry bond beam the strength is not as critical as complete filling and bond, the grout would be more appropriate.

Dick

 

[kdxbob]

They are formed tie beams - 8 X 16 mostly - with top and bottom bars and stirrups; some are 8 X 32 beams (no cmu below)