high air entrainment
high air entrainment
(OP)
On a current project, I received a concrete test report from the special inspector that indicates 12% air-entrainment on an exterior elevated topping slab. This slab is cast over 1.5" steel deck supported by HSS joists.
The general notes called for 5% +- 1.5% so this is nearly twice the max specified air. The steel deck will carry the required loads so I am more concerned about the durability of the concrete. The slab is exposed aggregate with a sealer.
What is the long-term affect of this much air in the mix.
I haven't yet received an answer from the special inspector as to why he didn't reject the truck.
The general notes called for 5% +- 1.5% so this is nearly twice the max specified air. The steel deck will carry the required loads so I am more concerned about the durability of the concrete. The slab is exposed aggregate with a sealer.
What is the long-term affect of this much air in the mix.
I haven't yet received an answer from the special inspector as to why he didn't reject the truck.






RE: high air entrainment
I'd be concerned with the permeability of the concrete. If the concrete is exposed to salts and it is reinforced then a sealer might not be good enough.
The final air content may be less if it was tested at the truck and pumped to the elevated slab (losses of 1 to 3% are typical).
RE: high air entrainment
RE: high air entrainment
Please note that a concrete surface which is subject to delamination will be adversely affected by freeze-thaw and deicing chemicals. Also note that freeze-thaw and deicing chemicals have only exposed a condition which was already present.
Please also note that ACI does not recommend air entrainment for interior slabs, which are most likely to be moderately to heavily troweled.
RE: high air entrainment
http:/
RE: high air entrainment
This is not a case of strength but of durability. The concrete in question is an exterior exposed aggregate slab on the shoreward side of a building approximately 200' from the ocean. The climate is subject to freeze/thaw.
My concern is for durability of the slab and corrosion of the rebar and decking.
RE: high air entrainment
Good luck.
RE: high air entrainment
RE: high air entrainment
Thanks for the comments.
I think that the bottom side is fairly well protected. I have specified a G90 galvanizing with an epoxy paint top coat so it should be okay. It is not in a constant wet condition and if it is kept clean will perform very well.
The surface in contact with the concrete is G90 but doesn't have the paint. I am just worried that if the concrete is more porous, it can get to a permanently wet condition which might compromise the galvanizing.
RE: high air entrainment
RE: high air entrainment
Agree with the others, such a high air content will affect durability, i.e. long term performance of the concrete.
RE: high air entrainment
You are in the ACI 318 C2 severe chloride exposure zone; Table 4.3.1 requires the concrete to have w/cm of 0.40 or less, and 5000 psi minimum strength. This application also warrants consideration of increased cover per 7.7.6 (two inch minimum for slabs.)
The concrete slab will need to support itself once the deck has failed. You mention rebar, so I assume it was designed for this.
The rebar would ideally have been protected from corrosion by one or more means (epoxy, galvanizing, cathodic protection, or use of stainless rebar) to extend the life of the structure.
You might consider a traffic membrane coating, or a trowel-applied epoxy-aggregate surface, to reduce water+Cl- intrusion.
RE: high air entrainment
processes at which the air content of the unhardened concrete is determined, that is, before or after the concrete goes through
a pump; and other factors.