Concrete Air Entrainment in Warm Climate? 3

[jrfroe]

I'm curious what everyone's opinion is on this and what you typically specify for air entrainment specifically in warmer climates.

Most of the work I do is in colder climates in the northern midwest, so its a given that all concrete exposed to the elements will contain an air entrainment admixture. Recently, we've had a project in Las Vegas where we also specified 4.5% air in a concrete mix for exterior slabs and footings (from ACI table 4.4.1 for class F1 and 1" aggregate) thinking that even if freeze-thaw cycles are somewhat rare that air entrainment still has other benefits for concrete durability. I found this article, which states that air is recommended in southern climates... granted its over 50 years old, but I didn't come across anything useful that is also more recent.

The ready-mix supplier is now pushing back a bit asking for the reason for the need for the higher air content since they use non-air entrained concrete all the time for exterior concrete... so I'm re-evaluating whether it has sufficient benefits.

Does anyone know of any guidelines for use of air entrainment in various climates? What does everyone else typically specify in warmer climates?

 

[SlideRuleEra]

Jrfroe - In South Carolina (temperature 101 F, right now) air entrained concrete is, and has been for decades, routinely specified for larger projects, such as bridges and electric power stations. Workability of the concrete, mentioned in the article at your link is justification enough.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Ron]

Agree with SRE....common. Also, I did a petrographic examination a few years ago of some exposed, failing concrete just north of Las Vegas. The deterioration was from freeze-thaw action on concrete without air entrainment.

 

[jrfroe]

Thanks guys! That is all I needed to hear.

 

[S3Engineers]

Hello,
I am located in Las Vegas. Non-air entrained concrete is typically used here. There are freeze -thaw issues with concrete "north of Vegas" - particularly in St. George.

That being said, most of Clark County has sulfates in the soil and there is significant sulfate damage to concrete and CMU in some locations - particularly where sprinklers repeatedly spray the surface. Yes, there are sulfates in the water too. Sulfate attack results in surface scaling that can look somewhat similar to scaling due to lack of proper air voids in a freeze thaw environment.

The important thing for concrete durability here is the use of 0.45 water cement ratio and F'c= 4500 psi. This seems to be the norm for concrete in contact with the soil, including footings, interior and exterior slab on grade.

If you go up in elevation (Mt. Charleston- close to Vegas) both 4500 psi and air entrained concrete are recommended for exterior applications.