Best Admixtures for Watertight Concrete 1

[ConcreteComedian]

I am currently researching various admixtures and sealers to enhance our university's design standards for concrete, with a focus on improving resistance to deicing materials, ensuring watertightness, and preventing reinforcement deterioration. Our standard specification for exterior concrete slabs is 4000 psi with 4-7% air entrainment and a water-cement ratio of approximately 0.45. The only admixtures we currently use are air-entraining and water-reducing agents.

This setup performs adequately in areas where deicing materials, particularly salts, are not frequently used. However, in regions where deicing salts are introduced, we have observed rapid concrete deterioration.

Has anyone had success in mitigating the effects of deicing salts using specific admixtures or sealers?

I am particularly interested in products like Hycrete CP or Hycrete WP and am considering introducing them to local concrete suppliers to evaluate their effectiveness against deicing materials.

 

[Canuck65]

In Canada we see a lot of freeze-thaw and deicing materials. The standard for non structurally reinforced concrete to withstand freeze-thaw and deicing materials is as follows:
Design Standard: CAN/CSA-A23.1
Exposure Class: C-2 Non-structurally reinforced (i.e. plain) concrete exposed to chlorides and freezing and thawing.
Maximum w/c ration: 0.45
Minimum specified compressive strength @ 28 days - 32 MPa (~4,600 psi)
Air Content: generally 4%-7% or 5%-8%, it varies depending on coarse aggregate size
Concrete curing is important to develop the full potential of the long-term durability and strength

These parameters are used extensively in aggressive winter environments with much success. My personal preference is to have a good quality concrete and forgo the specialty admixtures.

 

[ConcreteComedian]

@Canuck65 I forgot to mention that we typically use #3 rebar 12" O.C.E.W. due to a lot of heavy machinery during the winter on our sidewalks and slabs. Our director doesn't want to shy away from this reinforcement since during a period they would use 0 steel reinforcement and use fiber-reinforced concrete that would develop 1-3" cracks due to the heavy machinery load in multiple areas. I am more recent and do not know if they were spec'ing out 4500 psi concrete. It sounds like we were using 3000 psi at this time thinking we did not have to go stronger with our concrete possibly because of the fiber-reinforcement. Once we went back to these areas that developed these cracks and included the steel reinforcement we haven't had this issue besides where it's supposed to crack at our control joints. Where these cracks are less than a 1/16".

 

[Canuck65]

If the concrete is structurally reinforced, the following parameters would be appropriate:

Design Standard: CAN/CSA-A23.1
Exposure Class: C-1 Structurally reinforced concrete exposed to chlorides and freezing and thawing.
Maximum w/c ration: 0.40
Minimum specified compressive strength @ 28 days - 35 MPa (~5,000 psi)
Air Content: generally 4%-7% or 5%-8%, it varies depending on coarse aggregate size
Concrete curing is important to develop the full potential of the long-term durability and strength
I would add that concrete cover to the steel reinforcing is an important consideration. Usually in the 50mm - 60mm range to the top surface.

Keep in mind that fiber reinforcement will not increase the durability of the concrete.

 

[ConcreteComedian]

@Canuck65 Thank you for your insight!