Chloride and Sulphate Resistance with SuperP

[dik]

Type 50 (5) cement is used for sulphate resistance. It is my understanding that this is not recommended for exposure to both sulphate and chloride attack.

The material I've spec'd is what we refer to as HSb which is a blended sulphate resistant concrete; the cementitious material is often made up using Type 10 (Normal) with as much as 25% flyash. This can achieve both the sulphate and chloride resistance.

The contractor wants to provide Type 50 and to minimise the cement content (cost) and achieve the max w/c ratio, he wants to prepare a mix with minimum slump and use superplasticiser to improve the flowability.

Is anyone aware of a problem with using superplasticers that will reduce sulphate and chloride resistance (other than checking with the superP supplier)?

Dik

 

[Ron]

dik..I don't know of any issues with that. I can't think of any reason that SuperP would affect the sulphate and chloride resistance. It might actually help since you would expect better density in the concrete.

The contractor's approach to reduce the cement content and maximize the w-c ratio are not good for long term durability of the concrete.

 

[dik]

Thanks, Ron should have made it clear... he wants to max the w/c to 0.4. My error... Pretty much what I thought.

Dik

 

[conceng]

Depending on the cement and fly ash source, 25% fly ash with a type 10 (1) can achieve what's consider type 50(5) equivalent performance for up to class 2 sulphate exposure. See ACI 201 for the full story on that. I agree with Ron that the super will benefit by minimizing the w/c ratio and thus the permeability of the paste. Keep the bad stuff out, it won't hurt the concrete. Minimizing the paste volume is also a good idea by minimizing the cementitious materials, give the bad stuff less to work with. I'm not sure why he would so want to use the type 50 instead of his typical type 10 and fly ash.

 

[B16A2]

You would be better off using a normal cement, high range SP such as Glenium 3030 and pushing the w/c to below 0.35 and use internal curing to prevent self dessication shrinkage. This will give you a mixture that is HIGHLY resistant to anything because the paste is so dense.