adding frostproofer to postcrete

[nick9one1]

I need to replace e couple of fence posts and with it being cold at the moment (2C daytime and -3C night) I planned to add a bit of Sika Frostproofer to the postmix.

I have hanson postmix which requires two litres of water. I plan to quickly mix in a flexibucket then chuck it in the hole around the post.
But I cant quite work out how much frostproofer to use...

The directions have some calculations for concrete mixes. Then further down it says 1.25 - 2.5litres per 25kg of cement.

Assuming postcrete is a 123 mix, my 20kg bag would contain 3.3kg of cement.
at 1.25 litres per 25kg, this would work out at 170ml for 3.3 kg cement, so I roughly need to mix 1.8l water and 0.2l of frostproofer. Then add the postcrete.
Does that sound right?

 

[nick9one1]

I've just noticed it also says Do not use with high alumina cement

but Sika make another product called wintermix that doesn't have this limitation..
It has the same dosage rate so the question is still valid.

at 2.5 litres per 50kg, this would work out at 170ml for 3.3 kg cement, so I roughly need to mix 1.8l water and 0.2l of wintermix. Then add the postcrete.

Does that sound right?

 

[noseall]

I've just noticed it also says Do not use with high alumina cement

but Sika make another product called wintermix that doesn't have this limitation..
It has the same dosage rate so the question is still valid.

at 2.5 litres per 50kg, this would work out at 170ml for 3.3 kg cement, so I roughly need to mix 1.8l water and 0.2l of wintermix. Then add the postcrete.

Does that sound right?

View attachment 403637

Postcrete is already loaded with accelerators. Don't put any other additives in.

 

[^woody^]

Frost layer is up to 6" below the surface.

Don't over think it, these are fence posts.

 

[nick9one1]

Thanks for the replies.

The additive was only £5 and the postcrete instructions said min 5 degrees C.
When I bought it I thought I could just throw a bit in for extra protection.

 

[foxhole]

Use warm water , will be solid before any frost can affect it .

 

[Ivor Windybottom]

Postmix will set in about ten minutes anyway.

Perhaps just bung the scrunched up bag on top with a brick over as a precaution, but it's definitely not going to explode overnight with a bit of frost.