fly ash blend concrete or opc?

[Matt]

had quote of our usual supplier of concrete, and as far as i am aware they use the normal fly ash mix. Now had a quote of our builders merchant who they can supply concrete through he said they have switched to opc as its colder.
so what is better opc or the normal blend

 

[Matt]

of and the opc cement mix is coming out slightly cheaper

 

[Blue.]

of and the opc cement mix is coming out slightly cheaper

Prefer opc,I find fly ash sets to quick and cracks.

 

[Steevo]

Had a company doing concreting here once and they specified the concrete to be OPC so it could be power floated. That said, next company who did almost exactly the same I've a feeling they weren't fussed.

 

[Matt]

would the fly ash blend be better in colder conditions tho? one company said they are switching to opc as its coming cold the other does not...,