Hello,

Please have a look at the following publication (with full-text PDF):

http://www.concreteconstruction.net/concrete-construction/designing-concrete-mixes-for-increased-fire-or-he.aspx

This is also an interesting article on the topic of concrete properties vs temperature:

http://www.hindawi.com/journals/isrn/2014/468510/

and also these two:

http://fire.nist.gov/bfrlpubs/build02/PDF/b02171.pdf

http://www.besix.com/Besix/media/Besix_Media/pdf/Publications/Fire_resisting.pdf

I hope I helped!

Thanks !