Designing for Prestress

[MHobbs]

Hi all,

I'm trying to find methods or advice for mix design focused on the next day strength. Our concrete needs to be a C28 strength in about 18 hours so the beds can be detensioned and stripped. I'm working on what proportion of GGBS I could possibly aim to include but want to do some mix designs before starting testing. I'm aware that the high early strength requirement is not going to be easy with GGBS but want to have a place to start and something to put some numbers to.

Kind regards,

Matt

 

[TigerGuy]

When you start substituting GGBS, your mix becomes extremely sensitive to temperatures in the initial curing period. I worked with a mix on a number of projects with 50% GGBS. If the temperature was properly controlled, the strength gain was great. If the temperature wasn't, there were problems.

 

[MHobbs]

Thanks for the advice Tiger Guy, when it comes to production I can heat the beds but its still quite a variable environment.