Does a thicker concrete pad take longer to set up?

Question

I guess most concrete guys believe concrete obtains 95% of it's strength in about 28 days. Does that "rule of thumb" only work for "normal" thickness concrete (4" to 5")? Would a 16" thick slab take longer to obtain 95% of it's strength? If so, how much longer? Any concrete gurus please advise. Thanx!

Answer 1

Yes and no.  The longer concrete is allowed to cure (the slower it dries out), the stronger it ultimately gets.  The concrete at the core of a 16" slab will eventually become much harder than that of the outside because of the additional moisture trapped in the core.  So the concrete in a 16" slab will be as strong as any 4" slab after 28 days, but ultimately the core will be much stronger after several months.

Answer 2

www.cement.org/tech

Answer 3

the thicker the slab the faster the initial set as it produces more  heat  . you normally keep concrete moist so that it  can cure and gain strength with out shrinkage . it is the shrinkage which causes concrete to crack etc . It also depends on the strength of the concrete you ordered.