cracking slab

[Nicky]

I am going to be building a new garage and pouring a new driveway. I really hate when concrete cracks and I know it's a natural occurence but even with control joints there are so many times when I see it crack. How can this be prevented besides getting good compaction, letting it cure slowly and keeping it wet? Is there an additive or a stronger type of mix that can be poured? How much more costly is this? Thanks

[Rich]

You've got 2 of the more important factors already - good compaction and slow cure. You can get a stronger mix (4000psi) and pour it at 6" depth. You can add fly ash (concrete co will know what that is) which will make it more durable, although it does make it harder to work with and it sometimes unpredictable. Additional cost is minimal if you're looking to do it right - $14-16 / cy.

[roger g]

I onced asked a concrete guy who did alot of driveways and asked why they cracked so much even though all the right things were done, yet another driveway seems to go crack free. W hat he told me blew me away.
I,m talking about realllly cold weather living now. He said that in the winter the concrete and the ground froze many feet below grade, more than normal because we remove the warm blanket of snow on top plus we drive the frost deep just like on the roadways. I n the winter the sun gets very low on the horizon and if you have a fence or anything beside the driveway you get shadows where the sun never reaches. I think you can see where this is going. Maybe there is a chunk of driveway where you pile all your snow. What you get is sections of the driveway that thaw and sections that never get the sun. It's bad enough that the whole thing freezes and thaws every day but when you get huige slabs of concrete pulling and pushing against each other you get problems.
I don't know whether the guy was right or wrong but it made sense to me.


roger

[Dano]

In addition to new concrete...I have found that it will most likely spall if you use ice melting products (Calcium Chloride the worst)..we use sand for two years prior to these products.