I’m installing a 170 foot long French drain in my basement. We have to cover the trench with concrete to restore the basement slab. The basement is getting finished so it’s important that the replaced concrete over the trench matches up nicely and doesn’t shrink noticeably so flooring works nicely.

When I add the amount of water specified to bagged concrete mixes, it’s very dry and unworkable for me. I add about 15% more and it’s still dry, but workable enough. When I see videos of concrete pours the mix is very wet and very soupy compared to mine. Why?

I’ve read that aside from making the mix weaker, the more water the more shrinkage. Is there a way I can create a mix that flows better but won’t shrink excessively? Are there additives? What would they be?

BTW – I had installed underfloor piping for a bathroom a few years back and the concrete I used to restore the slab did shrink enough that it’s noticeable when dragging a shoe across the seams.

Thank you.

 

What the bag is recommending is a proper mix or at least a more proper mix. A dryer concrete mix can be worked but it's more work so many online videos go way over on the water. A very soupy mix can be easier because it almost self levels and it makes mixing easier but it can seriously weaken the pour. If you went 15% over on the water and got a mix you could work with I would put in the extra labor and work with the stiffer mix.