Hello, I'm looking at using slag c

[clayR]

Hello,
I'm looking at using slag cement and portland blend stabilized with bentonite for the purpose of backfilling an abondoned utility.
What is the best ratio between slag/portland?
My mix water will be at about 6% bentonite by wt of water, and I'm thinking a 2:1 water/slag+portland should give the 200 psi at 56 days? Does anyone have experience with a mix like this? clay

 

[Ron]

I would suggest you put sand in this mix as well. Using bentonite, portland cement, and ground blast furnace slag (GBFS)cement in a water slurry will result in high shrinkage on curing. I would suggest a 10% bentonite, 5% cement (50/50 blend), 85% sand mix with enough water to give placement consistency.

 

[clayR]

Ron,
Thanks for the reply, yes sand will reduce shrinkage but will also reduce my ability to pump any great distance. I want to pump 2,000 ft +/-. I think I can live with the shrinkage with the addition of post grout pipes fixed to the top of the box. I currently have mixes being tested to confirm 200 psi. Will keep you posted on the results. clay