mudjacking with grout or with polyurethane

You may want to read this article, and for more information you can dig into the references in the article http://hmicompany.com/blog/polyurethane-concrete-raising-vs-traditional-mudjacking/.

Note that the article points out that urethane foam mudjacking has advantages where the subgrade is weak, and the lower unit weight of polyurethane will not compress the subgrade as much as traditional mudjacking. In your case, the only way to evaluate which is better is to have knowledge of your subgrade, and a cost estimate so you can make a good comparison of the two approaches in your particular situation.

The base under the slab is gravel over clay. Mud jacking with grout was estimated at $1300 for slab 24x20 feet and 4x8 section of sidewalk. I am waiting for an estimate on urethane. I expect that to be at least twice as much and maybe more like 3x as much.

It's sometimes cheaper to replace than mud jack it, 6 1/2 cu. yds. in your case plus labor.

Just out of cuiousity, where do you live? Conventional mudjacking would be closer to $300-500 here in this area for that job, unless there's some obvious indicator that there's a huge void under the concrete currently.......

both have their fans & we've done both,,, i still like conc slurry better as its more predictable,,, posting where YOU are would've been polite, followed system's rqmnts, & not wasted jomama's time

Oh, sorry about not providing location. I didn't mean to be rude. I'm in eastern Iowa.