Laura, It sounds like you are dealing with contraction joints, not expansion joints. These joints are just meant to control cracking. The self-leveling sealer should work fine, however, I have to be honest I have limited experience with concrete patios. I design large concrete pavements for runways and airports. The applications are a little different. We seal our contraction joints with self-leveling silicone. My only fear is that your expectations might be a little overreaching. Your concrete is always going expand and contract, it's the nature of the beast. The sealer is really meant to eliminate water infiltration, not to provide a completely smooth surface. The troweled joints that you have may be very shallow as well, which might lend to the potential for the sealant to be pulled out due to the lack of vertical surfaces to adhere to. You might want to check with someone who pours concrete patio's or driveways and get their feedback. I don't think it could hurt to try it on a small area though to see if it meets your expectations. Let me know if I can be of any more assistance. Riles

Thanks for the responses. I live in Wenatchee, WA about 2-3 hours from Seattle. I checked with pool supply stores here but they have to order and it would take over a week. I can't think of any caulking or waterproofing supply around here other than Lowes or Home Depot and I don't think they carry this(Deck-o-Foam, Poli-Void) however I will be checking today. Problem is nothing else is open today so I may have to reschedule the concrete. Would anything else work?

DocZ, This area is often ignored, but it should also have an expansion joint. Joints are particularly helpful if the deck is poured all around the back of the spa. If the deck is only 3' or so, then the deck installer may be counting on the nearest expansions on either side of the spa to do the job. Concrete generally shrinks slightly after its poured.

Looks like the tool they used is to manage cracks. There should be a full expansion joint. This can easily be fixed by cutting the joint, then sealing it with a foam backer and self leveling crack caulking.