Expansion joints should have some sort of expansive material to allow for movement between the pieces of concrete. Your best bet is use some backer rod and silicone joint sealant. The backer rods purpose is just to save money on sealant. The sealant will actually serve adhere to the concrete and expand and contract with the slabs. The sealant should keep moisture and ants/dirt out of the joint.

Riles

Thank you for your reply.

I realized after I posted that I used the wrong term. I meant the saw cuts, not expansion joints. Does that change the answer?

These control joints should not be effected by putting the polymeric sand in them. Their sole purpose is to create a weakened plane in the concrete to control the cracking. I have never seen the polymeric sand used in this manner. Maybe someone else will chime in. I would think silicone or some other crack sealant would be more appropriate. Have you checked whats available at the local home improvement store?

Riles

Hold on ya little Buckaru....this whole thing is about Ants???

If so no amount of anything placed into the expand joints is going to help. You need to drift on over to the home depo and get>>>>>Terro ant killer