Can I use spray foam on my concrete foundation?

Yes, but closed-cell only.  Our closed cell soy spray foam is rated for sub-terrainian use, under concrete slabs and on foundation walls-both exterior and interior.  We routinely spray on bare ground under concrete slabs which gives huge insulation to the slab.  We also spray directly onto concrete, block, brick, and stone foundation walls.  Once cured, the foamed wall and floor makes a seamless envelope to protect against rodents, insects, water, and cold.