I agree with the epoxy filler. The compressive strength of epoxy compared to products like Sikaflex is ridiculous. You're talking somewhere around 8,000-10,000 PSI compared to a product that you can press in with your fingertip or a screwdriver.
For example.. One of my customers owns a powder coating facility. He rolls carts around all day in and out of powder booths, walk-in ovens, and across his concrete yard. His carts kept getting hung up on control joints. Some of the carts can weigh up to a few thousand pounds. I gave him 4 gallons of a 100% solids epoxy surfacing epoxy and a 10 LB bag of Aerosil 200 fumed silica to mix in to thicken it. He was originally going to go with some sort of polyurethane caulking. After installing the epoxy into hundreds upon hundreds of feet of control joints everything is holding up great 2 years later. BTW this is exterior exposed in the Arizona sun all day, everyday.