I have a 25 year old concrete patio that has several 2"X2" redwood expansion joints in it. These joints are now warping and are causing a safety hazard. Is there any polyurethane material that could be used to replace the redwood expansion joints? What would you suggest? I live in the Mission Viejo (Orange County) region of California. Are there contractors in that area that do this kind of work?
Thanks much for your assistance!
Mark :)

Call a good concrete contractor for an estimate. They have several materials to choose from including a grey liquid rubber that pours into the crack.

You might find a solution by contacting a swimming pool contractor... they have to install expansion material at the edge of every pool deck at the coping (border of the pool/deck) and the material that they use is very durable and flexible.