Yes they can. If there has been a few days since the concrete has been cast, the location of the shrinkage cracks has likely been determined. You may have cracking occur between the new installed joints. You often find cracks form near sawcut joints. I've seen it often with sidewalks and...
Thanks... if originally cedar, there are natural extractives that give it moisture, rot and insect resistance. Some cedars are better than others. Do you know if there are any tests undertaken to see if there's an improvement in the material?