Avoid cracking for a patio

[stewchi]

I have a very old patio like a checker board, of 2ft sq cement squares separated by 2x4s skinny side up. The patio was poured with the 2x4s in place (rebar runs through them) however its is between 50-100 years old and the 2x4s have rotted out. I have cleaned out the gaps and would like to fill them in, what is the best ,material to fill the gaps left by the old 2x4s. I would like to fill them in with colored cement but I am worried about cracking, as I live in the Chicago area the cold winters and warm summers may be a problem. I do not want to use sand or gravel or anything else that I can not hose or wipe down. Any ideas would be appreciated. Replacing the wood is another option but requires a lot of work to notch out the 2x4s were they intersect each other in the grid (144 notches, 1 notch per 2x4 at each of the 72 intersections, 2 2x4s at each intersection)

[Rich]

Any concrete product (except for very expensive mix designs) will end up cracking.. especially in that small of a cross section involving corners.

[mjpliv]

There was a time that you could by rubber pavers. They were manufactured with recycled car tires. If I am not mistaken they were about 2" thick and were popular for pool decks and playgrounds. You would be able to drop them in the space and if they were a little tight you wuld just beat them in with a mallet. If you encounter a piece of rebar notch the paver to slip over it. They were available in colors too!

[stewchi]

Would metal lath just below the surface help avoid cracking. I picked up some quickrete Non-Shrink Precision Grout to use in the 1-1/2wide by 3-1/2deep gaps between the cement squares. Would cutting 1-1/2 strips of lath to set just below the surface provide better resistance to cracking or does it matter?

[mjpliv]

I would suggest you ask your supplier about some sort of polymer additive. This is essentially the same thing that tile layers add to their grout to keep it flexible.

If it is available, follow the mixing instructions to the letter.