[randomsolutions]

Porous concrete has been useless. It clogs up eventually and loss it's ability to transport water.

The groundwater disappearing is a problem if you build up ag/industry/development based on the groundwater availability and then lose that source of water with no economical alternative.

[b112]

It also seems crazy in certain areas, such as where the ground freezes in winter. All those little pores will freeze and break, turning the entire concrete mass to powder.

People hate unneeded work, so in the old days, if there were large boulders of granite in fields to clear, they'd hand drill holes in the top. Then, over a few winters, the freezing water would break the granite.

[Retric]

It's less of a problem than you would think as water that's liquid will drain through it and snow etc doesn't expand. You generally get pot holes because water pools in an a layer and then expands and contracts, but if it's draining that's not a problem.

Also, air entrainment has long been (~1930's) used as a means of freeze thaw resistance because it allows some deformation without cracking. Porous concrete has similar flexibility.