4 ms·

The last time I saw something about these highly porous pavement alternatives, it was pointed out they tend to be very vulnerable to freeze-thaw damage and that

by gipp 9y ago

The last time I saw something about these highly porous pavement alternatives, it was pointed out they tend to be very vulnerable to freeze-thaw damage and that this damage also lowers the porosity dramatically. Basically making these kinds of materials unsuitable for urban use outside of tropical- or near-tropical areas. Has this changed?

galobtter 9y ago
http://www.cement.org/cement-concrete-applications/paving/pervious-concrete/pervious-concrete-and-freeze-thaw http://www.cement.org/cement-concrete-applications/paving/pe... "However, in climates prone to severe freeze-thaw cycles, some are hesitant to use pervious concrete pavements until it has been proven that pervious concrete can be made to resist freeze-thaw damage." Pittsburgh does go through freeze thaw cycle, so I assume there aren't much problems https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/pubs_specs_info/unhsc_houle_thesis_9_08.pdf https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/pubs_spe... According to this, it also reduces the amount of salt needed 75% for deicing and the pavement doesn't seem to have been damaged from reading the abstract.
- mcgrath_sh 9y ago
  Well, if Pittsburgh is using it, it is terrible. We have so many potholes (and huge ones). It has become much worse over the last ~5 years. For several months we had a multi-foot hole blocked off by cones until the city could fix it. It essentially was in the middle of a two way road. It was terrible. I see more and more each winter.
  - sonar_un 9y ago
    That's not because of the cement but the geology of Pittsburgh itself. Limestone bedrock and the "underground river" contributes to potholes and other geologic anomalies. If anything, adding bioswales and having a way to put the water back into the ground would stop the potholes from happening in the first place.
    - vwcx 9y ago
      Yes, but that still doesn't mitigate the rapid freeze/thaw effects on the concrete/asphalt that the City of Pittsburgh uses.
    - keenerd 9y ago
      I think you are confusing sinkholes and potholes. The two aren't really related.
  - ensignavenger 9y ago
    That sounds, from your description, more like a sink hole than a freeze-thaw induced crack? Hard to tell without seeing it.
roel_v 9y ago
Water flows through them, they don't really 'absorb' water. Of course there will be moments when it freezes when there's still water in them, but it's not equivalent to freezing a sponge. The parking lot on one of my buildings is paved with blocks like this (condition for getting the building permit), works great. Never slippery in winter, either. They weren't even more expensive than alternatives.
mabbo 9y ago
The main problem I see with them is people's perception about what porous pavements do. Great, water goes through them... and then what? The ground underneath the pavement is not some unlimited sinkhole for water. The ground table can and does fill up. Then it doesn't matter how porous your pavement is. Trees, grass, wetlands, etc, do better in part because they are preventing the water from leaving. They pool water in small puddles, they absorb water, leaves have water sit on them, etc.

by gipp 9y ago

galobtter 9y ago

http://www.cement.org/cement-concrete-applications/paving/pervious-concrete/pervious-concrete-and-freeze-thaw http://www.cement.org/cement-concrete-applications/paving/pe... "However, in climates prone to severe freeze-thaw cycles, some are hesitant to use pervious concrete pavements until it has been proven that pervious concrete can be made to resist freeze-thaw damage." Pittsburgh does go through freeze thaw cycle, so I assume there aren't much problems https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/pubs_specs_info/unhsc_houle_thesis_9_08.pdf https://www.unh.edu/unhsc/sites/unh.edu.unhsc/files/pubs_spe... According to this, it also reduces the amount of salt needed 75% for deicing and the pavement doesn't seem to have been damaged from reading the abstract.

mcgrath_sh 9y ago
Well, if Pittsburgh is using it, it is terrible. We have so many potholes (and huge ones). It has become much worse over the last ~5 years. For several months we had a multi-foot hole blocked off by cones until the city could fix it. It essentially was in the middle of a two way road. It was terrible. I see more and more each winter.
- sonar_un 9y ago
  That's not because of the cement but the geology of Pittsburgh itself. Limestone bedrock and the "underground river" contributes to potholes and other geologic anomalies. If anything, adding bioswales and having a way to put the water back into the ground would stop the potholes from happening in the first place.
  - vwcx 9y ago
    Yes, but that still doesn't mitigate the rapid freeze/thaw effects on the concrete/asphalt that the City of Pittsburgh uses.
  - keenerd 9y ago
    I think you are confusing sinkholes and potholes. The two aren't really related.
- ensignavenger 9y ago
  That sounds, from your description, more like a sink hole than a freeze-thaw induced crack? Hard to tell without seeing it.

roel_v 9y ago

Water flows through them, they don't really 'absorb' water. Of course there will be moments when it freezes when there's still water in them, but it's not equivalent to freezing a sponge. The parking lot on one of my buildings is paved with blocks like this (condition for getting the building permit), works great. Never slippery in winter, either. They weren't even more expensive than alternatives.

mabbo 9y ago

The main problem I see with them is people's perception about what porous pavements do. Great, water goes through them... and then what? The ground underneath the pavement is not some unlimited sinkhole for water. The ground table can and does fill up. Then it doesn't matter how porous your pavement is. Trees, grass, wetlands, etc, do better in part because they are preventing the water from leaving. They pool water in small puddles, they absorb water, leaves have water sit on them, etc.