Erwin Decoene wrote:Re-using old concrete is green because you prevent the dumping of the stuff in landfill. You also prevent the CO2 emissions and adding to the gaping holes in the ground that would be needed to mine new limestone or gravel. So re-use is sure greener than dumping and mining new building materials.
Concrete is not that polluting. Once the setting reaction is over it just weathers like natural rocks would do. Improperly set concrete or cement can seriously change the acidity of the soil and groundwater. I measured pH's of up to 11,5 in dirt because of improperly set concrete.
In some cases polluting stuff has been used as a filling material in the concrete/cement. A filling material is used to reduce the use of expensive cement. Mostly aggregates are used as filler but other stuff has been used as well. Eg Stay clear of concretelike building materials containing slag, cinders or ashes. Even if the bad stuff is not disolving it may cause trouble in the long run - releasing heavy metals in the environment.
If you re-use stuff, spend some tought on what has to happen to remove/recycle your building. One of the mayor problems with recycling building materials is the lack of knowledge concerning origin and composition of the materials used.
Gilbert Fritz wrote:I'm not sure about foundations, but I have some really cool retaining walls/ beds made of recycled concrete. I even got a bunch of iron oxide stained ones, which really looks like stone.