Glenn Herbert wrote:"plus we cannot trust industry to operate incinerators at any kind of thorough level"
True, except that the concrete industry needs to operate at extreme temperatures to make its product. If they skimped, they wouldn't be making functional concrete.
Moreover try as they might the producers can not exceed a certain percentage of "alternative fuel" addition (as the scrap tires and toxic waste are called in the industry) as they need to maintain the cement quality and stack emissions in limits.
With relatively long retention times and temperatures of ~2000 deg C range hardly any compound added to the kiln has a chance to survive in its original form.
The only issue may be of heavy metal leaching in acid environments.
I have designed concrete mixes in the past as a Civil Engineer.
There are a few points that need clarification.
'Cement quarry rocks' are really aggregate, [ stones], crushed usually from basalt outcrops, that become the aggregate or stones in a concrete mix.
Similar aggregate is used as the base for roads, in different sizes big ones at the bottom and smaller at the top, it is used as filling under concrete slabs
and anywhere are hard wearing non soluble material is required.
In fact in Australia, the dust from crushing plants is sold as Rock Dust and has many minerals which are claimed to be very good for the soil.
Cement is an additive to concrete, not the name of the final product.
Concrete is made from a mixture of Aggregate, sand and cement.
By varying the size and type of those items different strengths can be achieved. Generally the high strength concretes have more cement.
Cements themselves can vary and again have different results for different outcomes.
Admixtures are additional items put in the mix to slow down curing, speed up curing depending on the weather, some make it waterproof,
others, with different aggregate sizes make it flow better when being put inside hollow blocks.
Here Fly Ash has been banned, it creates problems for concretors, people wholly the concrete, and has caused issues with the concrete not gaining its full strength.
Concrete dust is as bad for humans as any other dust and care needs to be taken when grinding or cutting it.
Used properly it is a product that has enabled the type of structures people expect to have in communities today.
The use of lime with it changes its characteristics and many people like the benefit of it. For instance Limecrete is fantastic for exterior patio floors,
because it does not reflect heat the same way a concrete slabs does in hot climates.
I hope this helps with your understanding of the variations and the uses of concrete.
to label it as bad is something many would dispute.
John Daley Bendigo, Australia
The Enemy of progress is the hope of a perfect plan
Look up the toxins leached from cement and cinder blocks. The advice is to line beds to prevent soil coming into contact with cement, cinder blocks, concrete because most of it now contains fly ash and/or bottom ash from coal fired electricity plants.
Although fly ash is more stable when mixed with cement than when it is loose, it still leaches heavy metals in small amounts. A literature review could not recommend concrete for water tanks.
It is quite gutting, really, as my budding permaculture garden is in a back garden full of concrete.
However, heavy metal's concentrations leached from concrete containing FA (fly ash) are significantly inferior and very close to the EPA drinking water standard (except for Cr and Zn, which were slightly over the limits) (Fig. 4).
This is from the link Lara included. In other words, your irrigation water might be adding almost as much heavy metals to your garden as your concrete. (And I don't see Zn as a contaminant unless it is in crazy amounts.)
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