emilio57 wrote:Soil poor in clay and silt. However there is something more than sand, because it is paradoxically hard, compact, even where we have covered.
I just allow myself to copy a hypothesis formulated on page 3 of this thread:
Yes something is wrong ... And I repeat, on the basis of the few photos (aspect, color) and history described (gardens, houses of miners) an assumption of relatively substantial contributions over several decades of ashes I may be completely wrong, it would be no worse ... there is only a chemical analysis of soil that would allow to see clearly.
Composed mainly of SiO2 (sand to simplify), the main industrial use of coal ash is the incorporation into the clinker and cement production line, either upstream (in the "raw", before introduction into the furnace), or downstream (at the clinker grinding level). And in both cases it is not silica that is sought, but Al2O3 and calcium compounds ... which are the basis of a good cement!
Just a question to Emilio: in some places, when it's dry, stirring, you do not see tiny black particles, which would be the sign of unburned?
Let's be clear, I wish I was wrong!