Sure, I was only trying to distinguish cement dust from concrete dust, the OP mentioned concrete dust, not cement, and he mentioned it being "waste":
>Just try adding a bunch of concrete dust to your basil plant in the window sill, see what happens. Most likely this will be the source, as concrete waste is a huge issue in most population
About aggregation, there are usually big differences between the different kinds of cement, modern Portland cements tend to end hydration (and thus hardening) within months, whilst good ol' Pozzolanic went on for years.
But I wouldn't be surprised if such a massive pour as a dam would go on hardening for many years.
>Just try adding a bunch of concrete dust to your basil plant in the window sill, see what happens. Most likely this will be the source, as concrete waste is a huge issue in most population
About aggregation, there are usually big differences between the different kinds of cement, modern Portland cements tend to end hydration (and thus hardening) within months, whilst good ol' Pozzolanic went on for years.
But I wouldn't be surprised if such a massive pour as a dam would go on hardening for many years.