[ggm]

you know, if you showed us you are a soil agronomist, and cited something we might agree. Or, we might look at the other people commenting some of them who do cite references, who say this isn't retarding natural soil microbiota and isn't going to the at-worst case, making land unusable.

your example of "try this at home" is not actually good. concrete dust before hydration is completely different to the dust made post hydration, or fly ash, or surplus rock dust from mining. The properties of the pre-build and post-build chemical reactivity of concrete (its an exothermic reaction) need to be borne in mind.

That said, aggressive de-carbonisation of industry and agriculture, biochar, wetland remediation, re-forestation are probably vital, and urgent.

[jaclaz]

Maybe you are confusing (or I am not understanding) concrete dust with cement dust.

Concrete dust should be the result of demolition of concrete (already hydrated when it was cement to form the concrete, i.e. post exothermic reaction).

But, allegedly, the concrete surfaces (not reduced to dust) exposed in the Biosphere2 was sequestering both CO2 and oxigen, and - at least in that case - the "solution" was a supplement of oxygen, so maybe the concrete (not cement) dust uses both CO2 and oxigen while basalt only or mainly uses CO2?

Also, whether it is basalt or concrete dust, wouldn't this treatment alter the pH of the soil? (at least here historically where there is an excessively acid soil it is often corrected with additives like calcium carbonate or similar).

[ggm]

my answer was an attempt to get to this point because the OP said "get some cement and sprinkle it on your garden and see what happens" and the whole point was "thats not what people are doing in the farm sector here, they're not using pre-moistened cement dust, they are using post-pour concrete dust, the chemistry is different"

altering the PH can be desirable or harmful depending. thats where the 'get a soil agronomist into the convo' comes in.

from memory, there can be a significant non-bound component of concrete, and it can persist for years. so I accept there is a continuing risk of aggregation of the dust, because it doesn't completely process in immediate time-frame of the pour (I am told that the hoover dam continued to bake off for years afterward)

[jaclaz]

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.