Gardening Note: Toxins in Concrete Blocks and Concrete
By George Giltner, Adv. Master Gardener, MS Biology (and Pesticide Applicator Certified)
Gardeners love raised beds. And, raised beds are so easily built with concrete blocks which are thought of as the most inert and safest product on the market for gardening. Gee, I hate spoil your perceptions. Like the commercial food we consume, some is good and some is bad, just like concrete products used in gardening.
Masonry block and concrete producers use coal combustion byproducts in two ways – fly ash as a cement replacement and bottom ash as a partial replacement for the sand and/or coarse aggregate. The fly ash composition varies from 5 to 60+ percent depending on the product. Adding fly ash prevents hydration of lime which increases its strength and makes concrete less porous, makes finishes smooth, and eases concrete pours. Seems like the ideal…
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