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I have four 4 ft. x 4 ft. raised beds with a 3 ft. path between them forming a +. The raised beds are made from 2x8 untreated pine boards. The layout looks like this...

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I have a mix of concrete and clay brick pavers from last year's patio project that I would like to put in the middle to keep the weeds down and provide a nice hardscaped path between the planters but I'm worried they will put harmful chemicals into the soil that will leech into our veggies. Should I be concerned about leeching chemicals off of the pavers? Are there any other concerns to consider such as acidity from the concrete?

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I think you are worrying about nothing here. Concrete and clay bricks are essentially rock. They don't have any "chemical additives" in them.

In fact concrete is alkaline, not acid. If it does have any (small) effect on the soil chemistry, it will be beneficial in the same way as using agricultural lime.

Calcium levels in soil are gradually depleted because calcium is removed in the crops you harvest, and applying lime restores the correct balance. Of course you can overdo this to get an unsustainable short term benefit if you use lime and nothing else - there was an old English farming saying, "lime and lime and no manure makes fathers rich and children poor". But a few concrete slabs won't cause that sort of problem!

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With pavers I think the primary concern would be the possible usage of fly ash which in turn can contain dangerous heavy metals. From what I have read it is a hazardous waste leftover from coal manufacturing and may be used in making pavers and cinder blocks. Unfortunately you don’t really have any way of knowing unless there are tests you can pay a lab for but I would worry about inconsistencies leading to a sample being clean but the rest of the paver not. As to how much if any of the fly ash, if present, might leach into your food I haven’t found any articles only ones saying it may be a health hazard. That said with raised beds and the pavers not being under them I’m not sure I, personally, would be too concerned.

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