Void filling under footers for pier & beam from erosion

Have a property in north texas with clay soil. Lots of erosion with large voids under the perimeter concrete footers that i’d like to fill. Erosion issues have been corrected but need to fill these voids before encapsulating the crawl space. What is the best product to use to fill these voids? I was thinking of using sand which a structural engineer said should be fine but sand + clay soil is somewhat concerning. Also what impacts would that have in attracting bugs etc. over the years. Any foam based products seem very gimmicky and don’t seem to last. Is there any better suggestions on what should be used to fill these voids?
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Replies
evamore,
I would be more comfortable repairing the voids in a way that returned their ability to be load-bearing. As it would be difficult to compact any aggregate material you push under the footings, I would probably use concrete.