I recently built a side brick wall along the property, I end up with lots of this little rock used in the mixture with the sand and cement to pour it in the rebar reinforcement of the wall, since I don't have use for it I was considering use it as a mulch for keeping away weeds from the trees, would this be OK or damage the tree, soil, or something else? I'm thinking it could block oxygen into the soil but I'm not sure any guess?