Sharpening materials clog by the plastic very fast and smear the entire soil. Either one lives thereby, or one schmeisst it raus.
Agglomerates have always an inhomogenous abrasion and are actually unfit for a strained area.
They are by the way also inflammable, contrary to natural stones. If you liked to know more details about Agglo please short mail to transmit, I had some press articles over it written.