turning waste plastic into a lightweight aggregate primarily for use in the concrete industry. addressing two of our biggest environmental challenges with one product plazrok is a solution to the earths overwhelming plastic pollution problem while giving concrete manufacturers an eco-friendly alternative to standard aggregate.,selkirk soil and aggregate home facebook,selkirk soil and aggregate. august 7, 2018 . see one of our finished projects from this summer complete with retaining walls, patios, water features, and dozens of plantings. contact selkirk soil to inquire about our landscape and design services 2121. 3 comments 6 shares.