Recycling of Spent Abrasive Media in Nonstructural Concrete

Abstract

Spent abrasive media from bridge repainting operations contain metals which may result in the media being classified as hazardous under the Environmental Protection Agency (EPA) Toxicity Characteristic (TC) criteria. The management of spent abrasive media by recycling it as a component of nonstructural concrete was investigated. Success was measured with respect to the TC criteria for leaching and a compressive strength requirement of 6.9 MPa (1,000 psi). Portland cement, with and without the additives used, successfully immobilized the metals present in the media. However, not all of the mixes prepared set, indicating that there is a limit to the amount of media that can be recycled in a concrete product. Mixes incorporating 100% unseparated spent abrasive sand and dust or slag in place of clean sand successfully met the project criteria. Mixes containing up to 25% addition of separated spent abrasive dust met the project criteria with the inclusion of appropriate mix additives. Based on results from this and earlier studies, the Texas Department of Transportation has begun to recycle spent abrasive media using portland cement.