RECYCLING OF SPENT ABRASIVE MEDIA IN NONSTRUCTURAL CONCRETE

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) cri teria. The management of spent abrasive media by recycling it as a com ponent of nonstructural concrete was investigated. Success was measure d with respect to the TC criteria for leaching and a compressive stren gth requirement of 6.9 MPa (1,000 psi). Portland cement, with and with out the additives used, successfully immobilized the metals present in the media. However, not all of the mixes prepared set, indicating tha t there is a limit to the amount of media that can be recycled in a co ncrete product. Mixes incorporating 100% unseparated spent abrasive sa nd and dust or slag in place of clean sand successfully met the projec t criteria. Mixes containing up to 25% addition of separated spent abr asive dust met the project criteria with the inclusion of appropriate mix additives. Based on results from this and earlier studies, the Tex as Department of Transportation has begun to recycle spent abrasive me dia using portland cement.