The Effectiveness of Asbestos Stabilizers During Abrasion of Asbestos-Cement Sheets

The effectiveness of different organic stabilizers in stabilizing asbestos in fiber cement was evaluated using brush-abrasion tests on asbestos-cement (AC) sheets and counting the number of released respirable fibers using phase-contrast microscopy (PCM). All asbestos fibers released from the abraded sheets were identified as chrysotile. The binding effectiveness of the stabilizers varied from 35% (bitumen-based) to >90% (polyurethane resin (PUR), acrylic paint, flexible coating). Stabilizers with low binding efficiency, i.e., <80%, should not be used for coating. The 80% binding efficiency limit is suggested based on the performance of PUR stabilizer applied to the surfaces of AC sheets that were primarily in good condition. With very deteriorated surfaces, even the best performing stabilizers will not prevent fiber release on a scale comparable to that from unprotected sheets in good condition. The greatest effectiveness in binding asbestos fibers is achieved by applying stabilizers that combine a hard coating (PUR), high degree of flexibility (flexible coating) and adhesiveness (acrylic dispersion paint). A simple brush-abrasion test is recommended as an inexpensive, fast and reliable method for evaluating the performance of stabilizers. The brush-abrasion test can reveal invisible deterioration of the cement matrix weakening asbestos-fiber attachment to AC sheets.