The Methylene Blue Test for Bentonite Liner Quality Control

An in-situ procedure for evaluating the quality of soil and soil/bentonite admix liners is described. The methylene blue (MB) test is based on the principle that cationic dyes base exchange in proportion to the clay content in soils or clay slurries. The number of exchangeable ions present is determined by replacing these ions with methylene blue. The MB test is the accepted standard of measurement of clay levels in bentonite bonded molding sands used in the foundry and steel industries. Lab tests have shown that the methylene blue method is useful to test the quality of bentonite liners, bentonite slurries, and soil bentonite backfills for slurry trenches.