Compaction and consolidation behaviour of untreated and treated waste of Indian red mud

This study deals with the evaluation of the compaction and consolidation characteristics of untreated as well as hydrochloric acid (HCl)- and sodium chloride (NaCl)-treated red mud wastes. A series of standard and modified Proctor compaction and one-dimensional consolidation tests were conducted for the study purpose. Sodium chloride solutions of 1.71 and 3.42M and hydrochloric acid solutions with pH of 1, 1.5, 2, 3 and 4 are selected to treat the waste. Results show that standard Proctor compaction tests yield inconsistent and low dry unit weight values with relatively high optimum water content. On the other hand, modified Proctor compaction test produced consistent dry unit weight values with low optimum water content. There is only a marginal improvement in dry unit weight and compression properties of hydrochloric acid-and sodium chloride-treated samples; however, the treatment proved effective in reducing pH of the waste. It has been noticed that the compressibility of both untreated and treated samples is appreciably low. Results elucidate that parameters such as the size of the particles and their shape, chemical and mineralogical compositions and surface charge properties can influence the compaction and compressibility characteristics of the waste. Overall, the study demonstrates that the red mud waste could be a potential resource material for geotechnical engineering applications.