Abstract
Abstract The effects of inorganic ions, organic polymers, and fly ashes on the sedimentation characteristics of kaolinite suspensions, which include the particle associations, sedimentation mode, initial settling rate, final sediment height, and soil formation time, were systematically investigated through the batch sedimentation tests. The addition of salt and polymers were found to change the microfabrics of kaolinite and influence the sedimentation modes and settling rate of kaolinite suspensions. Due to the effects of charge neutralization and polymer bridging, cationic polymers such as cationic polyacrylamide (CPAM) and chitosan were found to facilitate flocculatation and aggregation of kaolinite, therefore, increased the settling rate and decreased the final sediment height. On the other hand, anionic polymers, for example, the polyacrylic acid (PAA), was found to relatively delay the process of settling and prolong the soil formation time due to the pseudoplastic nature and large repulsive forces among negatively charged polymers and negatively charged kaolinite particles. Fly ash hydration increased the ionic strength, which changed the the kaolinite from dispersed free settling to flocculated zone settling. In addition, fly ash particles were found to collide with the kaolinite particles during settling and form large agglomerates, therefore the settling rate of fly ash-soil mixture increased with the addition of fly ashes.
Published Version
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