Properties of dumped coal ash after soil mixing improvement


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Title: Properties of dumped coal ash after soil mixing improvement

Author(s): H. J. Liao, C. L. Hwang, S. H. Cheng, K. N. Wong, L. W. Quo and M. J. Lin

Publication: TCI Concrete Technology

Volume: 5

Issue: 4

Appears on pages(s): 52-60

Keywords: coal ash, ground improvement, slag cement, CLSM method, WILL method.

Date: 10/20/2011

The coal ash dump site studied consists of various proportions of fly ash, bottom ash, and slag. The particles of coal ash are porous and spherical in shape. The particles’ quality of high permeability and low shear strength is similar to that of silty soil in engineering properties. For this reason, it is not suitable to be utilized as building foundation without improvement. Therefore, soil mixing method is proposed here to improve the mechanical properties of in-situ coal ash. Two soil mixing methods were adopted: CLSM method for shallow depth improvement and WILL method for intermediate depth improvement. The former uses an on-site mixing plant to mix the coal ash with binder; the latter uses a special mixing arm to mix in-situ coal ash with binder and is capable to construct a grid type layout of ground improvement. The binder used in this study was slag cement. Sea water was used for coal ash mixing. Test results indicate that both methods can effectively increase the in-situ compressive strength of coal ash with the mixing proportion of 100kg binder per cubic meter of coal ash and with the water/cement ratio of 1.67. Also, both methods can have ideal efficiency in economic and practical aspects as applied to coal ash dump.
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