Soil Stabilization and Modification Using Fresh and Landfill Cement Kiln Dust (05-1892)**
Asha Shreekrishnavilasam, Purdue University
Sunie Rahardja, R.W. Armstrong
Robert Kmetz, Purdue University
Marika Santagata, Purdue University

A laboratory study was undertaken to evaluate the performance of two fresh and one landfilled cement kiln dust (CKD) for soil stabilization. The experimental program made use of three CL clays and included compaction, unconfined compression, swell, CBR tests as well as limits and pH measurements on the soil-CKD mixtures. Despite the strong similarity in composition and particle size the three CKDs performed very differently. Only one fresh CKD was found to be sufficiently reactive (thanks to presence of free lime), and showed potential to be used for soil stabilization at addition levels of 15% or greater. The treatment effectiveness was observed to be markedly soil dependent, and significant improvement in strength was observed only when the CKD addition was associated with small changes in the moisture-density relationship. The results for the other fresh and the landfilled CKD suggest that these materials may be used for treating wet subgrades or water logged areas. In presence of 10-20% of these CKDs it became possible to compact soils at water contents outside their compaction range, and the further addition of 1% Portland cement produced mixtures of considerable strength. The results obtained highlight the importance of knowing the plant operation history and chemical composition (specifically free lime) of each batch of CKD collected; they demonstrate that the loss on ignition is not a good indicator of the reactivity of a CKD; and suggest that the change in plastic limit and possibly in pH may give insight into the potential of a particular CKD for soil stabilization.