Experimental study of CKD as soil stabiliser

This study examines the uni-axial unconfined compressive strength of stabilized clay mixed with different types of binders [1]. The binders tested were cement kiln dust (CKD), lime (CaO) and ordinary Portland cement (OPC) exclusively or in different combinations. Samples were hardened for 1, 7, 28 and 61 days, respectively. It was concluded that up till 28 days neither additions of lime or CKD added much to the stabilizing effect of pure OPC. On the other hand the additions in general did not reduce the strength. Up to 28 days CKD was less effective than lime, whereas after 61 days of hardening the 75/25 CKD/cement blends performed as good as or better than the 75/25 CaO/cement blends. Except for the pure Kjøpsvik CKD specimens, all blends reached 28 day strengths values well above 200 kPa, even those with 75% CKD (Kjøpsvik) at binder dosages of 115 kg/m3 or more. One interesting feature is that the pure Brevik CKD reference specimens had 28-days strength over 250 kPa and a 61-day strength of 650 kPa at a dosage of 190 kg/m3. The values obtained are comparable with values reported in other studies. It is concluded that CKD can be used as binder for soil stabilisation in combination with cement, even at high dosages such as 75%/25% CKD/cement. But for short term periods till 28 days, mixes with lime are more efficient in the specific soil tested in this report. CKD can even be used as binder solely, but then its chemical composition has a great influence of the strength development.