Abstract
This paper presents a laboratory study on the use of Cement Kiln Dust (CKD) as an activator of fly ash when used in high volumes within concrete. Two separate batches of fly ash and CKD were tested to assess the effect of material variability on binder properties and compressive strength gain. Ternary blends of fly ash (55% - 65%), CEM 1 (30%) and CKD (5% - 15%) and quaternary blends that included moderate amounts (15% - 18.5%) of Ground Granulated Blast-Furnace Slag (GGBS) were prepared. Physico-chemical properties of individual binder materials were compared and concrete compressive strength was measured at 2 days, 7 days and 28 days. Ternary blends of 60% fly ash, 30% cement and 10% CKD resulted in moderate early age and 28 day strength and addition of GGBS enhanced strength significantly due to increased ettringite formation. Particle fineness, water demand and LOI content of fly ash and CaO and SO3 content of CKD were found to be the main physico-chemical factors that influence compressive strength gain.