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8This study investigated setting times and early age compressive strength of the high volume fly ash (HVFA) blended 9 pastes prepared with ground materials. The pastes consisted of 60% Fly Ash + 30% Portland cement (CEM I) + 10% 10 cement kiln dust (CKD) and tests were carried out for four different fly ashes. In phase 1, all the constituent binder 11 materials (class F-fly ash, CEMI and CKD) were initially mixed in the relevant proportions and were ground for 12 varying time periods (1, 2 and 4 hours). In phase 2, the CEM I and CKD were mixed and ground for different time 13 periods (1 and 2 hours) and then added to the unground fly ash. Both wrapped and submerged curing were used 14 for compressive strength test samples. Overall, grinding of constituents appeared to be largely ineffective at 15 increasing 2 day compressive strength although strength enhancements at 28 days were generally observed. Paste 16 samples that were made from interground constituents generally achieved higher 28 day strengths than 17 corresponding pastes where only the activators were ground, although this was not consistent throughout so 18 further investigation is suggested in this area. Submerged curing is generally less effective in increasing compressive 19 strength than wrapped curing as leaching of CKD is suspected to have occurred. 20 21

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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.