Activations and properties of cementitious materials made with cement-kiln dust and Class F fly ash

Activation methods and their effects on strength development of nonclinker cements made with 50% cement kiln dust (CKD) and 50% Class F fly ash (FA) were investigated. These activation methods included (1) ball mill cogrinding; (2) chemical (2 and 5% NaOH) addition; and (3) elevated temperature curing (38 and 50 degrees C). Particle size distribution, hydration products, and compressive strength of the CKD-FA binders were studied. Soluble alkali and chloride content as well as pH value of the CKD-FA pastes were evaluated. The results indicate that all activation methods improved binder strength development. The strength improvement was more significant at the early age than that at the later age. Curing at elevated temperature appeared to be the most effective activation methods compared with grinding and NaOH addition. Combined activation methods provided the binder with higher activation effectiveness than any single activation method. The CKD-FA pastes had much higher alkali and chloride contents but slightly lower pH value than the corresponding portland cement paste.