Utilization of modified CFBC desulfurization ash as an admixture in blended cements: Physico-mechanical and hydration characteristics

Circulating fluidized bed combustion (CFBC) desulphurization ash was modified by grinding and chemical activation. The particle-size distributions and water demand ratio of the different modified CFBC desulphurization ashes were studied. The strength and hydration products of blended cements with modified CFBC desulfurization ashes were also investigated. The results showed that particle size distributions of modified CFBC desulphurization ashes were effectively optimized and its water demand was obviously decreased. Strength of the blended cements increased significantly with the increase of grinding time, the strength increased due to the activation effects of the modifiers. Sample intergrinding with 0.5% w(1), 0.5% w(2) and 0.8% w(3) had the best activation effects. Moreover, when ash content was lower than 10%, the strength was higher than that of Portland cement (C-0), and the strength decreased with the addition of the modified ashes when its content was over 10%. However, the strength of mortars at 28 days was still comparable to that of C-0. The main hydration products of the blended cements with CFBC desulphurization ash were C-S-H (hydrated calcium silicate), AFt (ettringite), and portlandite. The results also indicated that the modified CFBC desulfurization ashes can be utilized as an admixture in cement or concrete. (C) 2012 Elsevier Ltd. All rights reserved.