Mechanical properties, microstructure and life-cycle assessment of eco-friendly cementitious materials containing circulating fluidized bed fly ash and ground granulated blast furnace slag

Abstract

To reduce CO2 emission from the cement industry and solve environmental issues caused by the accumulation of circulating fluidized bed fly ash (CFA), this study aimed to prepare eco-friendly cementitious materials using CFA and ground granulated blast furnace slag (GGBS) as supplemental cementitious materials. The hydration properties, reaction kinetics, microstructure and life-cycle assessment of blended cements were investigated. The results showed that the compressive strengths of the blended cement samples containing 10 % CFA and 20 % GGBS increased by 7.3 % and 5 % at 7d and 28d, respectively, compared to the pure cement paste. The hydration process was characterized using isothermal calorimetry and analyzed by the Krstulovic-Dabic (K-D) model. The blended cement paste with the best compressive strength exhibited the highest total hydration heat release throughout the hydration process, with extended reaction times. The synergistic effect of CFA and GGBS promoted the formation of C-(A)-S-H gel, consuming more portlandite and leading to a decrease in the most probable pore size and an increase in gel pore volume in the pore structure. From the perspective of cost, economy, and environment, the normalized strength cost, energy consumption efficiency index, and CO2 intensity index can be reduced by 16.1 %, 27.1 %, and 33.3 % respectively. This work contributes to a better understanding of the synergistic mechanism in the CFA-GGBS blended cement system, and serves as a significant reference for the development of economical and eco-friendly cementitious materials.