Abstract
Recycled brick powder (RBP) as an aluminosilicate-rich material has shown great potential as a new type of supplementary cementitious material (SCM). However, the interaction mechanism between cement and RBP has not been clarified yet. In this study, the pore solution chemistry, phase assemblage and nano-structures of RBP blended cement paste were revealed. The pore solution chemistry indicated that RBP facilitates the dissolution of C3S and the precipitation of C-S-H, but inhibits the precipitation of CH. Hydration kinetics modelling results showed that RBP accelerates the nuclei formation but retards the growth of hydration products during boundary nucleation and growth process. FIB-TEM and thermodynamic modeling results demonstrated that the additional [Si] and [Al] ions dissolved from RBP contribute to the reactions: (1) the [Si] and [Al] react with the CH to form C-A-S-H gel with Al/Ca and Si/Ca molar ratios of 0.32 and 0.62, respectively; (2) the [Si] and [Al] reorganize to form nano clusters, such as hydrotalcite-like phase, AFt nano-crystals, AFm phase and C-(A)-S-H gel. Therefore, blended mortar with 30–45 % RBP replacing cement has slight or no late-age mechanical properties loss and presents 25.2–30.3 % decrease in chloride ion diffusion coefficients. Additionally, compared to blended cement utilizing traditional SCMs, like FA and GGBFS, RBP blended cement presents a 6.4–26.1 % reduction in cost and 21.4–41.6 % decrease in natural resource consumption, which contributes to great economic and environmental benefits.
Published Version
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