Effects of early hydration of alite and belite phases on subsequent accelerated carbonation: Fid-Bau Portal

Effects of early hydration of alite and belite phases on subsequent accelerated carbonation

Yu, Hao / Tang, Chenxi / Mehdizadeh, Hamideh / Guo, Ming-Zhi / Ling, Tung-Chai

Abstract To better understand the early hydration impact of cement phases on subsequent accelerated carbonation, this study mixed alite (C3S) and belite (β-C2S) with 40 wt% of water for 2, 4, 8, 18 h hydration before exposing to 2 h accelerated carbonation. The results indicated that early hydration exerted a significant impact on C3S (particularly 4–8 h), which accelerated the subsequent carbonation degree (CD) with maximum of 57.27%. Over 8 h, however, packed hydrates impeded CO2 ingress, leading to a decelerated CD and co-existence of different calcium carbonate polymorphs: calcite (dominant for short hydration), aragonite and vaterite (dominant for long hydration). Differently, β-C2S samples with marginal hydrates continuously accelerated CD with time (32.23% after 18 h), and indicated a direct β-C2S carbonation. Detection of calcite and vaterite in carbonated β-C2S samples revealed that carbonates polymorphs varied with calcium silicate and their resulting hydrates participation. This study provides a viable strategy for CO2 storage and microstructure densification, distinct from conventional cement carbonation regime.

Highlights • Various early hydration times of C3S and β-C2S on subsequent accelerated carbonation were studied. • 4-h hydrated C3S pastes led to a higher subsequent carbonation efficiency. • Carbonation efficiency of hydrated β-C2S increased with early hydration time. • Carbonation of hydrated β-C2S was dominated by CH, and followed by direct β-C2S carbonation. • Calcite and vaterite were found in the carbonated β-C2S, along with that, aragonite was also found in the carbonated C3S.