The Hydration of β- and α'_H-Dicalcium Silicates: An X-ray Spectromicroscopic Study

Journal Article · Thu Dec 20 00:00:00 UTC 2018 · ACS Sustainable Chemistry & Engineering

DOI:https://doi.org/10.1021/acssuschemeng.8b05060· OSTI ID:1656495

Li, Jiaqi ^[1]; Geng, Guoqing ^[2]; Zhang, Wenxin ^[1]; Yu, Young-Sang ^[3]; Shapiro, David A. ^[3]; Monteiro, Paulo M. ^[1]

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1. Univ. of California, Berkeley, CA (United States). Dept. of Civil and Environmental Engineering
2. Univ. of California, Berkeley, CA (United States). Dept. of Civil and Environmental Engineering; Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. for Waste Management
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)

Dicalcium silicate (C₂S) is an important clinker mineral in Portland and belite-calcium sulfoaluminate cement. However, there is still a lack of information on the local degree of silicate polymerization and calcium coordination in C₂S hydration products. Here we aimed to fill this gap by characterizing the hydration of two C₂S polymorphs, the β- and α'_H- types, using scanning transmission X-ray microscopy coupled with ptychographic imaging. The results showed that the coordination of the Ca species in β- and '_H-C₂S had a distorted, cubic-like symmetry, whereas the Ca coordination of calcium silicate hydrate (C-S-H), the main hydration product, was structurally similar to that of tobermorite. The outer hydration product (Op) of both polymorphs exhibited an increasing degree of silicate polymerization over time. The inner hydration product (Ip) of β-C₂S polymerized slower than Op; however, the degree of silicate polymerization of both Ip and Op in the α'_H-C₂S hydration system was comparable. The polymerization degree of Op was relatively heterogeneous, whereas, in α'_H-C₂S, the polymerization degree was more homogeneous. Ptychographic imaging shows that the Op of α'_H-C₂S exhibits coarser fibrils than the Op of β-C₂S, and a clear Op–Ip interface of hydrated β-C₂S is observed.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1656495
• Journal Information: ACS Sustainable Chemistry & Engineering, Journal Name: ACS Sustainable Chemistry & Engineering Journal Issue: 2 Vol. 7; ISSN 2168-0485
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
calcium coordination
calcium silicate hydrate
dicalcium silicate
low carbon cement
morphology
portland cement
silicate chain polymerization