Identification of Chemical Bonds and Microstructure of Hydrated Tricalcium Silicate (C3S) by a Coupled Micro-Raman/BSE-EDS Evaluation.

Zheyu Zhu,Yue Zhou,Kai Wu,Yuting Chen,Zhongping Wang

doi:10.3390/ma14185144

Abstract

Identifying the phase evolution and revealing the chemical bonds of hydrated cements accurately is crucial to regulate the performance of cementitious materials. In this paper, a coupled Raman/BSE-EDS analysis was proposed to determine the chemical bonds of tricalcium silicate hydrates and the interface transition zone (ITZ) between inner C-S-H and anhydrates. The results show that the Raman/BSE-EDS method can accurately identify the chemical bonds of inner C-S-H and inner ITZ regions, which confirms the mixed structure of inner C-S-H and nano calcium hydroxide (CH). The inner ITZ shows a lattice change region with a thickness of 700–1000 nm, which can be attributed to the pre-disassembly process of C3S crystal. The successful application of coupled Raman/BSE-EDS provides new insight into the hydration process and multi-structure features of traditional cementitious materials.

Highlights

It is attractive to find solutions to tailor the performance of cementitious materials accurately in scientific and engineering society [1,2,3]
The analysis shows that the chemical bond provided an important indicator for this mixed structure
BSE-Raman correlative microscopy combined with Raman/BSE-EDS is a powerful method that can reveal the local micro-nanostructure, chemical bonds, and compositions of hydrated cementitious materials

Summary

Introduction

It is attractive to find solutions to tailor the performance of cementitious materials accurately in scientific and engineering society [1,2,3]. As the dominant mineral of Portland cement clinker, tricalcium silicate (C3S) reacts with water to form calciumsilicate-hydrate (C-S-H) and calcium hydroxide (CH), determining the final performance. Since this chemical reaction ensures the safe and high-efficiency service of concrete, it is necessary to enhance the understanding of the nanostructure of hydration products. Studies indicated that the inner C-S-H and nano-CH could be mixed with each other [9,10]. This assumption is consistent with the results of coupled SEM-nanoindentation analysis [9] and high X-rays adsorption analysis [10]. Direct experimental evidence on the local chemical features of mixed inner C-S-H and CH is still limited

Methods

Findings

Discussion

Conclusion