Influence of Ca/Si ratio of concrete pore solution on thaumasite formation. (30th October 2017)

• Record Type: Journal Article
• Authors: Zhou, Yang; Ma, Baoguo; Huang, Jian; Li, Xiangguo; Tan, Hongbo; Lv, Zhenghang
• Is Part Of: Construction & building materials. Volume 153(2017)
• Page Start: 261
• Page End: 267
• Publication Date: 2017-10-30
• Subjects: Thaumasite formation -- Ca/Si ratio -- Sulfate attack -- Concrete pore solution; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2017.07.104
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Thaumasite was not found in low Ca/Si ratio solution. The formation time of thaumasite was shorter with increasing of Ca/Si ratio. The formation of ettringite was prior to that of thaumasite. Abstract: To further understand the influence of Ca/Si ratio on thaumasite formation, in this work, reactant solutions with different Ca/Si ratios were prepared, mimicking concrete pore solution environment. Solution samples were then stored at 5 °C for a certain reaction time. Powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope with energy dispersive spectroscopy (SEM/EDS) were used to analyse solids produced in the solutions. It was found that ettringite was produced rather than thaumasite at low Ca/Si ratio (Ca/Si = 3) in reaction time of 6 months. However, the thaumasite was formed at higher Ca/Si ratio (Ca/Si = 6 and Ca/Si = 9), and the formation time of thaumasite became much shorter. Specifically, when Ca/Si ratio reached 9, thaumasite was formed in only 3 days. It could be inferred that in concrete or mortar, if Ca/Si ratio of pore solution was controlled at a certain low level, thaumasite formation could be effectively prevented.