Chloride-binding capacity of cement-GGBFS-nanosilica composites under seawater chloride-rich environment. (1st August 2022)

• Record Type: Journal Article
• Authors: Qu, Fulin; Li, Wengui; Guo, Yipu; Zhang, Shishun; Zhou, John L.; Wang, Kejin
• Is Part Of: Construction & building materials. Volume 342:Part B(2022)
• Publication Date: 2022-08-01
• Subjects: C-A-S-H Calcium aluminum silicate hydrate -- CBC Chloride-binding capacity -- CBR Chloride-binding ratio -- CH Portlandite -- C-S-H Calcium silicate hydrate -- CPP Cementitious paste powder -- DTG Differential thermogravimetric -- DW Deionized water -- EPP Exposed paste powder -- FA Fly ash -- FSS Friedel's salt -- FTIR Fourier transform infrared spectroscopy -- GGBFS Ground granulated blast furnace slag -- HCP New hydrated cementitious pastes -- ICP-MS Inductively-coupled plasma mass spectrometry -- KSS Kuzel's salt -- LOI Loss on ignition -- MK Metakaolin -- NA Nano-Al2O3 -- NS Nano-SiO2 -- NC Nano-CaCO3 -- OPC Ordinary Portland cement -- PC 100% Portland cement mixed with deionized water -- PC-GGBFS 30 wt% GGBFS replacing cement -- PC-GGBFS-NS1 30 wt% GGBFS and 1.0 wt% NS -- PC-GGBFS-NS2 30 wt% GGBFS and 2.0 wt% NS -- PT Potentiometric titration -- CH Calcium hydroxide -- RC Reinforced concrete -- SCMs Supplementary cementitious materials -- SEM-EDX Scanning electron microscopy with energy disperse spectroscopy -- SW Seawater -- TGA Thermogravimetric analysis -- TO Titanium oxide -- WCPP Well-hydrated cementitious paste powder -- XRD X-ray diffraction -- XRF X-ray fluorescence; Cementitious composites -- Chloride-binding ratio -- Corrosion -- Nanosilica -- Thermodynamic modeling -- Chloride-rich environment; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2022.127890
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: GGBFS significantly improved chloride-binding capacity and decreased the pH of solutions. NS increased physical chloride-binding capacity due to the formation of C-S-H/C-A-S-H gels. More chlorides were found to be bound when exposed to salts solutions with magnesium ions. The 30 % GGBFS and 1.0% NS can be used enhance the long-term chloride-binding capacity. Abstract: The effects of granulated blast furnace slag (GGBFS) and nano-silica (NS) on the chloride-binding capacity of cement paste after 6-month exposure to seawater chloride-rich solutions were investigated in this paper. The pH, chloride-binding ratio (CBR), leaching behavior, and phase transformation were investigated by various experimental and analysis methods. Thermodynamic modeling was also used to study the phase assemblages for the Portland cement-GGBFS-NS composites exposed to the NaCl and MgCl2 solutions. It was found that for all cementitious composites, more chlorides were bounded in samples exposed to the salt solutions with sodium ions than that with magnesium ions. Proper additions of GGBFS and NS can enhance the chloride-binding capacity of cementitious composites. The results confirm that the addition of GGBFS can improve the chemical chloride-binding capacity because of the increased amount of chloroaluminate. The increased amount of hydrated gels in the cementitious composites with GGBFS also improved the physical chloride-binding capacity. The addition of NS increased the physical chloride-binding capacity due to the more formation of C-S-H/C-A-S-H gels, while the excessive addition of NS left less aluminum phase available for the formation of chloroaluminate, thus further decreased the chemical chloride-binding capacity. Magnesium ions in solutions increased the amount of chloride in the diffuse layer of C-S-H gels and hydrotalcite. The related results provide novel insight into the influences of GGBFS and NS on the chloride-binding capacity of cementitious composites under chloride-rich environments.