The effect of chloride ingress in reinforced geopolymer concrete exposed in the marine environment

Characterization of an aged alkali-activated slag roof tile after 30 years of exposure to Northern Scandinavian weather

“…Solid state single pulse 29 Si, 27 Al, and 23 Na magic angle spinning (MAS) NMR data were obtained to examine the local structure of the reaction products in each sample. All 29 Si and 23 Na spectra were acquired at 11.7 T on a Bruker Avance III HD 500 spectrometer operating at Larmor frequencies 99.35 MHz and 132.29 MHz, respectively. A Bruker 4.0 mm dual resonance CP/MAS probe was used enabling a MAS frequency of 12.5 kHz.…”

“…23 Na MAS NMR spectra were acquired using a 3 ms nonselective (p/2) excitation pulse, a measured 10 s relaxation delay and a total of 128 scans per spectrum. All 29 Si and 23 Na spectra were referenced to the IUPAC primary references, pure tetramethylsilane (TMS) (d iso ¼ 0 ppm) and 1.0 M aqueous NaCl (aq) (d iso ¼ 0 ppm), respectively. 29 Single pulse 27 Al MAS data were acquired at 11.7 and 20.0 T using Bruker Avance III HD 500 and 850 spectrometers operating at the Larmor frequencies 130.28 and 221.49 MHz.…”

“…The 23 Na MAS NMR data for the aged roof tile sample (Fig. 7) shows a broad resonance spanning from d iso ¼ 0 ppm to À30 ppm, and centred at d iso ¼ À13 ppm.…”

“…9 shows a S 2p 3/2 signal at $169 eV, which indicates the presence Fig. 7 (a) 27 Al MQMAS NMR data (B 0 ¼ 20.0 T, n R ¼ 20 kHz) with the isotropic projection shown on the vertical axis and the 27 Al MQMAS NMR data acquired at B 0 ¼ 20.0 T shown on the horizontal axis, (b) 27 Al MAS NMR data (B 0 ¼ 20.0 T, n R ¼ 20 kHz, and B 0 ¼ 11.7 T, n R ¼ 12.5 kHz, as marked), (c) 23 Na MAS NMR data (B 0 ¼ 11.7 T, n R ¼ 12.5 kHz), and (d) 29 Si MAS NMR data (B 0 ¼ 11.7 T, n R ¼ 12.5 kHz) for the aged roof tile sample. of oxidized S(VI) species in metal sulfates.…”

Fly Ash-Added, Seawater-Mixed Pervious Concrete: Compressive Strength, Permeability, and Phosphorus Removal

“…Given the current freshwater stress and the future freshwater shortages, seawater has been a fit-for-purpose alternative mixing water for concrete production [21][22][23][24]. However, the applicability of seawater in concrete production is limited due to its high chloride content that induce corrosion of the reinforcing steel bars [25][26][27], although the corrosion potential can be reduced by using polymer-coated rebars [28]. It should be noted that pervious concrete is typically produced without reinforcing steel bars (commonly known as rebars), as opposed to ordinary concrete.…”