NOx degradation by photocatalytic mortars: the underlying role of the CH and C-S-H carbonation

Anna Kaja, Jos Brouwers, Qingliang Yu (Corresponding author)

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This study aims to understand the impact of carbonation mechanism of C-S-H and CH in photocatalytic mortars on NOx removal efficiency. Changes in surface chemistry and microstructure induced by the carbonation of portlandite and C-S-H (AFm/AFt) were correlated with the photocatalytic efficiency of the mortars doped with three types of titania-based photocatalysts. Furthermore, the influence of cementitious matrix on the photocatalytic selectivity was evaluated by studying the capacity of hydration/carbonation products to adsorb NO2. The study revealed that in terms of both photocatalytic efficiency and selectivity, mortars with microsilica addition exhibit superior properties over the pure cement-based mortars upon carbonation. Carbonation of C-S-H (AFm/AFt) gel results in the formation of capillary pores between10–50 nm, which outbalances the shielding effects of carbonates formed, leading to the enhanced photocatalytic properties. Moreover, C-S-H gel maintains its high NO2 adsorption capacity even after carbonation, resulting in the high selectivity of the photocatalysis.
Original languageEnglish
Article number105805
Number of pages11
JournalCement and Concrete Research
Publication statusPublished - Nov 2019


  • Photocatalytic mortar
  • Nitrogen oxides
  • Carbonation
  • Pore structure
  • Selectivity


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