Assessment of the single and combined effect of superabsorbent particles and porogenic agents in nanotitania-containing mortars

Abstract

This article reports an investigation on the development of multifunctional mortars with enhanced potential to passively adjust indoor RH levels and thermal conductivity, while reducing aerial pollutants (NOx) through photocatalysis. Superabsorbent polymer (SAP), Vermiculite (VER) and TiO2 nanoparticles (nT) were used as functional additives for mortars. Single and binary mixtures with 0–0.9 wt.% SAP and 0–15 wt.% VER were established based on flow table measurements (165–180 mm), while 1.0 wt.% nT remained invariable in all tested samples. In addition, the workability was adjusted by distinct amounts of water in the mixtures. In general, the effect of the VER particles predominated for most of the properties. SAP-single mixtures with similar workability showed distinct rheological behavior over time, while the yield stress represented better the continuous absorption of water molecules by SAP. VER single mixtures imposed deeper changes on the flow, hindering the rheological features. Changes on the apparent porosity, water absorption and capillarity limited the admissible VER level, but for SAP the compositional range is less restricted. In fact, no adverse effect or gain on the flexural strength was observed on SAP-containing mixtures. The internal pores created by VER reduced in 50% the thermal conductivity of 0.9SAP + 10VER in comparison to 0.9SAP + 0VER. In addition, a significant increment of moisture buffering value in VER-containing mortars was also reached by using SAP particles. Finally, all samples were photocatalytically active against NOx, reaching up to 80% reduction of its initial concentration, after 60 min, regardless the concentration of additives.