Innovative hydraulic lime-based finishes with unconventional aggregates and TiO₂ for the improvement of indoor air quality

Abstract

This paper reports a study on 8 unconventional hydraulic lime-based mortars able to improve indoor air quality by acting as passive systems. Mortars have been prepared with commercial sand or highly adsorbent materials as aggregates with/without TiO2 as photocatalytic agent, to test also the decomposition of airborne pollutants. Mechanical properties, hygrometric behavior, inhibition of growth of molds and depollution properties have been tested. Despite using porous materials (zeolite and activated carbon), in mortars with unconventional aggregates, compressive strength is higher than in sand-based ones, with a more than double higher water vapor permeability. Zeolite-based mortars have the highest moisture buffering capacity followed by silica gel- and activated carbon-based mortars (1.5–2 times higher than reference, respectively, because of the high porosity of unconventional aggregates). Sand-based mortars show optimum inhibitory capacity against fungal growth. Concerning unconventional aggregates, silica gel mortars have good inhibitory capacity, whereas zeolite and activated carbon give to mortars an optimum substrate for molds. Mortars with unconventional aggregates as silica gel remove more than 80% of tracer pollutant after 2 h of test, whereas zeolite-based mortars remove the 65% of it after 120 min. TiO2 enhances depollution properties as photocatalytic oxidation agent when the mortar is close to saturation.

Multifunctional Lightweight Mortars for Indoor Applications to Improve Comfort and Health of Occupants: Thermal Properties and Photocatalytic Efficiency

“…The mechanical strength and porosity of these mortars have been measured in a previous work (Giosuè et al, 2020). Here, the different compressive strength values are correlated with the corresponding microstructures observed by scanning electronic microscopy (SEM).…”

“…The compressive strength values already measured in Giosuè et al (2020) and the morphological observations obtained by SEM are reported in Figures 2, 3. For the sake of brevity, in Figure 3, only images of specimens manufactured with different aggregates and TiO 2 are shown.…”

“…The mixes are prepared by keeping constant the water to binder ratio at 0.6. Mix proportions, density, and accessible total porosity of cured mortars without TiO 2 (since these properties were not significantly affected by TiO 2 nanoparticles) are reported in Table 2 (Giosuè et al, 2020).…”

“…Properties such as mechanical performance, density, and porosity of these mortars have been already investigated in Giosuè et al (2020) and are briefly summarized in the current paper. Compressive strength is measured by means of a hydraulic press (Galdabini) after 28 days of curing.…”

“…In order to find the best mortar for improving the indoor comfort and health of indoor occupants, the corresponding thermal conductivity and photocatalytic activity are also tested. The previous work has demonstrated the optimum hygroscopic behavior of these mortars in terms of moisture buffering capacity and water vapor permeability but also a photocatalytic activity hidden by the adsorption process until saturation of specimens (Giosuè et al, 2020). Therefore, in this paper, to demonstrate the effectiveness of photocatalytic activity in batch, all mortars are tested in saturated conditions.…”