The effectiveness of TiO2 additions to mortar to maintain initial conditions in terms of its reflectance to solar radiation

Sérgio Roberto Andrade Dantas,Kai Loh,Fulvio Vittorino

doi:10.1590/s1678-86212017000300161

Abstract

Abstract Contact of facades with degradation agents and direct incidence of ultraviolet radiation on external coatings make them more opaque over time, affecting their colour and reflectance characteristics. This study evaluated the effect of adding different TiO2 contents to mortars applied in concrete substrates in order to verify the reflectance maintenance on surfaces after exposure over time. Mortar with different concentrations of TiO2 (1%, 5%, 10%) were produced in relation to the total dry premix, added as a powder and compared to unpainted mortar without TiO2 (type "A") and painted mortar without TiO2 (type "B"), both used as a reference for colour and reflectance. Exposed over 16 months to climate conditions in São Paulo, regarding the maintenance of reflectance and solar radiation, the results showed that type "B" (0%TiO2) painted mortar presented the best performance. Type "C" (1%TiO2) and type "D" (5%TiO2) unpainted mortar remained more stable. Type "A" (0%TiO2) and type "E" (10%TiO2) unpainted mortar showed greater differences according to the Just Noticeable Difference (JND) range caused by dirt pick up.

Highlights

Discoloration, appearances of stains, accelerated wear, fouling due to soot particles and corrosion or erosion caused by acids are some problems caused by the accumulation of pollutants on the building envelope. Due to these shells being constantly in contact with degradation agents and the direct incidence of ultraviolet radiation, coatings tend to become more opaque over time affecting their colour and reflectance characteristics
According to Seker and Tavil (1996), Santamouris, Synnefa and Karlessiet (2011) and Alchapar, Correa and Cantón (2012), heat gained through opaque surfaces, due to solar radiation, greatly influences the thermal comfort conditions of the internal environment
According to PérezLombard, Ortiz and Pout (2007), the demand for thermal comfort, artificial climate systems and their associated energy consumption have become unavoidable assets, accounting for almost half of the energy consumed in buildings and about 10% 20% of total energy consumption in developed countries

Summary

Introduction

Discoloration, appearances of stains, accelerated wear, fouling due to soot particles and corrosion or erosion caused by acids are some problems caused by the accumulation of pollutants on the building envelope. Due to these shells being constantly in contact with degradation agents and the direct incidence of ultraviolet radiation, coatings tend to become more opaque over time affecting their colour and reflectance characteristics. According to Seker and Tavil (1996), Santamouris, Synnefa and Karlessiet (2011) and Alchapar, Correa and Cantón (2012), heat gained through opaque surfaces, due to solar radiation, greatly influences the thermal comfort conditions of the internal environment. According to PérezLombard, Ortiz and Pout (2007), the demand for thermal comfort, artificial climate systems and their associated energy consumption have become unavoidable assets, accounting for almost half of the energy consumed in buildings and about 10% 20% of total energy consumption in developed countries. Santamouris, Synnefa and Karlessiet (2011) state that the materials used in facades have an important role in the thermal balance of a city, where high reflective coatings result in an efficient passive technique to reduce the demand for electrical energy in the thermal conditioning of environments. Alchapar, Correa and Cantón (2012) point out that if high reflective materials were used for building facades, there would be a decrease in the thermal loads in building interiors

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