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

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.

摘要 外墙与劣化因子接触，外加外部涂层直接受到紫外线辐射，会随时间推移导致涂层愈发浑浊，进而影响其色泽与反射特性。本研究针对混凝土基层所用砂浆中添加不同含量二氧化钛（TiO2）的效果开展评估，旨在验证长期暴露后砂浆表面的反射率保持能力。本研究以总干拌混合料为质量基准，制备了掺加不同质量分数二氧化钛（1%、5%、10%，以粉体形式添加）的砂浆，并以未掺二氧化钛的未涂装砂浆（A型）与未掺二氧化钛的涂装砂浆（B型）作为色泽与反射率的参照组进行对比。将上述试样暴露于圣保罗的自然气候环境中16个月，针对反射率与太阳辐射的保持情况开展分析后，结果显示：B型（0%TiO2）涂装砂浆表现最优；C型（1%TiO2）与D型（5%TiO2）未涂装砂浆的性能保持更为稳定；A型（0%TiO2）与E型（10%TiO2）未涂装砂浆的性能差异更为显著，这一差异符合积尘引发的恰可察觉差（JND）范围。