Mechanical characteristics, thermal reflective performance and energy-saving efficiency of nano TiO2 cement mortars for building envelopes

To overcome the persistent challenges of rapid aging and insufficient durability in organic thermal reflective coatings, this study designed an inorganic thermal reflective cement mortar incorporating rutile titanium dioxide (NT) as the core functional component. The relationship between NT particle size (25–2000 nm) and dosage (0–10 %) on both mechanical strength and thermal reflective performance was rigorously explored. Mechanisms driving reflectance degradation under prolonged curing and carbonation were quantitatively modeled, while energy-saving potential was validated via DeST simulation. Results demonstrated that under identical NT dosage, both mechanical strength and thermal reflective performance increased with larger NT particle sizes. For fixed NT particle size, these properties initially improved then declined with increasing NT content. Comprehensive analysis identified 2000 nm NT particles at 6 % optimal dosage as the balanced solution, achieving a 4.2 °C surface temperature reduction compared to the control specimen. The thermal reflective performance degradation followed a logarithmic model, showing merely 16.7 % reduction after 180 days of natural carbonation. DeST simulations confirmed that in Guangzhou’s air-conditioning season, the developed mortar reduced indoor temperature by 3 °C, decreased building energy consumption by 6.54 %, and reduced CO2 emissions by approximately 5.25 kg/m2. This work offers a scalable pathway toward carbon-neutral building envelopes.