## 2 Materials and Methods
### Experimental Research  
The principle of the method consisted in determining the surface water absorption of the specimens as an indirect indicator of the evaluated surface hydrophilicity. Cemertitious composite material prismatic specimens, with a 0.085 m\({}^{2}\) exposed area were prepared in order to evaluate this indicator. The preparation of the cementitious composites was performed by using white Portland cement as the binder and the nanoparticles were introduced as an addition in different mass percentages, relative to cement quantity: 1% (P2), 2% (P3), 3% (P4), 3.6% (P5), 4% (P6), 5% (P7), 6% (P8) and 10% (P9). The control sample, P1, was prepared without the TiO\({}_{2}\) nanoparticles addition. For all mixtures, the mass ratio of water / dry powdery material of 0.5 was maintained constant, where the dry powdery material represented the mass sum of the quantities of cement and TiO\({}_{2}\) nanoparticles. After casting, the test specimens were stored for 24 h inolds in a wet box (RH 90%, 20 \(\pm\) 1 \({}^{\circ}\)C). After demolding, the samples were immersed in water at 20 \(\pm\) 1 \({}^{\circ}\)C until the age of testing of 28 days. The test surface of the specimens (at 28 days age), conditioned by exposure to 105\({}^{\circ}\) until dried constant mass was reached, was exposed to testing with a tilt of 10\({}^{\circ}\) with respect to the vertical. From a distance of 30 cm, 5 mL of distilled water was sprayed every 2 min until a cumulative volume of 50 mL of water was used for each surface specimen. After each step (spray of 5 mL distilled water), the test specimens were weighed and water absorption was determined on the surface. All tests were carried out under laboratory conditions (20 \(\pm\) 2 \({}^{\circ}\)C, RH 50%). After testing, the specimens were dried until constant mass and exposed for 1 h to the action of UVA (Ultraviolet A: 400 - 315 nm) wave-length UV rays with light intensity of 405 lux, then the test was repeated. Subsequently, the specimens were dried until constant mass again, exposed another for 24 h to UV and the water absorption on the surface was measured. Prior to the surface water absorption test, porosity was evaluated by calculation for all cementitious composites. This method was used by assimilation with standardized methods for characterizing the porosity of concrete, which allow the determination of this parameter based on the apparent and absolute density of the material. Surface water absorption (Q) was calculated as an indirect indicator of the degree of hydrophilicity of the surface of the cementitious composite material (Equation (8)):  
\[Q_{t}=\frac{m_{t}-m_{0}}{A}\ (\frac{kg}{m^{2}}) \tag{8}\]  
where, m\({}_{t}\) is the sample mass at time t (2, 4, 6, 8, 10, 12, 14, 16, 18, 20 min) from the start of spraying, and corresponds to the specific volumes of sprayed distilled water (5, 10, 15, 20, 25, 30, 35, 40, 45, 50 mL); m\({}_{0}\) is the initial mass of the dry specimen at constant mass; and A is the exposed surface of the specimen. For the evaluation of the kinetic phenomenon, the rate of the surface water absorption was determined in terms of the water amount coming in contact with the surface at a given time. This was expressed as the slope of the graphical representation, namely, the tangent of the angle formed with the x-axis. The rate of evolution of the water absorption process, v, is defined as the ratio between the amount of water absorbed on the surface of the sample and the amount of sprayed water that reached contact with it (Equation (9)). The amount of water sprayed on the surface was calculated knowing that, throughout the procedure, a constant amount of 5 mL of water was sprayed at a constant interval of 2 min until the total volume of 50 mL of water was cumulated. Given that the exposed specimens were initially dried until constant mass was reached, the amount of water initially absorbed was considered to be 0 kg/m\({}^{2}\).