## 3 Results and Discussions
It is noted that although porosity is minimal for P5 (3.6% TiO\({}_{2}\)) and P6 (4% TiO\({}_{2}\)), they do not correlate with extreme values in terms of the amount of water absorbed on the surface; the corresponding water absorption curves are not positioned at the extremes of the graph. Moreover, the surface water  
Figure 3: Surface water absorption: (**a**) Non-UV exposed test specimens; (**b**) Specimens exposed 1 h to UV; (**c**) Specimens exposed 1 + 24 h to UV. absorption varies independent of the porosity variation when comparing close porosity values of the samples (P2, P3, P4, P7 and P9). Therefore, it can be assessed that for the analyzed cases under conditions of variation of porosity in the range of an average square deviation of 2.6, its influence on surface water absorption can be neglected. Figure 4 shows the rate of evolution of the surface water absorption process depending on the type of samples tested, the volume of sprayed water and the type of exposure. As seen in Figure 4, the rate of water absorption on the surface decreases continuously and constantly for all the analyzed samples when the amount of sprayed water is increased. This trend could probably indicate that the surface initially accumulates amounts of water and subsequently, once a film of water is formed, the excess slides more easily under the influence of gravitational efforts. This conclusion can also be supported by the slight flattening of the surface water absorption curves shown in Figure 3.  
The P8 with the 6% TiO\({}_{2}\) sample unexposed to UV rays shows the most intense kinetics of the surface water absorption process, therefore this process is the most favorable in terms of obtaining the optimized self-cleaning effect (as shown in the previous chapter, the property of self-cleaning is the result of a cumulation of properties between which the hydrophilicity of the surface has a particularly important role). P9 with the 10% TiO\({}_{2}\) sample shows a lower rate of the surface water absorption process which indicates that the kinetics of the phenomenon are not directly influenced by the quantity of TiO\({}_{2}\) addition in the cementitious matrix. This statement is also supported by the surface water absorption rate recorded by the P2 (1% TiO\({}_{2}\)) sample, which initially is high but then decreases quickly as the process progresses. P3 (2% TiO\({}_{2}\)) and P4 (3% TiO\({}_{2}\)) samples show similar behavior as the phenomenon progresses. The variations between the momentary rates for each of these two cases are rather low, which would suggest a saturation phenomenon after spraying 20-25 ml of water. P8 (6% TiO\({}_{2}\)) test specimens show the most intense kinetics of the process, with good results after exposure of 1 h UV action. The same intense kinetics are also seen for P5 (3.6% TiO\({}_{2}\)) samples. Sample P9 (10% TiO\({}_{2}\)) shows, again, a lower rate of the surface water absorption process, which supports the assertion that the kinetics of the phenomenon are not directly and proportionally influenced by the content of TiO\({}_{2}\) in the cementitious matrix; consequently, it can be concluded that an optimal range of TiO\({}_{2}\) nanoparticles addition or a certain dosage needs to be established. Although not showing an equally spectacular evolution regarding the rate of the phenomenon, P6 (4% TiO\({}_{2}\)) and P7 (5% TiO\({}_{2}\)) samples eventually reach the similar rate of P4 (3% TiO\({}_{2}\)) and P5 (3.6% TiO\({}_{2}\)) samples at the end of  
Figure 4: Rate of evolution of the surface water absorption process: (**a**) Non-UV exposed specimens, (**b**) 1 H UV exposed specimens, (**c**) 1 + 24 h UV exposed specimens. the test (50 mL water). This evolution cannot be interpreted independently, but only in the context of maintaining a balance as favorable as possible in terms of benefits accumulation. After exposure to 1+24 h UV action, P5 (3.6% TiO\({}_{2}\)) and P8 (6% TiO\({}_{2}\)) samples exhibit the most intense kinetics of the surface water absorption process.