Synthesis of SiO2@TiO2 Coating without Sonochemistry

For TiO2 sol preparation, after sol formation, a hydrolysis process was carried out with the addition of distilled water, added dropwise. The resulting solution was filtered, washed with distilled water and dried at room temperature for 18 h. Finally, a calcination process was carried out at 450 ◦C for 3 h.

For SiO2, a solution of distillated water, absolute ethyl alcohol and oxalic acid, in a 5/5/0.1 molar relation was prepared and stirred for 15 min. Afterwards, tetraethyl orthosilicate was added dropwise and stirred for 3 min. Then, polydimethylsiloxane was added dropwise and stirred continuously for 3 min.

Finally, the titanium dioxide particles and the silicon dioxide sol were mixed for 20 min. The resultant mixture was applied on mortar surfaces and dried at room temperature for at least 1 h.

### *2.2. Preparation of Mortar Samples*

The mortar samples were manufactured using a previous mix design (Table 1), the same local materials, and the ASTM method C192/C192M [16–18].


**Table 1.** Mortar components and proportions for 1 m3.
