ES2811649B2 - A product for the protection of concrete and other construction materials - Google Patents

Description

DESCRIPTION

A PRODUCT FOR THE PROTECTION OF CONCRETE AND OTHER CONSTRUCTION MATERIALS

TECHNICAL SECTOR.

The present invention refers to a product specifically designed for the protection of construction materials, which endows the material with a combination of water repellent properties in its porous structure with an induced hydrophilicity phenomenon, due to the effect of solar radiation or UV-A that it generates. , in contact with water, superoleophobic properties that facilitate the removal of any stain deposited on its surface.

BACKGROUND OF THE INVENTION.

Water is the main vehicle for degradation agents that affect construction materials, in processes such as salt crystallization, freeze-thaw cycles, colonization of microorganisms, etc. ( Romano P et al., Constr. Build. Mater., 47, 827, 2013; Jacques D et al., Cem. Concr. Res., 40, 1306, 2010; Pan X et al., Constr. Build. Mater ., 132, 578, 2017). For this reason, the application of waterproofing products that reduce water absorption is a widely used solution to increase the useful life of construction materials. Most of these products contain alkylsiloxanes that penetrate the porous structure of materials, due to their low viscosity, and polymerize in situ through a sol-gel route. The reduction of surface energy due to the presence of organic groups endows the treated materials with water-repellent properties, reducing water absorption ( Pan X., Constr. Build. Mater, 132, 578, 2017; Pan X et al., Constr Build. Mater, 133, 81, 2017).

On the other hand, in recent years superhydro-repellent products have been developed that are characterized by having high hydrophobicity (static contact angles greater than 150 ° and high repellency (hysteresis between advance and retreat angle less than 10 °). ( Moradi S et al., Colloid Polym. Sci., 291, 317, 2013; Lafuma A et al., Nat. Mater, 2, 457, 2003; Koch K et al., Soft Matter, 5, 1386, 2009). high repellency gives these surfaces self-cleaning properties. Specifically, water It is capable of capturing any species of hydrophilic nature from its surface ( Fürstner R., Langmuir, 21, 956, 2005; Manoudis PN et al., Surf. Coatings Technol., 203, 1322, 2009; Facio DS et al., Nanotechnology , 28, 2017).

Superhydrophobicity is obtained by the combination of low surface energy and the creation of roughness that promotes a Cassie-Baxter state. In this state, the water droplets remain on the roughness peaks, forming a solid-air interface ( Cassie ABD., Trans. Faraday Soc., 40, 546, 1944; Gao L et al., Langmuir, 25, 14105, 2009; Fürstner R et al., Langmuir, 21, 956, 2005). In accordance with this strategy, our research group has developed superhydrophobic products with application in construction materials ( Facio DS et al., ACS Appl. Mater. Interfaces, 5, 7517, 2013; Carrascosa LAM et al., Nanotechnology, 27, 2016) and a patent (N ° ES2423356). These products are obtained through a simple sol-gel route, in which a silica oligomer is mixed with an organic oligomer (polydimethylsiloxane, PDMS), which reduces surface energy, and silica nanoparticles (NPs), which create a Cassie surface. -Baxter. In addition, a non-ionic surfactant is added, which increases the pore size of the xerogel obtained, preventing its fracture.

However, the previously described solution does not show self-cleaning effectiveness in the case of oily stains / contaminants. In building materials, obtaining building materials with oil repellency is a key challenge for two reasons:

(i) most of the dirt on facades is due to compounds of this nature, which include pollutants caused by atmospheric pollution and graffiti.

(ii) the durability of superhydrophobic surfaces is affected by contamination due to oily substances, which promotes the loss of their self-cleaning action ( Li L et al., Chem. Rec, 118, 2017).

At present, obtaining construction materials with oleophobic properties is only achieved through the use of fluorinated compounds ( Facio DS et al., Nanotechnology, 28, 2017; Mosquera MJ et al., Pure Appl. Chem., 90 , 551, 2018; Aslanidou D et al. Mater. Des., 108, 736, 2016; Aslanidou D. et al. Materials, 11, 585, 2018), with all the environmental limitations involved in its application.

Regarding superoleophobity, the formation of a complex rough structure (shaped like a mushroom or T) is required, as described in the literature ( Darmanin T et al., Mater. Today, 18, 273, 2015; Xue Z et al. ., J. Polym. Sci. Part B Polym. Phys., 50, 1209, 2012; Yong J et al., Chem. Soc. Rev., 46, 4168, 2017). Obtaining these complex structures involves tedious processes that are difficult to apply to construction materials.

Recently, a strategy has been developed to produce self-cleaning surfaces, based on the ability of fish scales to stay clean, even in contaminated aqueous media. The presence of polar groups of a hydrophilic nature in the scales, combined with their structure in the form of micropapillae creates a Cassie-Baxter state, in which the solid-air interface is replaced by a solid-water interface that avoids the contact of contaminants. oily with said flakes ( Liu M et al., Adv. Mater., 21, 665, 2009; Yong J et al., J. Mater. Chem. A, 5, 25249, 2017). Based on this behavior, different materials have been designed with application as water-oil separation filters ( Wang Y et al., J. Mater. Chem. A, 5, 3759, 2017). However, the application of this strategy in the case of construction materials, would make the material hydrophilic, allowing the entry of water into its structure, the main vehicle for degradation agents in buildings.

In this invention, a strategy has been used that makes it possible to provide the surface of the building material with superhydrophilic properties while its internal structure possesses water-repellent properties, and therefore, the absorption of water is avoided. For this, titanium dioxide is used, capable of inducing superhydrophilicity in contact with solar radiation while the unexposed material maintains its hydrophobic behavior, preventing the penetration of water into its structure.

EXPLANATION OF THE INVENTION.

The product object of the invention is a sun that has low viscosity, and therefore can be applied by simple methods (spraying, brush ...), in situ, on any building or any other architectural element and, in addition, penetrates the porous structure of the building material.

The sun is composed of:

(i) A silica oligomer, which polymerizes spontaneously in the porous structure of the construction material, through a classic sol-gel process, increasing the interaction with it and the durability of the treatment.

(ii) A non-ionic surfactant (with a concentration between 0.05 and 0.4% vol / vol) and water. The nonionic surfactant is a primary amine, preferably n-octylamine. This surfactant plays two fundamental roles: (1) it acts as a basic catalyst for the sol-gel reaction, and (2) it generates a fracture-free mesoporous gel, through an inverse micelle mechanism ( Facio DS et al., Microporous Mesoporous Mater. , 247, 166, 2017).

(iii) Water, to promote the hydrolysis of the silica oligomer, generating silanol groups that, thanks to their high reactivity, cause the polymerization of the oligomers through condensation reactions, giving rise to the xerogel.

(iv) A compound with functional groups with low surface energy, capable of penetrating the porous structure of the construction material and forming copolymers with the silica oligomer, providing the material with water repellent properties. This group includes alkylalkoxysilanes, alkylsilanes, alkylsiloxanes and perfluoroalkylsiloxanes, preferably this being a polydimethylsiloxane (PDMS), with a concentration of 10% v / v.

(v) Titanium dioxide nanoparticles, necessary to induce surface superhydrophilicity and photocatalytic properties. The proportion of this component is between 2 and 10% w / v, preferably with a concentration of 5% w / v.

Titanium dioxide nanoparticles have a dual purpose:

(1) Create a nano-roughness characteristic of a Cassie-Baxter state. The synergy created between components (iii) and (iv) endows the material with superhydrophobic properties in the event that the coating does not come into contact with sunlight ( Facio DS., ACS Appl. Mater. Interfaces, 5, 7517, 2013; Facio DS et al., Nanotechnology, 28, 265601, 2017; Carrascosa LAM., Nanotechnology, 27, 2016) and previous patents (N ° ES2423356).

(2) In the presence of UV or solar radiation, an induced hydrophilicity phenomenon occurs as a consequence of the photo-activation of titanium dioxide ( Watanabe T et al., Thin Solid Films, 351, 260, 1999; Rudakova A V. et al., J. Colloid Interface Sci., 466, 452, 2016; J. Photochem. Photobiol. A Chem., 367, 397, 2018; Velayi E et al., Appl. Surf. Sci., 441, 156, 2018), producing a superoleophobic effect in contact with water. This effect gives the building material a self-cleaning ability against pollutants of an oily nature. On the other hand, the product that is not in contact with sunlight, located inside the porous structure of the building material, maintains its waterproofing properties, preventing the penetration of water.

A second aspect of the present invention is the procedure for obtaining the product described above. This procedure consists of a simple solgel route, which includes the following steps:

First, the mixture of the silica oligomer and the low surface energy compound is carried out. Subsequently, the titanium dioxide nanoparticles are dispersed. Finally, water and the surfactant are added, and homogenization is carried out.

With the described procedure, a sol with stability superior to 12 months is obtained, which allows its storage for commercial purposes.

The product can be applied on any construction material of a porous nature. Given the low viscosity of the product (around 6 mPas), it is possible to use application methods typically used in the field of building materials (spraying, brushing, brushing, etc.).

BRIEF DESCRIPTION OF THE FIGURES.

FIGURE 1.- Photographs of the cross section of a white cement mortar specimen, showing the penetration of the product object of the invention.

FIGURE 2.- Topography of the white cement mortar samples. SEM images (first row), AFM 3D images (second row), and 2D roughness profiles. (a) Untreated and (b) treated.

FIGURE 3.- Drops of chloroform deposited on samples of white cement mortar submerged in water. (a) Superhydrophobic surface, and (b) superhydrophilic surface. The values of the contact angles of drops of chloroform deposited on the evaluated mortars are included.

FIGURE 4.- Screenshots of chloroform droplets rolling on samples of white cement mortar under water. (ad) Superhydrophobic surface, (eh) superhydrophilic surface.

FIGURE 5.- Screenshots of the self-cleaning effect of the white cement mortar samples. (ad) Superhydrophobic surface stained with tile powder, (eh) superhydrophobic surface stained with tile powder contaminated with oleic acid, (il) superhydrophilic surface stained with tile powder contaminated with oleic acid.

FIGURE 6.- Photographs of the cross section of a cement mortar sample.

FIGURE 7.- SEM images of the surface of cement mortars. (a) Untreated and (b) treated.

FIGURE 8.- Screenshots of chloroform droplets rolling on cement mortar samples under water. (ac) Superhydrophobic surface, (df) superhydrophilic surface.

PREFERRED EMBODIMENT OF THE INVENTION.

Next, and in order to illustrate in more detail the product object of the invention, the results obtained in our research laboratory are described.

Specifically, Example 1 describes the synthesis of a product prepared according to the described method, and its application on commercial white cement mortars, supplied by the company Hermesa Stone S.L. Subsequently, the evaluation of the effectiveness of the product on the treated mortars is described. In the second example, the product prepared in Example 1 is applied to cement mortars prepared in accordance with the UNE-EN 12390-2 standard, and subsequently aged using freeze-thaw cycles.

EXAMPLE 1

The product object of the invention was prepared according to the following synthesis route: A silica oligomer (Wacker TES40, from Wacker Chemie) was mixed with a polydimethylsiloxane with terminal OH groups (PDMS, supplied by ABCR). ^{Subsequently, TiO 2} nanoparticles (NPs) (Aroxide P25, from Evonik) were dispersed in the sun, using an ultrasound probe (2 minutes, 1 W m L-1). Finally, water and the surfactant (n-octylamine, from Sigma Aldrich) were added, and the mixture was homogenized with the ultrasound probe (8 minutes, 2 W m L-1). The TES40, PDMS, n-octylamine and water proportions were 89.67, 10.00, 0.08 and 0.25% v / v, respectively. As for the TiO ² NPs, they were added in a proportion of 5% by weight, with respect to the total volume of the sol.

In order to check if the synthesized product has a suitable viscosity for its application on construction materials, its measurement was carried out using a Brookfield rotational viscometer (model DV-II +). The temperature of the experiment was kept constant at 25 ° C, using a recirculated thermostatic bath. The product presented a viscosity of 6.3 mPs, a value similar to that of impregnation products typically used in construction materials. ( Carrascosa LAM., Nanotechnology, 27, 2016; Pinho L et al., Appl. Catal. B Environ., 178, 144, 2015). Therefore, its adequate penetration in this type of substrates is ensured.

Furthermore, the spontaneity of the sol-gel transition of the product was evaluated. For this, 3 mL of sol were deposited in plastic Petri dishes. The product gelled within 24 hours due to the role played by n-octylamine as a basic catalyst ( Facio DS., Microporous Mesoporous Mater., 247, 166, 2017; Mosquera MJ et al., Langmuir, 24, 2772, 2008). It is important to note that the gelling of the product occurs spontaneously but not immediately. In this way, the penetration of the product into the porous structure of the construction material is ensured. The product also showed stability in a closed bottle of more than 12 months.

The prepared product was applied, in the form of the sun, by spraying (2 bar, 10 seconds), on specimens of 3.5 x 3.5 x 3.5 cm3 of white cement mortar supplied by the company Hermesa Stone S.L. (open porosity about 12%). The cement mortar samples were manufactured using type I white Portland cement and calcareous sand ($ 1-6 mm). The water: cement (w / w) and cement: sand (w / w) ratios were 1: 2 and 1: 5, respectively. The mortars were cured under water at 21 ± 2 ° C, for 28 days.

Consumption was calculated (amount of product absorbed) by weighing the specimens before and immediately after being treated, obtaining an approximate value of 150 g m -2. This low absorption value may be due to the low porosity of the substrate. After application, the samples were allowed to dry to constant weight. All the tests and results described below were carried out 6 months after applying the product.

First, the penetration of the product was evaluated. For this, the samples were cut in order to obtain cross sections of the same, and drops of a solution of methylene blue in ethanol were deposited on said sections. The area in which the product has penetrated significantly reduces its porosity, and therefore, the colorant accumulates on the surface, generating a more intense color in said area. Additionally, the higher affinity of silica gel for said dye can favor this phenomenon. In Figure 1, this chromatic difference can be clearly observed, which shows that the product has penetrated approximately 4 mm. The low porosity of this type of mortar produces low product absorption that directly affects these penetration values.

Next, the possible negative effects derived from the application of products that could limit their application were evaluated: change of the color of the substrate and reduction of permeability to water vapor. Regarding the color change, a Hunterlab ColorFlex reflection spectrophotometer for solids was used, with the following conditions: illuminant D65, 10 ° observer and CIEL * a * b * standard, the total color difference (AE *) was determined. The value obtained was less than 1, being imperceptible to the human eye (the threshold value for perception is between 3 and 5) and therefore suitable for use in the construction field and even in the most demanding situations. , as in the buildings and elements of the Cultural Heritage ( Pinto APF et al., J. Cult. Herit., 9, 38, 2008; Rodrigues JD et al., J. Cult. Herit, 8, 32, 2007).

On the other hand, the reduction in vapor diffusivity was evaluated using an apparatus developed in our research group ( Mosquera MJ et al., Cem. Concr. Res., 32, 1883, 2002), obtaining a reduction of approximately 45% . According to the literature ( Rodrigues JD., J. Cult. Herit., 8, 32, 2007), diffusivity reduction values lower than 50% are considered acceptable for the application in construction materials.

The surface topography of the untreated and treated concrete samples plays a critical role in the wetting properties. Specifically, obtaining a Cassie-Baxter state, through the development of an induced nano-roughness, is an essential requirement to obtain superhydrophobic behavior ( Gao L., Langmuir, 25, 14105, 2009; Kosak Soz C et al. , Polym. ( United Kingdom), 62, 118, 2015; Nosonovsky M et al., Microsyst. Technol., 11, 535, 2005). The surface roughness created by the product applied to the specimens under study was evaluated by Scanning Electron Microscopy (SEM, model NovaNanoSEM 450, from FEI) and Atomic Force Microscopy (AFM, Dulcinea model from Nanotec).

The SEM micrographs, Figure 2 (top row), show an evident modification of the surface after the application of the product. The untreated surface (Figure 2a) presented an irregular appearance with clearly visible mineral grains, typical of heterogeneous materials, such as concrete. In contrast, the treated surfaces (Figure 2b) showed a compact structure composed of densely packed NPs, demonstrating the formation of a coating on the surface. Said coating is constituted by the silica matrix that fulfills two functions ( Pinho L et al., Appl. Surf. Sci., 275, 389, 2013): (1) it acts as a bridge between the mineral grains and covers the pores of the substrate, increasing its compaction, and (2) acts as a matrix for the TiO ² nanoparticles, improving adhesion and favoring a homogeneous distribution on the surface. The TiO2NPs are responsible for the observed nano-roughness.

A more detailed textural study of the surfaces was obtained by analyzing the AFM images. The 3D topographic maps (Figure 2, second row), together with the RMS ( Root Mean Square) roughness values, showed that the roughness changes due to the presence of the TiO2 nanoparticles integrated in the silica xerogel, corroborating the information obtained in the SEM images. The untreated sample showed an irregular topography, with high roughness peaks separated by wide valleys, corresponding to the mineral grains and grain edges, respectively. This observation was also manifested by a high roughness value (165 nm), with a significant standard deviation (± 40), which confirms the heterogeneity. On the other hand, the samples treated with the product under study presented a hierarchical roughness composed of peaks of submicron scale and a secondary nanometric structure, giving an RMS roughness value of 64 ± 10 nm.

Differences in the size of the roughness peaks are more clearly observed in the 2D roughness profiles, shown in Figure 2 (bottom row). In the case of the untreated substrate, the mineral grains generate an irregular profile with peaks separated by distances between 0.5 and 3 pm. In contrast, the treated surface showed large peaks (60-100 nm) separated by similar distances, corresponding to the aggregates of TiO2 nanoparticles / silica matrix observed in SEM. The hierarchical roughness, constituted by micro / nano roughness of the surface, was clearly observed by the presence of submicron peaks, separated by distances between 150 and 300 nm, which are composed of peaks spaced 40-50 nm, corresponding to the TiO2 nanoparticles. .

The wetting properties of the specimens under study were evaluated by static and dynamic angle measurements, using an OCA15Plus video measurement device, from DataPhysics Instruments. The measurements were carried out according to the procedure followed in a previous publication ( Mosquera MJ., Pure Appl. Chem., 90, 551, 2018). The results obtained are observed in Table 1.

Table 1. Contact angle measurements of treated and untreated concrete surfaces, before and after irradiation.

Después de irradiación Muestra Ángulo Estático Histéresis Ángulo Estático HistéresisBefore irradiation

After irradiation Sample Static Angle Hysteresis Static Angle Hysteresis

* The hysteresis value could not be evaluated as the drop spread rapidly.

The untreated samples showed a hydrophilic behavior (static angle around 30 °, due to the presence of polar groups (Si-OH, CO32 ", etc.) in the cementitious material. In the case of the treated samples, values were observed of static angle close to 160 ° and hysteresis values lower than 4 °, typical values of a hydrophobic and water repellent behavior ( Simpson JT et al., Reports Prog. Phys., 78, 086501, 2015). This superhydrofuge behavior can be explained by the existence of a Cassie-Baxter state ( Cassie ABD., Trans. Faraday Soc., 40, 546, 1944), which predicts that the combination of a low surface energy and a hierarchical structure constituted by a nano / micro- Roughness, as previously described in SEM and AFM images (Figure 2), can lead to high contact angles due to the formation of air pockets between the roughness valleys. In addition, the organic component PDMS plays a fundamental role in reducing l to surface energy ( Koch K., Soft Matter, 5, 1386, 2009; Facio DS., ACS Appl. Mater. Interfaces, 5, 7517, 2013; LiX-M et al., Chem. Soc. Rev, 36, 1350, 2007).

In order to create an induced superhydrophilicity, the treated samples were subjected to solar irradiation, for 12 hours, in a CO.FRO.ME.GA SolarBox 3000eRH climatic chamber (500 W m -2, 50 ° C and 60% of RH). After irradiation, the contact angles were again measured.

The results obtained showed an effective change from superhydrophobic to superhydrophilic behavior, observing a reduction of the static angle to values lower than 10 ° after 12 hours of irradiation. As previously described in the literature ( Schneider J et al., Chem. Rev., 114, 9919, 2014), when TiO2 is irradiated with UV light, oxygen vacancies are created, which causes the conversion of Ti4 + into Ti3 +, promoting increased interaction with water due to dissociated water adsorption mechanisms ( Hugenschmidt MB et al., Surf. Sci., 302, 329, 1994). This effect leads to an increase in the number of hydroxyl groups on the surface, which induces superhydrophilicity ( Fujishima A et al., J. Photochem. Photobiol. C Photochem. Rev., 1, 1, 2000; Wang R et al., Adv. Mater., 10, 135, 1998). As can be seen in the SEM images (Figure 2), the TiO ² nanoparticles are perfectly exposed on the surface, and, therefore, their role in this phenomenon is confirmed.

Since the main objective of this invention is to exploit the underwater superoleophobic properties of superhydrophilic surfaces, this property has been evaluated. Specifically, static angles of chloroform microdrops (see Figure 3) were measured on treated (and subsequently irradiated) samples immersed in water. Since the oils float in water, due to their low density, chloroform was used to carry out the measurement. With a comparative effect, the measurement of non-irradiated samples was also carried out, which showed, due to the presence of the treatment, a superhydrophobic behavior. Specifically, the chloroform droplets spread rapidly on the superhydrophobic surface immersed in water (contact angle close to 10 °, Figure 3a), demonstrating the oleophilic character, under water, of this type of surface. On the contrary, the samples with photo-induced superhydrophilicity presented superoleofuge properties under water, with contact angles greater than 150 ° (see Figure 3b).

Furthermore, the oil repellency was demonstrated by a qualitative test. Specifically, droplets of chloroform (stained with methylene blue) were deposited on superhydrophilic concrete samples, immersed in water. Again, this test was also performed on superhydrophobic samples for comparative purposes. Figure 4 shows the screenshots of the video recorded during the experiment. The chloroform drops deposited on the superhydrophobic sample spread rapidly over it, leaving a blue stain (Figure 4, a-d). On the other hand, the chloroform droplets rolled rapidly on the superhydrophilic surface, avoiding staining (Figure 4, e-h). Therefore, the oil repellency of these surfaces is confirmed.

The self-cleaning properties against pollutants of an oily nature were evaluated by means of a simple experiment. First, tile dust was deposited on a specimen with a superhydrophobic surface. The screenshots shown in Figure 5 (ad) show that dust is easily removed by projecting a jet of water onto the surface, demonstrating the self-cleaning properties of the superhydrophobic surfaces ( Facio DS., Nanotechnology, 28, 2017; Mosquera MJ., Pure Appl. Chem., 90, 551, 2018). Subsequently, the same experiment was repeated contaminating the tile dust with oleic acid. In this case, the water was unable to remove the tile dust from the superhydrophobic surface, due to the water-oil immiscibility (see Figure 5, eh). This highlights the loss of effectiveness of superhydrophobic surfaces when contaminated by oily substances. Next, the tile dust contaminated with oleic acid was deposited on samples treated with the superhydrophilic product. In this case, the contaminant was easily removed by the water jet (Figure 5, il). This is due to the superhydrophilic character of the surface, which allows the water to spread below the contaminant, eliminating it.

Finally, the ability of the product to reduce water absorption by capillarity was evaluated. For this, a test was carried out in accordance with the UNE-EN 1925 standard. The experiment was carried out on untreated and treated samples, before and after being irradiated. Table 2 shows the total water absorption values after 48 hours.

Table 2. Percentages of water consumption at the end of the capillary water absorption test.

Before irradiation (w / w%) After irradiation (w / w%) Sample

Untreated 3.49 ± 0.17 3.45 ± 0.21

Treated 0.39 ± 0.16 0.40 ± 0.19

The untreated sample presented a water absorption of around 3.5%, which was reduced to 0.4% after applying the product, due to the superhydrophobic properties of this product. After irradiation of the treated samples, and despite their superhydrophilic behavior, it is important to highlight that the absorption of water was not increased. This shows that the change from superhydrophobic to superhydrophilic behavior only occurs on the surface, where the TiO ² is exposed to solar radiation. On the contrary, the part of the product that is within the porous structure of the material maintains its waterproofing properties, preventing the penetration of water.

EXAMPLE 2

In this second example, the product prepared in Example 1 was applied to cement mortar samples aged by freeze-thaw cycle. Specifically, the mortars were prepared in the laboratory according to EN 196-1, using standardized sand and CEM I 42.5R cement. The water / cement and cement-sand ratios were 0.5 and 1/3, respectively. After pouring into 16x4x4 cm molds, these were cured for 28 days and dried 4 days at 400C. The freeze-thaw aging process was carried out according to the ASTM C-666 standard.

Before applying the products, the mortars were cut into 4x4x4 cm3 blocks, washed with water and dried in an oven. The application was carried out by brush until apparent saturation. For this, 6 applications were made, leaving a waiting time of 4 minutes between each one in order to allow the product to penetrate.

The samples were weighed before and immediately after the application of the product in order to calculate its consumption, obtaining a value of approximately 310 g m -2. Additionally, the penetration depth of the product was also evaluated. For this, the treated samples were cut in half and water was deposited on the cross section, observing a penetration of 13 mm (Figure 6) corresponding to the dry part of the cross section. The product consumption data, as well as the penetration value, confirm that the applied product is absorbed within the porous structure of the cement mortar, the amount of product absorbed and consequently its penetration being significantly higher than the values obtained in the example. 1 as a consequence of the higher porosity (21%) of this material, mainly associated with the degradation process to which it has been subjected (freeze-thaw cycle).

The surface topography of the treated and untreated samples was evaluated by SEM, using the same equipment as in Example 1. Figure 7a shows the untreated surface, in which fractures caused by ice cycles can be observed. thaw. On the contrary, the sample treated with the product developed in this invention (Figure 7b) presents a surface composed of TiÜ ² nanoparticles integrated in the silica matrix, forming a continuous coating on the surface. mortar surface. As previously explained in Example 1, this type of topography is characteristic of a Cassie-Baxer regime. This, in combination with a reduction, will lead to super-repellent properties. In the case of irradiation of the material, a superhydrophilic behavior will be generated.

The wetting properties of the treated and untreated specimens were evaluated by means of contact angle measurements of micro-drops of water, following the procedure described in Example 1. Table 3 shows the static contact angle and hysteresis values. .

Table 3. Contact angle measurements of treated and untreated concrete surfaces, before and after irradiation.

Después de irradiación Muestra Ángulo Estático Histéresis Ángulo Estático HistéresisBefore irradiation

After irradiation Sample Static Angle Hysteresis Static Angle Hysteresis

Untreated 2 Treated 1

* The hysteresis value could not be evaluated as the drop spread rapidly.

The untreated surfaces showed a hydrophilic behavior, with contact angle values around 30 °. After applying the product, the static angle value increased to values of 144 °. Furthermore, the hysteresis value obtained (10 °) confirms the repellency of the evaluated surfaces.

The treated samples were subjected to UV-visible radiation for the purpose of evaluating their ability to induce superhydrophilicity. The results shown in Table 3 confirm the role of the TiU ² nanoparticles causing the change from superhydrophobicity to superhydrophilicity as explained in Example 1.

The superoleophobic properties under water of the superhydrophilic surfaces were evaluated by measuring the static contact angle of chloroform microdrops on treated mortar samples immersed in water. For this, the procedure and equipment used in Example 1 were followed. For comparative purposes, the measurement was carried out on samples treated before (superhydrophobic) and after irradiating with UV-visible light (superhydrophilic). Chloroform droplets deposited on the superhydrophobic surface spread rapidly, due to the oleophilicity of said surface. On the contrary, the droplets deposited on the superhydrophilic surface showed a hemispherical shape, with angles around 110 °. This confirms the oleophobicity under water of the surfaces treated with the product object of the invention.

Additionally, the repellency to oily liquids was confirmed by a simple experiment. Specifically, two treated specimens (non-irradiated and irradiated) were immersed in water, and drops of chloroform stained with a colorant were dropped on them. The experiment was recorded on video and in Figure 8 the captures obtained can be seen. In the case of the unirradiated sample (Figure 8a-c), the drops of chloroform spread on the surface and remained adhered to it. This confirms the oleophilic character of this surface, which shows a superhydrophobic character outside of water. On the contrary, the drops deposited on the irradiated sample (Figure 8d-f) rolled out of it due to its repellency to oily liquids. Therefore, the superoleophobic character of said surface is confirmed.

Finally, the ability of the product to avoid the absorption of water in the porous structure of the cement mortar was evaluated by means of a capillary absorption test. For this, the UNE-EN 1925 standard was followed, as in Example 1. Table 4 shows the percentages of absorbed water mass after 48 hours.

Table 4. Percentages of water consumption at the end of the capillary water absorption test.

Before irradiation After irradiation

Shows

(p / p%) (p / p%)

Untreated 5.7 ± 0.2 5.8 ± 0.3

Treated 0.4 ± 0.1 0.5 ± 0.1

As can be seen in Table 4, the untreated samples show significant water absorption as a consequence of their porosity, which is due to the degradation process (freeze-thaw cycles) to which they have been subjected. On the contrary, the application of the product significantly reduces the absorption of water. It is important to note that there are no notable differences between the unirradiated sample and the irradiated one. This confirms that the transition from superhydrophobicity to superhydrophilicity occurs only on the surface of the treated specimens. However, the product that penetrates inside the porous structure of the substrate, and therefore is not irradiated, maintains its hydrophobicity.

Claims (12)

1. A product for the protection of concrete and other construction materials comprising: a) A silica oligomer based on alkoxysilanes. b) A basic non-ionic surfactant. c) Water. d) A compound with low surface energy functional groups. e) Titanium dioxide nanoparticles with photoactive properties. 2. Product according to claim 1, where the non-ionic surfactant is a primary amine, its concentration being between 0.05-0.40% vol / vol. 3. Product according to claim 2, where the non-ionic surfactant is n-octylamine, 4. Product according to claim 1, wherein the compound with functional groups with low surface energy is selected from the group consisting of: alkyl alkoxysilanes, alkylsilanes, alkylsiloxanes and perfluoroalkylsiloxanes. 5. Product according to claim 4, where the compound with functional groups with low surface energy is a polydimethylsiloxane (PDMS), with a concentration of 10% v / v. 6. Product according to claim 1, wherein the proportion of the titanium dioxide nanoparticles is between 2 and 10% w / v. 7. Product according to claim 1, where the titanium dioxide nanoparticles have a concentration of 5% w / v. 8. Procedure for obtaining a product for the protection of concrete and other construction materials, according to claims 1 to 7, comprising the following stages: a) Mixture of the silica oligomer and the low surface energy compound. b) Dispersion of the titanium dioxide nanoparticles on the compound from the previous stage. c) Addition of water and surfactant on the previous dispersion. d) Homogenization of the mixture by ultrasound-assisted stirring. 9.

Procedure for obtaining a product for the protection of concrete and other construction materials, according to claim 8, in which a photo-activation step of the surface treated with the product is added using artificial UV-A light or exposure to light solar when it is desired to produce on the product obtained a superhydrophilic effect on the surface and a superoleophobic effect in contact with water. 10. Use of the product according to previous claims, to provide protection and self-cleaning effect against any type of contaminant, including those of a water-soluble and oily nature. 11. Use of the product, according to previous claims, to produce a superhydrophilic effect in the presence of solar radiation, as a consequence of its photocatalytic properties, producing a superoleophobic effect in contact with water, providing any building material with self-cleaning capacity against pollutants. , including those of an oily nature. 12. Use of the product, according to previous claims, to create a roughness characteristic of a Cassie-Baxter state on the building material, providing it with superhydrophobic properties, in case the photo-activation of the coating is not carried out with sunlight.