Method of applying a NOx degrading composition on a concrete element
11465944 · 2022-10-11
Assignee
Inventors
Cpc classification
C04B41/5089
CHEMISTRY; METALLURGY
B01D2259/4591
PERFORMING OPERATIONS; TRANSPORTING
B01D53/88
PERFORMING OPERATIONS; TRANSPORTING
C04B41/4578
CHEMISTRY; METALLURGY
C04B28/02
CHEMISTRY; METALLURGY
C04B28/02
CHEMISTRY; METALLURGY
B01D2257/404
PERFORMING OPERATIONS; TRANSPORTING
B01J21/063
PERFORMING OPERATIONS; TRANSPORTING
B01D2257/708
PERFORMING OPERATIONS; TRANSPORTING
C04B41/5089
CHEMISTRY; METALLURGY
International classification
C04B41/00
CHEMISTRY; METALLURGY
C04B41/45
CHEMISTRY; METALLURGY
B01J35/00
PERFORMING OPERATIONS; TRANSPORTING
B01D53/88
PERFORMING OPERATIONS; TRANSPORTING
Abstract
A method of applying a NOx degrading composition on a concrete element, including providing a concrete element having a surface, and applying a composition including photocatalytic titanium dioxide particles dispersed in a continuous phase on the surface of said concrete element. Also, a concrete element having NOx degrading properties. Also, a concrete element having photocatalytic titanium dioxide particles dispersed thereon.
Claims
1. A method of applying a NOx degrading composition on a concrete element, comprising providing a concrete element having a surface, and applying a composition comprising photocatalytic titanium dioxide particles dispersed in a continuous phase on the surface of said concrete element in an amount that equals or exceeds 100 ml/m.sup.2, wherein the composition further comprises a silica compound, wherein the ratio of the silica compound to titanium dioxide particles is between 1:1 to 15:1 wt % in the composition, wherein the continuous phase is water, and wherein said titanium dioxide particles are applied on the surface of the concrete element in an amount of 3 g/m.sup.2 or less.
2. A method according to claim 1, wherein a NOx degrading performance as measured in accordance with ISO 22197-1 test procedure equals or exceeds 10% at said surface of the concrete component.
3. A method according to claim 1, wherein the concentration of said titanium dioxide particles in said composition equals or is less than 2.5 wt %.
4. A method according to claim 1, wherein the composition at least partially permeates into a porous structure of the concrete element.
5. A method according to claim 1, wherein the water constitutes at least 50 wt % of the composition.
6. A method according to claim 1, wherein the composition is free from any binder.
7. A method according to claim 1, wherein said composition consists of the water, the photocatalytic titanium dioxide particles, a silica compound, and at least one additive.
8. A method according to claim 1, wherein said composition comprises 90-99 wt % of the water, 0.1-5 wt % of photocatalytic titanium dioxide particles, and 0.001-5 wt % of additives.
9. A method according to claim 1, wherein a density of the composition equals or is less than 1.5 g/ml.
10. A method according to claim 1, wherein said concrete element is essentially cured.
11. A method according to claim 1, wherein said concrete element is essentially uncured.
12. A method according to claim 1, wherein the upper surface of the concrete element obtains hydrophilic properties after application of the composition.
13. A method according to claim 1, wherein the NOx degrading performance equals or exceeds 2.5% at a depth of 0.5 mm below said surface of the concrete component.
14. A method according to claim 1, wherein the photocatalytic titanium dioxide particles have a primary size less than 50 nm.
15. A method according to claim 1, wherein the titanium dioxide particles are in anatase phase.
16. A method according to claim 1, wherein the concrete element is a concrete paving element or a concrete building element.
17. A method according to claim 1, wherein the silica compound comprises an alkali silicate.
18. A concrete element having NOx degrading properties, comprising photocatalytic titanium dioxide particles in an amount equal or less than 3 g/m.sup.2, an alkali silicate, wherein the ratio of the alkali silicate to titanium dioxide particles is between 1:1 to 15:1 wt % in the composition, and wherein a NOx degrading performance as measured in accordance with ISO 22197-1 test procedure equals or exceeds 5% at a surface of the concrete element.
19. A concrete element according to claim 18, wherein the photocatalytic titanium dioxide particles are provided in an upper portion of said concrete element.
20. A concrete element according to claim 19, wherein said upper portion is extending from an upper surface of the concrete element to a depth of 1.5 mm.
21. A concrete element according to claim 18, wherein the titanium dioxide particles are heterogeneously distributed in the concrete element.
22. A concrete element according to claim 18, wherein the NOx degrading performance equals or exceeds 2.5% at a depth of 0.5 mm below an upper surface of said concrete element.
23. A concrete element according to claim 18, wherein the photocatalytic titanium dioxide particles have a primary size less than 50 nm.
24. A concrete element according to claim 18, wherein the titanium dioxide particles are in anatase phase.
25. A concrete element according to claim 18, wherein an upper surface of the concrete element is hydrophilic.
26. A concrete element according to claim 18, wherein the concrete element is a concrete paving element or a concrete building element.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The present invention will by way of example be described in more detail with reference to the appended schematic drawings, which show embodiments of the present invention.
(2)
(3)
(4)
DETAILED DESCRIPTION
(5) A method of providing a concrete element 1 having NOx degrading properties will now be described with reference to
(6) The concrete element 1 comprises cement as a hydraulic binder, aggregate and water.
(7) The concrete element 1 may comprise a single layer of concrete material or more than one layer of concrete material. The concrete element 1 may have any shape, for example circular, rectangular etc. The concrete element 1 may be a continuous concrete surface, for example moulded to form a pavement or a road.
(8) A composition 2 comprising photocatalytic titanium dioxide particles 3 dispersed in a continuous phase, also called a photocatalytic dispersion hereafter, is applied on a surface 4 of the concrete element 1. The titanium dioxide particles 3 are photocatalytic nanoparticles. The titanium dioxide particles 3 are preferably in anatase phase. The composition 2 is preferably liquid.
(9) The titanium dioxide particles 3 may have a primary size in the range between 5 to 250 nm, preferably between 5 to 100 nm, more preferably between 5 to 50 nm, most preferably between 5 and 30 nm. The titanium dioxide particles 3 may have an agglomerate size of <300 nm<200 nm<100 nm, such as <80 nm preferably an aggregate size of <60 nm such as of <40 nm and even more preferably an aggregate <30 nm such as <20 nm.
(10) In an embodiment, the photocatalytic particles 3 may be doped with non-metals and/or metals. The TiO.sub.2 particles may be doped with non-metals and/or elements such as but not limited to the list of C, N, F, S, Mo, V, W, Cu, Ag, Au, Pt, Pd, Fe, Co, La, Eu, WO.sub.2, and PdO or a combination thereof. The photocatalytic particles may be visible light sensitive and/or UV sensitive photocatalytic particles.
(11) The continuous phase is a solvent, preferably water. The solvent may constitute at least about 50 wt % of the composition, preferably at least about 70 wt % of the composition, more preferably at least about 90% wt of the composition. The composition 2 may further comprise additives such as pH stabilisation agents, dispersion agents, wetting agents. Preferably, the composition comprises a wetting agent.
(12) In one embodiment, the composition 2 consists of the solvent, the photocatalytic titanium dioxide particles and at least one additive. Preferably, the composition is a waterbased dispersion. The composition is free from cementitious or hydraulic binder. Preferably, the composition does not cure but dries.
(13) The concentration of the photocatalytic titanium dioxide particles 3 in the composition may be less than about 5 wt %, preferably less than about 2.5 wt %, more preferably less than about 1.5 wt %, most preferably less than about 1.0 wt %.
(14) As an example, the composition 2 may comprise 0.1-5% by weight photocatalytic titanium dioxide particles. The composition may comprise 90-99% by weight solvent. The composition may comprise 0.001-5% by weight of additives such as pH stabilisation agents, dispersion agents, wetting agents. In one embodiment, the composition comprises 0.1-1% by weight of a wetting agent.
(15) In one embodiment, the composition comprises at least one silica compound. Preferably, the silicate compound comprises an alkali silicate (also known as waterglass) such as sodium silicate, lithium silicate and/or potassium silicate. In one embodiment, the silica compound may comprise silica, silanes and/or siloxanes. Said at least one silica compound is mixed with the titanium dioxide continuous phase to create a stabile dispersion that reduces the water absorption of the concrete element. The ratio between the amount of silica compound such as alkali silicate in relation to the amount of titanium dioxide in the composition may be in the range of about 1:1 to 15:1, such as about 1:1, 3:1, 6:1, 9:1 or 15:1. In this embodiment, 15 g/m2 or less of titanium dioxide particles may be applied, preferably 10 g/m2 or less, and more preferably 5 g/m2 or less of titanium dioxide particles. The composition may be applied in an amount that equals or exceeds 100 ml/m2, preferably equals or exceeds 150 ml/m2, more preferably equals or exceeds 200 ml/m2. The concentration of the titanium dioxide particles in the composition may equal or be less than 15 wt %, preferably equal or be less than 10 wt %, more preferably equal or be less than 5 wt %.
(16) The density of the composition may be less than about 1.5 g/ml, preferably less than about 1.3 g/ml.
(17) The photocatalytic dispersion 2 may be applied on the concrete element 1 before or after the concrete element 1 has cured. The photocatalytic dispersion 2 may be applied during production of the concrete element 1 when the concrete element 1 is essentially uncured. Alternatively, the photocatalytic dispersion 2 is applied when the concrete element is essentially cured. The photocatalytic dispersion 2 may be applied after production when the concrete element is essentially cured. The photocatalytic dispersion 2 may also be applied when the concrete element is installed. Thereby, the photocatalytic dispersion can be applied on an existing pavement, road, garden path, square, patio, building, bridge etc.
(18) The photocatalytic dispersion 2 may be applied by spraying, which is shown in
(19) The amount of the photocatalytic dispersion 2 applied may be about 50-500 ml/m.sup.2. Preferably, the amount of the photocatalytic dispersion applied is exceeding about 100 ml/m.sup.2, preferably exceeding about 150 ml/m.sup.2, more preferably exceeding about 200 ml/m.sup.2.
(20) The loading of photocatalytic titanium dioxide particles 3 applied may be about 0.5-10 g/m.sup.2, preferably about 0.5-5 g/m.sup.2. Preferably, the loading of photocatalytic titanium dioxide particles 3 applied equals or is less than about 10 g/m.sup.2, less than about 5 g/m.sup.2, less than about 3 g/m.sup.2, less than about 2 g/m.sup.2, less than about 1 g/m.sup.2.
(21) As an example, the amount of the photocatalytic dispersion 2 applied is exceeding about 100 ml/m.sup.2, preferably exceeding about 150 ml/m.sup.2, more preferably exceeding about 200 ml/m.sup.2, and the loading of photocatalytic titanium dioxide particles applied is less than about 5 g/m.sup.2, preferably less than about 3 g/m.sup.2.
(22) The photocatalytic dispersion 2 is applied on an upper surface 4 of the concrete element 1. The concrete material of the element 1 is porous, thereby allowing the photocatalytic dispersion to at least partially penetrate into the concrete element 1. The concentration of the photocatalytic dispersion 2 is decreasing with the distance form the upper surface 4 of the concrete element, which is shown in
(23) After the photocatalytic dispersion 2 has been applied to the upper surface 4 of the concrete element 1, the upper surface 4 of the concrete element 1 obtains hydrophilic properties. The contact angle with water is preferably less than 90°, more preferably less than 60°, and most preferably less than 30°.
(24) When the photocatalytic dispersion 2 has been applied, the titanium dioxide particles 3 are heterogeneously distributed in the concrete element 1 in a direction perpendicular to the surface 4 of the concrete element 1 as shown in
(25) The concrete element 1 may thus comprise photocatalytic titanium dioxide particles 3 in an amount of about 0.5-10 g/m.sup.2, preferably about 0.5-5 g/m.sup.2. Preferably, the amount of photocatalytic titanium dioxide particles 3 in the concrete element 1 is less than about 10 g/m.sup.2, is less than about 5 g/m.sup.2, is less than about 3 g/m.sup.2, is less than about 2 g/m.sup.2, is less than about 1 g/m.sup.2.
(26) The NO degrading performance as measured according to ISO 22197-1 at the upper surface 4 of the concrete element 1 may be exceeding about 5%, about 10%, about 15%, about 20%, about 30%.
(27) As an example, the concrete element 1 may thus comprise photocatalytic titanium dioxide particles 3 in an amount of about 0.5-5 g/m.sup.2, and the NO degrading performance as measured according to ISO 22197-1 at the upper surface 4 of the concrete element 1 may be exceeding about 15%, preferably exceeding about 20%, more preferably exceeding about 30%.
(28) When the concrete element 1 has been worn, the concrete element 1 still offers a NO.sub.x degrading performance. At a distance of 0.5 mm from the upper surface 4 of the concrete element 1, the NO degrading performance as measured according to ISO 22197-1 may be exceeding about 2.5%, preferably exceeding 5 about %, more preferably exceeding about 10%.
(29) The visual impression of the concrete element 1 remains essentially the same after application of the photocatalytic dispersion 2. The photocatalytic dispersion 2 does not essentially change the properties such as strength of the concrete element. In certain embodiments, such as when an alkali silicate is included in the composition, the concrete element may be reinforced by the applied composition.
(30) The NO degrading performance defined above is measured according to ISO 22197-1. Several parameters such as light intensity, unit area etc. differs from one test method to another, thereby results from tests using different test methods are not comparable.
(31) It is contemplated that there are numerous modifications of the embodiments described herein, which are still within the scope of the invention as defined by the appended claims.
EXAMPLES
Example 1
(32) Five commercial concrete pavement blocks, 50×50 cm.sup.2, were used to test the photocatalytic performance of a spray applied concrete block. 55 g/m.sup.2 of photocatalytic dispersion (PD) was applied on each concrete block with an airbrush. The photocatalytic dispersion was a 5 wt % waterbased TiO.sub.2 dispersion stabilized to pH 10-11 with ammonia. The average particle size in the dispersions (measured by Volume with Nanotrac NPA 252) was measured to 17 nm. The five concrete blocks were sprayed and left for ambient drying for 24 hours. After 24 hrs., the photocatalytic pavement blocks were cut into 5×10 cm.sup.2 pieces and analysed according to ISO 22197-1.
(33) ISO 22197-1 Test Procedure:
(34) The NOx degrading performance of the sample was tested according to ISO 22197-1. The initial concentration of NO was 1.0 ppm and the flow of NO gas over the sample was 3 l/min. The concentrations of NO, NO.sub.2 and NOx was analysed with a Horiba APNA NOx analyzer model 370. The test cell was purchased from an accredited institute. The light intensity was 1.0 mW/cm.sup.2 UVA measured with a PMA 2110 UVA detector and the relative humidity was kept constant at 45%±5%. The sample sizes in the test were 49×99 mm.sup.2.
(35) TABLE-US-00001 TABLE 1 NO degradation results after ISO 22197-1. 50 × 50 Pavement Block % NO degradation after 24 hrs. amb. Drying 15.8% % NO degradation after 0.5 mm wear abrasion 0.7%
Example 2
(36) A 50×50 cm2 grey pavement stone (IBF Module Pavement Stone 50×50 manufactured by IBF, Denmark) was cut into 5×10 cm2 pieces and two samples of each treatment, PB1 to PB3, were prepared according to the parameters listed in Table 2. A photocatalytic dispersion PD as described above with reference to Example 1 was used. 0.3 wt % wetting agent was added to the photocatalytic dispersion PD. The photocatalytic dispersion PD was applied on the samples and then ambient dried for 24 hours before the NOx performance was evaluated according to ISO 22197-1. The samples were tested in five steps: Step 1: NO degradation tested according to ISO 22197-1 after application of Photocatalytic dispersion and 24 hrs. ambient drying. Step 2: The samples tested in Step 1 were tested against out-washing by rain water by drop wise applying 900 ml de-ionized water to the 5×10 cm.sup.2 sample (appr. 30 min treatment). The sample was then ambient surface dried and then dried at 105° C. for 24 hours. Hereafter, the samples were tested for NO degradation according to ISO 22197-1. Step 3: The samples tested in Step 2 were worn down by 0.5 mm and then the NO degradation was tested according to ISO 22197-1. Step 4: The samples tested in Step 3 were worn down by 1.0 mm and then the NO degradation was tested according to ISO 22197-1. Step 5: The samples tested in Step 4 were tested against out-washing by rain water by drop wise applying 900 ml de-ionized water to the 5×10 cm.sup.2 sample (appr. 30 min treatment). The sample was then ambient surface dried and then dried at 105° C. for 24 hours. Hereafter, the samples were tested for NO degradation according to ISO 22197-1.
(37) The results for the pavement block samples treated with Step 1 to Step 5 are shown in Table 2.
(38) TABLE-US-00002 TABLE 2 NO degradation results after ISO 22197-1. PB1 PB2 PB3 Wt % TiO.sub.2 [%] 0.5 2.5 0.5 Amount [ml/m.sup.2] 200 200 500 Loading of TiO.sub.2 [g/m.sup.2] 1.0 5.0 2.5 % NO Degr. Step 1 37.0% 52.2% 44.2% % NO Degr. Step 2 34.8% 53.3% 44.1% % NO Degr. Step 3 10.5% 30.8% 17.7% % NO Degr. Step 4 7.4% 22.2% 11.0% % NO Degr. Step 5 6.4% 19.1% 10.1%
(39) The data in Table 2 show that it is possible to have both a high NOx degrading activity but also to have a NOx degrading activity more than 1 mm down in the pavement stone with TiO.sub.2 loadings of 1 to 5 g/m.sup.2 and by applying 200-500 ml/m.sup.2 of the photocatalytic dispersion.
Example 3
(40) IBF Modulserie 30×10×7.5 cm (manufactured by IBF, Denmark) was used to test the effect of applying different concentrations of a photocatalytic dispersion PD as described above with reference to Example 1 having different concentration of TiO.sub.2. 3 samples were made for each concentration and the average NOx degradation performances are listed in Table 3. The amount of photocatalytic dispersion was applied with a pipette. After application the samples went through Step 1 and Step 2 as described above in Example 2, following by testing the NOx degradation properties after the sample was worn a certain amount of mm down as listed in Table 3.
(41) TABLE-US-00003 TABLE 3 NO degradation results after ISO 22197-1. Stone1 Stone2 Stone3 Wt % TiO.sub.2 [%] 0.5 1.5 2.5 Amount [ml/m.sup.2] 200 200 200 Loading of TiO.sub.2 [g/m.sup.2] 1.0 3.0 5.0 % NO Degr. Step 1 29% 16% 16% % NO Degr. Step 2 58% 57% 54% % NO Degr. 0.5 mm 12% 14% 14% % NO Degr. 1.0 mm 9% 10% 13% % NO Degr. 1.4 mm not measured 10% not measured % NO Degr. 1.8 mm not measured not measured 7%
(42) The results in Table 3 show that the NOx degrading activity of the photocatalytic pavement stones depends to a higher extent on the total amount of fluid applied per m2 of the pavement stones than on the overall loading (g TiO.sub.2/m.sup.2) of TiO.sub.2 on the pavement stones.
Example 4
(43) IBF Modulserie 30×10×7.5 cm (manufactured by IBF, Denmark) was used to test the effect of the size in dispersion of the applied TiO.sub.2. Furthermore, the effect of amount and the application method was also tested. One series of experiments (Stone4) was applied as Stone1 explained in Example 3; however, instead of 17 nm TiO.sub.2 particles, TiO.sub.2 particles with an average size in dispersion of 73 nm were used where the average particle size in the dispersion was measured by volume with Nanotrac NPA 252. For Stone 5 and Stone 6 photocatalytic dispersion PD was used in a 5 wt % concentration.
(44) TABLE-US-00004 TABLE 4 NO degradation results after ISO 22197-1. Stone1 Stone4 Stone5 Stone6 Wt % TiO.sub.2 [%] 0.5 0.5 5.0 5.0 Size in Dispersion [nm] 17.5 73 17.5 17.5 Amount [ml/m.sup.2] 200 200 55 55 Loading of TiO.sub.2 [g/m.sup.2] 1.0 1.0 2.7 2.7 Application Type Pipette Pipette Pipette Airbrush % NO Degr. Step 1 29% 9% 11% 9% % NO Degr. Step 2 58% 10% 50% 37% % NO Degr. 0.5 mm 12% 2% 3% 5% % NO Degr. 1.0 mm 9% 1% 2% 2%
(45) The results in Table 4 show that by comparing Stone 1 and Stone 4 it is obvious that the overall performance and especially the activity down in the matrix of the stone is depended on the particle size. Comparing an average particle size of approximate 17 nm with an average particle size of 73 nm it shows 5-6 times higher activity for the 17 nm Stone (Stone 1) both as initial NOx degradation activity as well as 0.5 nm and 1.0 mm down in the stone matrix.
Example 5
(46) IBF Modulserie 30×10×7.5 cm concrete stone (manufactured by IBF, Denmark) was used immediately after production and before the stones have cured, which will in the following will be defined as a wet stone. The photocatalytic dispersion PD is used and applied with an automatic hydraulic nozzle set-up.
(47) TABLE-US-00005 TABLE 5 NO degradation results after ISO 22197-1. Stone10- Stone7 Stone8 Stone9 REF Wt % TiO.sub.2 [%] 0.5 0.5 0.5 0.0 Amount [ml/m.sup.2] 100 150 200 0.0 Loading of TiO.sub.2 0.5 0.75 1.0 0.0 [g/m.sup.2] Application Type wet-in-wet wet-in-wet wet-in-wet REF Application hydraulic hydraulic hydraulic — nozzles nozzles nozzles % NO Degr. Step 1 16% 16% 19% 0.3% % NO Degr. Step 2 26% 27% 29% 0.2% % NO Degr. 0.5 3% 5% 7% 0.1% mm % NO Degr. 1.0 2% 3% 3% 0.1% mm
(48) Table 5 shows that by applying the photocatalytic dispersion to an uncured wet concrete stone a high NOx degrading activity is measurable both initially and down in the matrix.
Example 6
Real Life Test
(49) IBF Modulserie 30×10×10 cm (manufactured by IBF, Denmark) was used to test the real life effect of produced photocatalytic concrete stones, in the following referred to as NOx-OFF stones. The amount of photocatalytic dispersion was applied with an automatic spraying set-up. 150 g/m.sup.2 of photocatalytic dispersion was applied on the stones with a hydraulic nozzle set-up. The photocatalytic dispersion was a 0.5 wt % water based TiO.sub.2 dispersion stabilized to pH 10-11 with ammonia. The average particle size in the dispersions (measured by Volume with Nanotrac NPA 252) was measured to approximate. 15 nm. 250 m.sup.2 of NOx-OFF stones were produced and dried before installing it on a parking lot. The NOx degrading properties of the NOx-OFF stones before installation were tested according to ISO 22197-1 as explained in Example 1.
(50) TABLE-US-00006 TABLE 6 NO degradation results after ISO 22197-1. Average of 6 NOx-OFF Stones Wt % TiO.sub.2 [%] 0.5 Amount [ml/m.sup.2] 150 Loading of TiO.sub.2 [g/m.sup.2] 0.75 % NO Degr. Step 1 10% % NO Degr. Step 2 23%
(51) The NOx-OFF stones were installed on a heavy duty traffic parking lot. The location was chosen so that next to the NOx-OFF stones was an equally sized reference area with conventional, non-photocatalytic, concrete stones. Furthermore, the chosen location was a payment car park so every car entering the car park on the NOx-OFF area was also to leave the car park on the reference area. Before installing the NOx-OFF stones the NOx level was measured on both areas for 41 days to be able to compare the air cleaning performance of the NOx-OFF stones. The NOx level was measured on both areas with a Eco Physics NOx analyzer with a multiplexing function measuring the NO, NO.sub.2 and NOx values each 30 sec. After the NOx-OFF stones were installed the NOx level was measured for a period of 43 days. Comparing the reference measuring period with the period after installing the NOx-OFF stones it can be concluded that the NOx level was reduced by 13% overall on the NOx-OFF area, the NOx data are shown in
(52) The real life data for NOx-OFF concrete stones clearly shows that the high NOx degrading activities characterized in the lab by the ISO 22197-1 test procedure can also be determined in real life. By installing NOx-OFF stones in real life it was in Example 6 shown that the overall level of NOx on a heavy duty traffic parking lot could be reduced overall by 13%.
Example 7
(53) IBF Modulserie (manufactured by IBF, Denmark) cut into the dimensions 10×5 cm was used to test the effect of applying different ratios of waterglass comprising alkali silicates with different concentrations of a photocatalytic dispersion being a waterbased TiO.sub.2 dispersion. Four samples were made and for each mixture of alkali silicate and photocatalytic dispersion the initial activity was compared to the activity after 260, 426, and 583 hours in accelerated weathering following EN 1297:2004. The hours in accelerated weathering are estimated to correspond to approximately 10, 18, and 24 months in real life conditions. The concentration and the average NOx degradation performances are listed in Table 7. The amount of photocatalytic dispersion including alkali silicate was applied with a pipette. The NOx degradation properties of the samples are listed in Table 7.
(54) TABLE-US-00007 TABLE 7 NO degradation results after ISO 22197-1. StoneA StoneB StoneC StoneD Wt % TiO.sub.2 [%] 15 7.5 5 1.9 Wt % Alkali Silicate [%] 15 20 22.5 26.7 Amount [ml/m.sup.2] 200 200 200 200 % NO Degr. Initial 37% 20% 8% 1% % NO Degr. 260 hr (EN1297) 45% 13% 5% 8% % NO Degr. 426 hr (EN1297) 35% 13% 4% 6% % NO Degr. 583 hr (EN1297) 54% 22% 7% 10%
(55) The data in Table 7 show that when applying a photocatalytic dispersion including alkali silicate the photocatalytic activity is still high after 583 hours in accelerated weathering or what corresponds to approximately 2 years in outdoor conditions. For Stone A the activity has increased after 583 hours in EN 1297:2004 and for Stone D the activity is ten times higher than the initial activity.
Example 8
(56) IBF Modulserie (manufactured by IBF, Denmark) cut into the dimensions 10×5 cm was used to test the effect of applying a photocatalytic dispersion including waterglass comprising alkali silicates and the consequence of water weathering on the sample and the photocatalytic activity right after water weathering. 4 samples were made and for each mixture of alkali silicate and photocatalytic dispersion comprising a waterbased TiO.sub.2 dispersion the initial activity was compared to the activity after drop test—Step 1 and Step 2 in Example 2 above, however the samples are tested directly after drop test and 1 hour ambient drying.
(57) TABLE-US-00008 TABLE 8 NO degradation results after ISO 22197-1. StoneA StoneD StoneE StoneF Wt % TiO.sub.2 [%] 15 1.9 2.9 1.4 Wt % Alkali Silicate [%] 15 26.7 13.3 6.7 Amount [ml/m.sup.2] 200 200 200 200 % NO Degr. Initial 45% 11% 5% 5% % NO Degr. Directly after 52% 8% 5% 5% drop test
(58) The data in Table 8 show that when applying a photocatalytic dispersion including alkali silicate, the photocatalytic activity is maintained after drop test even without additional forced drying.
Example 9
(59) IBF Modulserie (manufactured by IBF, Denmark) cut in the dimensions 10×5×1.5 cm was used to test the effect of applying a photocatalytic dispersion including waterglass comprising alkali silicates and TiO.sub.2 on water absorption compared to water absorption of a concrete sample without alkali silicate. The surface water absorption of StoneE from Example 8 and a reference concrete stone was tested. The StoneE and the reference stone were inserted with the surface pointing downwards in a container with 5 mm of de-ionized water. The weight of StoneE and of the reference stone were measured before being inserted in the de-ionized water and after being placed in the container with deionized water for 4 hours. The surface of the reference stone had absorbed 2.6% water of its total weight and the surface of Stone E had absorbed only 1.5% water of its total weight. The water absorption experiment shows that the photocatalytic dispersion including alkali silicate improved the resistance towards surface absorption of water.