Photocatalytic concrete product and a method to produce a photocatalytic concrete product

Abstract

The present invention relates to a photocatalytic concrete product and a method to produce a photocatalytic concrete product. In first aspect the invention relates to method of producing photocatalytic concrete product, said concrete product being photocatalytic by containing nano sized photocatalytic particles embedded in an section including a first surface, said first surface forming an exterior surface when the photocatalytic concrete product is used as cover/lining. The method comprises: providing a not-yet-set concrete product having a first surface, applying a dispersion containing nano sized photocatalytic particles, such as titanium dioxide nanoparticles a solvent including a humectant onto said first surface of the not-yet-set concrete product.

Claims

1. A method of producing photocatalytic concrete product (1), said concrete product being photocatalytic by containing nano sized photocatalytic particles embedded in a section (3) including a first surface (2), the method comprises: providing a not-yet-set concrete product (1) having a first surface (2); applying an aqueous dispersion onto said first surface (2) of the not-yet-set concrete product, the dispersion containing: nano sized photocatalytic particles or titanium dioxide nanoparticles; and a solvent including a humectant selected from the group of glycol, that includes one or more of glycerol, 1,2-butanediol, 1,4-butanediol, propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, hexasol, 1,5-pentanediol, 3-methyl-1, 5-pentanediol, isoprene glycol and/or selected from the group of polyethers that include one or more of polyethyleneglycols, polypropyleneglycols, polyethyleneglycol methyl ethers, polypropyleneglycol methyl ethers and/or selected from the group of amines that include one or more of ethanolamine, propanolamines, triethanolamine, polyether amines that include one or more of polyoxyethyleneamines, polyoxypropyleneamines, polyoxyethylene monoamines, polyoxypropylene monoamines, wherein the humectant is present in the dispersion in the range above 40 wt % and less than or equal to 50 wt %.

2. A method according to claim 1, wherein a concentration of the humectant in the dispersion is in the range between 45 wt % and 50 wt %.

3. A method according claim 1, wherein said dispersion comprises: a solvent or water; one or more co-solvents or alcohol or isopropanol up to 15 wt %; photocatalytic titanium dioxide nanoparticles in the range between 15 wt % and 2.5 wt %.

4. A method according to claim 1, wherein the dispersion comprises a dispersion agent for keeping the dispersion stable.

5. A method according to claim 1, wherein the dispersion is applied to said first surface in an amount of less than 200 ml/m2.

6. A method according to claim 1, wherein the dispersion is applied to said first surface during a time period of less than 5 minutes, during which time period the amount measured in ml of dispersion received at the first surface per time unit is constant.

7. A method according to claim 1, wherein the dispersion is applied to said first surface (2) by spraying the dispersion as droplets onto said first surface (2).

8. A method according to claim 1, wherein the non-yet-set concrete product is provided by filling the not-yet-set concrete (9) into a mould (6).

9. A method according to claim 8, wherein the not-yet-set concrete in the mould is compacted by vibrating and/or compressing the concrete while in the mould.

10. A method according to claim 9, wherein the compacting is performed not later than 30 minutes after the not-yet-set concrete (9) is filled into the mould (6).

11. A method according to claim 9, wherein the dispersion is applied to said first surface (2) after compacting the not-yet-set concrete (9).

12. A method according to claim 9, wherein the dispersion is applied to said first surface (2) prior to compacting the not-yet-set concrete (9).

13. A method according to claim 8, wherein the mould (6) is removed from the concrete product before the concrete is set, not later than 30 minutes after being filled into the mould.

14. A method according to claim 1, wherein the concrete product is allowed to set after the dispersion has been applied to the first surface.

15. A method according claim 1, wherein the not-yet-set concrete of the not-yet-set concrete product is form stable.

16. A method according to claim 1, wherein said nano sized photocatalytic particles or titanium dioxide nanoparticles, are discrete particles.

17. A method according to claim 1, wherein said nano sized photocatalytic particles or titanium dioxide nanoparticles, are chemically bond to the not-yet-set concrete.

18. A method according to claim 5, wherein said nano sized photocatalytic particles or titanium dioxide nanoparticles, in the first surface are in an amount of 10 g/m2 or less.

19. A method according to claim 1, wherein the nano sized photocatalytic particles or titanium dioxide nanoparticles, have a primary size less than 50 nm.

20. A method according to claim 1, wherein the nano sized photocatalytic particles or titanium dioxide nanoparticles, have an agglomerate size of less than 300 nm.

21. A method according to claim 1, wherein the nano sized photocatalytic particles or photocatalytic titanium dioxide nanoparticles, are in anatase phase.

22. A method according to claim 1, wherein the method is carried out on a conveyor (10).

23. A method according to claim 1, wherein a water to cement weight ratio is in the range of 0.3-0.7 w/c.

24. A method of producing photocatalytic concrete product (1), said concrete product being photocatalytic by containing nano sized photocatalytic particles embedded in a section (3) including a first surface (2), the method comprises: providing a not-yet-set concrete product (1) having a first surface (2); applying an aqueous dispersion onto said first surface (2) of the not-yet-set concrete product, the dispersion containing: nano sized photocatalytic particles or titanium dioxide nanoparticles; and a solvent including a humectant selected from the group of glycol, that includes one or more of glycerol, 1,2-butanediol, 1,4-butanediol, propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, hexasol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, isoprene glycol and/or selected from the group of polyethers that include one or more of polyethyleneglycols, polypropyleneglycols, polyethyleneglycol methyl ethers, polypropyleneglycol methyl ethers and/or selected from the group of amines that include one or more of ethanolamine, propanolamines, triethanolamine, polyether amines that include one or more of polyoxyethyleneamines, polyoxypropyleneamines, polyoxyethylene monoamines, polyoxypropylene monoamines, wherein the humectant is present in the dispersion in the range above 40 wt % and less than or equal to 50 wt %, wherein the dispersion comprises TiO2 in range of 0.5-10 wt %, an electrostatic stabiliser in the range of 0-10 wt %, a steric stabilizer in the range of 0-5 wt %, and 20-80 wt % solvent or water.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The method of producing concrete product and the concrete product according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(2) FIG. 1 shows a schematic drawing of a preferred embodiment of a production method for producing a photocatalytic concrete product,

(3) FIG. 2 shows a schematic drawing of a further preferred embodiment of a production method for producing the photocatalytic concrete product,

(4) FIG. 3 shows a schematic drawing of different moulds used for shaping the photocatalytic concrete product, and

(5) FIG. 4 shows a schematic 3-dimensional drawing of a photocatalytic concrete product according to a preferred embodiment of the invention; the product is preferably provided by a method according to the present invention.

(6) Reference is made to FIG. 1 illustrating schematically a method of producing photocatalytic concrete product 1. The concrete product 1 being photocatalytic by containing nano sized photocatalytic embedded in a section 3 of the product which section includes a first surface 2 of the product. The first surface 2 forms an exterior surface, when photocatalytic concrete product 1 is used as lining. As shown in FIG. 1, the method comprises the step of applying a dispersion containing nano sized photocatalytic particles, such as titanium dioxide nanoparticles, and a solvent including a humectant onto said first surface 2 of the not-yet-set concrete product.

(7) As the concrete is not-yet-set, the concrete is still porous and the dispersion will penetrate into the concrete forming the first section 3, in which the nano sized particles will be deposited. The thickness of the layer 3 may be controlled by the amount of dispersion applied and time left before the concrete sets.

(8) As presented herein, the concrete prior to application of the dispersion containing the nano sized particles is not-yet-set. Within the meaning of this is that the concrete can be moulded into a given shape and that the not-yet-set concrete is form stable. This moldability while still being form stable is provided by selecting the water content in the concrete sufficiently low while still being high enough to assure a setting of the product. In making a concrete product the water to cement ratio is a crucial parameter as it affects the setting time and also the porosity and permeability, consequently, the water to cement ratio influences the concrete strength and other detrimental chemical and physical processes. The normal accepted ratio of water-to-cement is in the range of 0.3-0.7 w/c to obtain the optimal performance of the concrete, such as but not limited to form stable and strength.

(9) As also presented herein, the laitance is avoided by including a humectant in the dispersion. A preferred humectant is selected from the group consisting of glycol, such as glycerol, 1,2-butanediol, 1,4-butanediol, propylene glycol, dipropylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, hexasol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, isoprene glycol, polyethyleneglycols, polypropyleneglycols, polyethyleneglycol methyl ethers, polypropyleneglycol methyl ethers and/or amines, such as ethanolamine, propanolamines, triethanolamine, polyoxyethyleneamines, polyoxypropyleneamines, polyoxyethylene monoamines, polyoxypropylene monoamines.

(10) The dispersion may comprise or further comprise an electrostatics stabilizing agent, such as alkaline compounds; for example amines and/or ammonia.

(11) The dispersion may further comprise a sterical stabilisation agent(s) with pigment affinic group such as a wetting and/or dispersing additive for aqueous and solvent systems and/or deflocculating additive, such as composed of copolymers with pigment affinic groups.

(12) The dispersion is applied to the first surface 2 in an amount of less than 200 ml/m.sup.2, such as 150 ml/m.sup.2, for example less than 100 ml/m.sup.2. In terms of amount of nano sized photocatalytic particles, the dispersion is applied to said first surface in an amount of less 10 g nano sized photocatalytic titanium dioxide/m.sup.2, less than 5 g/m.sup.2, less than 2.5 g/m.sup.2.

(13) In order to allow the dispersion to penetrate into the not-yet-set concrete product, typically without forming a liquid layer on top of the product due to setting of the concrete, the dispersion is applied to said first surface during a time period of less than 5 minutes, such as less than 2 minutes, preferably less than 1 minute, such as less than 30 seconds. Preferably, the amount measured in ml of dispersion received at the first surface per time unit is constant.

(14) The dispersion is applied to said first surface 2 by spraying the dispersion as droplets 4 onto said first surface 2. The droplets are provided by feeding the dispersion through droplet forming nozzles arranged above the surface 2 of the product 1.

(15) Reference is made to FIG. 2, showing a further embodiment of a method for producing a photocatalytic concrete product 1. As shown in FIG. 2, a mould 6 is arranged on a horizontally moving conveyer 10. The mould 6 is advanced to a position below a concrete filling machine 7 which fills not-yet-set concrete into the mould 6. After the desired amount of concrete is filled into the mould 6, the mould is advanced to a compacting position where the not-yet-set concrete in the mould 6 is compacted, preferably by vibrating and/or compressing the concrete while in the mould. As shown in FIG. 2, the compacting is carried out by pressing a piston 8 against the surface of the not-yet-set concrete arranged in the mould 6, while the piston 8 performs a horizontal reciprocating movement. The compacting provides a photocatalytic concrete product with a specific outer dimension, as the compacting assures that the concrete fills out the mould and reduces the thickness. Accordingly, the vertical movement of the piston 8 is limited downward to not exceed the thickness of the product. In some preferred embodiments, the filing and compacting is integrated in single operation and thus, the concrete product is not moved between filling and compacting.

(16) The photocatalytic concrete product may also be applied in an on-site casting of the photocatalytic concrete product. In such embodiments, the not-yet-set concrete is applied to the position where it is to form the lining, typically vibrated to compact it, and the dispersion containing the nano sized photocatalytic particles is sprayed onto the surface of the non-yet-set concrete.

(17) The compacting is preferably performed not later than 30 minutes, such as not later than 20 minutes, preferably not later than 10 minutes, such as not later than 5 minutes after the not-yet-set concrete 9 is filled into the mould 6 in order to assure that the concrete does not set prior to compacting and subsequent application of dispersion, as the dispersion is applied to the first surface 2 after compacting the not-yet-set concrete 9—in FIG. 2 this is shown by the concrete product being advanced to an application station where the dispersion is sprayed on to the surface 2. However, the dispersion may be applied to first surface 2 prior to compacting the not-yet-set concrete 9. In preferred embodiments, the compacting is in practise carried out within 30 seconds after the not-yet-set concrete is filled into the mould.

(18) As the concrete is form stable prior to setting, the mould 6 can be removed from the concrete product before the concrete is set. This preferably means not later than 30 minutes, such as not later than 20 minutes, preferably not later than 10 minutes, such as not later than 5 minutes after being filled into the mould. This has inter alia the advantage that the concrete product does not need to be located in a mould during setting whereby the product made of not-yet-set concrete may be left without a mould for setting and the mould used for production of other products. Thus, the concrete product is allowed to set after the dispersion has been applied to the first surface.

(19) The nano sized photocatalytic particles, are preferably titanium dioxide nanoparticles, and are preferably discrete particles. The nano sized photocatalytic particles, are in some embodiments chemically bond to the concrete and in other embodiments embedded in the concrete without chemical bonds.

(20) FIG. 3 shows schematically three different shapes of moulds 6. However, the invention is not limited to those three shapes but any other shape of mould can be used as long as the concrete can mimic the shape of the mould. In FIG. 3 is also shown the line A-A showing the cross section along which the mould of FIG. 2 is shown.

(21) Reference is made to FIG. 4 showing schematically a preferred embodiment of a photocatalytic concrete product 1. The concrete product 1 is a set concrete product 1 with photocatalytic nano sized particles embedded in a first section 3 of the concrete product 1. As shown, the first section 3 extends from a first surface (2) and at least 1 mm inward, such as at least 2 mm inward, preferably at least 5 mm inward. In a preferred embodiment, the first section 3 comprises photocatalytic titanium dioxide nanoparticles.

(22) As the appearance of nano sized photocatalytic particles in the first layer 3 is provided so that no or substantial no colouring and/or laitance effect occurs as a result of applying the particles, the concrete product may be given other colours than the colour of the concrete. This may be provided by the concrete product comprising a colouring agent embedded at least in the first section (3) of the concrete product. In a preferred embodiment, the colouring agent is mixed into the concrete prior to be filled into a mould and in such embodiment, the colouring agent is present throughout the concrete product.

(23) The photocatalytic composition including nano sized photocatalytic particles, humectant, optionally including a sterical stabilizer and a solvent is provided so that no or substantially no colouring and/or laitance effect occurs as a result of applying the particles and as the mobility of the cement and the aggregates is limited the distribution of e.g. cement, aggregate particles and nano sized photocatalytic TiO2 is substantially homogeneous distributed in the top layer of the concrete.

(24) While the method shown in FIG. 1-3 discloses a production of photocatalytic concrete products off-site, that is the linings are not cast at the site where it is supposed to form a lining, the method disclosed herein may equally well be applied to casting photocatalytic concrete product on-site.

Example 1

(25) Commercial concrete pavement blocks 50×50 cm.sup.2, from Gammelrand Beton, were used to test the photocatalytic composition applied with spray nozzles on the not-yet-set concrete blocks. 100-150 g/m.sup.2 of photocatalytic dispersion (PD) was applied on each concrete block with a hydraulic nozzle system. The photocatalytic dispersion was a 1.5 wt % water-based TiO.sub.2 dispersion stabilized to pH 10-11 with ammonia including 42% diethylenglycol as humectant and 5% Disperbyk 191. The average particle size in the dispersions (measured by Volume with Nanotrac NPA 252) was measured to 22 nm. The pavement concrete blocks were sprayed and left for ambient drying for 72 hours. After 72 hours, the visual appearance of the photocatalytic pavement blocks were evaluated by comparing to commercial pavement concrete blocks, commercial concrete blocks sprayed with 100-150 g/m2 water, commercial pavement concrete blocks sprayed with a 1.5 wt % water based TiO.sub.2 dispersion similar to PD but without humectant and without Disperbyk 191.

(26) The products were evaluated with colour measurement and abrasion test. The abrasion test was performed by rubbing the surface with a black cloth and evaluating if a white residue was present on the cloth after rubbing. Colour was measured with a SpectroEye from X-Rite. The colour of the reference and the spray applied samples were recorded as Lab (L.Math.a.Math.b) values and used to calculate the colour change as:
ΔL=abs(L.sub.(Ref)−L.sub.(Sample,x))
ΔE=sqrt((L.sub.(Ref)−L.sub.(Sample,x)).sup.2+(a.sub.(Ref)−a.sub.(Sample,x)).sup.2+(b.sub.(Ref)−b.sub.(Sample,x)).sup.2)
where the L scale defines light vs. dark and ΔE is the total colour difference.

(27) TABLE-US-00001 TABLE 1 Evaluation of pavement concrete blocks. Water with Photocatalytic Reference Water particles composition ΔL 0 20.0 21.7 0.48 ΔE 0 21.3 22.7 0.9 Abrasion No white White White residue No white residue residue residue

(28) The colour evaluation of the samples tested in Example 1 showed that the photocatalytic product had the same colour as the reference whereas the product sprayed with only water and the product sprayed with a water based TiO.sub.2 dispersion showed a clearly white colour compared to the reference when comparing the ΔL values and the overall color difference, ΔE. Furthermore, only the water and the water-based TiO.sub.2 applied sample showed a white residue when tested for abrasion. Both the white colour and the white residue from the abrasion test is an indication of laitance deposited on the surface of the water and water-based TiO.sub.2 applied products, whereas no laitance was present on the reference and the photocatalytic product.

Example 2

(29) 50×50 cm2 commercial grey pavement stones (Gammelrand Beton) were used to test the photocatalytic activity of the photocatalytic composition applied to the not-yet-set concrete pavement stone. The photocatalytic composition applied with spray nozzles on the not-yet-set concrete blocks. 150 g/m.sup.2 of photocatalytic dispersion (PD) was applied on each concrete block with a hydraulic nozzle system. The photocatalytic dispersion was a 1.6 wt % water-based TiO.sub.2 dispersion stabilized to pH 10-11 with ammonia including 42% diethylenglycol as humectant and 5% Disperbyk 191. The average particle size (of TiO.sub.2) in the dispersions (measured by Volume with Nanotrac NPA 252) was measured to 22 nm. The final composition had a pH of 8. The pavement concrete blocks were sprayed and left for ambient drying for 72 hours. After 72 hours, the concrete block was cut into 5×10 cm2 pieces and analysed according to ISO 22197-1.

(30) ISO 22197-1 Test Procedure:

(31) 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 were 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. The results are shown in Table 2, both for the sample directly after production and the same sample after 138 hr accelerated weathering according to EN1297:2004.

(32) EN 1297:2004 Test Procedure.

(33) The EN 1297:2004 test weathering procedure consists of a dry cycle followed by a wet spray cycle. The dry cycle is 300 min of 45 W/cm2±5 w/cm.sup.2 UVA (340 nm) and a chamber temperature of 60° C. (BST). The wet spray cycle is 60 min of spraying de-ionized water (max conductivity of 500 μS/m) at a flow rate of 10±3 l/min/m.sup.2 with an initial temperature of the water of 25±5° C. The test is continued by repeating step 4 and 5 for a predetermined number of hours.

(34) TABLE-US-00002 TABLE 2 NO degradation results after ISO 22197-1. NO activity [%] Directly from Production 9.6% After 115 hr ageing (EN1297:2004) 9.0%

(35) The data in Table 2 show that photocatalytic concrete stone has a high NOx activity. Furthermore, the activity after ageing is the same as for the sample before ageing. This means that the photocatalytic particles are not only present as a coating layer but are incorporated in the concrete layer and is not just washed away with water.

(36) Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms “comprising” or “comprises” do not exclude other possible elements or steps. In addition, the mentioning of references such as “a” or “an” etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

LIST OF REFERENCES USED

(37) 1 Photocatalytic concrete product 2 First surface of photocatalytic concrete product 3 Section of photocatalytic concrete producing having nano sized photocatalytic particles embedded 4 Droplets of dispersion containing nano sized photocatalytic particles 5 Spraying device, spraying the dispersion as droplet, atomized dispersion or a liquid curtain. 6 Mould 7 Concrete filling device 8 Compactor 9 Not-yet-set concrete 10 Conveyor