PhotoScaling Decision Maker

Score: Conformity Criteria (Indicators)
1. Photocatalytic Performance Efficiency (PPE)
1.1.a Band gap eV
The band-gap is an energy range in a semiconductor solid where no electron states can exist. The band gap is the difference in energy between the highest permitted energy level for the electron in the valence band and lowest permitted energy level in the conduction band. In other words, the band gap is the minimum energy of light required to make the material electrically conductive. Thus, the higher the band gap, the higher the energy of the photons needed to activate the photocatalyst. As an indication, Eg of TiO2 (anatase) is of 3.2 eV which corresponds to photons with a wave length of 388 nm. As the materials we are dealing with are not pure photocatalysts, the term of band gap would not be very accurate, so, the term we are using for complex materials is apparent photo-absorption edge, determined by diffuse reflectance.
1.1.b Position of the bands V (VB) V (CB)
The band-gap is an energy range in a semiconductor solid where no electron states can exist. The band gap is the difference in energy between the highest permitted energy level for the electron in the valence band and lowest permitted energy level in the conduction band. In other words, the band gap is the minimum energy of light required to make the material electrically conductive. Thus, the higher the band gap, the higher the energy of the photons needed to activate the photocatalyst. As an indication, Eg of TiO2 (anatase) is of 3.2 eV which corresponds to photons with a wave length of 388 nm. As the materials we are dealing with are not pure photocatalysts, the term of band gap would not be very accurate, so, the term we are using for complex materials is apparent photo-absorption edge, determined by diffuse reflectance.
1.2. Initial Efficiency RNOX %
NOX removal efficiency, RNOX [%], of the material following the standard ISO 22197-1:2007.
1.3. Adh. to the Substrate g/m2
 * Does not apply
To assess the adherence to the substrates, cross-cut test (ISO 2409:2013) are carried out. The specimens were prepared 16 hours before the test, at 23 °C and a relative humidity of 50 %. The samples were placed in a flat surface to conduct the tests. In each sample, a manual tool comprised of cutting multi-blades with a V-shaped 2 mm depth cutting edge was used to make a lattice pattern by making two horizontal and two vertical cuts. After this procedure, an adhesive tape is used to collect the detached material from the specimens, whose weight is the measured parameter.
1.4. Carbonation g/m2
 * Does not apply
In order to evaluate the susceptibility of the material to carbonation, after equilibration at 65 % HR for one week, the weight of the specimen is recorded and 100 % CO2 is passed through the carbonation chamber with the specimen completely sealed with the exception of the photocatalytic surface. When the chamber is full of CO2 at 65 % HR, the valves are closed and the specimen remains at this atmosphere for 24 hr, when the chamber is open, the weight is register and the process is repeated again. The value finally taken is the increase in weight (mg/cm2) taken by the specimen after 1 week of test.
2. Intrinsic Performance (IP)
2.1. Slippery Performance Rd
The slip resistance (Sr) is determined through the pendulum slip-meter according to EN 14231 standard, adopted by Spanish building technical code.
3. Undesired Secondary Effects (USE)
3.1.a. Leach. Ti (rain reg.) mg/m2
 * No leaching
The method chosen is the short version (until 9 days) of the CEN/TS 16637-2 standard: Construction products - Assessment of release of dangerous substances - Part 2: Horizontal dynamic surface leaching test. The test portion of the product is placed in a reactor/leaching vessel and the exposed surface is completely submerged in a leachant. The leachant is introduced in the reactor up to a given volume of liquid to surface area ratio (L/A ratio), at a given temperature and renewed at predetermined time intervals. This test method produces eluates, which shall subsequently be analyzed.
3.1.b. Leach. Ti (w. pres.) mg/m2
 * No leaching
The test portion of the product is placed in a leaching vessel and the sample is collocated in the middle of the vessel on the top of a supporting structure, with the face exposed 7-8 cm from the bottom of the vessel. A flow of 4.16·10-6 m3/s of pure water is sprayed on each sample. The duration of the tests is 1 minute for each sample. Then the eluate is analyzed for Ti.
3.2. Nanoparticles Emission 103#/cm2

The experimental conditions for assessment of nanoparticle emission intensity is undertaken using the experimental prototype TEMIS-1000. The characteristics of the prototype and the experimental conditions are the following ones (see table). The conditions for the asphalts are softer as the open asphalt did not supporter harder conditions.

3.3. Selectivity to NO3-
Titanium dioxide photocatalysis oxidises NOX to nitrate and thus reduces air pollution. However, during the photocatalytic process titanium NO2 in an intermediate that is also released in variable quantities. Being the NO2 more harmful than NO, it is necessary that the selectivity of the photocatalyst to nitrates is higher as possible. The nitrate selectivity is calculated according to [JZ Bloh, A Folli, DE Macphee - RSC Advances, 2014] as S=RNOX/RNO.

Sustainability: Life Cycle Analysis
Life Cycle Analysis (LCA) is a standardised method for measuring and comparing the environmental consequences of providing, using and disposing of a product. If the impact or burden is lower than the remediation, the difference will be negative. Negative differences state improvements compare to the original factors.
4. Characteristics of the material
4.1. Band gap eV (1.1.)
4.2. Lifetime of the material month
4.3. Reduction of NOX using Photonsite % (1.2.)
4.4. Mass of TiO2 per surface of pavement kg/m2
5. Environmental conditions on site
5.1. NO concentration in the street μg/m3
5.2. Atmospheric pressure atm
5.3. Average annual temperature in the street °C
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Rough estimation of removal NO2
This section contains a tool to obtain the percentage of NO2 removal efficiency using a GAM model trained using the data obtained in the PHOTOSCALING platforms. It considers the efficiency of the material itself as the average for one year at outdoor exposition without taking into account other effects as degradation due to tyres friction. Always consider that the assumptions and simplifications of the model make it an estimation for comparative purposes more than a prediction tool.
6. Values in the final place
6.1. Average concentration of NO2 in the area where the material is going to be placed μg/m3
6.2. Average concentration of NO in the area where the material is going to be placed μg/m3
6.3. Average radiation in the area where the material is going to be placed (W/m2)/m3
6.4. Average RH in the area where the material is going to be placed %/m2
6.5. Material of the support
6.6. Reduction of NOX using Photonsite % (1.2.)

This estimation is currently being refined. In the future, the result obtained might be different even if the same data are used.