Action B1 Part A: Study into the influence of determinant variables of photocatalytic activity in controlled conditions and regeneration trials. Part A) Accelerated full-scale road surface trial
CEDEX is responsible for studying the influence of environmental and mechanical parameters (traffic loads) on the photocatalytic products applied to the bituminous mixes in road surfaces. This study was carried out in a controlled environment prior to the product’s application to streets in Alcobendas.
This was undertaken simultaneously with Phase I of Action C3 (the monitoring of the project’s impact on the materials trialled in the laboratory and on the test track).
Two photocatalytic additives were applied to two different substrates, a dense graded bituminous mix and an open mix, at the CEDEX test track. Real traffic was simulated by the controlled application of loads in order to determine the structural and superficial response and the material’s behaviour under an accelerated process of damage accumulation. This was applied to a sufficient extent that there was one section that had been subjected to vehicle rolling and another that had not. The purpose of this was to be able to determine the effect of climactic variables from the influence of traffic in the 6 sections studied. The stability of the different additives against wear from rolling and water was also studied through the analysis of photographs.
The modifications caused by the incorporation of additives into bituminous mixes were evaluated through laboratory tests on the 6 sections in Action C3. In addition to this, core samples were tested to study the effect of traffic and environmental variables on the bituminous mixes.
The conclusions drawn are that all the additives applied have some effect on the substrate. In general, these consist in a slight loss of the characteristics of the substrate; moreover, low durability was observed for all products in the accelerated wear test with vehicles simulating traffic.
Action B1 Parts B and C: Part B) Trial into the photocatalytic activity of the selected materials. Part C) Trial into the regeneration of the material’s photocatalytic activity when subjected to washing.
A multivariable correlation parametric study was carried out, analysing the effect of flow, NO concentration, irradiance and relative humidity on photocatalytic activity. This employed the same experimental system that was developed to run the experiments required by standard ISO 22197-1.
Trials were also run to study the regeneration of the photocatalyst through gentle and heavy washing processes following prolonged exposure of the samples to outdoor conditions. Temperatura, pH, wash time and movement were some of the variables analysed. Photocatalytic activity was evaluated after the regeneration process was carried out for different test specimens both from building facades and from concrete and asphalt paving materials. This study was hindered by the loss of photocatalytic activity caused by the loss of the photocatalytic product both during the exposure period and during the washing process. Therefore, the intended method in for performing this task is to saturate the photocatalytic surface of the material in accelerated conditions with high NO concentration in the laboratory, throughout the execution timeframe for Action B1. A better correlation will thereby be established for the effect of the regeneration process without interference from other parameters, such as the loss of the photoactive material or the accumulation of other elements present in the air outdoors.
The following conclusions were reached:
Part ASections of the CEDEX test track treated with photocatalytic products. Measurement of environmental variables and road temperature Initial extraction of test samples at the CEDEX test track
Part BPhotographs of the change in appearance of the samples after 40,000 and 80,000 load cycles. SEM/EDX analysis of one of the samples following ageing by rolling traffic.