Avaliação das capacidades fotocatalítica, superhidrofóbica e autolimpante de misturas betuminosas funcionalizadas com TiO2 e ZnO

Dissertação de mestrado integrado em Engenharia CivilAtualmente, existe uma preocupação crescente acerca do esgotamento dos recursos naturais e do dano ao meio ambiente. A engenharia rodoviária em geral e particularmente o domínio dos pavimentos rodoviários pode contribuir de forma significativa para a mitigação destes problemas. A integração de nano/micromateriais nas misturas asfálticas que constituem as camadas superficiais dos pavimentos dotará essas superfícies de novas capacidades (funcionalização) particularmente em termos ambientais e em termos de segurança viária: (i) fotocatalíticas: capazes de fotodegradarem poluentes com o intuito de limparem o meio ambiente; (ii) superhidrofóbicas: melhor resistência à água e uma maior segurança rodoviária em períodos de chuva e de baixas temperaturas; (iii) autolimpantes: evitar problemas de derrapagem, facilitar a drenabilidade da água e dificultar o fenômeno da colmatação dos poros. Com o objetivo de dotar as superfícies dos pavimentos com estas novas capacidades funcionais, misturas asfálticas do tipo AC 6 e AC 14 foram funcionalizadas a partir da aspersão superficial dos semicondutores nano-TiO2 e/ou micro-ZnO. Previamente, a fim de avaliar o impacto químico e morfológico da aplicação dos semicondutores, foram realizados ensaios de Microscopia de Força Atômica (AFM) e Espectroscopia de Infravermelho Transformada de Fourier (FTIR) nos ligantes asfálticos usados para compor as misturas. A seguir, para verificar as novas capacidades, foram realizados ensaios de Ângulo de Contato e de Avaliação Fotocatalítica. Por fim, a melhor solução foi avaliada mecanicamente pela resistência à tração após o condicionamento por água para avaliar o impacto dos semicondutores. Os resultados indicam que houve um maior impacto superficial e químico pela técnica de aspersão da solução aquosa contendo ZnO. A combinação de TiO2 com ZnO promoveu propriedades fotocatalíticas, superhidrofóbicas e auto-limpantes, proporcionando a ambas as misturas asfálticas essas novas capacidades. Ademais a aspersão não causou impacto mecânico. Com o desenvolvimento dessas camadas, prevêem-se grandes benefícios para o ambiente e para a segurança rodoviária.Presently, there is a growing concern about the depletion of natural resources and environmental damage. The road engineering in general and road pavements can contribute significantly to mitigate these problems. The integration of micro/nanoparticles in asphalt mixtures that compose the top layer of the pavements will provide their surfaces with new capabilities (functionalization) particularly in environmental and safety related terms: (i) photocatalytic: able to photodegrade pollutants for the purpose of cleaning the environment; (ii) superhydrophobic: better water resistance and better road safety in periods of rains and low temperatures; (iii) self-cleaning: avoid slipping problems, facilitate the water drainability and prevent the pore clogging phenomenon. In order to provide the new functional capabilities to the surface of the pavements, asphalt mixtures AC 6 and AC 14 were functionalized with superficial spraying of semiconductors nano-TiO2 and/or micro-ZnO. First, in order to evaluate the chemical and morphological impacts of the application of the semiconductors, tests of Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) onto the asphalt binder that compose the mixtures were carried out. Next, in order to verify the new capabilities, tests of Water Contact Angle and Photocatalytic Evaluation were carried out. Finally, the best solution was mechanically evaluated through Indirect Tensile Strength after immersion to analyze the impact of semiconductors. The results show that there was a higher superficial and chemical impact onto the bitumen by the spray technique of the ZnO aqueous solution. The combination of TiO2 and ZnO promoted photocatalytic, superhydrophobic and self-cleaning properties, providing the asphalt mixtures these new capabilities. Besides the spraying technique did not cause mechanical impact. With the development of these layers, benefits to the environment and road safety are foreseen

Special issue: Functionalized and smart asphalt mixtures via the modification/application of nano/micromaterials

Asphalt pavements are designed to resist weathering and road traffic while guaranteeing safe and comfortable driving conditions at low cost and with minimal environmental impact [...]This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020 and UIDB/04029/2020 and also under the projects of MicroCoolPav project EXPL/EQU-EQU/1110/2021, and NanoAir project PTDC/FISMAC/6606/2020

Application of nano/microparticles on asphalt mixes to promote photocatalysis and superhydrophobicity

The integration of nano/microparticles in asphalt mixtures provides new capabilities (functionalization) such as: photocatalytic; superhydrophobic and self-cleaning, which can contribute to the mitigation of present public health problems as air pollution and road safety. Thus, the main goal of this research was to develop these capabilities on asphalt mixtures composed of raw and recycled materials and analyze the performance of an improved functionalization process using a resin spraying for the immobilization of the particles. Solutions composed of nanoparticles of titanium dioxide (nano-TiO2) and/or microparticles of polytetrafluoroethylene (micro-PTFE) and water, ethyl alcohol, and dimethyl ketone as solvents were produced and subsequently sprayed over a conventional AC 10. The best solution (BS) to proceed with the functionalization process was selected after the evaluation of the samples under dye degradation and wettability. Next, two successive spraying coatings were carried out over conventional and recycled AC 10 with Reclaimed Asphalt Pavement (RAP) and Steel Slags (SS): the first one with a diluted epoxy resin and the second one with the BS. In the first step of the functionalization process, the BS selected was composed of TiO2 (4 g/L) and PTFE (4 g/L) under an ethyl alcohol medium. The next steps showed that by increasing the amounts of resin, the photocatalytic efficiency decreases and the wettability increases, performing better for 0.25 g of resin with BS. All the mixtures achieved the superhydrophobicity property (water contact angle higher than 150°) and performed similarly regarding wettability with the lowest resin amount. Nevertheless, the conventional AC 10 presented the best results concerning photocatalysis. These functionalized pavement surfaces can degrade gases like SO2 and NOx, avoid accidents by removing the small dirt particles, degrade oils on the pavement surface, presenting great benefits to road safety and the environment. Multifunctional asphalt mixtures can be included in the sphere of Clean Technologies, and, in this framework, they contribute to the transition to the sustainable model “Green Recovery”. Moreover, this research presents a potential destination for the nano/micromaterials, the Civil Engineering fields, and, if incorporated on a large scale, can stimulate the dynamism of industry

Photocatalysis and smart asphalt mixtures

The application of photocatalytic semiconductors into asphalt mixtures give it better performance an new capabilities such as photocatalytic, superhydrophobic, self-cleaning, deicing/anti-ice, self-healing, thermochromic, and latent heat thermal energy storage

Photocatalytic and thermochromic materials applied to road engineering

[Excerpt] Materials Science knowledge has been applied to Civil Engineering to provide new capabilities and benefits for the environment and society. Through the functionalization process with nano/microparticles, Civil Engineering materials can become smart. This study presents the main results of the research work with photocatalytic (nano-TiO2 ) and thermochromic (Leuco dye) materials on road pavements and road markings [1-5]

Are there new ways to improve the asphalt mixtures' surface functions? For sure! By functionalization process

Titanium Dioxide (TiO2) semiconductor material and Polytetrafluorethylene (PTFE) have been applied in the form of nano/microparticles over asphalt road pavements to provide them with new surface functionalities. This is a FUNCTIONALIZATION process that aims to improve the sustainable characteristics of the asphalt mixtures through the photocatalytic, superhydrophobic, and self-cleaning capabilities, which are related to the degradation of hazardous pollutants from the atmosphere (NOx, SO2, among others) for environmental remediation and the cleaning of the road surface (dust, greases, and oils) for the mitigation of the decrease of friction. Thus, in this research work, dispersions containing TiO2 nanoparticles and PTFE microparticles were sprayed over an AC 10 asphalt mixture to coat and functionalize it. To confirm the photocatalysis, super hydrophobicity, and self-cleaning capacities, this smart material performance was evaluated under the degradation of the organic compound Rhodamine B (RhB) as a pollutant model and Water Contact Angle (WCA). The results indicate the photodegradation of the pollutant, confirming the proper functioning of the functionalization process, and a WCA of 150°, proving that the nanoparticles were well dispersed just over the surface of the asphalt mixture. In general, this multidisciplinary research contributes to social and environmental enhancement and enlarges the opportunities for applications of nanomaterials in a very large-scale field such as Civil Engineering. Moreover, it showed that the surface characteristics of the asphalt pavements could be studied and improved not only with a conventional approach based on noise, friction, texture, and rolling resistance measurements but also through a physicochemical approach, as the functionalization processes, using knowledge of Materials Science

Surface rehabilitation of Portland cement concrete (PCC) pavements using single or double surface dressings with soft bitumen, conventional or modified emulsions

Surface dressings are a sustainable maintenance alternative for pavements with surface distresses, due to the low amount of resources involved. This paper aims to analyze the viability of using twelve different surface dressing solutions, including three binders (conventional and modified emulsions, and a soft 160/220 bitumen) and a covering with diluted emulsion, for surface treatment of Portland cement concrete (PCC) pavements. Several test methods were used to evaluate the macrotexture, skid resistance, adhesion, and resistance to wearing on a large scale prototype. In general, single surface dressings increased further the macrotexture of the concrete pavement surface. The skid resistance of single and double surface dressings was similar. The best surface dressing in the pull-off test was that with the 160/220 bitumen. The conventional and modified emulsions presented similar mechanical adhesion in the Vialit plate test. Concerning the prototype wearing test, the best result was obtained for the double surface dressing with bitumen covered with diluted emulsion. Based on this work’s results, the surface dressings are a potential surface rehabilitation alternative for concrete pavements.This work was partially financed by FCT / MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020. This work is financed by national funds through FCT - Foundation for Science and Technology, under grant agreement SFRH/BD/137421/2018 attributed to the 1st author

Superhydrophobic asphalt pavements: surface improvement

The most adverse weather condition for road safety happens when there is water, snow, or ice on the road surface because their presence highly decreases friction. Therefore, it is essential to drain or repel them quickly. If the water drops are repelled from the surface or the ice/snow formation is avoided with the application of superhydrophobic coatings, roads become safer. In order to functionalize the asphalt mixtures used in road pavements, nano/micromaterials, such as Polytetrafluoroethylene (PTFE), TiO2, and SiO2, among others have been applied by spraying coating. The mixes are usually characterized by the water contact angle, and the surface roughness is typically assessed by optical and electron analysis. This research work aims to present a brief overview of superhydrophobic asphalt mixtures

Development of capacitive-type sensors by electrochemical anodization: Humidity and touch sensing applications

This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campaign carried out on different acid electrolytes, in which the anodization parameters were adjusted to investigate the effect of pore size and porosity on the capacitive sensing performance. Two sensor test cases are investigated. The first case explores the use of highly uniform NP-AAO structures for humidity sensing applications while the second analyses the use of NP-AAO as a capacitive touch sensor for biological applications, namely, to detect the presence of small "objects " such as bacterial colonies of Escherichia Coli. A mathematical model based on equivalent electrical circuits was developed to evaluate the effect of humidity condensation (inside the pores) on the sensor capacitance and also to estimate the capacitance change of the sensor due to pore blocking by the presence of a certain number of bacterial microorganisms. Regarding the humidity sensing test cases, it was found that the sensitivity of the sensor fabricated in a phosphoric acid solution reaches up to 39 (pF/RH%), which is almost three times higher than the sensor fabricated in oxalic acid and about eight times higher than the sensor fabricated in sulfuric acid. Its improved sensitivity is explained in terms of the pore size effect on the mean free path and the loss of Brownian energy of the water vapour molecules. Concerning the touch sensing test case, it is demonstrated that the NP-AAO structures can be used as capacitive touch sensors because the magnitude of the capacitance change directly depends on the number of bacteria that cover the nanopores; the fraction of the electrode area activated by bacterial pore blocking is about 4.4% and 30.2% for B1 (E. Coli OD600nm = 0.1) and B2 (E. Coli OD600nm = 1) sensors, respectively.This research was funded by: the Portuguese Foundation for Science and Technology (FCT) under the strategic funding grants UIDB/04029/2020, UIDB/04650/2020 and UIDB/04469/2020 units; and, the European Regional Development Fund under the scope of Norte2020 program grant NORTE-01-0145-FEDER-000004, BioTecNorte

Development of capacitive-type sensors by electrochemical anodization: humidity and touch sensing applications

This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campaign carried out on different acid electrolytes, in which the anodization parameters were adjusted to investigate the effect of pore size and porosity on the capacitive sensing performance. Two sensor test cases are investigated. The first case explores the use of highly uniform NP-AAO structures for humidity sensing applications while the second analyses the use of NP-AAO as a capacitive touch sensor for biological applications, namely, to detect the presence of small objects such as bacterial colonies of Escherichia Coli. A mathematical model based on equivalent electrical circuits was developed to evaluate the effect of humidity condensation (inside the pores) on the sensor capacitance and also to estimate the capacitance change of the sensor due to pore blocking by the presence of a certain number of bacterial microorganisms. Regarding the humidity sensing test cases, it was found that the sensitivity of the sensor fabricated in a phosphoric acid solution reaches up to 39 (pF/RH%), which is almost three times higher than the sensor fabricated in oxalic acid and about eight times higher than the sensor fabricated in sulfuric acid. Its improved sensitivity is explained in terms of the pore size effect on the mean free path and the loss of Brownian energy of the water vapour molecules. Concerning the touch sensing test case, it is demonstrated that the NP-AAO structures can be used as capacitive touch sensors because the magnitude of the capacitance change directly depends on the number of bacteria that cover the nanopores; the fraction of the electrode area activated by bacterial pore blocking is about 4.4% and 30.2% for B1 (E. Coli OD600nm=0.1) and B2 (E. Coli OD600nm=1) sensors, respectively.This research was funded by: the Portuguese Foundation for Science and Technology (FCT) under the strategic funding grants UIDB/04029/2020, UIDB/04650/2020 and UIDB/04469/20 units; and, the European Regional Development Fund under the scope of Norte2020 program grant NORTE-01-0145-FEDER-000004, BioTecNorte.info:eu-repo/semantics/publishedVersio